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International Sorghum and Millet Collaborative INTSORMIL Impacts and Bulletins Research Support Program (INTSORMIL CRSP)

6-8-1997

Proceedings of The Global Conference on Ergot of Sorghum

Carlos R. Casela

Jeffery A. Dahlberg

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This Article is brought to you for free and open access by the International Sorghum and Millet Collaborative Research Support Program (INTSORMIL CRSP) at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in INTSORMIL Impacts and Bulletins by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Global Conference on frgot of Sorghum ~...... The conference sponsors, EMBRAPA and INTSORMIL, gratefully acknowledge the contributions made to this conference by the following organizations.

American Seed Trade Association ICRISAT National Grain Sorghum Producers Novartis Seeds, Inc. Pioneer Hi-Bred International, Inc. Texas A&M University Texas Seed Trade Association USDA

Members of the Organizing Committee

Robert Schaffert, Chair, EMBRAPA, Sete Lagoas, Brazil Gisela de Avellar, EMBRAPA, Sete Lagoas, Brazil Ranajit Bandyopadhyay, ICRISAT, Hyderabad, India Tania M.A. Barbosa, EMBRAPA, Sete Lagoas, Brazil Carlos R. Casela, EMBRAPA, Sete Lagoas, Brazil Alexandre S. Ferreira, EMBRAPA, Sete Lagoas, Brazil Richard Frederiksen, Texas A&M University, College Station, TX Nicesio F.J.A. Pinto, EMBRAPA, Sete Lagoas, Brazil Soraya M. Santana, EMBRAPA, Sete Lagoas, Brazil Arnaldo F. da Silva, EMBRAPA, Sete Lagoas, Brazil J. Heltor Vasconcellos, EMBRAPA, Sete Lagoas, Brazil Geraldo Vilela, EMBRAPA, Sete Lagoas, Brazil John Yohe, INTSORMIL, University of Nebraska, Lincoln, NE Proceedings

of

The Global Conference on Ergot of Sorghum

June 1-8, 1997 EMBRAPA, Sete Lagoas, Brazil

Sponsored by Empresa Brasileira de Pesquisa Agropecuaria, Brazil (EMBRAPA)

and

International SorghumlMillet Collaborative Research Support Program (INTSORMIL)

This publication made possible through support provided by the U.S. Agency for International, Development under the terms of Grant No. LAG-G-00-96-90009-00. The opinions expressed herein are those of the author(s) and do not necessarily reflect the views ofthe U.S. Agency for International Development.

Edit by Carlos R. Casela and Jeffery A. Dahlberg

January 1999 Publication No. 99-1 Foreword

Why Ergot, Why Brazil and Why Now

In June 1996, several ofus had the opportunity to see sorghum ergot in Brazil and the damage that the disease can do. We saw severe damage in seed production plots and witnessed the pain that seed producers had to go through to deal with this new problem. There was a wide spread scare in the sorghum community in the Americas because ofthe infamous reputation ofthe disease in causing damage in seedprodu~ tionfields. As a silver lining, we also observedfirst hand, the excellent research pro­ gram that the Brazilians had in place. It became apparent that all ofthe sorghum re­ searchers, seed producers and regulators of plant pathogens worldwide needed to come together to study and review this disease. There could be no better venuefor such a Global Conference than Sete Lagoas, Brazil. Hence this meeting was proposed and with the support and assistance of the Director of Sorghum and Maize Research (CNPMS) ofEMBRAPA, this meeting has been arranged. At the time the meeting was proposed, the disease was known only in a few countries but it has spread today to in­ clude much ofthe Americas and Australia. Obviously, we can no longer avoid the dis­ ease, we can only learn to live with it and manage it infuture growing seasons. It has been my pleasure to work with the research leaders on ergot at EMBRAPA in develop­ ing this conference, to receive cooperation from many ofthe global leaders on ergot to bring their knowledge to the conference and financial support from the American Seed Trade Association, as well as the support and encouragementfrom Texas A & M University and INTSORMIL in recognizing the importance of our collaboration on combating sorghum ergot.

In this conference, we will learn from the experiences ofcountries where ergot had existedfor a long time while examining the ergot situation in newly invaded countries. We have several dedicated papers dealing with the biology ofthe pathogen, the epide­ miology of the disease, and disease management strategies. We will also chart the movement ofthe disease andplot ideas on how to collaboratively work to lessen the im pact ofsorghum ergot in the Americas.

Richard A. Frederiksen Professor, Plant Pathology Texas A&M University College Station, TX 77843--2132

iii Contents

Foreword - Richard Frederiksen ...... iii

Session I - Sorghum Ergot Around the World Session President - John Yohe (INTSORMIL)

Sorghum Ergot: An Overview - P.G. Mantle ...... 3

Geographic Distribution and Spread of Sorghum Ergot: Causes and Implications - R Bandyopadhyay ...... 10

Session II - Ergot Scenario in Brazil Session President - E. M. Reis (UFPF)

Sugary Disease of Sorghum in Brazil: An Overview - R. Casela, A.S. Ferreira and N.FJ.A. Pinto ...... 23

Strategies for the Control of Ergot in Sorghum Seed Production in Brazil - P.M. Ribas ...... 26

Session III - Country Reports Session President - G. Odvody Texas A&M University

Opening Remarks-G. Odvody ...... 35

Experiences with Ergot in Sorghum in Southern Mrica - D.C. Nowel and N.W. McLaren ...... 36

Sorghum Ergot in India - C.S. Sangitrao, S. Indira and R. Bandyopadhyay ...... 41

The Ergot Disease of Sorghum in Africa - S.Z. Mukuru ...... 55

Current and Future Research on Sorghum Ergot in Australia - M. Ryley, B. Blaney, and H. Meinke ...... 59

Sorghum Ergot in the United States - Public Sector Response - G.N. Odvody and T. Isakeit ...... 68

v United States Private Sector Response - W.E. Dolezal ...... 76

Sorghum Ergot in Argentina - L.M. Giorda, M.l Martinez, M. Nassetta, and S. Palacios ...... 79

Incidence of Ergot in Honduras - l Moran and F. Gomez ...... 84

Ergot, Honeydew or Sugary Disease of Sorghum in Venezuela - G. Malaguti and N. Pons ...... 88

Cereal Ergots in Uraguay - M.S. Pifieiro ...... 97

Sorghum Ergot in Mexico - lH. Torres-Montalvo, and N. Montes-Garcia ...... 101

Session IV - Ergot Biology Session President - R. A. Frederiksen,Texas A&M University

DNA Comparisons and Alkaloid Toxicity of the Ergot Fungi: A Contribution to Ergot Phylogeny - S. Pai'outova ...... III

Host x Pathogen x Environment Interaction in Sorghum Ergot Disease - N. W. McLaren ...... 122

The Lifecycle, Spread and Survival of the Sorhum Ergot Pathogens - D.E. Frederickson ...... 135

Putative Control of Ergot Disease Epidemics in Hybrid Sorghum Production through the Inhibition of Secondary Sporulation by Claviceps africana - H.A.G. Hassan, P.G. Mantle and N.W. McLaren ...... 141

Session V - Ergot Management Strategies Session President - Ranajit Bandyopadbyay (ICRISAT)

Host Plant Resistance: Sorghum Ergot - J.A. Dahlberg ...... 149

Chemical Control of Sugary Disease of Sorghum (C/aviceps africana) - N.FJ. del Almeida Pinto, A. da Silva Ferreira, and C.R. Casela ...... 158

Integrated Management of Sugary Disease of Sorghum - Practical Aspects - E.M. Reis and M.M. Casa Blum ...... 161

vi Session VI - International Collaboration in Ergot Research - Global Network Session President - R.E. Schaffert (EMBRAPAlCNPMS)

Role ofICRISAT in Sorghum Ergot Research - R. Bandyopadhyay ...... 169

The Role of the International Sorghum and Millet Collaborative Research Program on Management of Claviceps africana in Sorghum - R.A. Frederiksen and lM. Yohe ...... 178

The Role of USDA in Research on Sorghum Ergot - lA. Dahlberg ...... 180

Sorghum Ergot in Australia - M. Ryley and Bob Henzell ...... 182

Global Conference on Ergot of Sorghum - Recommendations Report ...... 191

Conference Participants ...... 195

vii Session I - Sorghum Ergot Around the World

Session President - John M. Yohe

1 Sorghum Ergot: an Overview

Peter G. Mantle

Ergot disease of sorghum appears to be disease was, and still remains, uncertain. a 20th century phenomenon, formally Indeed, in Africa the generally cryptic na­ recognized to the extent that some of the ture ofthe pathogen and its disease on sor­ first samples, from Burma (1927), Kenya ghum, not producing prominent sclerotia (1924), and Uganda (1926) were depos­ as does Claviceps purpurea, even failed ited in the herbarium of the former Corn­ to catch the attention of A. R. Loveless at monwealth Mycological Institute at Kew, the University of Southern Rhodesia who UK (Mantle 1968). Mycologically, the otherwise described several new aspect of the pathogen with the greatest Claviceps species in East Africa, most no­ obvious taxonomic value, in the absence tably Claviceps fusiformis (Loveless of any obvious sexual stage, was the 1967), the characteristic pathogen of sphacelial fructification established on pearl millet. It is, however, somewhat infected ovaries and associated with hon­ ironic that the common sorghum patho­ eydew exudate. Thus, the connection with gen in Africa was shown experimentally other ergot parasites was established by to infect pearl millet (Frederickson and the description of Sphacelia sorghi in In­ Mantle 1996), though this is probably not dia (McRae 1917). The material was important as a functional alternate host. characteristic of the Indian sub-continent and the description was the taxonomic ba­ The author first became involved with sis for recognizing sorghum ergot patho­ a sorghum ergot pathogen in the mid gens in both Asia and Africa for the next 1960s concerning sclerotia of Nigerian 70 years. origin thought to contain the alkaloid agroclavine. Scepticism about identifica­ In Africa the pathogen was recognized tion of that alkaloid led instead to the iso­ again in Tanganyika (1949), South Africa lation and characterization of a new (1953), Nigeria (1955), Zambia (1965), naturally-occurring dihydrogenated ergot Ethiopia (1973) and Mozambique (1984) alkaloid, dihydroergosine, and the recog­ but the disease became most prominent in nition of its reduced clavine alkaloid bio­ northern Nigeria in the early 1960s asso­ synthetic intermediates (festuclavine and ciated with sorghum hybrid breeding (Fu­ dihydroelymoclavine) as minor compo­ trell and Webster 1965, 1966) research nents (Mantle and Waight 1968). Atten­ when the particular natural susceptibility tion then focused on obtaining ergot alka­ of male-sterile sorghums became quite loid production in axenic culture in yields clear. However, the precise epidemiol­ of 0.5 mg ml-! (Mantle 1973) and the ex­ ogical source of the pathogen by which it tension of the technique to production in maintained its potential for opportunistic stirred fermenters of up to 300 L capacity (Attwell 1981). Efficient axenic culture led to experimental demonstration of the Peter G. Mantle, Biochemistry Department, Imperial College of Science, biosynthetic interactions between the Technology and Medicine. London SW7 2A Y. UK various alkaloids (Barrow et al. 1974) and

3 the flexibility of natural biosynthetic en­ tween abducted glumes. Consequently, zyme systems to accept an unnatural bio­ the disease was widely known as sugary synthetic precursor to produce, for exam­ disease because the honeydew stage was ple, the hydroxy-prolyl analogue of dihy­ the most diagnostic symptom. droergosine (Atwell and Mantle 1981). These secondary metabolite characteris­ In contrast, S. sorghi in India produced tics of the African sorghum ergot patho­ an elongated sclerotium, protruding up­ gen were thus recognized as a unique wards 1 cm from the floret, though only combination which, therefore, has in e:t: constituting a really compact sclerotial fect, diagnostic value for the fungus. body in its proximal portion. Sufficient However, it also implies affinity with the production of this tissue may give rise very special Claviceps gigantea which subsequently to the typical Claviceps parasitises maize exclusively in Mexico stromata in the capitula of which the te­ (Fuentes et al. 1964). e. gigantea also leomorphic formation of ascospores oc­ elaborates the dihydrogenated clavine al­ curs. A taxonomically valid short descrip­ kaloids, festuclavine and dihydroelymo­ tion of Claviceps sorghi was made (Kul­ clavine, but takes the biosynthetic path­ karni et al. 1976), from which it was way no further into the larger cyclic widely assumed that it applied also to S. tripeptide derivatives as does the African sorghi of Africa. No ergo line alkaloids sorghum pathogen. It is, however, hard to were detected in sclerotia ofe. sorghi but see whether there is any close phyloge­ an isolate was shown to produce agro­ netic relationship between the sorghum clavine in small amounts (23 Ilg mrl) af­ and maize pathogens that are separated ter 3 weeks of stationary liquid culture geographically by long distances, and (Manzarpour 1985). Agroclavine was therefore the dihydrogenation step in the recognized by thin-layer chromatography ergoline alkaloid biosynthetic pathway and by electron impact mass spectrome­ may have evolved independently in the try. This further emphasized genotypic two fungi. It is notable that infection of distinction between the African and In­ maize ovaries by the African sorghum dian ergot pathogens of sorghum. pathogen has been demonstrated experi­ mentally by the author, although the para­ Following fundamental studies on the sitic mycelium does not become organ­ mechanism of resistance of certain pearl ized into a typical sclerotium, confirming millets to ergot disease that was being ex­ findings of Futrell and Webster (1966). ploited at the ICRISA T Centre, Hydera­ bad (Willingale and Mantle 1985; Failure to differentiate a noticeable Willingale et al. 1986), attention was sclerotium in sorghum is a common fea­ redirected towards sorghum, using an ture of ergot disease in Africa. Either the Indian isolate of C. sorghi from fungus barely fills the floral cavity with a Maharashtra State as a model for defining sphacelium and then often becomes in­ the path of infection (Frederickson and fested with saprophytic fungi, including Mantle 1988). Concomitantly, the present Cerebella spp., or it may differentiate into author observed iterative germination of only a small, roughly spherical, sclero­ S. sorghi (e. sorghi) macrospores on agar tium 2-3 mm in diameter, located be- media, an observation which led to the

4 description (Manzarpour 1985) of the honeydew was more dilute than is natural, ation phenomenon, expression of which in the absence ofthe desiccating influence is regulated by temperature. At moderate of field conditions. Therefore, secondary temperatures, up to 27°C, virtually all sporulation is a constitutive characteristic spore germination was in the form of a of S. sorghi, whether as the expression of short sterigma-like projection from the the anamorph of the Indian or ofthe Afri­ top of which a secondary spore formed, can ergot pathogen of sorghum. The na­ usually at the complete expense of the cy­ ture of the relevant honeydews, that are toplasm of the macrospore. At tempera­ partly phloem exudate and partly the tures above 27°C, typical hyphal germ parasite's biotransformed excreta, influ­ tube germination occurred and became ences whether or not, and to what extent, the exclusive mode of germination at secondary sporulation of submerged 37°C. This did not seem to be importantto macrospores occurs. The question re­ the parasitic biology ofthe pathogen until mains why, when macrospores are spread the pathology of the Indian pathogen (c. across an agar surface in the laboratory, sorghi) was compared directly with that the normal mode ofgermination is itera­ of an African isolate in similar horticul­ tive and is only replaced by hypha forma­ tural tunnel conditions in England in tion at high temperatures. When macro­ 1989. However, it was readily apparent spores are deposited on the surface of a that the honeydew stages were quite dra­ stigmatic hair of sorghum, germination is matically different. C. sorghi produced consistently by hyphal formation and honeydew which was usually viscous and quickly leads to intercellular penetration rich in sugars and in which no macrospore and subsequently traverses through the germination occurred, whereas the Afri­ stigmatic transmission tract. Clearly, it­ can pathogen exuded a very dilute honey­ erative germination on a stigmatic hair dew which quickly became covered by a would be biologically futile and therefore white crust (Frederickson et al. 1991). macrospores respond to stigmatic influ­ This crust was shown to consist of a pali­ ences (whether chemical and/or physical) sade of secondary spores borne on sterig­ to ensure penetration tube production ir­ mata which pierced the honeydew liquid respective of the temperature, which may surface (Frederickson et al. 1989). There­ fluctuate between wide diurnal limits. In fore the secondary sporulation of C. sor­ the absence ofthe direct influence ofa po­ ghi was mainly a laboratory phenomenon. tential host, as in the case of being sub­ Analogous profuse parasitic manifesta­ merged in exuded honeydew, iterative tion was apparently confined to the Afri­ germination of macrospores is promoted can pathogen. Further study of secondary in principle, if not in rate of response, by sporulation in vivo was performed at IC­ lowering temperatures which in the field RISAT, Hyderabad (Bandyopadhyay et will be associated with night conditions al. 1990) showing that in high relative hu­ and the consequent diluted nature of midity under glasshouse conditions C. freshly exuded honeydew under high sorghi expressed secondary sporulation relative humidity. Whereas this may all on honeydew. Under these experimental make logical biological sense, it empha­ conditions it can be assumed that exuded sizes some sophisticated mechanisms of

5 signal recognition in a unicellular fungal ping. The spores can readily be recog­ spore of two remarkable ergot pathogens nized morphologically by their lemon of sorghum. However, the biological suc­ shape but extensive scanning of spore trap' cess of the African pathogen is largely slides would be very time-consuming. due to the versatile function of its macro­ Nevertheless, the dramatic spread of sor­ spores and perhaps it is not surprising that ghum ergot throughout much of South they have special abilities. Apparent reli­ America, after the causal agent was iden­ ance on asexual spores for parasitic estab­ tified as e. africana (Reis et al. 1996), lishment ofthe African pathogen is due to must be partly attributable to the wind­ the rarity of stromatal formation from borne dissemination of propagules and sclerotia, reported only in general terms the apparently susceptible sorghums by Mower et al. (1973) but later used spe­ grown extensively in South and Central cifically by Frederickson et al. (1991) as America and in the United States. Simi­ the basis for describing the african patho­ larly, the pathogen established a new en­ gen as Claviceps africana. This species is demic focus in Queensland, Australia. distinct from e. sorghi not only in myco­ These rather sudden aspects of global logical differences of the respective spread had been foreshadowed by dis­ Claviceps teleomorphs, but also by the semination at some stage from Africa to particular and consistent occurrence of di­ Thailand (Boon-Long 1988; Frederick­ hydroergosine and related clavine alka­ son et al. 1991) and to Japan as deter­ loids in sclerotia of e. africana. mined by Mantle and Hassan (1994) who warned of the danger of spread into the A remarkable feature of e. africana is Americas. its apparently spontaneous appearance in parts of Africa, particularly in male­ The relatively insignificant size of sterile sorghums grown even in virgin lo­ sclerotia ofe. africana has resulted in the calities for sorghum cultivation. It should principal focus of disease significance be­ be emphasised that, although variousSor­ ing purely on loss of grain. With an in­ ghum species can be, and are, hosts for e. crease in disease incidence, the fact that africana, no documentation of a plausible the pathogen is an ergot fungus, some of step-by-step sequence explaining the ori­ whose close relatives produce metaboli­ gin of epidemics of disease in seasonal ties which are toxic to animals, makes crops has yet been made. Assumptions possible toxicity worth considering. The are not adequate for explaining what is effect of sclerotia from Nigeria on repro­ becoming globally an important disease. ductive performance in mice revealed no All that was demonstrated experimentally effect even at very high intake (Mantle is the windborne spread by secondary 1968). This contrasts with the marked e:t: spores, registered on a spore trap, from an fect on both blastocyst implantation and insect-proof primary focus of infection lactation by alkaloids of the pearl millet across a plot of male-sterile sorghums to ergot pathogen e. fusiformis. It was con­ give a widespread high incidence of dis­ cluded, therefore, that e. africana sclero­ ease (Frederickson et al. 1993). Long dis­ tia did not constitute a significant toxic tance dissemination of secondary spores hazard to farm animals or to humans. This has not yet been detected by spore trap- was in spite of the fact that dihydroer-

6 gosine possesses some of the pharmacol­ Japan (T. Tsukiboshi, personal communi­ ogical activity of its close relatives er­ cation) which has a Sphacelia segetum­ gosine and ergotamine (Berde and Schild like (c. purpurea) anamorph and grey 1978). This view might be sustainable, in spur-shaped sclerotia containing only a general, were it not for recent definition of trace of some unusual ergot alkaloids a new dimension in C. purpurea toxicity (Ohmomo 1990). Asexual spores appar­ towards dairy cattle. A so-called 'summer ently do not undergo secondary sporula­ syndrome' in the Cape region of South tion in honeydew from parasitized male­ Africa has been ascribed plausibly to sterile sorghum in the present author's ex­ small amounts of ergot alkaloids in a perience, although the phenomenon was grass-seed based feed supplement used in observed in spores washed from their summer when pasture is in short supply. honeydew and then spread on agar media Decline in milk yield was attributed to re­ (Hassan 1996). In lacking a mechanism duced feed intake on account of the dis­ for long distance dissemination, and comfort of hyperthermia induced by pe­ therefore not necessarily a significant ripheral vasopressor effects of the ergot global threat to sorghum, the question alkaloids (Schneider et al. 1996) ascribed arises as to whether the association to sclerotia ofC. purpurea (Mantle 1996). between this fungus and sorghum is an The present author is also aware of an ancient one limited by geography, or analogous syndrome associated with whether it has arisen recently and is indi­ feeding ergotised sorghum to dairy cattle cating that an analogous association could in South Africa and this aspect of possible develop elsewhere in the world. toxicity will be explored further to estab­ lish whether there is a clear cause and ef­ Pearl millet, in common with some fect. It should also be noted that the ergot other grasses, has a special stigmatic pathogen of Paspalum grass (Claviceps mechanism for excluding from neo­ paspa/i) elaborates tremorgenic myco­ fertilized ovaries further ingress of pollen toxins that are the cause of the neurologi­ tubes or pathogen hyphae that traverse the cal disorder Paspalum Staggers that can pollen transmission tracts in the fused sty. affect cattle grazing tall ergotised Pas­ lodia (Willingale and Mantle 1985). The palum spp. forage. Sclerotia should be ex­ separate stigmas of sorghum have no such amined for any indole-diterpenoid com­ mechanism and indeed can still appear pounds which could have tremorgenic ac­ quite fresh after ingress by ergot tivity. However, a recent experiment in pathogens. There is nothing in the floral Australia with beef cattle found no obvi­ biology of sorghum to assist the relatively ous adverse effect of feeding ergotised slow pathogen-excluding histological sorghum (M.Ryley, personal communi­ changes that occur in the ovary following cation). fertilization. Several days may be re­ quired to differentiate tissues which con­ There is no monopoly of sorghum er­ stitute physical barriers to ergot penetra­ got disease causation by pathogens with a tion hyphae on their slower progress S. sorghi anamorph. An interesting addi­ towards the ovule. Ideally, self­ tional distinctive ergot pathogen was rec­ pollination should occur before floret ognized in, and is apparently confined to, gaping, which not only exposes the ovary

7 through the wall of which ergot penetra­ References tion can occur, but leaves one or both of Atwell, S.M. 1981. Fermentation production of er­ the feathery stigmas protruding from the got alkaloids. PhD thesis. University of Lon­ floret, trapped by the closing glumes. don. 150 pp. Atwell, S.M. and Mantle, P.G. 1981. Hydroxydi­ Such a system was found to explain the hydroergosine, a new ergot alkaloid analogue mechanism of one particularly 'resistant' from directed biosynthesis by SphaceZia sorghi. sorghum accession from East Africa (Fre­ Experientia 37:1257-1258. Bandyopadhyay, R., Mughogho, L.K., Manohar, derickson et al. 1994). Other accessions, S.K., and Satyanarayana, M.V. 1990. Stroma which are free from ergot in their locality development, honeydew formation and conid­ of origin, became susceptible when ial production in Claviceps sorghi. Phytopa­ thology 80:812-818. grown in a different latitude where their Barrow, K.D., Mantle, P.G., and Quigley, F.R. flowering behaviour was disturbed by the 1974. Biosynthesis of dihydroergot alkaloids. different daylength pattern. Regrettably, Tetrahedron Letters 16:1557-1560. Berde, B., and Schild, H.O. (eds.) 1978. Ergot alka­ it seems safe to conclude that there is no loids and related compounds. Berlin:Springer­ intrinsic exploitable natural resistance to Verlag. 1003 pp. ergot infection of Sorghum spp. other Boon-Long, T. 1988. Sorghum diseases in Thai­ land. Pages 41-43 in Sorghum and millet dis­ than efficient pollination which arises eases a second world review: W.A.l. de from the particular floral biology. In other Milliano, R.A. Frederiksen, and G.D. Bengston words, all unfertilized sorghum ovaries (eds.) Harare, Zimbabwe. International Crops Research Institute for the Semi-Arid Tropics. are susceptible to ergot at the time offirst Patancheru 502324. Andhra Pradesh, India. floret gaping. Frederickson, D.E., and Mantle, P.G. 1988. The path of infection of sorghum by Claviceps sor­ ghi. Physiological and Molecular Plant Pathol­ In conclusion, the way in which the ogy 33:221-234. ovary parasite of sorghum, with versatile Frederickson, D.E., Mantle, P.G., and de Milliano, and extensive powers of dissemination, W.A.l. 1989. Secondary conidiation ofSphace­ Zia sorghi on sorghum, a novel factor in the epi­ has been able to spread so fast globally, demiology of ergot disease. Mycological and to become so economically signifI­ Research 93 :497-502. cant, is a reflection partly ofthe extension Frederickson, D.E., Mantle, P.G., and de Milliano, W.A.J. 1991. Claviceps africana nov. sp.; the of monoculture agriculture. However, it is distinctive ergot pathogen of sorghum in Africa. more consequent on the artificial creation Mycological Research 95:1101-1107. Frederickson, D.E., Mantle, P.G., and de Milliano, and wide use of male-sterile hosts in F 1 W .A.1. 1993. Wind borne spread of ergot dis­ hybrid seed production which provides a ease (Claviceps africana) in sorghum A -lines in window ofopportunity for ergot pathogen Zimbabwe. Plant Pathology 42:368-377. spores to beat pollen grains for the con­ Frederickson, D.E., Mantle, P.G., and de Milliano, W.A.J. 1994. Susceptibility to ergot in Zim­ trolling influence over the fate ofunfertil­ babwe of sorghums that remained uninfected in ized sorghum ovaries. It is possible that their native climate in Ethiopia and Rwanda. disease control may be addressed agro­ Plant Pathology 43:27-32. Frederickson, D.E., and Mantle, P.G. 1996. Pearl chemically, at a recurring costthrough the millet as an alternate host of the sorghum ergot use of fungicides, but perhaps better pathogen, Claviceps africana. International strategies will focus on the male-sterility Sorghum and Millets Newsletter 37:83-85. Fuentes, S.F., Lourdes de la Isla, M., Ullstrup, A.J., which is at the center of the present and Rodrigues, A.E. 1964. Claviceps gigantea, globally-exacerbated disease problem for a new pathogen of maize in Mexico. Phytopa­ sorghum. thology 54:379-381.

8 Futrell, M.C., and Webster, 0.1.1965. Ergot infec­ Mantle, P.G., and Waight, E.S. 1968. Dihydroer­ tion and sterility in grain sorghum. Plant Dis­ gosine: a new naturally occurring alkaloid from ease Reporter 49:680-683. sclerotia of Sphacelia sorghi McRae. Nature Futrell, M.C., and Webster, 0.1. 1966. Host range 218:581-582. and epidemiology of the sorghum ergot organ­ Manzarpour, A 1985. Aspects of metabolism and ism. Plant Disease Reporter 50:828-831. physiology in Claviceps. Diploma of Imperial Hassan, H.A -G. 1996. Control of ergot disease in College thesis. Imperial College, London, UK. sorghum with particular reference to Claviceps 120 pp. africana. PhD thesis. University of London. McRae, W. 1917. Notes on some South Indian 240pp. fungi. Pages 108-111 in Madras Agriculture Kulkarni, B.G.P., Seshadri, V.S., and Hegde, RK. Yearbook 1917. 1976. The perfect stage of Sphacelia sorghi Mower, RL., Gray, G.R, and Ballou, C.E. 1973. McRae. Mysore Journal ofAgricultural Science Sugars from Sphacelia sorghi. Carbohydrate 10:286-289. Research 27:119-134. Loveless, AR. 1967. Clavicepsfosiformis sp. nov., Ohmomo, S. 1990. Alkaloids in sorghum ergot. the causal agent of an agalactia of sows, Trans­ Recent News of National Grassland Research actions of the British Mycological Society 50 Institute, Japan 5:49-50. (1): 15-18. Reis, E.M., Mantle, P.G., and Hassan, H.A-G. Mantle, P.G. 1968. Studies on Sphacelia sorghi 1996. First report in the Americas of sorghum McRae, an ergot of Sorghum vulgare Pers. An­ ergot disease, caused by a pathogen diagnosed nals of Applied Biology 62:443-449. as Claviceps africana. Plant Disease 80:463. Mantle, P. G. 1973. Production of ergot alkaloids in Schneider, D.J., Miles, e.0., Garthwaite, I., Van vitro by Sphacelia sorghi. Journal of General Halderen, J., Wessels, C. and Lategan, H.J. Microbiology 75 :275-281. 1996. First report of field outbreaks of ergot al­ Mantle, P.G. 1996. Detection of ergot (Claviceps kaloid toxicity in South Africa. Onderstepoort purpurea) in a dairy feed component by gas Journal of Veterinary Research 62:97-108. chromatography and mass spectrometry. Jour­ Willingale, J. and Mantle, P.G. 1985. Stigma con­ nal of Dairy Science 79: 1988-1991. striction in pearl millet, a factor influencing re­ Mantle P. G., and Hassan, H.AG. 1994. Widening production and disease. Annals of Botany geographical distribution of Claviceps a/ri­ 56:109-115. cana, an important ovary pathogen of grain sor­ Willingale, J., Mantle, P.G. and Thakur, RP. 1986. ghum. International Sorghum and Millets Post-pollination stigmatic constriction, the ba­ Newsletter 35:97-98. sis of ergot resistance in selected lines of pearl millet. Phytopathology 76:536-539.

9 Geographic Distribution and Spread of Sorghum Ergot: Causes and Implications

R. Bandyopadbyay

Abstract

Sorghum ergot was observed for the first time in 1915 in India and remained re­ stricted in Asia and Africa. The distribution of the disease expanded outside these continents when it was found in Brazil in 1995, and in Australia in 1996. Since 1995, it has been reported in quick succession in 14 countries in South, Central and North America including the u.s. In Brazil and Australia, the introduced pathogen was Claviceps a/ricana. The pathogen was probably introduced with seed or as airborne secondary conidia, but other possibilities of introduction exist. The disease spread rapidly in seedproductionfields due to conditions thatfavoredproduction and spread of spores (primarily airborne secondary conidia) and predisposed flowers to infection. Due to the vulnerability ofmale-sterile lines to the disease, its importance has increased internationally since male-sterile based hybrids are used in these countries. The intro­ duction of the disease will impinge on quarantine regulations, seed production, com­ mercial grain production, seed trade (including prices) and research prioritization.

Sorghum [Sorghum bicolor (L.) grow the crop almost completely as ani­ Moench] is the fifth most important cereal mal feed. The most significant crop and cultivated on about 45 million ha technological change since the 1960s was for food, feed, beverage and fodder. Nor­ the development and use ofF I hybrid seed mally the crop is grown in drought-prone (FAD and ICRISAT 1996) that lead to a areas where few other crop choices are dramatic improvement in productivity of available. In most parts of Asia and At: the crop. For example, India has experi­ rica, and some parts of Latin America and enced 55% coverage of the rainy season the Caribbean, sorghum is primarily sorghum area under hybrids and a dou­ grown for food under low input produc­ bling of yield in the 30 years since hybrids tion systems by resource-poor farmers. were first introduced. Sorghum cultiva­ Yields average less than 1 t ha- 1 and vary tion in intensive, commercialized systems substantially from year to year. In con­ relies almost totally on F I hybrid seeds, 1 trast, sorghum cultivation in Australia, and yields average 3-5 t ha- • the United States, most South and Central American countries, and parts of South The sudden observation and rapid Africa is characterized by intensive, com­ spread of ergot in Latin America begin­ mercial production systems optimized to ning in Brazil in 1995, and in Australia in 1996 perplexed the sorghum industry around the world. The global appearance of ergot made U.S. sorghum workers and R Bandyopadhyay, International Crop Research Institute for the Semi-Arid Tropics (lCRISAT).Patancheru 502324, Andhra Pradesh, India quarantine officials feel rather vulnerable

10 to the potential introduction of ergot. tributors for lowering or nullifying pollen However, the importance of sorghum er­ activity (McLaren 1992), adversely af­ got in hybrid seed production was high­ fecting efficient pollination and fertiliza­ lighted in the mid-sixties in Nigeria (Fu­ tion that protects flowers from infection trell and Webster 1965). Indeed, the dis­ (Futrell and Webster 1965, Musabyimana ease gained prominence only after the et al. 1995). introduction of F I hybrids in India since A-lines are vulnerable to the disease. This The Afro-Asian era not only makes F I hybrid seed production difficult, but also creates problems in pro­ Sorghum ergot was first observed in ducing adequate quantities ofA-line seed. India in 1915 and described by McRae in 1917. That it was more widespread in In­ Ergot is a disease of the ovary. It re­ dia was confirmed in 1948, when Ra­ duces grain yield because the ovary of an makrishnan recorded ergot in Madras infected flower is replaced by a fungal State (Sangitrao et al. 1999, for distribu­ mass that secretes a sweet fluid, called tion in India). In 1927, ergot was reported honeydew. Healthy grain are smeared in Burma. These reports and samples rep­ with honeydew on which fungal sapro­ resent the pathogen e. sorghi. In Africa, phytes grow thereby reducing seed qual­ sorghum ergot was recognized first in the ity, making threshing difficult, reducing eastern region, having been sampled in germination and seedling emergence, and Kenya in 1924. Table 1 summarizes the predisposing seedlings to other diseases first reports of occurrence of the disease (McLaren 1993). Two teleomorphs of the in different countries. The disease was ergot pathogen have been described. also observed in experimental hybrid seed These are Claviceps sorghi by Kulkarni et production plots in Mali and Burkina al. (1976) and C. africana by Frederick­ Faso in West Africa (D S Murty, personal son et al. (1991). The anamorph of both communication), but the identity of the teleomorphs is Sphacelia sorghi (McRae pathogen is not known. The fungus Cere­ 1917). bella andropogonis normally grows on the sugar exudates of S. sorghi and is a This paper provides a brief account of good indicator of ergot in the field. A few the distribution of the disease and the reports of ergot, such as those from pathogens, the possible reasons for the Ghana, Sudan, and the Philippines, are sudden resurgence of the disease, and its based on the association ofe. andropogo­ implications. nis with the sphacelial stage of S. sorghi.

Distribution The pathogen in Indi"a and Myanmar was identified as e. sorghi (Kulkarni el al. The disease is normally not of concern 1976, Mantle 1968). All reports and sam­ in warm and dry areas, where sorghum is ples from Africa, mentioned in Table 1, traditionally grown. The problem be­ possibly represent the distinctive patho­ comes acute in cool temperature (even on gen C. africana (Frederickson et al. male-fertile cultivars) and in male-sterile 1991). In 1991, the ergot pathogen in lines. These two factors are primary con- Thailand was, contrary to expectations,

11 Table 1. Distribution ofsorgbum ergot in different countries until 19911. Continent/Country Reference Remarks Africa Angola de Milliano et aI. 1991 Botswana Molefe 1975 1930992 & 193661 Burundi -3 R. Bandyopadhyay, personal observation Ethiopia Woldekidan 1985 88616 & 225570 -4 5 Ghana Cerebella andropogonis , 63524 Kenya McDonald 1924 C. andropogonis, 91149 Lesotho de Milliano et aI. 1991 Malawi de Milliano et aI. 1991 Mozambique de Carvalho 1958 Nigeria Wiltshire 1956 6280 & 99530 Rwanda -3 L.K. Mughogho, personal communication Senegal Jaubert 1953 South Africa Dyer 1947 C. andropogonis Sudan Anonymous 1932 C. andropogonis Swaziland de Milliano et aI. 1991 Tanzania Mason 1926 C.andropogon~,5541 Uganda Small 1926 C.andropogon~, 14170 Zambia Angus 1965 90016b Zimbabwe Whiteside 1966

Asia Burma Rhind 1471, 1472 India McRae 1917 First report Japan Nishiltara 1973 Philippines Langdon 1955 C. andropogonis Sri Lanka Petch and Bisby 1950 C. andropogonis,43654 Taiwan Chen et aI. 1991 Thailand Boon-long 1983 Yemen Arab Republic Kamal and Agbari 1980

)Based on CABI (1987) 2IMI numbers that refer to records in the herbarium of the CAB International Mycological Institute. 3 Observed in 1987 40bserved in 1956 SAssociation with C. andropogonis. identified as C. africana, not C. sorghi ghum was similarly identified (Mantle (Frederickson et al. 1991), and in Japan, and Hassan 1994). The second Claviceps one of the ergot species infecting sor-

12 species in Japan is yet to be identified zil) is pending, but is most likely C. afri­ (Bandyopadhyay et al. 1996). cana. Rapid dissemination of information on spread throughout the Americas was The America-Australian era due to the e-mail network and the World Wide Web. This period begins in 1995 when the disease appeared for the first time outside Sources of Ergot Inoculum and Mode Asia and Africa causing a widespread epi­ of Pathogen Spread demic and serious losses in hybrid seed production plots in Brazil (Bandyopadh­ An understanding of sources of pri­ yay et al. 1996, Reis et al. 1996). In an­ mary inoculum and mode of spread ofthe other geographically distant continent, pathogen is required to postulate hypothe­ Australia, the disease appeared in 1996 on ses for its introduction and spread in new forage sorghums (Ryley et al. 1996). For­ areas. The primary sources of inocula in­ tunately most of the commercial sor­ clude sclerotia, infected plant debris, co~ ghums had flowered, thereby escaping in­ lateral hosts, and secondary condia (Fre­ fection. C. africana was identified as the derickson 1999). Ergot-infected spikelets causal fungus in Brazil (Reis et al. 1996) exude sweet, sticky drops of fluid honey­ and Australia (Ryley et al. 1996). In Aus­ dew containing macroconidia and micro­ tralia and the Americas alike, the disease conidia. Rain splashes (Bandyopadhyay spread very rapidly after initial appear­ et al. 1991) and possibly insects (Futrell ance causing widespread concern. and Webster 1966) spread conidia borne in the honeydew matrix. These two Following the appearance of ergot in modes of spread are more relevant for Brazil in February, 1995, the disease was short distance spread than longer distance monitored carefully in South and Central transport. Wind dissemination of secon­ Americas and the Caribbean given the dary conidia is the most significant mode high volume and frequency of seed ex­ of dispersal for both local and long­ change in the region for research and distance spread of the sorghum ergot trade purposes. By mid-1996, the disease pathogen (Frederickson et al. 1989 and had been recorded in Argentina, Bolivia, 1993). Secondary conidiation occurs Paraguay, and Uruguay; by the end of when RH rises and temperature falls (Fre­ 1996 in Colombia, Venezuela and Hon­ derickson et al. 1989 and 1993). These en­ duras; and during the first quarter of 1997 vironmental conditions also predispose in Puerto Rico, Haiti, the Dominican Re­ flowers to infection by reducing pollen public, Jamaica, and northern Mexico. On activity and dispersal. 26 March 1997, the disease was observed in the U.S. on ratooned tillers in a sor­ Disease Introduction ghum field just North of the Rio Grande River near Progresso, TX. The disease is The recent intensification in the geo­ most likely present in other countries of graphic distribution of the disease is in­ the Americas from where it has not been triguing. Why was the disease found in reported as yet. The formal identity of the geographically distant Brazil and Austra­ pathogen in these countries (except Bra- lia within a year of each other after being

13 restricted in Asia and Africa for 80 years? fictional, but explains why ergot What was the mode of entry ofthe pathcr appeared simultaneously on sor­ gen into these two countries? Was the di~ ghum and pearl millet in Brazil. Al­ ease present in these countries earlier but though Mantle and Hassan (1994) not noticed? Is it related to the recent ex­ claimed that secondary conidia are pansion in the collaborative seed ex­ short-lived, research is required to change programs between seed compa­ determine the longevity of secon­ nies and movement of genetic material of dary conidia. transnational seed companies, NGOs, • Ergot could have been introduced to Brazil and Australia earlier than farmers' groups, private farmers and sci­ 1995 and was present in low, unde­ entists across national boundaries? The t~ctable frequencies. The excep­ ergot pathogen in Brazil and Australia has tIOnally favorable conditions in been identified as C. africana, the same as 1995 (in Brazil) and 1996 (in Au~ the one that is endemic in southern Africa tralia) could have helped the devel­ and Thailand. Besides sorghum, ergot opment of easily noticeable epi­ was also reported for the firsttime in 1995 demics. on pearl millet in Brazil and Australia. • Someone walking through an in­ The pathogens causing ergot on sorghum fested field in a C. africana en­ and pearl millet are different but cross­ demic region could have had their inoculation experiments have shown that apparel smeared with honeydew, the sorghum ergot pathogen can infect and/or brought back some soil pearl millet in Australia (Ryley et al. (with macroconidia) on footwear. 1999). No one may ever know how the The same person perhaps walked sorghum ergot pathogen was introduced into a sorghum field in Brazil wear­ to Brazil and Australia, despite strict ing the contaminated clothes and/or quarantine. We can only hypothesize shoes, thereby introducing the now: pathogen. Macroconidia can ger­ minate on soil to produce secon­ • Sorghum seeds contaminated with dary. conidia which, being airborne, ergot sclerotia from a C. africana can mfect sorghum. endemic region may have been ille­ • With increased air cargo shipments gally carried and sown in Brazil and internationally, the pathogen may Australia. have moved in cargo holds from er­ • Due to an unusual intercontinental got endemic Africa to Brazil. Such air current pattern from southern a theory has been propounded for Africa to South America, secon­ introduction of Kamal bunt of dary conidia could have been lifted wheat into the U.S. from Africa to the cloud layer, • A naturally occurring ergot pathcr crossed the Atlantic, and subse­ gen on grasses may have under­ quently deposited in southern Bra­ gone a change in virulence to diver­ zil. A similar case may be true for sify its host range to include sor­ Australia with the origin of the ghum. The possibility of such a pathogen being a south-east Asian change occurring simultaneously country. This may sound science in Brazil and Australia is unlikely.

14 Initially, infection in the introduced In Australia, the disease was first seen countries could have been in low propor­ in Gatton on 26 April 1996. Within one tion, but suitable weather helped develop week the disease was confirmed over an 2 an epidemic from a few small foci. The area of approximately 16,000 krn , which, pathogen has remarkable ability to rap­ within a month, had expanded to 70,000 idly spread from a small focus particu­ km 2 around the locality of the first sigh~ larly when susceptible panicles are con­ ing. The disease was found throughout tinuously available (Bandyopadhyay et Queensland in 1996 and now occurs also al. 1994 and 1994, Frederickson et al. in New South Wales (Ryley et al. 1999). 1993). An understanding of the mode of Disease spread to New South Wales was introduction of the pathogen may help to most likely due to secondary conidia with devise methods to prevent its spread to sclerotia playing an insignificant role, if new areas. any. This is because seed movement from Queensland to New South Wales was al­ Disease Spread lowed after sclerotia were removed by floatation in salt solution. The introduction of the disease to Bra­ zil and Australia, and its spread within In the Americas, it is most likely secon­ these countries and across national dary conidia played a major role in the boundaries offer good examples of the progressively north-eastward sightings of potential for long-distance spread. It also the disease from South America, to Latin exemplifies the rapidity with which epi­ America, to Central America and the Car­ demics can develop to cover large geo­ ibbean, to Mexico, and then to the US. An graphical areas. In Brazil, the disease was examination of the weather parameters first noticed during mid-February in seed and air movement patterns over these production plots in Sao Paulo state. countries up to a month before disease Within a few weeks, the disease was re­ sightings can provide useful clues for the ported from Ribeiro Preto, Capinopolis, mode of spread. Whether sclerotia also Lavras, Sete Lagoas, Pirapora, Paracatu, were responsible for the spread is unde­ and Parana towards the north, and Xapeco termined due to unconfirmed reports of (Santa Catarina state), and Pelotas (Rio shipments of ergot-contaminated seed Grande state) towards the south. The lo­ from Brazil to other South American cations where the disease was found sur­ countries and to the Bajio of Mexico rounded an area approximately 800 000 (Bandyopadhyay et al. 1996). 2 km • The distance from Paracatu in the north to Pelotas, the farthest point of in­ Environment and the fection in the south, is nearly 2000 km. Recent Epidemics The magnitude of the area and distance within which the disease was noticed Environment has played a major role in within a short time show the extraordi­ fueling the ergot epidemics in Brazil and nary capacity of the pathogen to develop Australia after the introduction of the into an epidemic rapidly in terms of both pathogen. Two distinctly different envi­ time and space. ronmental factors were perhaps responsi-

15 ble; wetness in Brazil and low tempera­ tion by inactivating pollen (Ryley et al. ture in Australia. 1999).

Examination of Brazilian weather data Implications of the Disease for January and February 1995 (provided by Dr. O. Brunini, Instituto Agronomico There are several ramifications of the de Campinas, Campinas, Sao Paulo) enhanced geographic scope of the disease showed that nearly twice the normal rairr in newer areas of the world where sor­ fall occurred in February in central and ghum cultivation is dependent on hybrid southern Brazil. The 25-day period before seed. the first report of occurrence of the dis­ ease in Ribeiro Preto (15 February) was Plant Quarantine Regulations extraordinarily wet. During this period, 446 mm rainfall occurred in 21 days. One ofthe immediate issues pertains to From 1 to 15 February alone, 343 mm of the plant quarantine policy owing to the rain fell in 14 days. Minimum tempera­ seedborne nature of the pathogen. Na­ ture during mid-January to February was tional policies for local and international between 19-21 °C and, therefore, not lim­ quarantine regulations will require imme­ iting for pollen production. However, the diate attention. Bandyopadhyay et al. exceptionally wet conditions severely af­ (1996) suggested that imported seed must fected anther emergence, anther dehis­ be viewed as an important source of infec­ cence, and pollen deposition. The ineffi­ tion and thoroughly inspected for sclero­ cient pollination of male-sterile lines pre­ tia, sphacelia, and honeydew before dis­ disposed their stigmas to infection. The tribution is permitted. However, experi­ wet conditions and cloudy weather also ences in the U.S. and Australia have provided an ideal environment for the shown that quarantine had limited impact continual production of abundant secon­ in preventing disease introduction and dary conidia. Therefore, all the constitu­ spread due to the extraordinary capacity ents for an epidemic were available at the of ergot to spread rapidly by means other same time--a susceptible host with an ex­ than seed. Nevertheless, quarantine may tended susceptible period, that was ex­ delay disease spread into new areas by posed to abundant inoculum of a newly eliminating introduction of new disease introduced pathogen during favorable foci through seed. Research information weather. A shorter incubation period, ex­ can provide a valuable framework upon tended susceptible period, longer favor­ which to base quarantine regulations for able period for infection and sporulation, reducing the chances of disease spread and rapid transport of airborne secondary without unduly constraining seed trade conidia aided several cycles of infection and exchange. in the same area, and long-distance spread to newer areas. Seed Trade

In Australia, exceptionally cool and The potential for introduction is inti­ wet weather before and during flowering mately associated with the high frequency predisposed the sorghum crops to infec- of sorghum seed exchange and trade

16 among countries of South and Central date more pollen-donating restorers, America, and to some extent, the United rouging of infected plants, modification States. The global nature of the hybrid of seed processing facilities, additional sorghum industry, with seed production quality control tests, and some loss in seed in one region and its distribution for plant­ yield and quality despite these practices to ing at multiple distant locations, increases control the disease would increase the the chances of pathogen spread through price of the seed. According to an esti­ seed. The high vulnerability of the male­ mate in Australia, an additional A$800 sterile parent, and possibly the enhanced would be required to produce 1 t seed (M. survival of the pathogen in the cool, dry Ryley and others, unpublished). hybrid seed storage conditions further in­ crease disease risk. In 1996, there was a Commercial Production fear of banning seed imports from ergot infested countries to non-ergot countries Grain production in newly ergot-prone (Bandyopadhyay et al. 1996) due to the areas that are characterized by cool tem­ restricted distribution ofthe disease in the perature during the pre-flowering stages Americas. With the pathogen's presence and wet conditions at flowering will be at in the major sorghum-growing countries, an increasing risk due to the introduction the disease has become endemic across of the disease. Damage will be accentu­ national boundaries by-passing the quar­ ated in hybrids that have inherently pro­ antine stage. Therefore, the scenario of longed time interval between stigma seed import bans can be now avoided, if emergence and fertilization necessitating appropriate seed certification and sanita­ withdrawal of productive hybrids. In the tion standards are maintained. Neverthe­ absence of ergot, such a trait would have less, restrictions on the movement of seed been oflittle consequence and productive from infested to non-infested areas are hybrids would have continued to be pro­ likely to continue until shown ineffective. duced. Risk avoidance may necessitate alterations in normal sowing dates Seed Production thereby reducing flexibility of sowing time and forcing growers to reevaluate the The hybrid seed industry will be most value of sorghum in their farming strate­ affected by the introduction of C. afri­ gies. Infected late tillers may continue to cana requiring changes in several opera­ produce honeydew when the main crop is tional and policy aspects such as seed pro­ ready for harvest, thus, making combine duction, processing, quality control and harvesting difficult. Honeydew­ handling practices; contractual arrange­ encrusted panicles complicate threshing, ments with seed growers; pricing of seed, resulting in further grain losses. Such etc. (Dolezal 1999; Ribas 1999). Tradi­ threshed grain may have poor storability tionallocations and sowing dates for seed and marketability because honeydew production may require changes to avoid lumps absorb moisture, become sticky, risk-prone areas and time, but cannot form clumps of grain, and the grain lots guarantee total control. Repeated applica­ may become unsatisfactory. tion of fungicides, reduction in the number ofmale-sterile rows to accommo-

17 Genetic Vulnerability Research Priorities

Male-sterile genotypes are particularly An added dimension of the introduc­ vulnerable to ergot because they do not tion of ergot to countries dependent on produce functional pollen. Ergot suscep­ sorghum hybrids is the change in research tibility in relation to cytoplasmic male­ priorities necessary to find solution to a sterility has been demonstrated in ergot of new important problem that is specific for pearl millet caused by C. fusiform is (Tha­ hybrid seed. The criteria used to prioritize kur et al. 1989). Effective pollination re­ problems by different organizations and duces susceptibility so that male-fertile their mandates would determine the prior­ varieties rarely exhibit high ergot severi­ ity, resource allocation, and role of each ties. Cool, wet conditions before or during organization. Reliable assessments of the pollination reduce pollen fertility and pol­ impact of the disease should consider as­ len deposition, resulting in increased er­ pects of sorghum research, production, got infection in all genotypes (McLaren processing, marketing, utilization and 1992). Valuable or scarce seed stocks of trade. Unless new sources of funding are male-sterile lines are thus at risk of deple­ available, it would entail diversion of re­ tion if conditions allow extensive ergot sources for research and development as­ infection at the production stage. To pects from other important problems. Due avoid the loss of valuable male-sterile to the major implication of the disease for lines, seed should be multiplied at multi­ the seed sector, it is hoped that the seed in­ ple locations preferably minimizing the dustry would playa major role in ergot re­ ergot risk by manipulation of the planting search. It is encouraging to note that this is date or through the use of fungicides. occurring in a few countries. Adequate stocks of diseasefree seed should be maintained. Conclusions

Potential Toxicity to Animals Sorghum ergot has become an interna­ tionally important disease within a short The question ofthe potential toxicity of span of two years since 1995. This i~ be­ sorghum ergot sclerotia inevitably arises cause adequate availability and profit­ through analogy with C. purpurea and C. ability of FJ hybrids seeds, one of the fusiformiS, which synthesize such potent mainstays of intensive and productive alkaloids as ergotamine and agroclavine. sorghum agriculture in the developing However, the quantity and spectrum ofal­ and developed world alike, is at risk. kaloids found in sorghum ergot sclerotia Commercial production of sorghum hy­ are not significant to cause toxicity in ani­ brids is also threatened, particularly in ar­ mals (Bandyopadhyay et al. 1996, Mantle eas where sorghum experiences cool tem­ 1968). Therefore, it is highly unlikely that perature at or before flowering. It is not a sclerotia contaminated sorghum grain has new disease. Nor is this the first time that any implications for animal health. For it is causing concern to the sorghum seed more detailed information, see Mantle industry having been a problem in India, (1999). Zimbabwe and South Africa. The present worldwide attention that the disease is re-

18 ceiving stems from the rapid spread of the de Carvalho, T., and Mendes, 0.1958. Doencas de plantas em Mocambique. Lourenco Morques, disease in the Americas and Australia Mocambique: Direccao de Agricultura e where it can cause potential damage. Sor­ Florestas. 84 pp. ghums in these geographical areas have de Milliano, W.AJ., Tavares Nogueira, M.F.R., Pomela, L.M., Msiska, F.S., Kunene, S., Mata­ never been exposed before to the ergot laote, B., Mbwaga, AM., Kaula, G.M., and pathogens and have not gone through the Mtisi, E. 1991. New records of ergot of sor­ natural selection processes. The disease ghum caused by Sphacelia sorghi in southern Africa. Plant Disease 75:215. provides new challenges, opportunities Dolezal, W. E. 1999. United States private sector and partnerships for the sorghum commu­ response. Pages 76-78 in Proceedings of the Global conference on Ergot of Sorghum, J.A nity. Dahlberg and C.R. Casela eds. 1-8 June 1997, Sete Lagoas, Brazil. INTSORMIL, University References of Nebraska, Lincoln, NE. Publication 99-1. Dyer, R.A 1947. Investigations of plant diseases, Anonymous. 1932. List of intercepted plant pests and botanical surveys. Farming in South Africa (list of pests recorded during the period January 22: 1082-1085. 1, 1930 to June 30, 1931, inclusive as inter­ FAO/ICRISAT (Food and Agriculture Organiza­ cepted in, on, or with plants and plant products tion of the United StateslInternational Crops entering United States territory. United States Research Institute for the Semi-Arid Tropics). Department of Agriculture Plant Quarantine 1996. The world sorghum and millet econo­ and Control Administration pp 201-368. mies: facts, trends and outlook. Viale delle Ter­ Angus, A 1965. Annotated list of plant pests and mie di Caracalla, 00100 Rome, Italy, and diseases in Zambia (Northern Rhodesia) Part 7. Patancheru 502 324, Andhra Pradesh, India: (R to Z). Zambia: Mount Makulu Research Sta­ FAOIICRISAT. 68 pp. tion. 56 pp. Frederickson, D.E. 1999. The lifecycle, spread and Bandyopadhyay, R., Frederickson, D. E., survival ofthe sorghum ergot pathogens. Pages McLaren, N. W., and Odvody, G. N. 1996 Er­ 135-140 in Proceedings of the Global confer­ got, a global threat to sorghum. International ence on Ergot of Sorghum, J.A Dahlberg and Sorghum and Millets Newsletter 37: 132. C.R. Casela (eds.) 1-8 June 1997, Sete Lagoas, Bandyopadhyay, R., Mughogho, L.K., and Brazil. INTSORMIL, University of Nebraska, Sharma, H. C. 1991. Source of primary inocu­ Lincoln, NE. Publication 99-1 lum and spread of ergot. Pages 24-25 in Cereals Frederickson, D.E., Mantle, P.G., and de Milliano, Program annual report 1990. Patancheru 502 W.AJ. 1989. Secondary conidiation ofSphace­ 324, Andhra Pradesh, India: International lia sorghi on sorghum, a novel factor in the epi­ Crops Research Institute for the Semi-Arid demiology of ergot disease. Mycological Bandyopadhyay, R., Yang, X.B., and Satyanaray­ Research 93:497-502. ana, M.V. 1994. Mapping the spread and focus Frederickson, D.E., Mantle, P.G., and de Milliano, formation of sorghum ergot over time. Phytopa­ W.AJ. 1991. Claviceps africana sp. nov., the thology 84:1358. (Abstract.) distinctive ergot pathogen of sorghum in Africa. Bandyopadhyay, R., Yang, X.B., and Satyanaray­ Mycological Research 95:1101-1107. ana, M.V. 1994. Analysis of disease cycles of Frederickson, D.E., Mantle, P.G., and de Milliano, sorghum ergot in relation to plant flowering. W.AJ. 1993. Windborne spread of ergot dis­ Phytopathology 84: 1390. (Abstract.) ease (Claviceps africana) in sorghum Alines in Boon-long, T. 1983. Ergot of sorghum in Thailand. Zimbabwe. Plant Pathology 42:368-377. (In Th Summary in En.) Journal ofThai Phyto­ Futrell, M.C., and Webster, OJ. 1965. Ergot infec­ pathological Society 4:219-221. tion and sterility in grain sorghum. Plant Dis­ CABI. (Commonwealth Agricultural Bureau Inter­ ease Reporter 49:680-683. national). 1987. Claviceps sorghi Kulkarni. Futrell, M.C., and Webster, OJ. 1966. Host range 1987. Commonwealth Mycological Institute and epidemiology of the sorghum ergot organ­ Distribution Maps of Plant Diseases. no. 582, ism. Plant Disease Reporter 50:828-831. edn 1. Kew, Surrey, UK: CABI 2 pp. Jaubert, P. 1953. Liste annottee des principales af­ Chen, G.M., Cheng, Q.H., and Yeh, C.C. 1991. Er­ fectations parasitaires (mycosses, bacterioses, got disease of sorghum in Taiwan. (In Ch. Sum­ viroses) ainsi que des affections de causes mal mary in En.) Plant Protection Bulletin (Taiwan) definies et des plantes nuibles aux cultures du 33(2):223-226. Senegal. Bulletin Centre Recherches Agro­ nomique Bambey 7:2-39 (Cyclostyled).

19 Kamal, M., and Agbari, AA 1980. Revised host Petch, T., and Bisby, G.R. 1950. The fungi ofCey­ list of plant diseases recorded in Yemen Arab Ion. Paradeniya Manual No. VI. Colombo, Cey­ Republic. Tropical Pest Management 26: 188- lon: Government Publications Bureau. 193. Reis, E.M., Mantle, P.G., and Hassan, H.AG. Kulkarni, B.G.P., Seshadri, V.S., and Hegde, R.K. 1996. First report in the Americas of sorghum 1976. The perfect stage of Sphacelia sorghi ergot disease, caused by a pathogen diagnosed McRae. Mysore Journal of Agricultural Sci­ as Claviceps africana. Plant Disease 80:463. ences 10:286-289. Ribas, P. M. 1999. Strategy for the control of ergot Langdon, R.F. 1955. The genus Cerebella. Myco­ in sorghum seed production in Brazil. Pages 26- logical PaperNo. 61. Kew, Surrey, U.K.: Com­ 32 in Proceedings of the Global Conference on monwealth Mycological Institute. 18 pp. Ergot of Sorghum, JA Dahlberg and C.R. Mantle, P.G. 1968. Studies on Sphacelia sorghi Casela eds. 1-8 June 1997, Sete Lagoas, Brazil. McRae, an ergot of Sorghum vulgare Pers. An­ INTSORMIL, University of Nebraska, Lin­ nals of Applied Biology 62:443-449. coln, NE. Publication 99-1. Mantle, P.G. 1999. Sorghum ergot: An overview. Rhind, D. 1928. India: Mycological notes on Pages 3-9 in Proceedings of the Global confer­ Burma. International Review of Agriculture ence on Ergot of Sorghum, lA Dahlberg and 19:744-745. C.R. Casela (eds.) 1-8 June 1997, Sete Lagoas, Ryley, M.J., Blaney, B., and Meinke, H. 1999. Cur­ Brazil. INTSORMIL, University of Nebraska, rent and future research on sorghum ergot in Lincoln, NE. Publication 99-1 Australia. Pages 59-67 in Proceedings of the Mantle, P.G., and Hassan, HAG. 1994. Widening Global Conference on Ergot of Sorghum, J.A geographical distribution of Claviceps a/ri­ Dahlberg and C.R. Casela eds. 1-8 June 1997, cana, an important ovary pathogen of grain sor­ Sete Lagoas, Brazil. INTSORMIL, University ghum. International Sorghum and Millets of Nebraska, Lincoln, NE. Publication 99-J. Newsletter 35:97-98. Ryley, M.J, Alcorn, lL., Kochman, lK., Kong, Mason, E. W. 1926. On two species of Tolypospo­ G.A and Thompson, S.M. 1996. Ergot on Sor­ rium Woronin recorded on cultivated sorghum. ghum spp. in Australia. Australian Plant Pathol­ Transactions ofthe British Mycological Society ogy 25:214. 11: 284-286. Sangitrao, C.S., Indira, S., and Bandyopadhyay, R. McDonald, 1 1924. Annual Report of the Mycolo­ 1999. Sorghum ergot in India. Pages 41-54 in gist for the year 1923. Pages 81-85 in Colony Proceedings ofthe Global Conference on Ergot and Protectorate of Kenya Annual Report ofthe of Sorghum, J A Dahlberg and C.R. Casela eds. Department of Agriculture for the year ended 1-8 June 1997, Sete Lagoas, Brazil. INT­ 31st December 1923, Nairobi, Kenya. SORMIL, University of Nebraska, Lincoln, McLaren, N.W. 1992. Quantifying resistance of NE. Publication 99-1 sorghum genotypes to the sugary disease patho­ Small, W. 1926. Report of the Mycologist for the gen (Claviceps a/ricana). Plant Disease period January Istto September 30th. Pages 23- 76:986-988. 24 in Uganda Protectorate Annual Report ofthe McLaren, N. W. 1993. Effect of sugary disease exu­ Department of Agriculture for the year ended dates on germination, seedling development 31st December, 1925. Entebbe, Uganda. and predisposition to seedling diseases of sor­ Thakur, R.P., Rao, V.P., and King, S.B. I 989b. Er­ ghum (Sorghum bicolor). South African Jour­ got susceptibility in relation to cytoplasmic nal of Plant and Soil 10: 12-16. male sterility in pearl millet. Plant Disease McRae, W. 1917. Notes on some south Indian 73:676-678. fungi. Pages 108-111 in Madras Agriculture Whiteside, 10. 1966. A revised list of plant dis­ Yearbook 1917: 108-111. eases in Rhodesia. Kirkia 5:85-196. Molefe, T.L. 1975. Occurrence of ergot on sor­ Wiltshire, S.P. 1956. Plant diseases in British Colo­ ghum in Botswana. Plant Disease Reporter nial Dependencies: a half-yearly report. F AO 59:751-753. Plant Protection Bulletin 4:66. Musabyimana, T., Sehene, C., and Bandyopadh­ Woldekidan, T. 1985. A review of research on yay, R. 1995. Ergot resistance in sorghum in re­ maize and sorghum diseases in Ethiopia. Pages lation to flowering, inoculation technique and 21-24 in A Review of Crop Protection in Ethio­ disease development. Plant Pathology 44: 109- pia. Proceedings of the First Ethiopian Crop 115. Protection Symposium, 4-7 Feb 1985, Addis Nishihara, N. 1973. Bibliography of soiling crop Ababa, Ethiopia: Institute of Agriculture Re­ diseases in Japan II. Diseases of Sorghums. (In search. Ja.) Bulletin of the National Grassland Re­ search Institute (Japan) 3:143-154.

20 Session II - Ergot Scenario in Brazil

Session President - E.M. Reis (UFPF)

21 Sugary Disease of Sorghum in Brazil: an Overview R. Casela, A. S. Ferreira and N. F. J. A. Pinto

Abstract

Since it was observed in Brazil in April 1975 sugary disease ofsorghum (C/aviceps africana) has been a serious threat to seedproduction. The impact ofthe disease on sor­ ghum seed business in Brazil resulted in an integrated effort involving private sector, University ofPasso Fundo and Empresa Brasileira de Pesquisa Agropecuaria (Maize and Sorghum Research Center) to develop strategies to adequately manage this disease. This paper summarizes the achievements jrom this effort.

Sugary disease of sorghum, caused by were estimated at roughly US $400,000 Claviceps ajricana Frederickson, Mantle and was primarily due to the effects of & de Milliano, was reported for the first sugary exudation on seed quality. In the time in Brazil in April, 1995 simultane­ second year, in an attempt to escape from ously in Cravinhos (Sao Paulo) and more favorable environmental conditions Lavras (Minas Gerais), 400 km apart. In a for disease development, seed production period of 30 days, several additional re­ fields were established earlier than usual. ports of the presence of the disease were This change resulted in poor nicking of made from different locations including flowering in the parental lines and poor the states of Minas Gerais, Sao Paulo, pollen production. Losses were higher Mato Grosso do SuI, Goias and Parana. and estimated to be around U$800,000. The disease was later reported in the State of Rio Grande do SuI in a late plantings of Research Achievements sorghum. Honeydew exudations were and Decisions Taken also observed in many different grasses close to the sorghum crop. Due to the impact of the disease on the sorghum production and seed business in The primary concerns of sorghum sci­ Brazil, an proactive effort including the entists in Brazil about the disease were its private seed sector, Empresa Brasileira de impact on hybrid seed production in the Pesquisa Agropecuaria (EMBRAPA), country and the presence of any substance and the University of Passo Fundo (RS) that could be toxic to animals. According was initiated in June 1995 to develop to reports from private companies, the strategies for adequately managing this majority of seed production fields were at disease. Part of the achievements result­ the grain filling stage when the disease ing form these efforts will be reported in was first observed. Losses at that time this paper, and in more details by others in these Proceedings.

*R. Casela, A. S. Ferreira and N. F. J. A. Pinto, CNPMSIEMBRAPA. CP 151, Sele Lagoas, MG. Brazil. *Corresponding author.

23 Sources ofResistance Brachiaria decunbens (brachiaria), Sor­ ghum verticulijlorum, Cenchrus sp., Zea The greatest need of sources of resis­ mays, and Pennisetum typhoides (pearl tance to sugary disease is in male-sterile millet). In all tests a non-inoculated corr lines. Chances of identifying male-sterile trol was included. Test hosts were also irr resistant lines are very small considering oculated with honeydew from sorghum. the role of pollen in the disease (Bandyo­ Isolates from P. maximum, Panicum sp., padhyay 1992). Despite this low prob­ B. mutica, and B. decunbens had low ability, all A lines of the sorghum breed­ pathogenicity to sorghum and isolates ing program of CNPMS/EMBRAPA from sorghum were nonpathogenic to P. were evaluated under natural infection in maximum, Panicum sp., and B. decunbens 1996. All lines evaluated were suscepti­ and of low pathogenicity to B. mutica. ble. Isolates from sorghum were of intermedi­ ate pathogenicity to S. verticilijlorum. Irr Chemical Control fectivity of inoculum from S. verticilijlo­ rum plants was not tested on sorghum. Information on chemical control of C. ajricana on sorghum are very limited. In Other Initiatives South Africa, the fungicides benomyl, bitertanol, carbendazim + flusilazole, As part of an integrated strategy sev­ procymidone, propiconazole, tebucona­ eral decisions were taken in the search for zole, and triadimenol did not control C. ways to minimize the problem, These irr ajricana economically when sprayed clude: once at flowering time (McLaren, 1994). Results obtained by scientists of • Several meetings involving farm­ CNPMSIEMBRAPA showed that fungi­ ers and the extension services were cides Tebuconazole and Triadimenol held to inform them about the pres­ were efficient in the control C. ajricana, ence of the disease in Brazil. although Triadimenol showed some phy­ • Training courses in seed produc­ totoxicity to sorghum seeds. More recent tion and seed quality control, to correctly identify the disease sym p­ results have indicated that the fungicide toms in the field and the presence of Propiconazole and the mixture Propi­ sclerotia in contaminated seeds. conazole + Difenoconazole are also effi­ • A 0% tolerance of sclerotia was cient in the control ofthis pathogen (Pinto fixed as a standard in all processed et al. 1999). seed for the State of Minas Gerais. • Registration of a fungicide for the Alternate Hosts control of C. ajricana in sorghum, based on research conducted by The host range of C. ajricana under CNPMSIEMBRAPA. Brazilian conditions has been examined • Monitoring of seed production at CNPMSIEMBRAPA. Sorghum was fields and elimination of sclerotia inoculated with honeydew fromPanicum during seed processing. maximum (colonHio), Panicum sp. (colo­ nHiozinho), Brachiaria mutica (ben go ),

24 • A national workshop on ergot was References held to establish standards in seed Bandyopadhyay, R. 1992. Sorghum ergot. Pages quality control on a national basis. 235-244 in: Sorghum and millets diseases: a second world review. (W. A J. de Milliano, R. Final Comments A Frederiksen, and G. D. Bengston eds). Patancheru, A P. 502324, India: International Sugary disease of sorghum has become Crops Research for the Semi Arid Tropics, McLaren, N. W. 1994. Efficacy of systematic fun­ a serious constraint in hybrid seed pro­ gicides and timing of preventive sprays in the duction in Brazil as well as in other parts control of sugary disease of grain sorghum (Sor­ of the world where the disease was re­ ghum hieolor). South African Journal of Plant and Soil 11 :30-33. cently observed. The collaborative re­ Pinto, N. F. J. A, da Silva Ferreira, A, and C. R. search program developed by Brazilian Casela. 1999. Chemical control of sugary dis­ scientists, from the public and private sec­ ease of sorghum (Clavieeps afrieana). Pages158-160 in Proceedings of the Global tor, has been, mostly successful in fmding conference on Ergot of Sorghum, J.A Dahlberg ways to reduce the impact of the disease and C.R. Casela (eds.) 1-8 June 1997, Sete La­ goas, Brazil. INTSORMIL, University of Ne­ on the sorghum seed business despite the braska, Lincoln, NE. Publication 99-1. large area and explosive occurrence ofthe Pinto, N.FJ.A, Ferreira, AS., and Casela, C.R. Er­ disease in the country. We believethatthe got (Claviceps african) ouenca acucarada do sorgo. Sete Lagoas, MG:EMBRAPA-CNPMS, establishment ofresearch strategies based 1997. 24 pp. (EMBRAPA-CNPMS. Circular on international cooperation, which is the Tecnica, 23). main goal of this Conference, is funda­ mental for the control of this disease

25 Strategies for the Control of Ergot in Sorghum Seed Production in Brazil

Paulo Motta Ribas

Abstract

A sudden outbreak ofthe sugary disease (ergot disease) ofsorghum in Brazil, in the fall of1995, forced the public and private sectors to act rapidly to reduce or neutralize its effects on hybrid sorghum seedproduction. A strategy was established to seek short, medium and long term research solutions combined with communication, education and training ofresearchers, extensionists, seedproduction technicians,farmers and usersof forage and grain sorghum. Government sectors were sensitized to participate in the joint effort. The outcome ofthese efforts guaranteed the production and supply ofseeds in the first two years of coexistence with the sugary disease.

The private sector has played a strong amounts of seed sold in Brazil from 1991 role in Brazilian research, development to 1996 and its value was estimated at and production of sorghum hybrid seed nearly US $15 million in 1997, according since its introduction to the country in the to the national sorghum seed market. The late sixties. National and international crop is likely to occupy the huge savanna companies established in the country, to­ (cerrado) areas of the country's West­ gether with Empresa Brasileira de Pes­ Center and should be integrated into the quisa Agropecmrria (EMBRAPA), are re­ Northeast semi-arid production system. sponsible for the development and local Its' excellent adaptation to water stress, production of almost 100% of sorghum prevalent in these regions, and the grow­ seed sold in Brazil. The volume of im­ ing need for grains and forage for animal ported seed into Brazil is currently not feed in agro-industrial projects being set significant. Practically 100% of the sor­ up in the area, may be the decisive factors ghum seed planted in the country is hy­ from which Brazil will become one ofthe brid. The amount of open pollinated va­ greatest cultivated areas ofsorghum in the rieties commercialized is negligible. The South American continent. sorghum business in Brazil is small when compared to other grain crops, such as Impact of the Outbreak of Sugary com, soybeans, rice and dry beans. In the Disease on Hybrid Sorghum Seed last six years, however, interest in the Production in Brazil. crop and the utilization of its products as an animal feed has generated a growing The area dedicated to sorghum seed demand for seed. Table 1 shows the production in Brazil is concentrated in a region that spans from the North of Sao Paulo state (20°) to the Southwest of Goias state (17°). After the summer crops Paulo Motta Ribas, Agronomist and General Sorghum Manager, Sementes (com and soybeans), sorghum is sown be­ Agroeeres S/A. P.D.Box: 81, 38360-000, Capin6polis, MG., Brazil tween January and March. The crop is

26 Table 1. Sorghum seed market in Brazil: Sales evolution from 1991 to 1997·. Total Seed Sale Change in sale Value Agricultmal Year (20 kg hags 44 Ih ) from previous year(%) (JJS $00) 1991192 95,700 0.0 2.661 1992/93 152,500 59.3 4.497 1993/94 131,000 -14.0 4.285 1994/95 152,100 16.1 6.042 1995/96 182,800 20.1 7.706 1996/97 223,800 22.4 10.037 1997/98 336,000 501 14192 'Production estimate: Source: Pro-Sorgo Group/APPS 1997

harvested between July and August. Less under low temperatures in the Triangulo than 30% of the area is cultivated without Mineiro region, resulting in the total loss irrigation. In the remaining irrigated ar­ of seeds smeared with honeydew. In gen­ eas, center pivot sprinkler systems are eral, the losses of the seed industry in preferred. 1995 did not jeopardize that year's seed supply and the financial loss did not sur­ In the fall of 1995, around the 24-25 pass US $0.5 million. April, the seed industry acknowledged the outbreak ofthe sugary disease in Bra­ In 1996, with control measures recom­ zil, through simultaneous reports from mended by research already in use by the Lavras, South ofMinas Gerais, and Crav­ industry, some indirect losses occurred. inhos, North of Sao Paulo. These places Unsure of the efficiency and workability are 400 krn apart. of the fungicide applications at flowering time, some companies decided to alter the Examinations carried out by the Plant sowing date, so that flowering could coin­ Pathology Department of the Lavras Fed­ cide with periods of high temperatures in eral University, confirmed the presence February and March, reSUlting in less in­ of the fungus of the genus Claviceps, a fection. The results of this action were fact later reconfirmed by EMBRAPA. negative. Although the fungicide applic~ Within 30 days, the disease was reported tion was efficient, unexpected wet condi­ in various regions in South-central Brazil, tions harmed pollination and general field from the northern parts of Parana state in performance. This resulted in an esti­ the South, to the West of Goias in the mated loss of US $1 million to the indus­ North and from Sete Lagoas, MG in the try, indirectly caused by the sugary dis­ East, to Campo Grande, MS in the West. ease. The reduction in seed production of By this time, seed production fields were these companies was counter-balanced in the final phase of flowering or begin­ by the competition, so the market was re~ ning to fill grain. However, the disease sonably supplied again in 1996. With two symptoms were observed in tillers or iso­ years of experience behind us, we expect lated plants that were not properly polli­ a normal market supply in 1997. nated. Later, however, heavy losses oc­ curred in late-planted fields that flowered

27 The Reaction of the Private Sector strategies to tackle the problem, in a meet" ing in Ribeirao Preto-SP, in August 1995. Once the first moments of incredulity, perplexity and almost panic had passed, Integrated actions private companies started to confront the new situation with the certainty that the EMBRAPA and the University of disease was here to stay. The first and ob­ Passo Fundo divided the scientific work. vious action was to relay all the informa­ The task of CNPMS was to immediately tion we had to the Centro Nacional de organize a breeding program aimed at va­ Pesquisa de Milho e Sorgo (CNPMS), of rietal resistance. The University of Pas so EMBRAPA, and to propose an immedi­ Fundo took responsibility for the basic ate meeting to evaluate the situation and studies on the biology ofthe pathogen and to establish a strategy to confront the epidemiology ofthe disease. Private com­ problem. Technicians from EMBRAPA panies and EMBRAP A rapidly began and representatives ofPr6 Sorgo - a group testing fungicide seed treatment and spray of sorghum seed producing companies - application for controlling the disease as met on 14 June 1995 in Uberaba, MG. In indicated by the international literature the meeting, it was decided to integrate (McLaren 1994, Bandyopadhyay et al. private and public action on ergot with 1996). shared efforts and resources, with the fol­ lowing objectives: Besides the scientific activity, the Pro­ Sorg6 Group and EMBRAPA initiated in­ • Guarantee the continuity of sor­ tense activity in other areas. It was neces­ ghum hybrid seed production in sary to avoid the panic which is very com­ Brazil. mon in Brazil every time an epidemic at­ • Inform, educate and train research­ tacks some segment of the agricultural ers, production technicians, exten­ sector. Past experiences such as the coffee sionists, producers and sorghum rust and the African swine pest, and, par­ consumers in general about ergot. ticularly the official report of sorghum • Inform and sensitize government downy mildew in 1974, left no doubt sectors responsible for the regula­ about what to do about the sugary disease. tion of seed production control in The immediate spread of correct informa­ the country about ergot. • Manage the information propa­ tion to the farmers and users of grain and gated by the national media. forage sorghum was necessary. Toxico­ logical analyses of infested plant parts It was also decided to invite Dr. Erlei and silage samples were performed to Melo Reis, from the University of Passo confirm the safety of these feeds to ani­ Fundo, Rio Grande do SuI, a recognized mals. Many technical meetings and re­ specialist ofthe genus Claviceps in winter leases to the press were made and con­ cereals, to participate in the joint effort. tinue to be made throughout the country. Dr. Melo Reis accepted the invitation. Panic was contained. Apparently, sor­ EMBRAPA, private companies and the ghum farmer's confidence was not University of Passo Fundo established shaken. On the administrative and politi­ cal levels, action was concentrated in the

28 State Seed Sub-commissions, technical continue calling the disease "ergot"; sug­ and administrative committees compris­ ary disease was more appropriate. ing of government and private sector rep­ resentatives, to establish quality stan­ The seed industry needed quick an­ dards and norms for the production of cer­ swers to solve urgent problems. Some tified seed in the country. The seed lots were impregnated by the honey­ information about the disease and the de­ dew, posing problems with seed quality bate about its consequences to sorghum (McLaren 1993). The question was: seed production were introduced in the should another product be added to the Sub-commissions meetings. conventional Captan treatment? Or should Captan be replaced to guarantee In 1996, The Minas Gerais State Sor­ inactivation of conidia? Researchers at ghum Sub-commission, (the most impor­ the University of Passo Fundo showed tant sorghum seed producing state in the that conidia were inactivated by Captan country) also joined the effort to control alone, at the same concentration used by the sugary disease, and monitored all seed the industry. production fields in the state. Also, regis­ tration of commercial fungicides for ap­ Next question: what level of control plications in sorghum seed production would application of fungicides offer in fields was extended. Results began to ap­ the field and what kind of operational pear from this defined strategy and ac­ problems would it pose to the industry? tions co-financed by the Pro-Sorgo The efficacy offungicides was tested con­ Group. currently by EMBRAPA (Sete Lagoas­ MG), Agroceres S/A (Capinopolis-MG) Results and Zeneca (Cravinhos-SP), in August and September, 1995. The results ob­ The identity of the Brazilian sorghum tained were similar and indicated the tria­ ergot pathogen was established as zole group of fungicides could be used by Claviceps africana, Frederickson, Mantle the seed industry (Ferreira et al. 1996). & de Milliano (Reis and Blum 1996), te­ Table 2 shows a summary of the results leomorphic or sexual form of the imper­ for 1995. As reported above, commercial fect form Sphacelia sorghi McRae. This products based on tebuconazole and was possible due to collaborative work of propiconazole were recommended for Drs. Melo Reis and Peter Mantle, Impe­ use in sorghum, through an effort of the rial College of Science, Technology and Sorghum Sub-commission of Minas Medicine, UK. It became especially clear Gerais. to the Brazilians that risks of ergot toxic­ ity were negligible. Also the shape of One last question remained: how to ap­ sclerotia could easily be confused with at­ ply the fungicides on a commercial scale? rophied sorghum grains (Frederickson et Practice brought the answer. Between al. 1991). Until then, we were looking for March and May 1996, seed companies spur shaped structures (the meaning of er­ that opted for land application had to got). It was not, therefore, appropriate to mount relatively complicated operations to be able to spray all their fields at 5-7

29 I Table 2. Chemical control of the sugary dis­ tion using tractors (average of 350 I ha- ) ease (SphaceJia sorghi McRae) in the made the operation more complex than field. Tested fungicides, dosages, and normal, requiring the use of tank trucks selected products for chemical use. for constant refilling of equipment. The Dosage (g or ml operational efficiency was considered Tested Fungicides ofa i ha,l) 375.0 low. Tebuconazole' 250.0 125.0 625 The importance of uniform crops to 250.0 limit the number offungicide applications Propiconazole' 125.0 to a maximum ofthree became clear. Aer­ 625 250.0 ial spraying, with low volume of mixture, Triadimenol 125.0 was duplicated to guarantee the perfect 625 Benomyl 500.0 wetting of the panicles, increasing the 7500 cost significantly. Table 3 shows com­ Carbendazin 500.0 parative costs of the aerial and land sys­ Thiabendazole 100.0 Mancozeb 2400.0 tems. The use ofthe center pivot irrigation Fentin Hydroxide 500.0 to deliver fungicides needs more analysis Metalaxyl + Mancozeb 960.0 + 216.0 Tiofanatn Metllicn 7000 before it can be recommended.

'Recommended for commercial use at 250 g or 250 ml of a. i. ha'l total dose, divided in 3 or 4 applications; 300 to 400 I of Sclerotia Elimination spray volume ha". Source: EMBRAPAlPr6,Sorgo Group 1996 Elimination of sclerotia m seed lots day intervals during flowering using high was another challenge. Technicians were spray volumes (300-400 I ha'I). Other trained to monitor the sclerotia during companies chose aerial spraying, with seed processing. Ample training for field much less operational complexity, but at a and lab technicians, research and produc­ higher cost. A third group used the center tion managers and government inspectors pivot irrigation system to apply the fung~ was provided in February 1996 atthe Col­ cide, with mixed results. In spite ofthe in­ lege of Agriculture-USP, with participa­ direct losses mentioned earlier, the indus­ tion from EMBRAPA, the University of try managed to contain the disease, com­ Pas so Fundo and the Pro-Sorgo Group. bining traditional management practices The harvest of 1996 was well monitored to improve 'nicking' between parents in by companies and inspecting services for the seed production field and fungicide the presence of sclerotia. applications. The total elimination of sclerotia was Fuugicide Application obtained during several normal steps in seed processing, with practically no new Experimental work indicated the need investment required in processing (Ta­ for 3 applications at 5 to 7 day intervals, bles 4, 5 and 6). Combine harvesting re­ from the beginning ofanthesis to the com­ covered most of the sclerotia and the plete flowering, covering a period of 20 gravity table removed the remainder to a days in the field. The large volume of "zero" level. The majority of sclerotia spray mixture required for land applica- present in the field are discarded at the

30 1 Table 3. Comparative cost (US$ ha- ) ofland­ Table 4. Ergot infected sorghum plants found based and aerial application offungi­ during inspection of hybrid seed pro­ cides for the control of sugary disease duction fields ofsorghum Plants Plants Land Air Area evaluated infected % Hybrid Field (ha) (No) Infected Application. Application .. (No) I 15 1,000 89 8.9 I-Product 2 43 2,000 123 6.1 Fungicide 42.45 169.80 3 60 3,000 8 0.3 Surfactant 3.02 12.08 A 4 30 4,000 16 0.4 Sub-Totall 45.47 181.88 5 48 6,000 16 0.3 6 30 3,000 23 0.8 II-Services 7 25 2,500 30 1.2 Application 20.21 100.00 I 58 2,000 3 0.2 Water transport 5.90 B 2 12 3,000 85 2.8 Labor . 2.88 3 100 5,000 4 1.7 Sub-Total II 28.99 100.00 I 35 4,500 78 1.7 III-Grand Total 74.46 281.88 c 2 106 7,000 148 2.0 3 50 5,000 14 0.3 4 70 8000 306 38 IV-Seed yield*** 80 80 Source: Pro-Sorgo Group 1996. V-Increase in cost for 20 kg bag 093 352 • Fungicide: I I ha-!; Surfactant: 2 I ha-! •• Fungicide: 4 I ha-!; Surfactant: 8 I ha-! Table 5. Evaluation of the presence of ergot ••• 20 kg (44 lb.) ha-!. Source: Pro-Sorgo Group 1997 sclerotia in various stages of sor­ ghum seed processing % of Sclerotia' Pbases Sub-Field I Sub-Field 2 harvesting stage and fall or return to the Pre-Harvest 0.24 2.34 soil, and this situation needs better Post-Harvest 0.10 1.65 evaluation; up to what point does sclerotia Post Cleaning 0.10 0.84 Post Air Column 0.04 0.56 in the soil make these areas potentially Post Sizing 0.04 0.32 unsuitable for seed production? Work post Gravity Table 000 000 • % of sclerotia in 500 g samples. Source: Pro-Sorgo Group conducted in 1996, however, indicated 1996. that the abundant production of sclerotia could be minimized by a combination of Table 6. Presence of ergot sclerotia in com­ field management practices and also that bined samples" of hybrid sorghum they could be totally eliminated by ade­ seed lots:" quate processing. Hybrid Seed lots No of sclerotia Sampled (ND ) present per IDt 29 0 Marketing of Sorghum Seed Without A Sclerotia: a Challenge and a Pledge of 4 quality from the Brazilian Seed Industry. B 38 0 C 7 0 The Brazilian seed industry has been D II 0 able, in general, to evolve with our coun­ 'Samples of 500 g lor! try's agriculture, supplying it with quan­ "Lot of 8 metric tons. Source: Pro-Sorgho Group 1996 tity and quality seed, even to the point of reaching foreign markets. Sorghum hy-

31 brid seed production is a private-sector break is to establish an union of efforts activity supervised by the government in among all the sectors connected with the Brazil. These companies are also reach­ affected activity, devoid of all vanity or ing out to export markets. any other secondary interest.

The State Commissions are preparing Secondly, that science from the North themselves to adopt the "zero sclerotium" must be involved in all actions and deci­ standard in their certified seed. The Minas sions. We don't solve a problem of this Gerais State Commission, leader in the nature under the influence of emotions or sorghum seed production in the Country, utilizing attitudes that are against reason has already adopted it. By the end of the or ethics. decade no Brazilian State will be produc­ ing sorghum seed that does not comply The seed industry thanks the organiz­ with this quality standard, essential in ing committee for providing the opportu­ helping to control the spread of this dis­ nity to speak in an event of such quality ease. with the hope that our modest contribu­ tion can be useful to reduce the "phan­ Conclusion tom" of sugary disease to a dimension that is realistic and manageable by all of us. The results obtained by the Brazilian strategy for the disease control will be References certainly debated and analyzed in the con­ Bandyopadhyay, R, Frederickson, D. E., McLaren, ference. Our work is just beginning, and N.W., andOdvody, G. N. 1996. Ergot,Aglobal many questions concerning the seed in­ threat to sorghum. International Sorghum and dustry are still without a conclusive an­ Millets Newsletter, 37: 1-32. Ferreira, A S., Pinto, N. F. J. A, and Casela, C. R. swer. From on-going research projects we 1996. A valiarrao de fungicidas para 0 controloe expect, for example, a better definition of de Ergot ou doenrra arrucarada (Clavieeps afri­ the epidemiological role of sclerotia, as eana) em sorgo. Pesquisa em andamento, EM­ BRAPA, CNPMS ISSN 0101-5559, Sete well as better ways to manage sclerotia in­ Lagoas-MG, 4 p. fested fields. Frederickson, D. E., Mantle, P. G., and de Milliano, W. A 1. 1991. Clavieeps afrieana sp nov.; the distinctive ergot pathogen of sorghum in Africa. The Brazilian private sector makes it­ Mycological Research. 95(9):1101-1107. self completely available to the national McLaren, N. W. 1994. Efficacy of systemic fungi­ and international scientific community, cides and timing of preventative sprays in the control of sugary disease of grain sorghum (Sor­ here represented by eminent researchers, ghum hieolor). South African Journal of Plant for the exchange of experiences that could and Soil. 11:30-33. lead to the control of this disease by sor­ McLaren, N. W. 1993. Effect of sugary exudates on germination, seedling development and predis­ ghum producing Countries. position to seedling diseases of sorghum (Sor­ ghum hieolor). South African Journal of Plant Our short experience with the sugary and Soil. 10:12-16. Reis, E. M. and Blum, M. M. C. Doenrra arrucarada disease-but our past experiences with do sorgo. Apostila de curso: Detecrrao do agente other epidemics-authorize us to state that causal do Ergot (Doenr;a Ar;uearada) em se­ the first and strongest factor of success in mentes de sorgo. ESALQIUSP-Piracicaba-SP. 22-23/04/1996. 12 p. any strategy to control an epidemic out-

32 Session III - Country Reports

Session President - Gary Odvody

33 Introduction to the Country Reports Section at theGlobal Conference on Ergot of Sorghum

Gary Odvody Texas A&M University

The country and regional reports sec­ gen. There will be both a uniqueness and a tion of the global conference on ergot of similarity in each ergot experience that sorghum represents both the new and the represents the interaction of the ergot old concerning experience with these pathogen with the regional environments pathogens. A few scientists will relate and local sorghum production systems. their many years of research and interac­ This chronology of ergot spread and re­ tion with ergot; however, most will share gional response provides us with a current about a pathogen that suddenly swept into yet historically unique perspective ena­ ·their country or region within the last year bling analysis of an ongoing global epi­ or the last few months even as this confer­ demic of a plant disease. More impor­ ence was already being assembled. A pre­ tantly we have the opportunity to gain a ponderance of the reports are from the collective insight into the biology and epi­ Western hemisphere where in a majority demiology of the ergot pathogens, espe­ of the countries there was first a sudden cially C. Ajricana, and to identify the re­ awareness ofClaviceps africana, then ex­ search, management, and regulatory ef­ pectation and finally occurrence across forts in process. Our collective many sorghum production areas. The re­ knowledge, interaction, and collaboration ports will chronicle preparation and re­ on several issues involving sorghum er­ sponse to that ergot invasion, current dis­ gots will be necessary to sustain the inter­ tribution and impact of ergot, and other national and global nature ofthe sorghum reactions to the occurrence of the patho- seed industry.

35 Experiences with Ergot of Sorghum in Southern Africa

D. C. Nowell and N. W. McLaren

Abstract

Ergot (C/aviceps africana) has been present in the Southern African region for many years. However, it was only in the mid-1980s that the disease increased in importance, and started causing economic losses. Although ergot can be ofeconomic importance in commercial sorghum production, seed production fields are most affected by the di!r ease. The disease became more important in the region with increased hybrid seedpro­ duction, and the introduction offoreign germplasm (primarily from the USA). Losses are linked to a number ofdifferent attributes, with grain yield (seed set andfill), harves­ tability, plantability, germination and seedling vigor being the more important. The at­ tributes are ofparticular importance to the seed industry. Considerable effort has to be expended to ensure a high quality seed reaches the farmers. Controlling the disease is complex and includes managing planting date, irrigation, cleaning of the seed, fungi­ cide application, cold tolerance ofgerm plasm, pollen pressure, and cultivar choice.

Ergot of sorghum in Southern Africa is gion are not known. Thus, the disease has caused by the fungus Claviceps africana been present in the Southern African re­ Frederickson, Mantle & de Milliano (Fre­ gion for a considerable period. derickson et al. 1991) and not by Claviceps sorghi Kulk et al. as originally Ergot of sorghum was considered to be assumed (Mantle 1968, Sundaram 1980, of limited economic importance and was Frederickson and Mantle 1988, Freder­ associated only with specific cold and ickson et al. 1989, McLaren and Wehner moist conditions. By the late 1980s, the 1990, Bandyopadhyay 1992, de Milliano pathogen had increased in economic im­ 1992). Although the fungus was first portance and was considered a serious listed in South Africa in 1953 by Doidge economic threat to the production of hy­ et al. (1953), a specimen, found in brid seed (Bandyopadhyay 1992). This KwaZulu-Natal, was deposited in the Na­ increase in economic importance was tional Herbarium in Pretoria in 1936 by mirrored in the Southern African region. Sellschop (No. 28658) but it is thought to Ergot only became a significant economic have been present in South Africa prior to problem in this region when a late 1970s this. The exact time ofthe first occurrence and early 1980s in hybrid seed production ofthe disease in other countries in the re- fields. In South Africa, the first major er­ got epidemic in seed production fields oc­ curred during the 198511986 growing sea­ son. Significant losses (quality and seed D. C. Nowell, Plant Protection Service, FAO of the United Na­ yield) were experienced, and have been tions, Rome 00100; N. W. McLaren, ARC-Grain Crops Institnte, Private Bag X1251, Potchefstroom, 2520, Republic of South Af­ present since then to a greater or lesser de- rica

36 gree in most seasons. This increase in in­ ProblemslLosses cidence, and severity of ergot in the re­ gion coincided with increased hybrid seed The major practical problem with ergot production, and the increased direct use infection is the sugary exudate that forms ofinbreds from the U.S. in these hybrids. on the head. This substance is very sticky, It can be concluded that ergot is wide­ and interferes with harvesting of the crop spread and economically important in and processing, as well as planting, if des­ commercial and seed production fields, tined for the seed market. At the end ofthe but primarily of economic importance in season, sclerotia are formed in the in­ seed production. fected glumes. However, these sclerotia seldom have the typical black outer layer The causal organism will not be de­ and seldom germinate to produce perithe­ scribed as a detailed description ofe. afri­ cia. In a seed crop, the seed contaminated cana can be found in Frederickson et al. with ergot exudate tend to aggregate, par­ (1991 ). Similarly, Frederickson and Man­ ticularly under conditions of high relative tle (1988) and Frederickson et al. (1989) humidity, making harvesting, processing have described the infection process and and planting extremely difficult, if not disease development. impossible. This means that seed compa­ nies have to wash the seed once it has been Distribution harvested to remove the exudate from the seed. This process is time consuming and This fungus is widely distributed in the seed has to be artificially dried imme­ Southern Africa with Angola, Botswana, diately after having been washed. It is es­ Lesotho, Malawi, Mozambique, Na­ timated that this process costs the industry mibia, South Africa, Swaziland, Zambia (valued at about $2 million per annum), and Zimbabwe having recorded the which is small on an international scale, pathogen (Bandyopadhyay 1992, de Mil­ an additional $200 000 per annum. Simi­ liano 1992, Nowell unpublished). The se­ lar losses are experienced in Zimbabwe verity of the disease varies considerably but the value of the crop and losses are within, and between growing seasons, lower. McLaren (1993) showed that ergot and over locations. exudate could significantly affect both germination ofthe seed and plant vigor. If The infection of sorghum, and subse­ this washing process is not completed quent development, of ergot is highly correctly, the quality of the seed can be weather dependent (Sundaram 1980, Fre­ adversely affected due to increased mois­ derickson and Mantle 1988, Frederickson ture of the grain and the toxic effect of the et al. 1989, McLaren and Wehner 1990 exudate. It has also been found that stor­ and 1992, Bandyopadhyay 1992). Cli­ age life ofthe seed can be reduced as a re­ matic conditions will be dealt with in sult of lower quality grain. depth in another paper during the confer­ ence (McLaren 1999). It has been found Infection of the sorghum head also re­ that overhead irrigation can significantly sults in a decrease in seed set and hence a increase ergot severity. decrease in the grain yields. Under ideal conditions for e. africana, the effect on

37 yield can be large. The yield loss ranges temperatures will limit the amount from 0-$900 ha-l (70%) in seed produc­ of infection and the night tempera­ tion fields. tures will not predispose the plants to infection (McLaren and Wehner Mantle (1968) found that culture fil­ 1990 and 1992, McLaren unpub­ trates of a Nigerian strain of Sphacelia lished). This has found to be true in sorghi produced the alkaloids dihydroer­ India as well (Anahosur and PatH gosine, festuclavine, pyroclavine, dihy­ 1992). droelymoclavine and chanoclavine, ii. irrigation management - overhead which accounted for over 99% ofthe total irrigation can significantly decrease alkaloid production. These alkaloids are the ambient temperature and thus of relatively low toxicity. Feeding of C. make conditions suitable for infec­ africana sclerotia to mice failed to inhibit tion by C. africana. Thus irrigation lactation or implantation. Indications are should be undertaken in such a way that the alkaloids produced by this strain as to not lengthen the dew period. ofS. sorghi are the least toxic of all the al­ kaloid containing ergots. iii. cleaning of seed before harvest - seed produced under overhead irri­ There are large variations in hybrid or gation can be washed shortly before inbred susceptibility to ergot in the field. harvest while still on the head should Resistance to ergot in sorghum does not there be a very large amount of exu­ increase in a linear manner with increased date present. However, the wetting disease pressure. However, specific lines/ ofthe grain at this stage significantly hybrids are consistently more resistant to increases the risks of reduced seed the fungus than others lines/hybrids quality, vigor and viability. (McLaren 1992). This can be seen very iv. cleaning of seed during processing clearly when a number ofhybrids are pro­ - infected seed crops have to be duced in the same region and are planted washed during the seed conditioning at the same time. Seed and quality losses process. Failing to do this could re­ for each inbred vary significantly. sult in reduced germination, plant­ ability and seedling vigor after Solutions planting. Another factor that plays a role is the aggregation of exudate In order to control the pathogen it is contaminated grain during storage necessary to use integrated management and before planting when the rela­ practices. In South Africa the following tive humidity increases. The whole guidelines are used: packet of seed can become a solid, unusable, sticky mass of seed. i. planting date ensure that the seed crop is planted so that the crop flow­ vi. slight seed contamination - slight ers when the mean maximum daily contamination can cause a buildup temperatures are above 28°e and of exudate in the planter hopper dur­ mean night temperatures are above ing planting. Although planting may 13°e. This will ensure that daily be perfect in the beginning, the

38 amount of seed planted becomes tolerant/ergot resistant hybrids progressively less and will result in a should be planted in areas of high progressively lower plant density risk for ergot. (after 3 hours of planting the amount of seed planted is half of the desired x. seed treatments - the use of fungi­ plant density, and after 6 hours of cide seed treatments are used on seed planting the amount of seed planted that had been infested in the fields to is <1 0% ofthe desired plant density). improve storage and seedling vigor. This problem can only be eliminated However, they will have no effect on through washing the seed during the incidence of ergot. processing/conditioning. Future vi. Fungicides - fungicides can be used to limitthe amount of infection. Primarily the research in Southern Af­ However, the cost effectiveness of rica will be focused on: such a practice is questionable (McLaren 1994) and will vary be­ 1. the identification of resistant/cold tween each country. tolerant germplasm in the field. This could be supplemented by the identi­ vii. timing of pollen production and silk fication of molecular markers for re­ emergence - as the S. sorghi co­ sistance/cold tolerance. nidia compete with the pollen for fer­ tilization/colonization of the 11. improved seed production practices embryo, it is vital to have early, high 111. identifying the most suitable seed and viable pollen pressure. Failure to production regions have this increases the risks of ergot greatly. iv. improving seed processing practices viii. ratio of males to females -linked to v. testing the newer generation fungi­ vii is the ratio of male rows to female cides for efficacy against C. africana rows as this has a large effect on the pollen pressure. Normally, the vi. testing fungicide seed treatments to Southern African region works on 4 improve germination and seedling or 6 rows of females to 2 rows of vigor of infected seedlots. males. In exceptional circumstances References (when the male is a very strong pol­ len parent and cold tolerant) 8 rows Anahosur, K. H. and Patil, S. H. 1982. Effect of offemales to 2 males can be planted. date of sowing on the incidence of ergot of sor­ ghum. Indian Phytopathology. 35: 507-509. Bandyopadhyay, R. 1992. Sorghum ergot. Pages ix. cold tolerance - due to the predis­ 235-244 in Sorghum and millet diseases: a sec­ position of the plants to ergot infec­ ond world review, W. A. J. de Milliano, R. A. tion by a cool period «13°C night Frederiksen and G. D. Bengston (eds.) Patancheru 502324, Andhra Pradesh, India: In­ temperature) before flowering in ternational Crops Research Institute of the some germplasm, it is important to Semi-Arid Tropics. plant the more cold tolerant parents de Milliano, W. A. J. 1992. Sorghum diseases in in areas of higher ergot risk. Cold Southern Africa. Pages 9-19 in Sorghum and millets diseases: a second world review, W. A.

39 J. de Milliano, R. A. Frederiksen and G. D. ghum (Sorghum hieolor). South African Bengston (eds.) Patancheru 502324, Andhra Journal of Plant and Soil 10:12-16. Pradesh, India: International Crops Research McLaren, N. W. 1994. Efficacy of systemic fungi­ Institute ofthe Semi-Arid Tropics, Patancheru, cides and timing of preventative sprays in the India. control of sugary disease of grain sorghum (Sor­ Doidge, E. M., Bottomley, A. M., van der Plank, J. ghum hieolor). South African Journal of Plant E., and Pauer, G. D. 1953. 'n Hersiende lys van and Soil 11:30-33. plantsiektes in Suid Afrika. Wetenskaplike McLaren, N. W. 1999. Host x pathogen x environ­ Pamflet Nr. 346, Departement van Landbou, ment interaction in sorghum ergot disease. Die Staatsdrukker, Pretoria, South Africa. Pages 114-134 in Proceedings of the Global Frederickson, D. E. and Mantle, P. G. 1988. The Conference on Ergot of Sorghum, J. A. Dahl­ path of infection of sorghum by Clavieeps sor­ berg and C. R. Casela eds. 1-8 June 1997, Sete ghi. Physiological and Molecular Plant Pathol­ Lagoas, Brazil. INTSORMIL, University of ogy.33:221-234. Nebraska, Lincoln, NE. Publication 99-1. Frederickson, D. E., Mantle P. G., and de Milliano, McLaren, N. W. and Wehner, F. C. 1990. Relation­ W. A. J. 1989. Secondary conidiation of ship between climatic variables during early Sphaeelia sorghi on sorghum, a novel factor in flowering of sorghum and the incidence of sug­ the epidemiology of ergot disease. Mycolologi­ ary disease caused by Sphaeelia sorghi. Journal cal Research. 93:497-502. ofPhytopatholology 130:82-88. Frederickson, D. E., Mantle P. G., and de Milliano, McLaren, N. W. and Wehner, F.C. 1992. Pre­ W. A. J. 1991. Clavieeps afrieana sp. nov.; the flowering low temperature predisposition of distinctive ergot pathogen of sorghum in Africa. sorghum to sugary disease (Clavieeps afri­ Mycological Research. 95:1101-1107. eana). Journal of Phytopathology 135:328-334. Mantle, P. G. 1968b. Studies on Sphaeelia sorghi Sundaram, N. V. 1980. Sorghum ergot. Pages 377- McRae, an ergot of Sorghum vulgare Pers. An­ 379 in Sorghum diseases: a world review, W. A. nals of Applied Biology. 62:443-449. J. de Milliano, R. A. Frederiksen and G. D. McLaren, N. W. 1992. Quantifying resistance of Bengston eds., Patancheru 502324, Andhra sorghum genotypes to the sugary disease patho­ Pradesh, India: International Crops Research gen (Clavieeps afrieana). Plant Disease. Institute of the Semi-Arid Tropics. 76:986-988. McLaren, N. W. 1993. Effect of sugary disease exudates on germination, seedling development and predisposition to seedling diseases of sor-

40 Sorghum Ergot in India

c. S. Sangitrao, S. Indira and R. Bandyopadbyay

Abstract

Ergot is the most important disease constraint in sorghum seed production causing 10-80% yield losses. The biology ofthe pathogenClaviceps sorghi and ergot epidemiol­ ogy have received considerable research attention in India. The roles ofsclerotia and collateral hosts in the disease cycle have been established Sclerotia could be separated from seed by flotation in 10% salt solution. Delayed sowing, non-synchronization of seed parents, and poor crop management are some of the factors that favor the inci­ dence, development, and spread ofergot in F! hybrid seedproduction fields. Varieties, hybrids, and their seedparents have variable degree ofsusceptibility. Varieties are le!B susceptible than hybrids. Male-steriles are more susceptible than maintainers and re­ storers. In spite ofself-pollination, varieties and Band R lines are also susceptible. ReG­ ommended strategies for integrated disease management in India include early sowing, synchronization ofmale andfemale parents, destruction ofinfected panicles and collat­ eral hosts,jungicide application, removal ofergot sclerotia byflotation in salt solztion, and adherence to seed certification standards.

India is a major sorghum growing Low-yielding traditional varieties in country in the world. Sorghum is culti­ the major sorghum-growing areas have vated on 12.55 million ha in this country, been gradually replaced by high-yielding representing 30% ofthe world's sorghum hybrids since the release of the first hy­ area. The total annual production of 11.8 brid CSH 1 in 1964 in India. Hybrids are million t constitutes 11.6% of the total now extensively grown in almost 80% of world production (FAO 1996). Sorghum the area in the major sorghum growing is also the third major cereal in India after State of Maharashtra where productivity rice and wheat. It is extensively grown for has increased from 587 kg ha-! (in 1970) human food, animal feed, fodder and to 1407 kg ha-! (in 1996-97). Doubling other industrial uses under rain-fed condi­ grain yields in the last 30 years in India tions in the dry regions with unpredictable has been possible due to the release of 15 rainfall. hybrids for country-wide cultivation by the All India Coordinated Sorghum Im­ provement Project (AICSIP), Hyderabad, of the Indian Council of Agricultural Re­ ·C.s. Sangitrao, Associate Professor, Department of Plant Pa­ thology, Dr. Panjabrao Desbmukh Krishi Vidyapeeth, Akola 444 search (lCAR), New Delhi, and rapid ! 04, Maharasthra, India; S. Indira, Principal Investigator (pathol­ adoption of hybrid technology. In the last ogy), National Research Centre for Sorghmn (NRCS), Rajen­ dranagar 500 030, Hyderabad, Andhra Pradesh, India; R. Bandy­ decade, more than 30 private seed compa­ padhyay, Senior Scientist (pathology), International Crops Re­ nies have become active contributing sig­ search Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, Andhra Pradesb, 502 324 India. ·Corresponding nificantly to this achievement. Of the re­ author. leased hybrids, CSH 5, CSH 6, CSH 9,

41 and CSH 14 are highly popular in the Disease Distribution rainy season. McRae (1917) reported ergot for the According to an estimate, more than 24 first time in the world after he observed 000 t of certified F] hybrid seed are pro­ the sphacelial stage of the disease in Ma­ duced in India which is sufficient to sow dras State, India, in 1915. Since then, the only 3.4 million ha in the rainy season out disease has been reported in other Indian of the 7 million ha area under high­ States such as Maharashtra (Ajrekar yielding varieties (B.S. Rana, personal 1926), Karnataka (Kulkarni 1942), Tamil communication). Presently there is a Nadu (Nath and Padwick 1941, Thomas shortfall in supply, and hybrid seeds are in et al. 1945, Ramakrishnan 1947) Andhra great demand. Pradesh (Ramakrishnan 1948; Sundaram 1967, 1969; Patil et al. 1968), and Delhi In Maharashtra State, where primarily and Haryana (AICSIP 1969-70). Ra­ hybrids are grown, and several seed com­ makrishnan (1963) observed the sclero­ panies are located, 10-80% losses in seed tial stage of the pathogen in Koilkuntla, yield have been reported due to ergot. Se­ Andhra Pradesh. The disease is endemic vere incidences of this disease and grain in Maharashtra (Vidarbha and Ahrnedna­ mold have forced the seed companies to gar regions), Karnataka, Andhra Pradesh, shift seed production from Maharashtra to and Tamil Nadu. AICSIP takes advantage the States of Andhra Pradesh and Karna­ of this endemic nature to test breeding taka. In spite of shifting the seed produv lines in these States. tion to the normally hot and dry areas of Andhra Pradesh and Karnataka, the dis­ The Pathogen ease continues to be a threat to seed pro­ Sphacelia/ Stage duction particularly when cool and humid weather occur during anthesis. For exam­ In India, McRae (1917) described the ple, during 1994-96, seed production of imperfect, sphacelial stage of the ergot the most popular hybrid CSH 9 was only pathogen of sorghum as Sphacelia sorghi. 1.25 t ha-], compared with the expected Subsequently, the sphacelial stage was 3.75 t ha-] (B.N. Khule, Maharashtra State described with respect to conidiophores, Seed Corporation, India, personal com­ conidia, and variations in the size and munication). Ergot has gained economic shape of conidia, (Ajrekar 1926, Ra­ importance after the introduction of hy­ makrishnan 1948, Sundaram et al. 1970, brids, and has made it difficult to produce Chinnadurai and Govindaswamy 1971, F] hybrid seed and the female parent. Khadke 1975, Kulkarni et al. 1976, and Sangitrao 1982). Microconidia were al­ We briefly review research done in In­ most of the same dimensions irrespective dia on the different aspects of sorghum er­ ofthe source, butthe size of macroconidia got, and highlight the thrust areas to help varied (Sangitrao 1982). Secondary co­ formulate future strategies. nidia are also known to occur in the green-­ house and in the field (Bandyopadhyay et al. 1990).

42 Conidial Germination IS 8070, only one ovary was infected (Sangitrao and Bade 1979). Conidial germination was from both or either ends of the spore (Ajrekar 1926). Sclerotial Germination Another report (AICSIP 1965-67) men­ tioned that, within 3 h, the macroconidia Sclerotial germination was tried by Ra­ germinated by thin germ tubes ending in makrishnan (1948) by exposure to alter­ pyriform, hyaline secondary conidia that nating temperatures of 5 and 20°C. In­ detached and in turn also germinated. stead of germination, sclerotia turned into This was confirmed by Sangitrao (1982). a slimy mass (AICSIP 1965-67, Sunda­ Germination of both macroconidia and ram 1967). Rama Sastri (1973) men­ microconidia in 5% sucrose solution has tioned that there is no possibility of exis­ been reported (Sangitrao, 1982). Germi­ tence of physiological races since sclero­ nation of conidia from different tia failed to germinate. hosts-Sorghum hieolor, Pennisetum ty­ phoides, lsehaemum pilosum, Diean­ Kulkarni et al. (1976) for the first time thium annulatum, Dieanthium earieosum successfully germinated sclerotia from a and Sehima nervosum was only 2.5% in genotype IS 5353 in 35 days by keeping it the first 9 h, 50-70% in 12 h, and 95-98% in moist soil, near an open window in the in 48 h. laboratory, but sclerotia from CSH 1 did not germinate when kept for even up to 2 The conidia of S. sorghi remained vi­ months. able on the heads for 1 year when main­ tained at room temperature (max 29°C In his detailed studies using a "sclero­ and min 17°C). When smeared on the tial germination assembly", Sangitrao seed surface, 1-2% conidia germinated (1982) reported that up to 55% sclerotia for up to 48 h, and lost viability com­ germinated at 27°C. The sclerotia absorb pletely in 72 h. Conidia developed on water and the basal ends become swollen modified Kirchoffs medium showed 80- in 15-20 days of incubation, and subse­ 100% germination (Sangitrao 1982). quently develop a white tuft of mycelium in 5 days. Pinhead-sized, pinkish r~d Sclerotial Stage stroma, 6-15 mm long, developed from the base ofthe mycelial tuft. A single scle­ The perfect stage of S. sorghi in India rotium was seen to produce 1-7 stroma. has been reported as Clavieeps sorghi. Sometimes, during the initial stages of Several workers reported variation in sclerotial germination, a number of slimy color, shape, size and mass of sclerotia pinkish pinnotes were seen on the surface (Ramakrishnan 1948, Tarr 1962, Patil et of sclerotia, and contained numerous al. 1968, Kulkarni et al. 1976). But all macroconidia and microconidia (Sangi­ these variations were due to the differ­ trao 1982). ences in genotypes, climatic conditions and the stage of development (Sangitrao Another interesting feature observed 1982). Though there are two ovaries in while germinating the sclerotia on differ­ twin-seeded cultivars as in Lav-Kush and ent substrates and positions is that they

43 germinated when placed horizontally on ~m. The perfect stage ofS. sorghi in India sterilized sand, while they did not germi­ was named as Claviceps sorghi. nate in the vertical position. Fragments of sclerotia with intact basal ends germi­ The perfect stage in Akola was also nated to produce stroma, while fragments confirmed as C. sorghi (Sangitrao 1982) from other parts did not germinate. corresponding to 1M! herbarium number 262578 for the species originally depos­ Sclerotia were viable for 3 years at ited by Kulkarni et al. (1976). However, room temperature in the laboratory, and the pinnote formation and stages of peri­ germinated when kept up to 60 cm deep in thecial forni~tion were reported for the soil in the greenhouse. Germination of first time by Sangitrao (1982). sclerotia obtained from different geno­ types ranged from 50-55% (in CK60 A Ascospore Germination and IS 84) to 25-35% (in 2077 A, CSH 1, and R 473). This suggests that the effI­ Ascospore germination was studied ciency of germination is affected by host using 5% sucrose solution. Initially they genotypes. Fungicides such as Aureo­ became swollen and broke into fragments fungin®, Bavistin®, Ceresan®, thiram, before germination began. Germination and captan did not completely inhibit ger­ was 1-3% after 9 h, 5-7% after 12 h, 12- mination but reduced it to 2.3%. 20% after 24 h, and 15-24% after 48 h. Each fragment produced germ tubes In a study on biological control, the (Sangitrao 1982). fungus Chaetomium globosum was most effective in inhibiting sclerotial germin& Infectivity ofSpores tion while Rhizoctonia, Azotobacter, Fu­ sarium, and Curvularia had very little or The efficiency of infection was tested no effect (Sangitrao 1982). by using spores from different pathogen propagules. Inocula used were: 1) conidia Internal Structures ofStroma from artificial cultures, fresh sphacelium, on Germinated Sclerotium inner part of sclerotia, and pinnotes on germinating sclerotium; and 2) asco­ Kulkarni et al. (1976) observed asco­ spores obtained from well developed stro­ spores in the stromata of germinated scle­ mata. All these sources of inocula initi­ rotium in Dharwad, Karnataka. Perithecia ated 100% disease incidence within 6-8 containing ascospores were em bedded in days when applied artificially on the the stroma and were flask-shaped, heads of male-sterile 2077 A and CK60 A slightly protruding at the ostiolar region, under controlled conditions. The conidial and measured 132.8-232.4 x 66.4-124.5 inocula produced 30-60% disease sever­ ~m. Asci were hyaline, cylindrical with ity, compared with only 2-3% severity somewhat tapering ends with a hyaline with ascospore inoculum (Sangitrao cap at the apex, and measured 56-112 x 1982). 2.4-3.2 ~m. Ascospores were eight per as­ cus, filiform, measuring 40-85 x 0.4-0.8

44 Toxicity to Animals also occurred. Histopathological changes in the affected part of the tail include oc­ Poisoning due to sorghum ergot result­ clusion of the blood vessels due to the ing in injury to either humans or animals presence of red thrombi and necrosis. has not been reported in India. Ra­ Further critical studies on toxicity to live­ makrishnan (1948) assayed sclerotia of stock are required to determine if ergot sorghum but failed to demonstrate the sclerotia are hazardous to animals. poisonous alkaloid ergotoxin. Chinnadu­ rai and Govindaswamy (1971) obtained Flowering Behavior alkaloids to the extent of 0.025% in hon­ eydew and 0.08% in sclerotia of sorghum Quinby (1958) described that the long ergot, as ergotinine equivalent, and rec­ stigmas in sorghum, which extend be­ ommended the study of mammalian tox­ yond the glumes after the flower closes, icity of sorghum ergot sclerotia. They did remain receptive to pollen and could be a not specifically extract and assay alka­ route for infection by the pathogen. loids but assayed powdered sclerotia. The House (1980) described that all the heads result probably reflects the general detec­ did not flower at the same time, the an­ tion of indolic compounds by the reagent thers dehisced when they were dry. When p-dimethy laminobenzaldehyde. Sangi­ caught in the rains, pollen dispersal was trao (1982) and Phadnaik et al. (1994) re­ restricted because rain washed them ported that sorghum ergot sclerotia con­ away. Similar observations were made tained clavine derivatives, and that the to­ for stigma receptivity by Chopde et al. tal alkaloid content varied from 0.008 to (1973). 0.0032% (expressed in terms of er­ gometrine base) in the cultivar 2077 A. Shekar et al. (1981) showed that seed setting was poor upon pollination on the Phadnaik et al. (1994) studied the tox­ first day following anthesis, and was up to icity on albino mice. They reported that 83% on the second day in 2077 A and 296 low alkaloid content explains the high A. Temperature below 10°C also affected LD50 value (1.875 g kg-I) of sorghum er­ anther dehiscence in 296 B, resulting in got on experimental mice, compared with no seed set in 296 A, the female parent of 100 mg kg-I in rhesus monkeys for pearl the popularly grown sorghum hybrid millet ergot. Mortality in mice occurred CSH 9. In a few cases low temperature even at a single oral dose of 0.75 g kg-I has been found to restrict the release of body weight. Common symptoms oftox­ pollen from anther sacs (Sangitrao 1982). icity were diarrhea, dyspnea, muscular spasm, hyperexcitability and gangrene. In Puranik et al. (1973) observed that the chronic toxicity studies, diarrhea was ob­ fertilized ovaries were susceptible to in­ served on the second day after administer­ fection for 3 days. The time of pollination ing one-sixth of the LD50. Significant re­ and fertilization in sorghum is 2-4 h duction was observed in body weight and (Neergaard 1977), and the embryo has a relative organ weight of lungs, liver, dormant period of 6-22 h (Paulson 1969) heart, spleen, and kidney. Shrinkage at without any cell division. This suggests the tail tip, gangrene, and sloughing oftail that infection can take place even after

45 fertilization, but this hypothesis needs canthium caricosum could infect sor­ confirmation. ghum in India.

Pollination, Fertilization, and Ergot Epidemiology

When pollen and conidia were placed Environmental Effects simultaneously on the stigmas, pollen germinated earlier than the conidia and Sugary disease is severe when cool cli­ the pollen tube reached the embryo faster matic conditions prevail at the time of than the fungal hyphae. In pollinated and flowering (Tarr 1962). Environmental fertilized pistils, the fungus grew slowly conditions favorable to the disease have or failed to grow, resulting in reduced er­ been reported by several workers. These got incidence. Sangitrao (1982) and Ban­ include: cool temperatures of 21-27°C dyopadhyay et al. (1992) observed that (Ajrekar 1926, Chinnadurai et al. 1970); fertilization was effective in controlling 19±I°C and humid and cloudy weather ergot. However, fungal hyphae were (Sundaram 1970) and 17±2°C (Ram a found in the fertilized ovaries, which Sastri 1973). Sangitrao (1980) observed needs to be confirmed. that temperature ranging from 13° to 19°C and relative humidity of76-94% fa­ Host Range vored disease spread under artificial in­ oculation. Similar studies have been con­ There are numerous reports on possible ducted by Sundaram (1970). collateral hosts of e. sorghi. The compre­ hensive list given by Bandyopadhyay In five years of detailed epidemiologi­ (1992) indicates that alternate hosts ofe. cal studies, Sangitrao (1982) revealed that sorghi include Cenchrus setigerous, 1s­ more than 75% relative humidity (RH) chaemum pilosum, Pennisetum orientale, and 15-19°C minimum temperature were Sorghum arundinacearum, S. caffrorum, favorable for disease development. The S. haiepense, S. membranaceum, S. incubation period ranged from 5 to 15 nitens, S. verticilliflorum, and Zea mays. days, with an optimum of 7 days. Conflicting results have been reported for C. ciliaris and Pennisetum typhoides Sclerotial formation is favored by dry (Sundaram et al. 1970, Chinnadurai and weather. Bandyopadhyay et al (1990) re­ Govindaswamy 1971, Sundaram 1974). ported that 14-28°C and >90% RH for 12- Besides these, a few more hosts and non­ 16 h, and 28-35°C and <80% RH for 12 h hosts were recorded by Ramakrishnan were favorable for conidial and sclerotial (1947), Singh (1964), Reddy et al. (1969), production, respectively. Sundaram (1970), Chinnadurai and Govindaswamy (1971), Mutkekar and In India, weather conditions in 38th to Madane (1976), Patil and Madane (1979), 4th meteorological weeks were favorable and Sangitrao (1982). Sangitrao and for 80-100% of disease incidence, and 35- Moghe (1995) reported that a triangular 70% disease severity. Sclerotial forma­ spore form ofS. sorghi collected from Di- tion was directly proportional to the se­ verity of the sphacelial stage. Cool tern-

46 peratures, high humidities, rain splashes, eral hosts, thus completing the disease cy­ and constantly changing wind direction cle. are congenial for the spread ofthe disease (Sangitrao 1980). Disease Survey and Yield Loss Estimation Dispersal of Conidia During 1978-81, a survey of the Such insects as thrips, Orius species, Vidarbha region and western Maharash­ beetles, midge, head bugs, and hymeno­ tra for sorghum ergot (Sangitrao 1982) pterous insects failed to transmit the concluded that certain factors accounted pathogen when released in cages contain­ for the incidence and spread of the dis­ ing susceptible panicles suggesting that ease. These were: insects do not play any role in the spread of the disease. The groups of insects that • Delayed sowing normally visit flowering panicles and • Late rains panicles with developing grains are dif­ • Non-synchronization of male and ferent (Bandyopadhyay et al. 1991). female parents Sangitrao (1982) observed that ovaries • Presence of grass weeds harboring primary inoculum with midge maggots were later utilized by • Improper crop management, e.g., the ergot fungus and developed honey­ use of poor quality seed resulting in dew for further spread. Bandyopadhyay low male parent population, un­ et al. (1991) observed that secondary co­ even growth in the field, inadequate nidia were produced when honeydew control of pests and weeds, and im­ dropped on wet soil. These secondary co­ proper application of fertilizer nidia can act as the source of primary in­ leading to failure of staggering or oculum. proper nicking for pollination. • Non-removal of diseased panicles Disease Cycle and tillers in rejected or harvested plots. Based on field observations, Singh • Disposal of infected panicles close (1964) and Sangitrao (1982) hypothe­ to the fields. sized that conidia and ascospores could infect collateral hosts that flower before Sangitrao (1982) conducted a repli­ sorghum, thus providing primary inocu­ cated trial in the field to ascertain the yield lum. The ascospores from sclerotia can losses due to sorghum ergot. Sixteen sor­ infect sorghum or collateral hosts in the ghum cultivars including two male-sterile following season. Macroconidia are pro­ lines (CK60 A and 2077 A) were evalu­ duced and protected in the sc1erotiallocu­ ated under an infector row system. Re­ les (Sangitrao 1982), and in due course duction in yield was correlated with dis­ sclerotia disintegrate and release macro­ ease incidence and severity of honeydew conidia. These macroconidia can germi­ and sclerotial stages. There were signifi­ nate on moist soil surface, produce secon­ cant differences among the cultivars with dary conidia which can infect the collat- respect to incidence and severity of hon­ eydew and sclerotial stages. Loss in yield

47 had a linear relationship with honeydew lines affecting seed set in male-sterile incidence. A logistic equation explained lines of various hybrids including the the yield loss when plotted against honey­ most popular CSH 9. dew severity, sclerotial incidence, and sclerotial severity (Fig. 1). The practices followed to manage the disease in seed production plots are: Seed Production Programs • Proper staggering with 4th and 7th The major areas of seed production day of sowing ofthe male parent for programs in India are mainly concen­ synchronization. trated in Andhra Pradesh and Karnataka. • Spraying 2% urea to make up In these States, seed production plots are growth of male or female parent for sown during OctoberlNovember such synchronization. that warm and dry weather normally pre­ • Removal of a few alternate leaves vails at the time of flowering. However, to retard the growth. the crop succumbed to ergot in recent • Spraying gibberellic acid (20 ppm) years due to delayed sowing and erratic growth hormone to induce quick growth of the male parent. rains during flowering. Both these situa­ • Fungicidal sprays. tions led to parental lines flowering in cool, and humid climate, and resulted in poor pollen production of the restorer

70 70 60 60 50 50 ~ ~ j 40 j 40 30 30 l! l! ~ 20 Y = 0.9971x· 0.3997 ~ 20 Y = 22.605Ln(x) . 20.272 10 R' =0.9665 10 R' =0.8957 0 0 0 20 40 60 80 0 10 20 30 40 Honeydew Incidence ('!o) Honeydew severity ('!o)

70 60 60 50 50 a:. ~ 40 40 j j 30 30 32 Y• 22.319Ln(x)· 3.9466 20 20 ~ Y =40.245Ln(x)· 81.975 ~ R' = 0.749 10 R' =0.8859 10 0 0 0 10 20 30 40 0 5 10 15 20 Sclerotia Incidence 1%) Sclerotia severity 1%) ------

Figure 1. Effect of honeydew incidence and severity and sclerotial incidence and severity on yield loss in the sorghum male-sterile 2077 A.

48 Disease Control Strategies Table 1. Efficiency of separation of Claviceps sorghi sclerotia from sorghum seed Cultural Methods by different methodsl Separation Effect ofSowing Dates Method efficiency (04)

Hand winnower 86 At Navasari (Gujarat), sorghum sown Machine winnower 84 later than normal on 20 July showed less Grading sieve 7/64 88 Grading sieve 8/64 89 infection in all the cultivars (Desai et al. Grading sieve 9/64 89 1979). A similar report by Sangitrao et al. Gravity separator 91 Colorimetric sortex 94 (1979) showed disease escape on the crop Belt draper 98 sown on 15 July at Akola (Maharashtra). Salt solution (1004) 100

Anahosur and Patil (1982) emphasized 1 Source: Sangitrao (1982). and Kalmegh (1994). early sowing to escape the disease, but this was not always possible in Dharwad (Karnataka) where cool and humid rator, colorimetric sortex, and belt draper weather prevailed at flowering suggest­ (Table 1). ing that early sowing is location specific. Reduction of Inoculum and Effect of Fertilizer Seed Certification Standards

The incidence of sugary disease in­ The male-sterile lines CK60 A, 2077 creased significantly with more nitrogen A, 2219 A, and 296 A are female parents and less potash. Phosphorous did not in­ ofCSH 1, CSH 5, CSH 6 and CSH 9, re­ fluence disease incidence, but appeared to spectively, and are highly susceptible to stimulate honeydew production. the honeydew and sclerotial stages.

Physical Methods Ad hoc seed certification standards were introduced in 1976, following ergot Separation of sorghum sclerotia using incidence during 1967-75 in parts of 30% salt solution was found to render the western Maharashtra and Vidarbha (East­ grain safe for sowing and human con­ ern Maharashtra). A Government circular sumption (More et al. 1977). This recom­ declared the disease as objectionable and mendation was adopted by the Govern­ seed producers were instructed to rogue ment of Maharashtra. Later, Sangitrao infested heads showing sclerotial forma­ (1982) reported that even 10% salt solu­ tion. The permissible limits were 1:2500 tion can also separate 100% sclerotia. heads for certified seed plots, and 1 :5000 for foundation seed plots. Four field in­ Several methods have been evaluated spections were recommended to record to remove ergot sclerotia from large quan­ infected heads. At the last field inspection tities of seed (Kalmegh et al. 1994). (preharvest), the seed plot would be liable Among these, 10% salt solution removed for rejection if the heads with ergot scle­ 100% sclerotia. The separation efficiency rotia were more than the prescribed limit. was more than 90% with the gravity sepa-

49 Using these seed certification standard sphacelial stage. However, it reduced the guides (Anonymous 1977), seed pro­ disease severity. The Cerebella colonies duced in a few seed processing plants appearing on the sphacelium were more were rej ected during 1976-79 in Ma­ in number in the treated heads than in un­ harashtra. However, the suitability ofthis treated heads affecting the sclerotial de­ certification is often questioned, due to velopment. The application of C. volken­ the presence of other, more efficient sii at 50% and at complete flowering had sources of primary inoculum. only 7.9 and 4.7% sclerotial severity, against 14.3% in the untreated control. Pollen-Based Management Chemical Control Chinnadurai et al. (1970) reported that pollination of susceptible varieties with Ergot control by fungicides in seed fertile pollen reduced spore germination, production plots of sorghum is the most and hence host infection by the ergot effective preventive measure. Fungicidal pathogen. Sangitrao (1982) and Sangitrao control of C. sorghi has been extensively et al. (1992) observed the effect of polli­ investigated in India (Nagaraj an and nation at different times, before and after Saraswathi 1971, Gangadharan et al. inoculation at 100% anthesis, on disease 1976, Sundaram 1976, Anahosur 1979, severity of the honeydew stage. The re­ and Sangitrao 1982). Two or three sprays sults indicated that pollination 8 h before of 0.2% Ziram®, thiophanate methyl, Vi­ inoculation reduced the disease severity tavax® and captafol at 2-week intervals to 5-8% in five male-sterile lines 36 A, starting at the panicle emergence stage in­ 1 CK60 A, 296 A, 2077 A, and 2219 A, creased yield from 1 to 4 t ha- • Two compared with 49-56% severity in the in­ sprays ofBavistin® 0.1 %, one at the time oculated non-pollinated control. of 50% flowering and the second after a fortnight was also effective. However, Biological Control Nagarajan and Saraswathi (1971) ob­ tained little field control ofC. sorghi with Reddy et al. (1965) reported the pres­ systemic fungicides Benlate®, Vitavax ence of Cerebella volkensii at the sphace­ 75W®, and Tecto 60®. This is true in lial stage. When conidia of C. volkensii field situations when disease pressure is and S. sorghi were sprayed together, the high, but disease control by fungicides is sphacelial stage ofthe pathogen appeared usually better than unsprayed situations if initially without any trace of growth ofC. inoculum pressure is low. volkensii. However, after 3 weeks, there were numerous stromata of C. volkensii Host-Plant Resistance associated with sphacelia of S. sorghi suggesting that the sphacelia is important Not much work has been reported on for the growth of C. volkensii stromata. resistance in sorghum to ergot disease. Subsequently, Sangitrao (1982) reported Ajrekar (1926) tested numerous varieties that the application of a culture of Cere­ at Pune and Dharwad, under natural con­ bella at different stages of flowering had ditions and found that none was immune. no significant effect on incidence of the

50 Resistance to ergot on sorghum has search is conducted. Among these, ergot been extensively reported. However, due naturally appears in Akola, Dharwad, Co­ to lack of proper screening techniques and imbatore, Surat, and Palem where breed­ unreplicated trials, many lines previously ing lines are evaluated for ergot reaction. reported resistant have proved to be sus­ Table 2 shows that most of the elite varie­ ceptible in subsequent trials across loca­ ties, hybrids, and their seed parents have tions. A list of sorghum lines reported to variable degree of disease susceptibility. be resistant in India has been published In general, the varieties (average score (Bandyopadhyay et al. 1996). 2.40 on a 1-5 scale where 1 = no disease, and 5 = maximum disease) were less sus­ Bandyopadhyay and Reddy (1991) ceptible than the hybrids (average score tested male-sterile and male-normal sor­ 2.91). The seed parents had a higher de­ ghum and inoculated at various times at: gree of susceptibility (average score 3.47) ter pollen shed. They concluded that those than their maintainer (average score 2.87) panicles that were more efficient self pol­ and restorer parents (average score 2.69). linators were more effective in escaping It is evident that in spite of self pollina­ the disease. There is a need to develop re­ tion, varieties, and B and R lines also have liable and rapid methods for identifying moderate susceptibility to disease. these efficient self-pollinators. Integrated Disease Management In India, AICSIP has a network of 16 locations and several cooperating test Integrated disease management in­ centers in eight States where sorghum re- cludes cultural and chemical methods,

Table 2. Ergot severity! in high-yielding sorghum varieties, hybrids, and their seed parents in field screening at five locations1 during 1992-96. Culti:!lar 1992/93 1993/94 1994/95 1995/96 1996/97 Mean Va r i e tie s SPY 462 3.1 1.2 2.9 2.3 2.4 2.58 SPY 881 2.8 1.4 2.3 3.0 2.37 CSV 13 2.8 1.3 2.8 2.8 2.8 2.50 CSV 15 3.2 1.2 2.6 2.2 2.2 2.28 Mean 2.43

Hybrids CSH5 3.4 1.0 3.2 3.0 3.2 2.76 CSH9 3.5 2.2 4.2 2.2 3.2 3.06 CSH 14 3.2 2.2 3.3 2.7 3.1 2.90 Mean 2.91

Parents 296A 3.9 4.2 3.2 3.3 3.65 296B 2.8 3.1 3.2 3.9 3.1 3.22 RS29 2.7 2.0 2.7 3.2 2.8 2.68 AKR 150 3.0 2.5 2.8 2.7 2.5 2.70 AKMS14A 3.4 4.0 2.3 3.4 3.30 AKMS 14B 2.9 3.1 1.8 2.3 2.52 Mean 301

JMean of five locations. Disease severity scored on a 1-5 scale, where I = no disease, and 5 = maximum disease. 2Tbe locations were Dharwad, Coimbatore, Akola, Surat, and Palem.

51 biocontrol, and genetic resistance. The evaluation. Such studies should following practices are recommended in include the role of environmental India: factors in the production, spread, and survival of secondary conidia. • Early sowing to escape disease. • Better understanding of the effect • Synchronization of male and fe­ of environmental conditions, par­ male parents to ensure availability ticularly low temperature, on infec­ of ample viable pollen for effective tion and flowering biology and fertilization of A lines. their interactions. • Rouging of early infected panicles • A disease forecasting model based to reduce the sources of inoculum on environment and host parame­ for secondary spread. ters is required to predict the occur­ • Destruction of collateral hosts by rence of disease in seed production mechanical removal and weedicide plots. This will enable judicious sprays. and need-based use of fungicides. • Preventive sprays of fungicides are necessary. Host-Plant Resistance • Mechanical removal of ergot scle­ • Exploit the use ofrapid self pollina­ rotia by flotation of seeds in 10% tion under low temperature as a salt solution. means of escape resistance in male­ Research Needs fertile cultivars. There is a need to develop appropriate methodolo­ Though the biology of the pathogen gies to assess rapid self pollination. has been well studied, considerable gaps • Intensify search for resistance in male-steriles. remain in our understanding of the epide­ miology ofthe disease and the practicality References of ergot management strategies under field conditions. Some of the specific ar­ All India Coordinated Sorghum Improvement Pro­ ject (AICSIP). 1965-67. Progress Report of the eas that need attention are: All India Coordinated Sorghum Improvement Project, 1965-67. Indian Council of Agricul­ Biology tural Research and Cooperative Agencies, 125- 158. All India Coordinated Sorghum Improvement Pro­ • Studies on taxonomic features of a ject (AICSIP). 1969-70. Progress Report of the large number of isolates of the All India Coordinated Sorghum Improvement pathogen to determine if variation Project. 1969-70. Indian Council of Agricul­ exists at the species level. tural Research and Cooperative Agencies. 138- 146. Anonymous. 1977. Ergot disease in hybrid Jowar Epidemiology seed plots. Circular No.SCS-3277 (Hints)-D-2- AH-16, Dept. of Seed Certification, Directorate • Understand the sources of primary of Agriculture, M.S. ,Nov. 1977. inoculum and their relative rele­ Ajrekar, S. L. 1926. Observations on a disease of jowar (Sorghum vulgare) caused by Sphacelia vance to initiate the disease in the (conidial stage of Claviceps). Journal ofthe In­ field. dian Botanical Society 5:55-61. • The extent of pathogen spread by Anahosur, K. H. 1979. Chemical control of ergot of secondary conidia needs a critical sorghum. Indian Phytopathology 32:487-489.

52 Anahosur, K H., and Patil, H. S. 1982. Effect of House, L. R. 1980. A guide to Sorghum Breeding. date of sowing on the incidence of ergot of sor­ ICRISAT Patancheru, Andhra Pradesh, India. ghum. Indian Phytopathology 35:507-509. 233 pp. Bandyopadhyay, R., Mughogho, L. K., Manohar, Kalmegh, V. B., Mohammad Wassem., and S. K, and Satyanarayana, M. V. 1990. Stroma Borkar, P. A. 1994. Separation of sorghum scle­ development, honeydew formation, and conid­ rotia by belt drapper, P.K.V. Research Journal ial production in Clavieeps sorghi. Phytopa­ 18:193-194. thology 80:812-818. Khadke, V. D. 1975. Studies on sugary disease of Bandyopadhyay, R., Mughogho, L. K., and sorghum. M. Sc. thesis submitted to the MPKV, Sharma, H. C. 1991. Source of primary inocu­ Rahuri (M. S.), India. 71 pp. lum and spread of ergot. Pages 24-25 in Cereals Kulkarni, B. G. P., Seshadri, V. S., and Hegde, R. Program annual report 1990. Patancheru 502 K 1976. The perfect stage of Sphaeelia sorghi 324, Andhra Pradesh, India: International McRae. Mysore Journal ofAgricultural Science Crops Research Institute for the Semi-Arid 10:286-289. Tropics. Kulkarni, G. S. 1942. Ergot in India. Current Sci­ Bandyopadhyay, R. 1992. Sorghum ergot. Pages ence 11:246. 235-244 in Sorghum and millets diseases: a sec­ McRae, W. 1917. Notes on some south Indian ond world review. W.A.1. de Milliano, R.A. fungi. Pages 108-111 in Madras Agriculture Frederiksen, and G.D. Bengston (eds.) Yearbook. Patancheru 502 324, Andhra Pradesh, India: In­ More, B. B., Khadke, V. D., and Patil, P.Y. 1977. ternational Crops Research Institute for the Ergot on sugary disease of jowar caused by Semi-Arid Tropics. Sphaeelia sorghi McRae. Paper presented at Bandyopadhyay, R., Mughogho, L. K, and Te­ Plant Protection Symposium (Western Region) gegne, G. 1992. Role of pollination and inocula­ Aspee Agricultural Research and Development tion on ergot development in sorghum. Foundations Malad, Bombay, Feb 1977. Phytopathology 82:241 (Abstract). Mutkekar, M. L. and Madane, P. B. 1976. Occur­ Bandyopadhyay, R., and Reddy, B. V. S. 1991. rence of sphacelia stage on 'Pawna grass' (Se­ Identification of ergot resistance in hybrid par­ hima nervosum). Indian Phytopathology ents. Pages 25-26 in Cereals Program annual re­ 29:332-333. port 1990. Patancheru 502 324, Andhra Nagarajan, K, and Saraswathi, V. 1971. Effect of Pradesh, India: International Crops Research systemic fungicides on the sugary disease or­ Institute for the Semi-Arid Tropics. ganism. Sorghum Newsletter 14:41. Bandyopadhyay, R. Frederickson, D. E., Mclaren, Nath, P., and Padwick, G. W. 1941. Ergot in India N. W., and Odvody, G. N. 1996. Ergot, a global Current Science 10:488-489. threat to sorghum. International Sorghum and Neergard, P. 1977. Seed Pathology, Vol. I 1977. Millets Newsletter 37: 1-32. The Macmillan Press Ltd., Landon and Baring­ Chinnadurai, G., and Govindaswamy, C. V. 1971b. stoke Associate companies, New York, Dublin, Host range of sorghum sugary disease patho­ Melbourne, Johannesburg and Madras. 840 pp. gen. Madras Agricultural Journal 58:600-603. Pati], B. K, and Madane, N. P. 1979. New grami­ Chinnadurai, G., Govindaswamy, C. V., and Ra­ naceous hosts of Sphaeelia in nature. Indian makrishnan, K 1970a. Studies on the effect of Phytopathology 32(4):631-652. stigmatic exudates of sorghum on the parasit­ Patil, P. Y., Raut, N. K., and Deshpande, P. M. ism of Sphaeelia sorghi McRae, Phytopatholo­ 1968. A note on the occurrence of ergot; sugary gische Zeitschrift 69:56-61. disease on the hybrid jowar in Maharashtra Chopde P. R., Wanjari, K B., and Wadhokar, R. S. (Parbhani). College of Agricultural Parbhani 1973. Stigma receptivity in male sterile parents Magazine Vol. IV:93-94. ofPSH-2 (PMS -1036A) and CSH-3 (ms 2219 Paulson, I. W. 1969. Embryogeny and caryopsis A). Sorghum Newsletter 16:53-54. development of Sorghum hieolor (L.) Moench. Desai, K. B., Joshi, H.U., Kikani, B. K. and Crop Science 9:97-102. Rajkule, P. N. 1979. Effect of seeding date on Phadnaik, B. S., Sangitrao, C. S., and Moghe, P. G. sugary disease appearance. Sorghum Newslet­ 1994. Toxicity studies in sorghum ergot ter 22: 11 0-111. (Clavieeps sorghi) in mice. PKV Research FAO. 1996. Agrostat-PC, 1961-1994. Rome, Italy: Journal 18:240-242. FAO. Puranik, S. B., Padaganur, G. M., and Hiremath, R. Gangadharan, K, Subramanian, N., Kandaswamy, V. 1973. Susceptibility period of sorghum ova­ T. K, and Sundaram, N. V. 1976. Control of ries to Sphaeelia sorghi. Indian Phytopathology sugary disease of sorghum. Madras Agricul­ 26:586-587. tural Journal 63:411-413. Quinby, 1. R. 1958. Grain sorghum production in Texas. Texas Agricultural Experiment Station

53 Bulletin no. 912. College Station, Texas, USA: Journal of Maharashtra Agricultural University Texas A & M University. 17(3):495-496. Ramakrishnan, T. S. 1947. The natural occurrence Shekar, V. B., Jillani, S., and Wadhokar, R. S. of ergot in south India. Proceedings of the In­ 1981. Stigma receptivity studies in female of dian Academy of Science B 26: 136-14l. CSH-5 (2077A), CSH-9 (296 A). Unpublished Ramakrishnan, T. S. 1948. Ergot sclerotia on Sor­ data from Sorghum Breeding report, Sorghum ghum vulgare Pers. Current Science 17:218. Research Unit, PKV. Akola, India. Ramakrishnan, T. S. 1963. Disease of millet. In­ Singh, P. 1964. Sugary disease of sorghum. Pages dian Council of Agricultural Research, New 29-33 in progress report of the Accelerated Hy­ Delhi. 152 pp. brid Sorghum project and Millet Improvement Rama Sastri, D. V. 1973. Studies ofthe sugary dis­ Programme. New Delhi India. Indian Council ease of sorghum caused by Sphacelia sorghi of Agricultural Research. 81 pp. McRae. Ph.D. Thesis. Division of Mycology Sundaram, N. V. 1967. Sugary disease of sorghum. and Plant Pathology, Indian Agricultural Re­ Page 50 in Proceedings of the International search Institute, New Delhi, India. Symposium on Plant Pathology, New Delhi, Reddy, S., Subbaiah, 1., and Appa Rao, A. 1965. A Dec 27,1966 to Jan 1, 1967. note on the occurrence ofCerebella volkensii on Sundaram, N. V. 1969. Current plant pathological the sugary disease of Jowar. Andhra Agricul­ problems is new agricultural strategy with spe­ tural Journal 12(5):185-186. cial reference to sorghum and millets. Indian Reddy, K., Govindaswamy, C. V., and Vidhy­ Phytopathological Society Bulletin 5:62-72. asekaran, P. 1969. Studies on ergot disease of Sundaram, N. V. 1970. Sugary disease of sorghum. Cumbu (Pennisetum typhoides). Madras Agri­ Pages 435-439 in Plant Disease Problems: Pro­ culture Journal 56:367-377. ceedings of the first International Symposium Sangitrao, C. S. 1980. Possibilities of spread and on Plant Pathology (Raychoudhuri, S.P. et aI., perpetuation of sorghum ergot in India. A paper eds) New Delhi, India: Indian Phytopathologi­ presented in 67th Annual Meeting ofIndian Sci­ cal Society. ence Congress, Calcutta, Feb 1980. Sundaram, N. V. 1974. Natural occurrence of Sangitrao, C. S. 1982. Studies on ergot disease of Sphacelia sorghi on Pennisetum typhoids. In­ sorghum in Vidarbha. PhD Thesis, Punjabrao dian Phytopathology 27: 124-125. Krishi Vidyapeeth, Akola, India. 212 pp. Sundaram, N. V., Bhoumick, T. P., and Khan, I. D. Sangitrao, C. S., and Bade, G. H. 1979b. Morpho­ 1970. A New Host for Sphacelia sorghi. Indian logical studies of sclerotia of sorghum ergot. Phytopathology 23: 128-13l. Sorghum Newsletter 22: 1 08. Sundaram, N. V. 1976. Sorghum diseases and their Sangitrao, C. S., and Moghe, P. G. 1995. Triangu­ control. Pesticides Information Oct-Dec. 16-21. lar conidia of Sphacelia sorghi on grass weed Tarr, S. A. 1. 1962. Diseases of Sorghum, Sudan Dicanthium caricosum. Indian Phytopathology Grass and Broom Com. Kew, Surrey, UK: 48:490-492. Commonwealth Mycological Institute. Sangitrao, C. S., Taley, Y. M., and Moghe, P. C. Thomas, K.M., Ramakrishnan, T.S., and Shrini­ 1979. Effect of planting date on the appearance vasan, K. V. 1945. Natural occurrence of ergot of sugary disease. Sorghum Newsletter 22: Ill. in South India. Proceedings ofthe Indian Acad­ Sangitrao, C. S., Moghe P.G., and Ghoderao, B. N. emy of Science (B) 21 :93-100. 1992. Effects of pollination on sorghum ergot.

54 The Ergot Disease of Sorghum in Africa S. Z. Mukuru

Abstract

Sorghum is an important staple cereal crop in most countries ofAfrica. The crop is primarily cultivated by small scale resource poor farmers. Most ofthese farmers grow their local landraces. A total ofover 20 million hectares are under sorghum cultivation in Africa. Nigeria and Sudan are the major sorghum producers in Africa but sorghum is widely cultivated and a key food staple in large parts of the continent.

Sorghum in Africa is attacked by a va­ bella volkensii (syn C. sorghi vulgaris) riety of diseases including ergot but inci­ may overgrow the honey dew and convert dence and severity of anyone of the sor­ it into a sticky matted black mass. ghum diseases depends to a large extent (Mughogho 1988, Bandyopadhyay 1992, on climatic condition. Ergot caused by Sundaram 1980). Sphacelia sorghi has been observed on sorghum in many countries of Africa but Primary infection in the field is proba­ it is generally of low economic impor­ bly established by conidia from collateral tance. The disease affects individual flo­ hosts and infected panicle debris in soil. rets in a panicle causing poor develop­ The spread of the disease in the field is by ment or preventing grain development. conidia disseminated from panicle to This paper reviews the geographic distri­ panicle by insects, wind and rain splashes. bution and importance of ergot in Africa (Tarr 1962, Bandyopadhyay 1992). and discusses strategies for its control. Geographical Distribution and The Ergot Disease Importance of the Disease Symptoms and Cycle Ergot, also commonly known as honey The disease affects individual florets in dew or sugary disease has been observed a panicle causing grain yield reductions on sorghum in several countries of Africa because the infected florets do not pro­ where the crop flowers under cool wet cli­ duce grain. The disease is recognized by matic conditions. Ergot was observed and the presence of sticky pinkish to brownish reported on sorghum in Uganda and liquid drops that exude from infected ova­ Kenya in 1926, Tanzania in 1949, Repub­ ries. The drops, which contain masses of lic of South Africa in 1953 and Nigeria in conidia of the causal fungus, are sweet to 1956 (Tarr 1962). Ergot has since then taste and attract numerous insect which been observed in Sudan, Rwanda, Bu­ feed on them and spread the conidia to rundi, Malawi, Zambia, Mozambique, other florets. A saprophytic fungus Cere- Zimbabwe, Lesotho, and Botswana (de Milliano 1992, Mughogho 1988). In 1987 ergot epiphytotics occurred in Lesotho and Malawi (de Milliano 1992). Mengistu S.Z. Mukuru, Fonnally with: ICRlSAT Nairobi C/O ICRAF, United Nations Ave., Gigiri, P. o. Box 39063, Nairobi, Kenya and Gebrekidan (1980) reported that er-

55 got is relatively new in Ethiopia. It was Resistance to Ergot recognized in 1972 in experimental plots at Alemaya. Ergot was also reported to be In Ethiopia and Rwanda where ergot bothersome at Arsi Negele, Ethiopia. disease is regarded as a priority disease for research, a collaborative research pro­ Incidence and severity of ergot on sor­ gram between the national programs of ghum depends mostly on weather condi­ these countries and with SAFGRADIIC­ tions at the time of flowering. If days are RISAT in Nairobi and ICRISAT Center cool (minimum of 19°C ± 1°C), highly hu­ in India began in 1987. The objectives of mid and cloudy during the anthesis peri­ the collaborative research was to develop od, the spread of the disease is rapid and a resistance screening technique and iden­ damage can be severe (Sundaram 1980). tify sorghum germ plasm resistant to er­ The disease is more common on sorghum got. in medium and high altitude areas of east­ ern Africa. In Rwanda and Ethiopia ergot Screening Technique/or is regarded as a priority disease for re­ Ergot Resistance search and these countries have had a re­ search program on ergot. In Southern Af­ An effective and simple field technique rica, ergot is important in Zimbabwe and was developed and used by the national Botswana especially on tillers of late programs of Rwanda and Ethiopia (ICRI­ planted sorghums. The disease is of low SAT Annual Report 1989). The technique economic importance in West Africa. is as follows:

Ergot is, however, important in exotic • All spikelets that underwent anthe­ breeding material at research stations. sis prior to inoculation are removed Male steriles or plants with unfertilized from the panicles. florets are highly susceptible. We have • The remaining spikelets are sprayed with a conidial suspension frequently observed a high incidence of 6 1 (1 x 10 conidia ML- ) prepared ergot in male steriles and hybrids and from fresh honeydew. other exotic breeding material at Alupe, • Inoculated panicles are covered Western Kenya. with paper bags to enhance humid­ ity. Strategies for Controlling the Disease • Bags are removed 2 days after in­ oculation, panicles are reinoculated Several strategies for the control ofsor­ and rebagged. ghum ergot have been proposed. These • Bags are finally removed 7-10 days include sowing of cultivars resistant to er­ after first inoculation. got, cultural practices and use of fungi­ • Five panicles of each genotype are cides to control the disease. Sowing of re­ evaluated 24-25 days after first in­ sistant cultivars is regarded as the most oculation by counting infected practical, economical and effective spikelets in 100 spikelets born on method to control ergot (Bandyopadhyay primary branches. Ergot severity is 1992). recorded as the percentage of ergot­ infected florets.

56 Sources ofResistance to Ergot screened for ergot resistance at Arsi Ne­ gele (Bandyopadhyay 1980). Twenty The national programs of Ethiopia and seven accessions with less than 5% in­ Rwanda in collaboration with ICRISAT fected florets were selected. The selected carried out a major ergot resistance lines were screened at Arsi Negele for screening activity in 1987 and 1988 at three years and ergot resistance con­ "hot spot" locations in both countries. firmed in six lines (ETS 1446, ETS 2448, ETS 2465, ETS 3155, ETS 4457 andETS In Rwanda, 65 local varieties were 2113). screened at Rubona and Karama. Six lines IS 25535, IS 25549, IS 25550, IS 25553, Research on ergot in both these coun­ IS 26669 and Ikinyaruka were identified tries has since been abandoned due to to be resistant. In 1988, an additional 245 shortage offunds. Because ofthis, several genotypes collected from Ethiopia, lines that were initially identified as ha¥­ Rwanda, Yemen, Lesotho and Burundi ing good levels of ergot resistance have were screened at Karama and Rubona and not been confirmed and utilized in bree~ 34 lines that had up to 10% ergot infected ing. florets were selected for advanced screen­ ing (Table 1) (Musabyimana 1988). Other Control Strategies

In Ethiopia, 248 genotypes with inter­ Other ergot control strategies other mediate and highland adaptation were than resistance reported in the literature

Table 1. Origin and ergot reaction of selected l genotypes screened for ergot resistance in 1988 at Rubona, Rwanda. Sarghllm gl:naQ1pl: Origin °to infeC1l:d flarl:ts IS N° Origin o&, infectl:d flarets IS 25543 Rwanda 10 Yemen IS 25561 Rwanda 4 28994 YAR-I Yemen 3 IS 25565 Rwanda 4 29011 YAR-8 Yemen 5 IS 25584 Rwanda 5 29012 Y AR-19 Yemen 3 IS 25588 Rwanda 5 29013 YAR-20 Yemen 0 29089YAR-101 10 IS 25590 Rwanda 10 29381 PHM-25 Lesotho 10 IS 25591 Rwanda 3 29382 PHM-26 Lesotho 1 IS 25593 Rwanda 3 29404 PHM-48 Lesotho 1 29405 PMH-49 0 ET 2427 BG-15 Ethiopia 5 29407 PHM-51 Lesotho 0 ET 2787 BG-75 Ethiopia 10 29420 PHM-64 Lesotho 5 ET 2531 BG-120 Ethiopia 5 29438 PHM-83 Lesotho 3 ET2421 BG-9 Ethiopia 0 29446 PHM-91 Lesotho 7 ET 2467 BG-55 Ethiopia 10 ET 2413 BG-I Ethiopia 5 29421 PHM-65 Lesotho 0 29421 PHM-95 Lesotho 3 25485 PB-21 Burundi 7 ET 2440 BG-28 Ethiopia 6 25489 PB-27 Burundi 10 ET 2423 BG-19 Ethiopia ET 2443 BG-13 Ethiopia

I The selected genotypes had up to 10% ergot infected florets. Source: Musabyimana (1988).

57 include the following (Tarr 1962, Sunda­ References ram 1980). Bandyopadhyay, R. 1992. Sorghum ergot. Pages 235-244 in Sorghum and millets diseases: a • Identify suitable sowing dates in re­ second world review, W. A. J. de Milliano, R. lation to climatic conditions to A Frederiksen, and G. D. Bengstorn (eds.) Patancheru 502 324, Andhra Pradesh, India: In­ avoid ergot attack. ternational Crops Research Institute of the • Destruction of wild grasses espe­ Semi-Arid Tropics. cially perennials, which are collat­ de Milliano, W.AJ. 1992. Sorghum disease in eral hosts. Southern Mrica. Pages 9-19 in Sorghum and Millets diseases: a second world review, W. A • Rouging of ergot infected plant to J. de Milliano, R. A Frederiksen, and G. D. prevent spread in the field. Bengston (eds.) Patancheru 502 324, Andhra • Sowing of un infected seeds Pradesh, India: International Crops Research Institute of the Semi-Arid Tropics. • Crop rotation to avoid sowing sor­ I CRISAT (International Crops Research Institute ghum in fields which had an in­ for the Semi-Arid Tropics). 1990. Annual Re­ fected crop in the previous season. port 1989. Patancheru, AP. 502324, India: IC­ • Using fungicides to control the dis­ RISAT. Mengistu H. and Gebrekidan B. 1980. Diseases of ease. sorghum in Ethiopia. Pages 36-39 in Proceed­ ings ofthe International Workshop on Sorghum Conclusion Diseases, R. 1. Williams, R. A Frederiksen, and L. K. Mughogho, (eds.) 11-15 December 1978, Ergot on sorghum has been observed in Hyderabad, India. Mughogho, L.K., 1988. Opportunities for collabo­ several countries in Africa but is only of rative research on sorghum diseases in Eastern minor importance except in Ethiopia and Africa. Pages 151-171 in Proceedings of the Rwanda. However, most national re­ Sixth Regional Workshop on Sorghum and Mil­ let Improvement in Eastern Africa. 20-27 July, search programs in Africa have initiated 1988, Mogadishu, Somalia. Nairobi, Kenya: research to develop sorghum hybrids and SAFGRAD (Semi-Arid Food Grain Research and Development)IICRISAT (International it is expected that hybrids will become Crops Research Institute for the Semi-Arid popular with farmers in future. Tropics) Eastern Africa Regional Program. Musabyimana, T. 1988. ISAR-ICRISAT collabo­ Ergot is a serious limiting factor in pro­ rative projects on ergot and downy mildew of sorghum. Pages 197-200 in Proceedings of the duction of hybrid seeds, particularly if Sixth Regional Workshop on Sorghum and Mil­ fertilization in male steriles is delayed due let Improvement in Eastern Africa. 24-27 July, to lack of viable pollen caused by non 1988, Mogadishu, Somalia. Nairobi, Kenya: SAFGRAD (Semi-Arid Food Grain Research synchronous flowering of male steriles and Development)IICRISAT (International and restorers (Bandyopadhyay 1992). Er­ Crops Research Institute for the Semi-Arid Tropics) Eastern Africa Regional Program. got is therefore likely to become increas­ Sundaram N. V. 1980. Sorghum Ergot. Pages 377- ingly important as demand for hybrid 379 in Proceedings of the International Work­ seed increases. shop on Sorghum Diseases, R. J. Williams, R. A Frederiksen and L. K. Mughogho (eds.). 11- 15 December 1978, Hyderabad, India. It is essential that effective ergot con­ Tarr, S. A J. 1962. Diseases of Sorghum, Sudan trol methods should be developed and dis­ grass and broom corn. Commonwealth Myco­ logical Institute, Kerr, Surrey, U.K. Pages 190- seminated to farmers and seed companies 193. to ensure that high quality hybrid seeds free of ergot are produced.

58 Current and Future Research on Sorghum Ergot in Australia

Malcolm Ryley, Barry Blaney and Holger Meinke

Abstract

Research on sorghum ergot in Australia is being conducted in 3 major areas-toxicity, fungicide efficacy and climate risk analysis. The effects ofsclerotia of Claviceps afr;' cana (containing 0.1% dihydroergosine) on grazing cattle, andpigs and chickens in in­ tensive situations, have been studied. Cattle grazing on a standing sorghum crop with 0.3% sclerotia were not adversely affected, whereas pigs fed 5% sclerotia displayed rf? duced growth, and some chickens fed the same sclerotia concentration displayed diar­ rhoea and/or died. In a fungicide efficacy trial, triadimenol at 62 and 125 mL a. i. h(i and tebuconazole at 250 mL a. i. hdl provided very high levels ofprotection. A climatic risk analysis indicated that there was a higher probability ofergot infection at the begh­ ning and at the end ofthe Australian sorghum growing season (November-April) than in the middle ofthe season. The following research needs have been identified in Australia - toxicity studies on lotfed beef, development of fungicide spraying protocols, importance and control ofseedborne inoculum, taxonomy and genetic relationships of Claviceps on sorghum, and novel genes for resistance. Australia has the expertise and facilities to conduct much of this research, but there is considerable scope for fully collaborative international research.

Current Research purea (Fr.) Tul. and Clavicepsfusiformis Loveless. In Queensland only a single Toxicity Studies batch of sclerotia-contaminated sorghum grain has been obtained in sufficient It is generally considered that C. afri­ quantity for toxicity studies. Sclerotia cana is unlikely to be a major threatto ani­ from this crop had a morphology identical mal health, based on the work of Peter to C. africana and had an average alkaloid Mantle and his colleagues. Mantle and concentration of approximately 0.1 %. Waight (1968), and Frederickson et al. The primary alkaloid detected was chro­ (1991) demonstrated a relatively low tox­ matographically identical to DHES. icity of its major alkaloid component, di­ hydroergosine (DHES) to mice and rats A herd of 23 cattle (14 heifers and 9 compared to alkaloids of Claviceps pur- steers) was grazed for 28 days on this grain sorghum crop to assess the acute toxicity of sclerotia of C. africana. The

·Malcolm Ryley, Queeusland Department ofPrimruy Industries, crop was sampled before and after graz­ PO Box 102, Toowoomba, Queensland 4350, Australia; Barry ing for nutrient analysis, and the sclerotia Blauey, Animal Research Institute, Locked Mail Bag 4, Moorooka, Queensland 41 OS, Australia; Holger Meinke, APSRU, concentration in the average diet was esti­ PO Box 102, Toowoomba, Queensland 4350, Australia. ·Corre­ mated at 0.3% by weight. No clinical sponding author.

59 signs associated with ergot alkaloid po}. in growth overall compared to controls soning were observed during the trial. was slight. Diarrhoea is among the effects The animals grazed and exercised nor­ noted in cocks dosed with ergotamine and mally. Consumption offeed and nutrients related alkaloids, and gasping for breath was estimated as being above mainte­ has been reported in rodents given er­ nance, although insufficient for maxi­ go sine and related alkaloids. However, mum growth, and the animals maintained these effects have not been reported to oc­ liveweight. cur with dihydrogenated derivatives (Loewet aI. 1978). In fact, the general ef­ Several tons of contaminated grain fects of dihydrogenated alkaloids tend t~ were then harvested from the remaining wards behavioural depression. Although area of the same sorghum crop and a no clinical signs associated with effects sclerotia-rich fraction was separated from on the vascular system were observed, it the grain by flotation in a solution of 10% is noted that the dihydrogenated ergot al­ NaCh, then air dried. The concentration kaloids tend to lower body temperature in of sclerotia in a sub-sample of this frac­ rabbits, in contrast to the hyperthermia tion was determined by visual separation caused by their respective parent com­ and weighing. It was then incorporated pounds (Loew et al. 1978). In any case, into pig and meat chicken diets, which these broiler chickens were housed in were otherwise similar in nutrient con­ temperature-controlled sheds. tents. Total alkaloid intake of pigs fed the 5% Pigs averaging 20 kg liveweight were ergot was estimated to be approximately fed the equivalent ofup to 5% sclerotia for 50 mg day-I, or about 2.5 mg per 28 days in a growth trial. No significant liveweight kg day" I during the 28 day clinical abnormalities were observed. trial. The chickens fed 5% ergot would Slight impairment of performance (re­ have ingested a similar amount on a ductions in feed intake and poor feed con­ liveweight basis. These intakes ofDHES version) was observed over the first 7 appear low to account for the depressed days with diets containing more than performance observed. Manev, Pericic 0.6% sclerotia, and over the 28 day trial and Muck-SeIer (1989) found that single period growth was reduced by 30% in doses of 10 mg liveweight kg-I (intra­ pigs receiving 5% ergot sclerotia. peritoneal) inhibited fighting between mice, but we did not observe any behav­ Meat chickens were fed the equivalent ioural changes in our animals. of up to 5% sclerotia from 3 to 23 days of age. Diarrhoea was observed in up to 31 % Agalactica is one serious effect of ofthe birds fed 5% sclerotia, and mortal­ some alkaloids that our trials have not yet ity at this concentration was 21 %. In a few addressed, but Frederickson (in Bandyo­ cases, apparent gasping for breath pre­ padhyay et al. 1996) found that diets of ceded death. Growth of surviving birds 50% ergot sclerotia (15 mg alkaloid day" I, was reduced by about 8% compared to presumably about 500 mg live weight controls. Diarrhoea was also significant kg-I) had no effect on lactation in mice. in birds fed 2.5% sclerotia, but reduction

60 Although our results support previous were determined in a trial conducted near work showing that e. africana has a low Gatton, southern Queensland (Table 1). toxicity to livestock compared to other The A-line was planted in mid February, Claviceps species, they do not support the 1997 and watered by furrow irrigation proposition that it is harmless. The de­ when necessary. Plot size was 3 x 7 m pressed performances of pigs and chicken rows, 70 cm apart, with only the center fed with diets containing 5% sclerotia row being sprayed and rated, and there may be due to the presence oflow concen­ were 4 replicates. Fungicides were ap­ trations of alkaloids other than DHES in plied at 200 L water ha- I using a handheld the sclerotia. It might even be due to non­ boom, with one hollow cone Teejet® alkaloid components ofthe ergot. Modern TX4 nozzle above the row and two TX4 commercial breeds of pigs and chickens nozzles on droppers on either side of the are genetically selected for maximum row directed towards the panicles. Pres­ growth under ideal nutritional conditions, sure at 450 kPa was supplied by propane and may have a different order of suscep­ gas. The first spray was applied approxi­ tibilityto certain alkaloids than laboratory mately 5 days before first stigmas were animals. Investigations are underway to visible, and a further 6 applications were clarify some ofthese issues. As an interim made at 4 day intervals except for the last measure, Queensland has placed a limit of spray which was applied 6 days after the 0.3% for sclerotia ofe. africana in stock­ previous spray. The adjuvant Nufarm® feeds (as compared to 0.02% for other Spraymate Bond, a sticker/extender con­ Claviceps species). sisting of450 g L- 1 synthetic latex and 100 g L -I surfactant was added to the fungicide Fungicides solutions at 0.1 %. In each plot, % infected panicles was determined and the % spike­ The relative efficacies of 10 fungicide lets infected on each infected panicle was x concentration combinations for the con­ assessed on 2 occasions. trol of Claviceps africana on an A-line

Table 1. Efficacies of fungicides for control of Claviceps africana. Fungicide and active rate (mL or g ha-I

Triadimenol (125) o o o o Tebuconazole (250) 1.2 2.3 0.1 Triadimenol (62) 4.6 3.1 0.2 Mancozeb (1500) 18.6 58.9 2.6 -10 Fluazinam (500) 23.3 52.3 1.5 -5 Benomyl (1000) 34.7 58.9 0.9 -10 Fluazinam (250) 46.7 89.4 5.6 -70 Procymidone (250) 57.8 96.9 5.0 10-70 Untreated 58.0 96.5 7.4 10-80 Triademorph (300) 60.4 88.1 7.0 10-70

IMean rating for each treatment 2Range of ratings for each treatment

61 Triadimenol (Bayfidan®) at 125 mL tion between disease incidence and a.i. ha-1 was the best treatment, followed minimum daily temperatures <14°C bytebuconazole (Folicur®) at250 mL a.i. at microsporogenesis, approxi­ l l ha- and triadimenol at 62 mL a.i. ha- . The mately 21 days prior to anthesis. efficacies of these fungicides have been 2. Maximum daily temperatures reported previously (0. Odvody, unpub­ <27°C for at least 2 consecutive days lished data), and are now confirmed under at anthesis combined with at least 5 Australian conditions. The results of an­ mm ofrain during that period. A sig­ other trial conducted in southern nificant relationship between max~ Queensland suggests that triadimenol mum daily temperatures <27°C and may have eradicant properties. The pro­ ergot incidence was established by tectants mancozeb (Mancozeb®, Penn­ McLaren and Wehner (1992). The cozeb®) and benomyl (Benlate®) pro­ rainfall requirement assumes over­ vided reasonable control in the A-line and cast weather and a necessity for free may prove to be particularly useful in moisture on stigmas for infection by commercial seed production blocks to re­ conidia. duce costs. The threat of strains ofC afri­ cana resistant to the DMI fungicides de­ 3. A minimum of3 80 thermal units (ac­ veloping after repeated applications of cumulated daily average tempera­ fungicides such as triadimenol and tebu­ ture) and a maximum of 510 thermal conazole must be averted by the use of units separating periods 1 and 2 other fungicides in alternating blocks. (Hammer and Muchow, 1994). 4. Anthesis occurring between 15 Oc­ Climatic Analysis tober and 1 May, except for Kunun­ urra, Western Australia (1 June-15 In response to considerable grower and September). industry concern after the outbreak of er­ got in southern Queensland, a climatic A similar analysis was conducted for risk analysis was conducted to assess the. hybrid seed production, using only rules 2 likely timing and frequencies of further and 4, and assumed <100% pollination. outbreaks ofthe disease on grain sorghum Multiple events can occur in each season across the main growing areas in Austra­ and are accounted for in the analysis. To lia (Meinke and Ryley 1997). The follow­ analyse the frequency distribution and ing set of rules, based on published re­ timing of events the flowering window search results and other information, was was split into 10-day intervals and the used to interrogate long term weather data number of events within each 10-day in­ (1960-1990) for 10 localities. terval was accumulated over the 30 year period. 1. Minimum daily temperature <14°C for at least 3 consecutive days, 14-21 For grain sorghum production a bimo­ days before anthesis. This rule was dal distribution was apparent at most lo­ based on the results of McLaren and cations, showing a high probability of in­ Wehner (1990) who established a fection events occurring at the beginning highly significant positive correIa-

62 and at the end of the growing season in Centres (CRCs), and private companies Australia. Based on this analysis, the risk (including seed companies). of ergot infection when the vast majority ofgrain sorghum is flowering in Australia As in other countries, governments are (January-March) is low. In October, 1996 turning towards agriculture industries to ergot was found on grain sorghum ratoon pay for research undertaken in their inter­ crops in central Queensland, confirming est. Consequently, while government this prediction; however ratoon cropping maintains much of the research infra­ is not a common practice in Australia. structure, most of the operational funding Sorghum crops (particularly tillers) flo~ for agricultural research is sourced from ering late in the season when tempera­ industry-funded agencies such as Grains tures are lower are at a high risk from in­ Research and Development Corporation fection, as experienced in the 1995-96 (GRDC) and Rural Industry Research and and 1996-97 seasons. A general north­ Development Corporation (RIRDC). south, as well as a west-east, gradient was Growers pay a production levy into these apparent, whereby the number of events agencies which is matched on a $ for $ by late in the season increased for locations the Commonwealth government. Alloca­ further south and further east. The tempo­ tion of funds for research is on a competi­ ral and geographic risk patterns for hybrid tive basis. CSIRO is a Commonwealth­ seed production (and on forage sorghum) funded research organisation, whose agri­ followed the same trend, but the numbers cultural research budget is derived mainly of events were greater than for grain pro­ from the external agencies such as duction. The analysis predicted the likeli­ GRDC. Universities have a duel role of hood of ergot infection at Narromine, teaching and research, with funding for central New South Wales (a seed produc­ the latter coming from external sources tion area) in mid season - C. africana was and from within the University system. first reported in that area in February, The Cooperative Research Centre con­ 1997. There is an extremely low probabil­ cept was designed by the Commonwealth ity of sorghum ergot at Kununurra, where Government to enable researchers with a winter hybrid seed production and parent common interest from different organiza­ seed production is conducted. tions (both public and private sector) to conduct research. Funding for CRCs is on Future Research a competitive basis, and there are inputs of staff and facilities from the contribut­ Research Agencies and Funding ing organizations. Funding for research within these Centres is derived from the Agricultural research in Australia is CRCs and from external funding agen­ conducted by state departments of agri­ cies. The Cooperative Research Centre culture, [such as the Queensland Depart­ for Tropical Plant Pathology (CRCTPP) ment of Primary Industries (QDPI)], Uni­ at the University of Queensland, is a part­ versities, CSIRO (Commonwealth Scien­ nership between the University of tific and Industrial Research Queensland, QDPI, CSIRO, Bureau of Organisation), Cooperative Research Sugar Experimental Stations and the Queensland University of Technology.

63 The CRCTPP has a major interest in mo­ Lotfed beef is a very valuable export for lecular biology, including molecular­ Australia, and considerable interest in the based pathogen identification, genetic en­ potential effects of sclerotia­ gineering for disease resistance, and the contaminated grain on lotfed cattle has genetics of host-parasite interactions. been generated. Large scale trials will be conducted in the near future to study these Research Needs effects. To our knowledge, similar field studies have not been conducted else­ In Australia we have identified a where; in the past the effects ofergot alka­ number of areas of research on sorghum loids have been determined on ergot which we believe are essential for laboratory-bred animals. the development of effective manage­ ment strategies for the commercial grain Fungicides industry and for the seed industry. There is considerable expertise in Australia to Although trials conducted overseas, conduct critical studies in most of these particularly in Brazil, and more recently areas. Undoubtedly, some generic work in Australia have identified effective fun­ can be conducted elsewhere, and in addi­ gicides for application in seed production tion there is considerable scope for col­ blocks and in nurseries at flowering, there laborative research with other researchers is a critical need for further research in a overseas. However, some areas of re­ number of areas. Firstly, the fungicides search, particularly those involving tax­ found to be most effective (triadimenol, onomy, fungicide efficacy for registration tebuconazole and propiconazole) belong purposes and epidemiology will need to in the dimethylation inhibitor group be conducted in Australia. (DMI), and there is a risk that the repeated applications necessary in seed production Toxicity Studies blocks and nurseries could lead to the de­ velopment of fungicide-resistant isolates. Studies on the toxicity of sclerotia of Effective fungicides from other groups C. africana to grazing cattle, and to pigs must be identified to enable a fungicide and poultry in intensive situations are be­ rotation strategy to be developed. In- par­ ing conducted in DPI in response to con­ ticular, fungicides with eradicant activity siderable grower concern by a team ofsci­ or residual activity would be particularly entists led by BJ. Blaney. The team in­ useful. Our trials indicated that the pro­ cludes J.S. Kopinski, R.A. McKenzie, tectant fungicide mancozeb may have a P.F. Mannion, P.R. Martin, K.G. role to play in such a strategy. We do not Reichmann and R. Maryam, ably sup­ have the resources in Australia to conduct ported by a number of colleagues. large-scale fungicide screening trials and will have to rely on overseas workers to Protocols for the extraction of alka­ identify effective fungicides. However, loids have been set up, and the alkaloid efficacy trials will still have to be con­ profiles of collections of sorghum ergot ducted on candidate fungicides for regis­ sclerotia from throughout Queensland are tration purposes. Appropriate application being compared to assess their variability. techniques, especially for aerial spraying

64 will also need to be developed. Australia Hammer (1995) used a similar approach has a small role to play in this area, and we to quantify possible yield losses due to believe that a process for the exchange of rain at harvest for the Australian peanut information on fungicides will greatly a!r industry. Further, a simulation approach sist in the development of effective fungi­ would allow the integration of recent ad­ cide protocols. vances in long-range weather forecasting (Stone et al. 1996) to develop a probabil­ Effective fungicides are needed for the istic forecasting system with a minimum control of sclerotia and conidia in honey­ lead-time of 3 months (Meinke et al. dew in infested seed lots, but before this is 1996; Meinke and Hammer 1997). This done the relative importance of these would give the industry and producers an sources of inoculum in initiating epidem­ indication oflikely production risks either ics needs to be established. In addition, prior to, or shortly after, sowing a crop, the roles that alternative hosts, volunteer thus allowing strategic adjustments to sorghum and fallen infected heads which their operations. GRDC and CRCTPP survive from one season to the next, play have provided short-term funding to Drs. in the survival of sorghum ergot must be Holger Meinke and Malcolm Ryley to de­ studied. We are planning to conduct re­ velop such models. search into some ofthese areas, in particu­ lar the survival of conidia in seed lots and Taxonomy and Genetic Relationships their control with fungicides, and the im­ within Claviceps Species on Sorghum portance of sclerotia in the biology of the pathogen. As pointed out in a previous paper in this Conference (Sorghum Ergot in Aus­ Climatic Analysis tralia) some collections in Australia dif fered in critical morphological character­ Many of the parameter values used in istics to C. africana. It is possible that the analysis outlined previously in this pa­ there is more than 1 species of Claviceps per are not very well defined and it is on sorghum in Australia, or that there is therefore paramount to closely monitor considerable morphological and/or ge­ the critical environmental and host factors netic variation in C. africana. Studies on associated with ergot epidemics (Meinke the morphology and development of the and Ryley 1997). Such monitoring will anamorphs and teleomorphs of a range of provide the necessary benchmark data to collections from throughout Australia enable a better quantification of the di!r could be supplemented by comparing ease risk. A more thorough analysis could their alkaloid profiles, and by conducting be conducted using dynamic simulation RFLP analyses. A knowledge of the ge­ models ( ego Hammer and Muchow 1994) netic variation within the Claviceps spe­ combined with the rule-based system out­ cies on sorghum and their relationship to lined in this study. This would integrate virulence is essential if novel sources of our physiological understanding of sor­ resistance are to be effective. RFLP ghum growth and development, and the analysis of populations over time may interactions between disease outbreaks also assist in determining the role that and environmental factors. Meinke and sexual reproduction plays in the life cycle

65 of species. There is also scope to study the ment and assessment of such genotypes is genetic relationships between popula­ considerable and may require the sharing tions in Australia and in nearby Southeast of resources and technology. However, Asian countries. The CRCTPP has the ex­ issues of patents and intellectual property pertise and resources to conduct such are likely to impede this exchange. studies. International Collaboration Host Plant Resistance to C. africana There is considerable scope for a fully According to published literature, collaborative international effort to con­ there are no sources of effective resis­ duct research on many areas of the biol­ tance in Sorghum bicolor. However, there ogy and management of sorghum ergot. is considerable variation for pollen pro­ The success of such an approach depends duction, particularly under cool condi­ on the willingness of major research or­ tions, in species. Breeders can therefore ganisations in each country to cooperate, have a significant impact on the disease in and on the free exchange of results and commercial lines. sorghum germplasm. Specific research in each country should be concentrated in The problem of susceptibility of A­ areas where there is the expertise and fa­ lines remains. Novel genes for resistance cilities. However, aspects of intellectual offer some hope. Antifungal proteins property, patents and plant variety rights (AFPs) which inhibit germination and/or may impact on the effectiveness of inter­ growth of a pathogen have been identified national collaboration. by a number of research centres, includ­ ing the CRCTPP. Researchers at this cen­ Acknowledgments tre have a number of AFPs derived from Australian native flora which have activ­ The authors wish to thank staff of ity against ubiquitous pathogens such as QDPI and APSRU for their assistance in Sclerotinia sclerotiorum (Lib.) de Bary the research on toxicity studies and in the and Sclerotium rolfsii Sacco We have ob­ climatic risk analysis, and staff of Pacific tained funding from GRDC to conduct a Seeds/A vanta, in particular M. Whiting preliminary screening of these AFPs for and D. Weier, for applying fungicides and activity towards isolates ofe. africana. If maintaining the fungicide efficacy trial. one or more ofthese AFPs is shown to be effective considerable research will still References be needed before resistant genotypes are Bandyopadyay, R., Frederickson, D. E., McLaren, developed. The AFPs must be tested for N. W., and Odvody, G. N. 1996. Ergot, a global their effects on pollen germination and threat to sorghum. International Sorghum and Millets Newsletter 37:1-32. pollen tube growth, genes which encode Frederickson, D. E., Mantle, P. G., and de Milliano, the AFPs must be identified and cloned, W. A. 1. 1991. Claviceps africana sp. nov., the the genes must be expressed in transgenic distinctive ergot pathogen of sorghum in Africa. Mycological Research 95:1101-1107. plants, and there will be a need to pyramid Hammer, G. 1., and Muchow, R. C. 1994. Assess­ different genes to ensure that the resis­ ing climatic risk to sorghum production in tance is durable. The costs of develop- water-limited subtropical environments. I. De-

66 velopment and testing of a simulation model. cana). Journal of Phytopathology 133:328- Field Crop Research 36:221-34. 334. Leow, D. M., van Deusen, E. B., and Meier-Ruge, Meinke, H., and Hammer, G. L. 1995. Cliamtic risk W. 1978. Effects on the central nervous system. to peanut produion: a simulation study for Pages 421-531 in Ergot alkaloids and related northern Australia. Australian Journal of Ex­ compounds. B. Beredand and H.O.Schild perimental Agriculture 35:777-780. (eds.). Berlin, Heidelberg, New York: Springer­ Meinke, H., and Hammer, G. L. 1997. Forecasting Verlag. regional crop production using SOl phases: a Manev, H., Pericic, D., and Muck-SeIer, D. 1989. case study for the Australian peanut industry. Inhibitory influence of dihydroergosine on the Australian Journal of Experimental Agriculture aggression of rats and mice. Pharmacology, 48:in press. Biochemistry, and Behavior 32:111-15. Meinke, H., and Ryley, M. 1997. Effects of sor­ Mantle, P. G., and Waight, E. S. 1986. Dihydroer­ ghum ergot on sorghum production - a prelimi­ gosine: a new naturally occuring alkaloid from nary climatic analysis. Australian Journal of the scelrotia ofSphacelica sorghi (McRae). Na­ Experimental Agriculture 48:in press. ture 218:581-582. Meinke, H. Stone, R. C., and Hammer, G. L. 1996. McLaren, N. W., and Wehner, F. C. 1990. Rela­ Using SOl phases to forecast climatic risk to tionship between climatic variables during peanut production: a case study for northern early flowering of sorghum and the incidence of Austalia. International Journal of Climatology sugary disease caused by Sphacelica sorghi. 16:783-89. Journal of Phytopathology 130:82-88. Stone, R.C., Hammer, G.L., and Marcussen, T. McLaren, N. W., and Wehner, F. C. 1992. Pre­ 1996. Predicton of global rainfall pribabilities flowering low temperature predisposition of using phases of the Southern Oscillation Index. sorghum to sugary disease (C/aviceps afri- Nature384:252-255.

67 Sorghum Ergot in the United States - Public Sector Response G. N. Odvody and T. Isakeit

Abstract

Spread of sorghum ergot (C/aviceps africana) to the United States was confirmed with its late March 1997 observation on sorghum regrowth ofabandoned commercial grain sorghumfields in the Rio Grande Valley (RGV) of Texas adjacent to the border with Mexico. The pathogen was subsequently observed on grain sorghum regrowth and onjohnsongrass (Sorghum haJepense) proximal to thesefields and it continued to in­ crea~e on these hosts during persistent cooler and wetter than normal conditions. By mid-May ergot was observed on the current grain sorghum crop (trace to 10% inci­ dence, minimal severity) and had reached the northern limits ofthe RG V which is sepa­ ratedfrom the next major sorghum growing Coastal Bend by 80 km ofrangeland Ergot is anticipated to eventually spread throughout Texas and threaten the 114, 000 ha (qua,.. ter million acres) sorghum hybrid seedproduction industry on the High Plains ofTexas. Spread throughout all sorghum growing regions ofthe United States is also anticipated but with minimal impact on commercial grain sorghum production except for possible cool temperature pollen sterility in northern production areas. This increased ergot sus­ ceptibility could similarly affect winter nurseries in Southern regions and increase eIgot incidence onferal sorghum hosts includingjohnsongrass. Chemical control ofergot on seed and in hybrid production fields is being pursued with extensive collaboration be­ tween public researchers, governmental regulatory agencies, commodity groups, and private companies. Collaboration is both national and international in scope.

In 1996 grain sorghum [Sorghum bi­ (Figure 1). More importantly, sorghum color (L.) Moench] production was a $2.2 ergot, Claviceps africana Frederickson, billion dollar (U.S.) industry in the United Mantle, & de Milliano (Frederickson et States (National Grain Sorghum Produc­ al. 1991), threatens the 114, 000 hectares ers Association, NGSPA, Abernathy, (quarter million acres) devoted to hybrid TX). Most ofthe 20.4 metric tons (4.5 bil­ seed production on the High Plains of lion lbs) ofgrain produced was consumed Texas (Figure 1). This production repre­ domestically and 30% went to the export sents about 35% of the hybrid seed pro­ market with Mexico as the largest im­ duced in the world and 90% of that pro­ porter. The main U.S. production areas duced in the United States. Sorghum er­ are several states in the middle of the got represents a serious threat to the entire country in a region called the Great Plains sorghum industry because ofthe extreme vulnerability of male-steriles to C. afri­ cana. Commercial grain sorghum pro­ duction itself may have little direct dam­ ·G.N. Odvody, Texas A&M Research and Extension Center, Rt. 2 age from ergot due to its high self-fertility Box 589, Corpus Christi, TX 7841 0; T. Isakeit, Dept. of Plant Pa­ but all producers will be affected if con­ thology and Microbiology, Texas A & M University, College Sta­ tion, TX 77843. 'Corresponding author. trol ofergot forces higher seed production

68 11 ,394 x 1000 acres harvested for grain in 1996. Amount shown by state x 1000 acres~

_ Highest Risk: Hybrid Production _155to225 490 to 4,600 Ii:!:!!!!!:!:!:!:~ 5 to 72

Figure 1. Sorghum production areas in the United States potentially vulnerable to sorghum ergot. costs that must be passed on to the con­ prevent or slow the spread of ergot in the sumer. There is the possibility that ergot Western Hemisphere and provide for rap­ could also reduce the availability and idly implementable controls once the quality of seed. pathogen spread to new geographic areas including the U.S. Issues concerning need Concern about the eventual introduc­ for and efficacy of seed import quaran­ tion or spread of ergot to the United States tines and other public policy concerning began with the initial reports of ergot in ergot were not fully resolved before the Brazil in 1995 (Ferreira and Casela 1995, advent of Claviceps ajricana at the South­ Reis et al. 1996). In 1996 with continued ern border of Texas with Mexico in late spread across the Western Hemisphere March 1997. The rapid spread of ergot to and elsewhere, global research collabora­ the U. S. was anticipated since its initial tion was sought by U.S. scientists with observation in Mexico in late February scientists having both an extensive and 1997. The mode ofintroduction ofe. ajri­ developing experience with ergot in vari­ cana into the U.S. is unknown but the ous countries around the world. The hope pathogen probably spread across the bor­ was that participation in development of der as aerial conidia. ergot controls in other countries would

69 Initial Observation and Spread Texas and Northern Mexico where many of the same hybrids are grown. Reasons The first report of ergot on sorghum in for higher vulnerability to ergot in these the United States was on ratooned and hybrids is unknown but probably involves volunteer sorghum (plants established some factors related to incomplete fertil­ from F2 seed that remained in the field ity or delayed fertilization under the wet, from the harvested crop) in a field adja­ rainy conditions. The diversity of plant­ cent to the Rio Grande River near Pro­ ing dates in the RGV and elsewhere gresso, Texas on March 26, 1997. The er­ across South Texas also assures that the got was subsequently identified on simi­ ergot infection in the primary crop will lar sorghum in abandoned fields and in provide inoculum for spread to later­ johnsongrass [Sorghum halepense (L.) blooming heads and fields if conditions Pers.] at several sites in the Rio Grande remain favorable for infection. Valley (RGV) near the southernmost tip ofthe state. Full identification ofthe ergot Incidence of ergot in johnsongrass also pathogen has not been completed but it is increased from initial early April observa­ almost surely C. africana because this is tions but the disease appeared to occur the only species spreading across the primarily in subpopulations that may Western Hemisphere on sorghum and its have had some infertility that contributed characteristics are consistent with this to a higher incidence of ergot. Often only species. a small rhizomatous clump of related til­ lers ofjohnsongrass would have a high in­ From those initial observations the er­ cidence of ergot and other nearby john­ got has continued to increase on later songrass at the same maturity would have blooming (May) sorghum tillers at the almost no visible ergot infection. These same locations. By mid-May ergot began observations are consistent with reports to be observed in several commercial that some johnsongrass populations are grain sorghum fields just completing essentially sterile. To date, ergot in john­ bloom in the RGV. Incidence ranged songrass has only been observed near its from a trace to 2 to 10 % of the heads and occurrence on commercial grain sor­ severity was generally at one to a few flo­ ghum. rets infected per head but a few self-fertile sorghum heads had 35 to 50% of the flo­ By the end of May 1997 the northern rets infected. The cooler than normal tem­ limit of sorghum ergot in the U.S. and peratures and continued high rainfall and Texas was in commercial sorghum pro­ high humidity during flowering and polli­ duction fields at the northern edge of the nation are thought to have contributed to RGV near Raymondville. Natural spread the higher than expected amount of ergot of the pathogen by aerial inoculum would seen in the self-fertile commercial sor­ require crossing an 80 km region of the ghum crop of the RGV. There are appar­ King Ranch to the North before contact­ ent differences in susceptibility to ergot ing sorghum production fields again near among commercially-available grain sor­ Riviera, Texas. ghum hybrids that is only now becoming apparent in field observations in South

70 Potential for Ergot by Climate and vest and, under continued wet conditions, Geographical Location in the United it supports growth of saprophytic fungi. States Endemic Nature of Sorghum A greater knowledge of the biology Ergot in the United States and epidemiology of C. afrieana is needed, especially concerning aerial Once ergot is established in the U. S., it spread and seed dissemination of inocu­ will probably become endemic in feral lum, and survival ofthe pathogen on seed, johnsongrass which is present throughout and in soil and on alternate hosts in nature. most of the Great Plains sorghum produc­ As in most other affected countries there ing states but its highest populations oc­ are questions about how the variable envi­ cur in Texas and other states across the ronments and climates across diverse sor­ Southern U.S. The potential role that ghum production areas will affect inci­ johnsongrass may have in the survival dence and severity of C. afrieana on both and spread of C. afrieana is further in­ cultivated and feral sorghum and other creased by the probability of cool tem­ hosts. The impact of sorghum ergot in the perature sterility increasing ergot inci­ U. S. will probably be determined by the dence on this host in the more Southern differential susceptibility that exists in the regions of the U.S., especially if a killing types of sorghum being grown and by en­ frost is delayed or does not occur. The dif­ vironments present during time-critical ferential susceptibility that may exist in phases of their floral development and johnsongrass populations even under during bloom when infection actually oc­ warmer environments could also be an curs. Commercial grain sorghum hybrids important factor affecting the endemic across most of the u.s. will likely sustain nature of ergot in the United States. The little damage from ergot through their initial observation of ergot on surviving self-fertility that provides an escape type ratooned and volunteer sorghum despite of resistance. However, pollen sterility killing frosts in extreme South Texas indi­ associated with cool temperatures in cate an even greater risk of ergot increase some sorghum production regions in the and survival in winter months when frosts Northern Plains or winter production in are marginal in their intensity or they do Southern regions could increase the risk not occur. Early season growth of john­ of ergot in any sorghum crop (McLaren songrass at Southern locations may also and Wehner 1992). Forage sorghums rep­ increase the likelihood of initial inoculum resent an increased ergot risk but sterile and pathogen increase prior to the com­ forage hybrids are likely to sustain the mercial crop reaching the bloom stage. greatest damage from ergot because they Shattercane, a feral weedy grain sorghum have no pollen source and tillering pro­ (s. hieolor) more common in the North­ vides a succession of sorghum flowers for ern sorghum growing regions of Kansas rapid cycling of the disease. While seed and Nebraska, needs to be investigated production is not of importance in these for possible contribution to long term sur­ latter forages the high incidence of ergot vival and establishment of C. afrieana in would produce tremendous amounts of this region. honeydew that could interfere with har-

71 Concern about Spread of C. africana eas and by their generally higher suscepti­ by other than Natural Means bility than commercial grain sorghum hybrids. These sorghums usually have a Ergot may naturally spread rapidly by higher incidence of ergot that is related to aerial conidia but there may also be inad­ their incomplete fertility which can vary vertent man-derived dissemination across highly between different hybrids and va­ more vast regional areas through various rieties. The sterile sorghum-sudan hy­ other means. These may include planting brids are extremely susceptible to ergot ergot-contaminated seed in non-ergot ar­ because they have no intended pollen eas, or the transport of ergot­ source and they are constantly producing contaminated seed, other crop materials, tillers of susceptible inflorescences. equipment, or wearing apparel to or Timely harvest offorages before heading through non-ergot areas. These and other would minimize this risk. Sclerotial pro­ potential sources of introduction require duction requires a extended time period consideration to determine their actual (Bandyopadhyay et al. 1996) so only for­ risk and the feasibility of making any ap­ age remaining in the field long after ma­ propriate response through sanitation, ex­ turity would appear to be a sclerotial risk. clusion or other methods. Under wet conditions saprophytic fungal growth and colonization of sphacelia by Ergot-contaminated seed from com­ Cerebella reduce the production of sclero­ mercial grain sorghum production might tia but raise questions about toxicity be­ potentially introduce inoculum ofe. afri­ yond that of ergot-derived tissues them­ cana during its transport to and through selves. The survival of conidia in dried areas where ergot has not yet been ob­ honeydew on forage sorghum heads and served. In March 1997, near Tampico, other plant tissues would probably be Mexico, ergot was common on plants es­ maximized if cutting, drying and baling tablished along the roadsides from har­ of the forage occurs soon after infection vested seed, which had fallen from grain has occurred but prior to saprophytic transport equipment or trucks. An addi­ colonization. Bales from such fields at tional concern is for the possibility of least theoretically might pose the greatest pathogen introduction through honeydew risk of introduction into new areas. John­ or sclerotia which may remain in harvest songrass as a primary component or con­ equipment that progressively moves into taminant in hay bales may also function in non-ergot regions to the North as the crop the same regard. matures for harvest. In the latter case, in­ troduction of ergot might not be readily Industry Response and Domestic and apparent until the next cropping season. International Research

The popularity of sudan grass or sor­ Collaborative research and other coop­ ghum x sudan grass hybrids (both sterile erative initiatives between various U.S. and self-fertile) planted for forage or hay seed industry organizations, regulatory across the Great Plains and Southern agencies, and public institutions from the states further increases the risk of ergot U.S. and other countries will enhance the spread both by introduction into new ar- ability of participant countries in deter-

72 mining mutually beneficial control ap­ reduce spread of ergot to non-ergot areas proaches for sorghum ergot. Examples in­ and provide for appropriate controls in clude formal collaboration like Texas current and potential areas of distribution. A&M with INIFAP of Mexico and EM­ The committee will address various do­ BRAPAlCNPMS of Brazil, and INT­ mestic and international issues concern­ SORMIL projects with ergot research and ing seed distribution policies and regula­ control objectives. However, informal tions and the production, processing, collaborative linkages among public and quality and treatment of seed from ergot private sorghum researchers across the areas,. The committee will also promote sorghum producing states have been es­ research and other efforts to (1) develop tablished to provide for rapid communi­ fungicide controls for ergot in hybrid pro­ cation and information exchange regard­ duction fields and for use as seed treat­ ing the most current status of ergot distri­ ments, (2) identify and develop host plant bution and the results ofresearch. Several resistance, (3) identify and recommend state universities and organizations in­ feasible cultural and other alternative cluding the National Grain Sorghum Pro­ controls, (4) identify and develop recom­ ducers Association, State sorghum mendations for the special needs associ­ boards, the American and Texas Seed ated with maintenance ofprivate and pub­ Trade Associations, the Texas Depart­ lic sorghum research programs and sea­ ment of Agriculture, and various compo­ sonal nurseries in ergot regions, and (5) nents of the VSDA have also been at the promote industry education about ergot. forefront of ergot awareness and educa­ tion efforts that have both national and in­ Of these goals, education of the indus­ ternational implications. This communi­ try, the producer, and the general public cation effort is also reflected in a similar concerning sorghum ergot is probably the global exchange of ergot information and most important initial objective. Commu­ research data concerning sorghum ergot. nicating knowledge about ergot sympto­ Computer access to e-mail and postings matology, biology, epidemiology, rela­ on World Wide Web sites has greatly en­ tive economic threat, toxicity, and other hanced the effectiveness ofthe communi­ relevant ergot issues will be a continuous cation process because of its ability to process undertaken by various public and contact a wide audience rapidly and eco­ private sorghum workers across the V.S. nomically. The ability to share digital im­ ages as well as text in this manner has A primary immediate benefit will be greatly aided education efforts concern­ the ability to more accurately and rapidly ing sorghum ergot which was largely un­ determine the current distribution and recognized by sorghum workers in the spread of ergot throughout the V.S. Ster­ Western Hemisphere prior to 1995. ile sorghum x sudangrass hybrids and other highly susceptible sorghums are be­ An ad hoc committee of the American ing used as indicator or trap crops across Seed Trade Association is gathering all large areas of the V.S. sorghum growing relevant data about the biology, epidemi­ region to facilitate detection and docu­ ology, and control ofC. africanato deter­ mentation of the spread of ergot through mine V.S. industry strategies to prevent or the region. Information about ergot from

73 informed, knowledgeable sorghum work­ commercial companies to determine the ers will provide for a more timely re­ most appropriate time of initial fungicide sponse by the industry, regulatory agen­ application and the best balance of water cies and public researchers and reduce content and pressure to maximize fungi­ time-consuming diagnostic errors. Edu­ cide coverage and penetration of the head cation will also promote a more stable, for aerial application. Other triazole fun­ reasoned response to the threat of ergot by gicides are also being evaluat~~ for ef!"I­ cacy in control of ergot. FungICIdes WIth minimizing the prospect of either an over other modes of action are also being reaction to the threat of ergot or an equally evaluated so that fungicide application unwise dismissal of its potential eco­ schemes might be devised to reduce the nomic impact on sorghum. risk of selecting fungicide tolerant strains ofe. africana. The majority of the hybrid Chemical Control of Ergot seed production areas are planted during in Hybrid Seed Production Fields May on the High Plains of Texas. Fungi­ cide control results from small research One ofthe more immediate concerns of plots in the RGV and from commercial the U.S. sorghum industry is the develop­ hybrid production fields in the RGV and ment of chemical control methodology international locations including North­ that will provide for near 100% control of ern Mexico are hoped to provide the in­ ergot in hybrid seed production fields. formation base for an effective aerial ap­ Chemical controls are being pursued plication chemical control methodology based on the methodologies successfully for the High Plains production region if utilized in Brazil (Ferreira et al. 1996) needed. where triazole fungicides were applied to sorghum heads at strategic intervals be­ Chemical Seed Treatments ginning at initiation of bloom. The U.S. industry will largely depend on aerial ap­ Although not empirically proven, ergot plication of the fungicides. The efficacy contaminated seed planted in another re­ of aerial applications versus the more ac­ gion has the potential to introduce e. afri­ cana either from honeydew-encrusted curate ground equipment applications are seed or as sclerotia. Encrusted seed could currently being evaluated on hybrid pro­ provide aerial inoculum for susceptible duction fields in Northern Mexico and hosts if it remains on a moist soil surface South Texas. and sclerotia may either later germinate to produce ascospore inoculum or they may A crisis exemption has been granted by have viable conidia surviving in sclerotial the EPA (Environmental Protection cavities (Bandyopadhyay et al. 1996). Agency) to allow application of Tilt Standard seed treatment with the contact (propiconazole) to control sorghum ergot fungicides captan and thiram prevent ger­ in hybrid production fields in the United mination of macroconidia in encrusted States. The exemption allows Tilt to be honeydew on seeds (G. Peterson unpub­ applied at 125 g a.i. ha- I (4 oz ac- I of Tilt I lished information). Most commercial 3.6E, O.I13lb a.i. ac- ) in each ~ft~~ee ap­ seed companies already use captan above plications for a total of725 g a.I. ha . Cur­ levels known to completely inhibit conid­ rently there is much experimentation by ial germination in honeydew on seeds and

74 the Texas Department of Agriculture has Conclusions issued guidelines for seed treatment with captan or thiram to reduce the risk of The emergence of e. africana as a planting seed produced in ergot areas. global disease problem on sorghum has These contact fungicides may do little or created considerable concern about its nothing against the sclerotial stage of e. present and future impact on hybrid seed africana where triazoles might be more production and the entire sorghum indus­ effective since they are reported to be try. That concern and the continuing more active against those of other spread of sorghum ergot, especially in the Claviceps spp (Bandyopadhyay et al. Western Hemisphere, has generated an 1996). increasing amount of research into virtu­ ally every aspect ofthe biology ofe. afri­ Host Plant Resistance and Cultural cana that can be potentially exploited to Practices to Control Ergot provide for control of sorghum ergot. In the same manner that the global nature of Initial effort in development of host the sorghum industry and the interna­ plant resistance is being conducted byes­ tional seed trade probably contributed to tablishment of nurseries to evaluate previ­ the spread of e. africana it is also this ously reported sources of host plant resis­ same factor that will encourage scientists tance. Many ofthese nurseries are located from around the world to collaborate in in ergot areas at various global locations their development of integrated and sus­ with several participating international tainable controls for sorghum ergot. and V.S. scientists exchanging germ­ plasm. All current male-sterile sorghums References appear to be fully susceptible to ergot and Bandyopadhyay, R., Frederickson, D. E., it will take considerable time and possibly McLaren, N. W., and Odvody, G.N. 1996. Er­ some novel breeding approaches to de­ got, a global threat to sorghum. International velop adapted, agronomically acceptable Sorghum and Millets Newsletter 37: 1-32 ergot-resistant sources. Because chemical Ferreira, A. S., and Casela, C. R. 1995. Ocorrencia de Claviceps sorghi, agente causal da doenca controls are expensive and may not be ergot no Brasil. Fitopathologia Brasilerira 100% effective it will be necessary to in­ 20:302. corporate all feasible cultural and other Ferreira, A. S., Pinto, N. F. 1. A.,and Casela, C. R. 1996. Avaliacao de fungicidas para 0 controloe ergot control or prevention methods into de ergot ou doenca acucarada (Claviceps afri- hybrid production schemes. Any cultural cana) ern sorgho. Pesquisa Ern. • practice which will facilitate rapid and Frederickson, D. E., Mantle, P. G., and de Milliano, maximum pollination of the female par­ W. A. 1. 1991. Claviceps africana sp. nov.; the distinctive ergot pathogen of sorghum in Africa. ent will directly reduce the risk of ergot Mycological Research 95:1101-1107. and complement the effectiveness of ap­ McLaren, N. W. and Wehner, F. C. 1992. Pre­ plied fungicides. Although ergot is not yet flowering low temperature predisposition of present in the primary hybrid production sorghum to sugary disease (Claviceps africana) Journal of Phytopathology 135:328-334 region many commercial V.S. companies Reis, E. M., Mantle, P. G., and Hassan, H. A. G. are already implementing some of these 1996. First report in the Americas of sorghum practices including multiple planting ergot disease, caused by a pathogen diagnosed dates of the male pollinator and a smaller as Claviceps africana. Plant Disease 80:463. ratio of female to male rows.

75 United States Private Sector Response

W. E. Dolezal

Abstract

Ergot has been positively identified in the u.s. andposes a threat to sorghum produGo tion. Private seed companies, in cooperation with governmental agencies, seed trade organizations,federal and university plant pathologists have developed a voluntary aGo tion plan for reducing the risk of accidental seed transmission of C/aviceps africana into disease free areas. The view expressed in this paper represent those ofPioneer Hi­ Bred International Inc., and not those ofthe entire seed industry. Details ofthe plan for ergot management in commercial, parent seed and research nurseries are presented

Ergot has long been recognized as a se­ thologists. The views expressed in this rious disease of sorghum [Sorghum bi­ presentation reflect only the views ofPio­ color (L.) Moench]. The disease is caused neer Hi-Bred International, Inc (PHI). by fungi within the genus Claviceps, most These views are not intended to represent commonly two species. C. sorghi and C. those 6fentire U.S. sorghum seed produc­ africana. The recent introduction and the ers. PHI is a member of the American rapid spread ofthe pathogen in the Ameri­ Seed Trade Association (ASTA) and has cas poses new challenges for the US sor­ collaborated with that association, and ghum producers. Discovery of C. afri­ other private sector agencies, in develop­ cana infected sorghum plants near Wes­ ing the ergot management action plan prt>­ laco, TX. Texas confirmed the pathogen's sented in this paper. Compliance with this spread into the U.S. Most ofthe U.S. sor­ action plan is strictly voluntary. ghum seed producers believe that C. afri­ cana will be disseminated, via wind, to The accidental introduction and rapid the major sorghum seed production re­ spread of C. africana in the Americans gion known as the Texas High Plains. and Australia has brought the potential for Seed producers recognize that there is a major economic losses to several busi­ risk factor in transporting the pathogen nesses in the agricultural community. via seed movement. A voluntary ergot There is possibly one benefit from this management policy was developed disease. It has brought together many of through the cooperative efforts of person­ the world's leading agricultural scientists nel from sorghum seed companies, seed to assist in a worldwide problem, as dem­ trade associations, agricultural profes­ onstrated by this conference. It has also sional societies, federal and state regula­ help foster a new era of cooperative re­ tory agencies and university plant pa- search between governmental agencies, between countries and between public and private institutions. Pioneer Hi-Bred

W.E. Dolezal. Pioneer Hi-Bred International, inc., Des Moines International, Inc. conducts sorghum re­ Corporate Headquarters, 400 Locust Street, Suite 800, P.O. Box search at 18 worldwide locations, work­ 14453, Des Moines, IA 50306-3453 ing with many public institutions to help

76 develop our products. This disease has ness relationships are built on trust, a trust caused a shift in research priorities within between the customer and the company. our company. Resources are being reallo­ The goal is to have the customer purchase cated to meet this new threat. Part ofthese his seed from us year after year. There is resource reallocation involves PHI per­ also a trust built between the company sonnel being reassigned new ergot re­ and phytosanitary regulatory officials. search goals, while another involves pro­ The accidental introduction of an exotic viding increased financial support to pub­ disease into an agricultural region can lic research programs which are focused cause severe economic damage to the on ergot. Budgetary constraints over the farmer and his community. The linkage of past few years have reduced staffing at that accidental disease introduction with a many public institutions to low numbers. private seed company can have a severe Many national and local disease surveys economic impact to the business. Finan­ have been discontinued due to staffing cial losses to the company may occur shortages. This has resulted in limited or through litigation cost, civil penalties and no pathogen monitoring database. PHI loss of business reputation and the loss of and other private seed companies have future seed sales. A company must often cooperated in sharing ergot disease data make a choice between a legally correct with the public sector. Special ergot web­ versus a biologically correct phytosani­ sites, like the one established by the tary decision. It may be legal to import USDA-ARS-TARS, have been very help­ seed with a known exotic pathogen, how­ ful in monitoring the spread ofthe fungus. ever, the pathogen may not be on the cur­ rent phytosanitary restricted listing. It Today's telecommunication systems, would be a poor decision based on bio­ like electronic mail, allow for instant up­ logical standards, but it is a legally correct dating of developing disease situations. one under current law. PHI and other There needs to be more effort to establish companies impose higher internal quality a worldwide database for pathogen moni­ standards than what are legally required. toring, especially for the newly emerging PHI imposes internal quarantines on seed diseases. Public institutions and private movement from various regions. These companies need to share their disease restrictions are necessary to reduce the monitoring data to help develop research risk of accidental pathogen introduction. priorities and update phytosanitary laws. PHI has long maintained this restriction on seed movement from Africa to the A successful private company, like Americas because of the risk of ergot. PHI, wants to follow a good agricultural stewardship policy. This includes practic­ All researchers, both in the public and ing a sound phytosanitary policy. It is a private sector should review the biologi­ good moral policy to follow, but it also cal risk factor in moving seed from one makes good business sense. Good busi-

77 continent to another. Legal restrictions • Seed known to be infected should may prevent the movement, but when le­ not be shipped into known disease gally permissible, the risk for pathogen free production areas (Zero toler­ introduction need to be determined. There ance of seed with honeydew & vi­ can probably never be a total elimination able conidia). of risk, it can be minimized by imple­ menting a high seed quality policy (use of Worldwide standards need to be estab­ fungicides, insecticides, etc.). lished for determining seed quality for seed production in areas where ergot is Ergot Management Quality Plant known to occur. Seed from ergot infected adopted by PHI, and other private seed regions should be allowed to be shipped companies, for reducing the risk or trans­ to other ergot infected regions, but this porting C. africana with sorghum seed seed must meet the grain quality stan­ shipments in 1997, is as follows: dards established for each country. This is not a quarantine issue but it is a seed qual­ Commercial & Parent ity issue. Can we determine what is a real­ Seed Production Fields: istic, and physically obtainable, quality standard for sclerotia and honeydew seed • Appropriate fungicides will be ap­ using industry standard seed cleaning plied to fields during pollination equipment (gravity tables & aspirators) • Fields will be regularly inspected commonly used at most sorghum produc­ for the presence of ergot tion facilities? What is the point of dimin­ • Segregate seed lots pending seed ishing return in cleaning seed lots for scle­ health testing rotia? What are the risk factors of sclero­ • Seed should be cleaned and treated in the country of origin tia contamination versus economic cost of • Seed from infected areas should not seed production? Other questions to be re­ be shipped into known disease free solved involve use of seed treatment fun­ production areas gicides. Companies often face the di­ • Zero sclerotia tolerance in seed lemma of a mandated seed treatment fun­ shipped into disease free areas gicide in the country of production that is not approved for use in another county Research Nurseries: where the sorghum seed is sold. Can regu­ lations be amended for these circum­ • Proactive fungicide applications during pollination stances? • Fields regularly inspected for the presence of ergot Ergot will continue to challenge sor­ • Panicles inspected during harvest. ghum researcher and seed producers. The Infected panicles are to be de­ finding from research presented at this stroyed. conference should help the entire seed in­ • All panicles dried and threshed in dustry in the years to come. Pioneer Hi­ the country of origin. Bred International, Inc. is pleased to be an • Nursery seed treated with appropri­ active participant in this conference and ate fungicide in the country of ori­ will continue collaborative research ef­ gin. forts with the public sector.

78 Sorghum Ergot in Argentina L.M. Giorda, M.J. Martinez, M. Nassetta, and S. Palacios.

Abstract

In 1996, sorghum ergot was observed for the first time in Argentine during MarchiApril and identified as Claviceps africana. The outbreaks ofergot disease in Ar­ gentina were mainly associated with cool weather conditions during the growing sea­ sons of 1996 and 1997. The average minimum and maximum temperatures were 14.1 and 27. 9°C prior to and during anthesis and were within favorable limits for disease d~ velopment. Flowering by the end ofJanuary resulted in a low risk offavorable disease conditions in both years. Consequently, early sowing allowed to escape from the dis­ ease. Different experiments carried out at Manfredi Experiment Station, Cordoba ind~ cated that Astyllus atromaculatus Blanchard transmitted C. a/ricana locally.

Grain sorghum in Argentina is culti­ farmers' fields where honeydew was vated throughout the subtropical and tem­ present and resulted in problems of har­ perate regions between latitudes 22-40° vesting the crop. South and longitude 56-66° West. It is grown primarily as a feed crop on ap­ Ergot Alkaloids proximately 800,000 ha in dryland areas (Giorda 1997) and is usually cultivated in Sclerotia and honeydew from infected a rotational system with either soybeans sorghum male sterile lines were collected or peanuts. Sorghum production is con­ in 1997 and used to extract ergot alka­ centrated in the states of C6rdoba, Santa loids. The extracts were separated by thin Fe, Entre Rios, and La Pampa. layer chromatography (TLC) on silica gel. The alkaloids were visualized by di­ During March and April 1996, ergot methylaminobenzaldehyde spray as blue­ was observed for the first time in Argen­ purple spots (Fig. 1) and seen as blue fluo­ tina in commercial fields of grain and for­ rescent spots under long-wavelength UV age sorghum F I hybrid seed production light (Giorda 1997, Mantle and Waight and identified as Claviceps africana 1968, Mantle 1968, Stahr 1991). Er­ (Giorda et al. 1996). In 1997, the disease gometrine was used as the standard of er­ appeared earlier which affected some got alkaloids. late-planted seed production plots and Sclerotia from 1996 and 1997 showed similar TLC patterns with an average Rf value of 0.61 for the major alkaloid com­ ponent. The alkaloid spectrum in sclerotia L.M. Giorda, Sorghum National Coordinator, Plant Pathologist and Associate Professor, EEA. INTA Manfredi, 5988 Manfredi­ collected from diverse sources and years Cordoba, Argentine; MJ. Martinez, PhD student, Fac. de Ciencias Agropecuarias-UNC; M. Nassetta, and S. Palacios, Principal Re­ was uniform but their concentrations searchers and Associate Professors in Organic Chemistry, CE­ were different. PROCOR, 5000 Cordoba, Argentine.

79 solvent level-)o

Ergometrln.9 Argentine Argentine Bolivian SclerotIa Honeydew Sclerotia 1997 1997 1996

origin -. ------_-

eluent: chloroform/methanol (4:1)

Figure 1. Thin layer chromatography on silica gel visualizing ergot alkaloids from sclerotia and honeydew of Sphacelia sorghi collected from Argentine infected sorghum fields. Er­ gometrine was used as the ergot alkaloids standard.

Epidemiology Table 1. Average minimum and maximum The outbreak of ergot disease in 1997 temperature and relative humidity at Manfredi Experimental Station, was mainly associated with cool weather Cordoba, Argentina during the 1997 and a mean relative humidity (RR) of growing season*.

75.7%. The average minimum and maxi­ ~ .. ~ RH mum temperatures were 14.1 and 27.9°C. M .... n January 18.4 30.7 83.7 These temperatures and humidity levels February 14.1 27.9 75.7 following panicle emergence or about 10 March 14.7 26.8 70.9 days prior to onset of anthesis and during Anri! 111) 27_Ll fl. n anthesis, were sufficient for infection and • planting date: I I Nov 1996; main flowering period: 25 Jan 1997; anthesis period oflate flowering male-sterile development ofthe disease in male sterile lines: 15-25 Feb 1997; and disease occurrence: 4 Apr 1997 sorghum lines (Table 1).

The first symptoms of ergot were ob­ Pergamino, Buenos Aires state, about 500 served on 4 Apr 1997 on late flowering fe­ km away from Manfredi, with similar male lines at the Manfredi Experiment minimum and maximum temperatures Station (Cordoba nursery located at 31 ° (14.5 and 27.6°C) and higher humidity 49'12" South latitude and 63° 46'00"10n­ prior and during flowering (Table 2). The gitude and 292 m above sea level). At the prevailing wind directions were from the same time, the disease was also observed north and northeast with some air move­ on a F I hybrid seed production field near ments from the south and southeast.

80 Table 2. Average minimum and maximum McLaren (Bandyopadhyay et al. 1996) temperature at Pergamino Experi­ in South Africa used the maximum daily mental Station, Buenos Aires, Ar­ temperature of 28°C (temperature above gentina during the 1997 growing which disease incidence is minimal) and season. 12°C minimum temperature (temperature ;:T~! below which maximum predisposition occurs) to identify high and low risk flow­ ering periods. Using McLaren's methods • Average from the fIrst 15 days of the month. and Argentina's environmental data of 1996 and 1997, we determined low and Minimum and maximum temperature high-risk periods for the country (Figures of about 14 and 28°C combined with RH 2 and 3). However, the average minimum levels of70-90% are conducive to conid­ temperature used in our analysis was ial production (Bandyopadhyay et al. slightly higher (14 and 28°C; 15 and 27°C 1996) and hence pathogen spread. These for 1996 and 1997, respectively) than environmental conditions are similar to those mentioned by McLaren (Bandyo­ those that occurred in Argentine in 1996 padhyay et al. 1996). and 1997 in various sorghum locations from mid-February and March. Flowering before the end of January re­ sulted in low risk of ergot favorable dis­ The average mean RH was 85.4% and ease conditions in both years. Conse­ 87.9% during February and March 1996, quently early sowing favored escape from respectively; corresponding RH in 1997 the disease whereas later sowing, that re­ were 75.7% and 70.9%, respectively (Ta­ sulted in flowering during the cooler part bles 1,3). The dry weather after infection of the season (by the end of February), during the 1997 season suppressed the de­ promoted ergot incidence. velopment of different saprophytes which were very common during the 1996 sea­ In other experiments conducted at the son when the spread of C. africana oc­ Manfredi Experiment Station, we found curred more rapidly and intensively. that the latent period varied between 4 to 8 days depending on environmental condi­ tions. Honeydew exudation initiated two Table 3. Average minimum and maximum temperature and relative humidity days after the sphacelium was observed. at Manfredi Experimental Station, Cordoba, Argentina during the 1996 Local Spread Vectors growing season*. Infected spikelets exude sticky drops of fluid honeydew containing macroco­ nidia and microconidia. Several authors suggested that conidia are spread also by insects that feed on honeydew while oth­ • planting date: 30 nov 1995; main flowering period: 6 Feb through 6 Mar 1996; anthesis period of late flowering male­ ers (Bandyopadhyay et al. 1996) sug­ sterile lines: 6-15 Mar 1997; and disease occurrence: 25 Mar gested that insects may not playa signifI­ and 15 Apr 1996 cant role in ergot spread.

81 °C 35

30 ------

25 Maximum temperature

20

15 - - - - -

10 ------Minimum temperature 5 r - January February March April , II I ',I :; ,111111111111 !III .illil 111111 o ;111,1111111111111111111111111111",11111111 I " 1 5 10 15 20 25 31 5 10 1520 25 1 5 10 1520 25 31 5 10 15 20 25 30 Days Figure 2. Maximum and minimum temperatures at Manfredi Exp. 8ta., Cordoba, Argentina as­ sociated with ergot disease development. First symptoms and signs appeared on late flowering female lines in 03/04/97.

OC 30

18 ' l:r'~~~~~(-97-)·1------~t-(9-6)------~-'

,February March April ' o ------. 1 5 10 15 20 25 1 5 10 15 20 25 301 5 10 15 20 25 30 Days ~------~- -Tem.min.97 -Tem.min.96 -Tem.max.96 - -Tem.max.97

Figure 3. Daily minimum and maximum temperatures at Manfredi Exp. 8ta., Artentina. 1996 and 1997. Arrows indicate outbreak of ergot disease.

Experiments carried out at Manfredi transmitted C. africana. Fifteen grain sor­ Experiment Station, Cordoba, indicated ghum panicles of female lines were cov­ that Astylus atromaculatus Blanchard ered with pollination bags 8 days before

82 flowering, and were infested one day bef­ before flowering (thiabendazole, ore anthesis or at the onset of anthesis propiconazole and terbuconazole with two honeydew-contaminated insects might be effective as preventive but per panicle. An additional 15 panicles not as curative treatments). were inoculated with a honeydew suspen­ • Pollen-based management sion. Control panicles were protected • Use seed free from sclerotia (within from contact with insects by bagging tolerance levels) and disinfected them with thick pollination bags 8 days with fungicides. before flowering until the dough stage of • Develop a forecasting system based on temperature and relative growth. The trial was repeated three times humidity conditions. and performed during March and April. • Identify host-plant resistance Visible ergot symptoms were observed 8 to 9 days after vector inoculation while Acknowledgment fewer days (4 to 5 days) were needed for disease development when panicles were We would like to thanks Ing. Agr. C. inoculated with honeydew suspension. Barberis for providing the Pergamino, No infection occurred on the protected Buenos Aires data, to Geol. E. F. Lovera control panicles. Astylus atromaculatus for providing the meteorological data normally "feeds" on pollen and it is con­ from Manfredi Experiment Station, Cor­ ceivable that the insect became infested doba and to D. Alverani for his collabora­ with conidia and consequently served as tion on the field and laboratory trials. vectors References Management Strategies Bandyopadhyay, R., Frederiskson, D. E., McLaren, N. W., and Odvody, G. N. 1996. Er­ Considerable research information is got, A global threat to sorghum. International available on different aspects of the biol­ Sorghum and Millets Newsletter 37:1-32. Giorda, L. M., Martinez, M. J., Palacios, S., and ogy of the pathogen. However more work N ass etta M. 1996. Occurrence of sorghum ergot is needed on the disease epidemiology disease in Argentina and Bolivia. Page 649 in and variability ofthe pathogen to develop Proceedings ofthe International Conference on Genetic Improvement of Sorghum and Pearl an integrated ergot management strategy. Millet. Lubbock, Texas, USA. Sep.22-27. INT­ Based on the scarce data available from SORMIL, University ofNebraska, Lincoln, Ne­ the two years of ergot incidence in Argen­ braska, USA. Publication 97-5. Giorda, L.M. (ed.). 1997. Sorgo granifero. INTA tina, the following management practices Centro Regional Cordoba. EEA Manfredi. are suggested: 71pp. Mantle, P. G., and Waight, E. S. 1968. Dehydroer­ gosine: a new naturally occurring alkaloid from • Early planting dates (October to be­ the sclerotia of Sphacelia sorghi (McRae). Na­ ginning ofNovember) to escape the ture 218:581-582. disease. Mantle, P.G. 1968b. Studies on Sphacelia sorghi • Chemical control in hybrid seed McRae, an ergot of Sorghum vulgare Pers. An­ nals of Applied Biology 62:443-449. production fields. Systemic fungi­ Stahr, H. M. 1991. Analytical Methods in Toxicol­ cides mixed with contact fungi­ ogy. John Wiley & Sons, Inc. New York. 130 cides and applied 3 times at 5-7 pp. days intervals, beginning 10 days

83 Incidence of Ergot in Honduras

J. Moran and F. Gomez

Abstract

Ergot is a very aggressive disease with a capacity jor wide dispersal, compared to other sorghum diseases. In 1996, it movedfrom Brazil to Bolivia, Argentina, Colombia and Venezuela. Also in 1996, ergot was identified in Honduras, specifically in the vaJ. leys ojZamorano, Jamastran, Comayagua, and Talanga in yield trials and in a commer­ cialfield

Most of the sorghum in Honduras, opment and therefore, yield loss. In Hon­ mainly maicillos criollos, is grown in the duras, the most common sorghum patho­ southern region where the yields are very gens are Colletotrichum graminicola, 1 poor (854 kg ha- ) due to unfavorable Peronosclerospora sorghi, Cercospora weather conditions such as low precipita­ fascimaculans, Gloeocercospora sorghi, tion and high temperatures. The northeast Puccinica purpurea and Exserohilum tur­ region of the country is second in impor­ cicum which can cause yield losses of up tance with a mean yield of 2,826 kg ha- 1 to 80%. Ergot (Claviceps africana) was since the farmers in this region (mainly reported for the first time in 1996. Olancho) have adopted improved grow­ ing and harvesting technologies including Spread of Ergot in Honduras more uniform high yielding hybrids com­ pared to the maicillos criollos. Also Ergot was observed in Zamorano (Fig. weather conditions in this region are more 1) in a 1996 commercial sorghum hybrid favorable for growth and development of strip test. The trial was established on sorghum. There are limited commercial August 31 and consisted of 29 commer­ hybrid production areas in the eastern part cial hybrids from six different private of the country, such as the Jamastnin val­ companies from the USA, Mexico, Gua­ ley, and recently an increase in sorghum temala and Brazil. Seeds from all hybrids production throughout the north coast were treated prior to planting with Pro­ was observed. metAL Each plot consisted of four rows; 125 m long, and 80 cm in width. Different Basically, sorghum is grown in many maturities were observed, with anthesis regions with a wide range ofweather con­ ranging from 63 to 79 days after planting ditions. These diverse environments pro­ (dap). Honeydew was observed in some vide ideal conditions for pathogen devel- panicles of the hybrid ICI 730 produced byZENECA.

In the following weeks, white crusts of

• J. Moran and F. Gomez, Departamento de Agronomia, Escuela honeydew were observed on the leaves of Agrilcola Panamericana, Apartado Postal 93, Tegucigalpa D.C., ICI 730 which produced secondary inocu­ Honduras. 'Corresponding author. lum that infected other hybrids and ergot

84 ~9 Caribbean Sea

Guatemala

Nicaragua el Salvador

Figure 1. Geographical locations where ergot was confirmed in Honduras. symptoms developed on nearby hybrids. randomized complete block design with Of the contaminated hybrids, ICI 737 30 entries and four replications. The hon­ showed the greatest amount of honeydew eydew was observed in almost all pani­ although it was 25 meters away from ICI cles and is attributable to the small size of 2 730. However, we were unable to deter­ the plot (16 m ). As in the strip test, ICI mine if the presence of ergot in ICI 737 737 exhibited honeydew symptoms after was the result of inoculum from ICI 730. ICI 730. With time, the exudation was Differences in ergot appearance between colonized by secondary organisms and the hybrids could be caused by variation assumed a blackish appearance. in blooming as ICI 730 bloomed 63 dap and ICI 737 five days thereafter. Honey­ Climatic conditions during anthesis in dew was only observed on the north and Zamorano were: south borders of the research plot and not observed in the middle. • Accumulated precipitation: 60.1 mm Honeydew exudation was also ob­ • Mean maximum temperature: served in ICI 730 in the PCCMCA trial in 25.9°C a nearby field. This trial was arranged as a • Mean minimum temperature: 16.4°C

85 • Mean relative humidity at 7:00: Seed samples from the PCCMCA trial 95% were sent to Dr. Richard Frederiksen at • Mean relative humidity at 13:00: TAMU, to determine if seed was the con­ 84.1% duit for ergot introduction. All the seed were treated with recommended fungi­ The PCCMCA trial was also estab­ cides before sowing. Since seed treatment lished at two other locations in Honduras kills conidia of C. africana on seed sur­ (Fig. 1): Comayagua, at Centro de Entrtr face and no sclerotia were found in the namiento y Desarrollo Agricola (CEDA); seed lots, it was not possible to conclude and Jamastnin, at Las Acacias Experi­ that contaminated seed was the cause for ment Station. Comayagua is a valley lo­ introduction of ergot to Honduras (R. A. cated 80 km northwest from Tegucigalpa Frederiksen, personal communication). at 580 meters above sea level (masl). At this location, the trial was established on The PCCMCA trial was distributed Septem ber 19 and was identical to the Za­ throughout Central America and Mexico: morano trial. Time to anthesis ranged two locations in Mexico, three in Guattr from 63 to 70 dap. Up to 100% of the mala, one in EI Salvador, two in Nicara­ plants ofICI 730 were infected. Other hy­ gua, one in Costa Rica, two in Panama, brids sowed near, showed some exuda­ and one in the Dominican Republic. tion; however, the same hybrids failed to When we found out that ICI's hybrid produce any honeydew iflocated far from might be a possible source of ergot, we ICI 730 plots in other replications. Also in contacted the other regional locations to two replications, ICI 737 had 15% disease find out if ergot had shown up. Fortu­ incidence. With time, white crusting was nately, none reported the appearance of observed on leaves, similar to plants in ergot in their trials. Zamorano and the panicles eventually were colonized by secondary organisms. Recently Mr. Jaime Paredes, a sor­ Low ergot incidence was reported in Ja­ ghum researcher from EI Salvador, diag­ mastnin valley, which is, located 70 km nosed ergot in that country. A seed in­ east of Zamorano at 600 masl. Ergot inci­ crease nursery of sorghum lines had up to dence in ICI 737 was as low as 5%, but, 80% incidence of ergot. This nursery was other hybrids were ergot-free. located only 100 meters from the field where the PCCMCA trial was planted in A research group from INTSORMIL 1996. In October 1996, ergot was re­ who visited the country in early Decem­ ported on a commercial hybrid in the Ta­ ber confirmed ergot. Drs. Gary Peterson, langa valley, located 50 km northeast of Darrel Rosenow, William Rooney and Tegucigalpa (Fig 1.). That hybrid was the Mr. Delroy Collins identified the disease 887 V2, produced by Cristiani Burkard in the three locations previously men­ S.A., a seed company from Guatemala. tioned. At the same time Dr. Phil Arntr This same hybrid was used as a check in son, a pathologist from Cornell Univer­ the strip test established at Zamorano ear­ sity, identified ergot in four different lier that year. However, honeydew was weeds but it is unknown if the causal not observed in the panicles at Zamorano. agent was C. africana. In commercial fields, ergot incidence was

86 minimal. Honeydew was observed on The main objectives of these research plants at the margins of the field where efforts include: pollen availability was minimal. 1. Evaluate resistance to C. ajricana Future directious from different sorghum genotypes that will be used directly in breeding A germplasm grant was approved by programs or as genetic sources. the Sorghum Germplasm Committee for evaluation of sorghum lines for ergot re­ 2. Characterize major resistance sistance. We will cooperate with Dr. Wil­ mechanisms for use in development of integrated control of ergot. liam Rooney from TAMU. Lines will be evaluated for genetic variability to C. af­ 3. Evaluation sites ofergot to the exotic ricana. sorghum germplasm will be at two or more locations in Honduras to maxi­ mize screening opportunities.

87 Ergot, Honeydew or Sugary Disease of Sorghum in Venezuela Gino Malaguti and Ninoska Pons

Abstract

Sugary disease ofSorghum [Sorghum bicolor (L.) Moench] appeared, suddenly, in Venezuela by June 1996. FI hybrid seed and commercial grain sorghum production fields as well as the common weeds S. halepense, S. arundinaceum, S. verticillijlorum and Panicum maximum, were infected The diseased panicles exhibited abundant, sticky, sugary exudation whichflowed down as droplets,falling on leaves and soil be} ore drying to form creamy whitish crusts. Microscopic examination ofcross sections of infected ovaries revealed the presence ofstroma, conidiophores and conidia with char­ acteristics referable to the species Sphace/ia sorghi. On the basis of the analysis of sugar composition of dried drops of honeydew, this anamorphic state was related to Claviceps africana by P. G. Mantle. The sphacelial structures were colonized by the fungus Cerebella andropogonis. Ascogenous forms were not observed It can be as- sumed that the primary inoculum comes from wild hosts or volunteer sorghum plants growing alongfields or roadsides andfrom infected debris, containing conidia which are easily transported by the wind or animals. Until resistant lines are available, protee­ tive fungicide treatments, integrated with suitable agronomic practices are being em ployed

Sugary disease or honeydew of sor­ the states of Carabobo (San Joaquin and ghum [Sorghum bicolor(L.) Moench] has Guacara), Aragua (Magdaleno,. Cagua been known since 1917 in many regions and Villa de Cura) and Anzmitegui (EI Ti­ of India and various countries of Africa gre). It was also observed, but with a less (Bandyopadhyay et al. 1990,1996). In incidence, in extensive hybrid plantations 1995, it was reported in Brazil where an for commercial grain production in epidemic covered far and wide in a few Guarico state (Altagracia de Orituco, months. Later it was found in Argentina, Chaguaramas and other localities). In Colombia, Paraguay (Bandyopadhyay et Venezuela, about 350,000 ha ofgrain sor­ al. 1996) and, in 1996, in Venezuela. ghum is annually sown with hybrid seed, which are mostly produced in the country. In Venezuela, the disease appeared suddenly in male sterile lines of sorghum The first visible and distinctive mani­ in the F I hybrid seed production fields, in festation ofthe disease is the abundant se­ cretion of a honey-like, sticky exudation that flows down from the flowers infected by the fungus Sphacelia sorghi McRae; °Gino MaIaguti and Ninoska Pons, Fondo NacionaI de Investiga­ ciones Agropecuarias, Centro NacionaI de Investigaciones Agro­ mentioned as the anamorph or imperfect pecuarias, Apartado 4653, Maracay 2101, Venezuela. ·Corre­ sponding author.

88 stage of species of Claviceps (Ascomy­ fall during 1995 was twice than normal; in cete). Venezuela (Maracay, Aragua state) dur­ ing 1996, it was 1421 mm, which was The fungus penetrates the flowers higher than the annual rainfall average through the emerging stigma and style, during the past 12 years (1078 mm) at the replaces the ovary with its own mass same locality. These wet conditions are thereby preventing grain formation. The regarded to be favorable to epiphytotic damage is extremely severe in fields for outbreaks ofthe disease (Bandyopadhyay hybrid seed production if the male sterile et al. 1996). flowers remain nonpollinated for a long Symptoms time. The fertilizing pollen, from the re­ storer lines, is sometimes delayed, be­ The first symptom and sign of the dis­ cause of poor synchronization or adverse ease is the sticky sugary exudation. This is environmental conditions, thus allowing so abundant that it comes from the ovaries the fungus to penetrate through the of infected flowers as translucent drops, stigma, and colonize the ovary. The which flow down along the panicle, fal­ ovule, once fertilized, is mostly resistant ling on leaves of the plant or on the soil to the infection (Bandyopadhyay et al. (Figures 1 and 2). It seems that the patho­ 1996) gen S. sorghi secretes inhibitory enzymes which prevent the conversion of plant The role of pollination in reducing in­ sugars into starch as have been shown for fection was reaffirmed in an experimental Claviceps purpurea (Campbell 1959). field for seed production, where in the These sugary drops, at first colorless, later same male sterile plants, the side of the tum opaque and brown, and when dry, panicles exposed to wind carrying pollen, produce a whitish powdery cracked crust had more normal grains than in the oppo­ on panicles, leaves and soil (Figure 3). site side of the panicle, where more in­ The diseased panicles may be easily fected ovaries were found (M. Riccelli, recognized by their whitish dry-sugary personal communication). crust, which contains a great amount of conidia. Later and especially under high In the commercial F 1 hybrid used for grain production, the flowers produce humidity, the infected panicles tum to a normal pollen leading to rapid fertiliza­ blackish color and the deformed ovaries tion. Therefore, infection is restricted to a enlarge and crack and are later colonized few flowers. It has been observed that the by parasitic or saprophytic fungi. sugary sticky honeydew exudation causes The described symptoms, induced by difficulty during the harvesting opera­ Sphacelia sorghi, were also observed in tions. the wild sorghums (Sorghum halepense Ergot of sorghum is favored by abun­ (L.) Pers.; S. arundinaceum (Desv.) dant and prolonged rains which keep rela­ Stapf; S. verticilliflorum (Steud.) Stapf, tive humidity higher than 90% and tem­ and Panicum maximum Jacq. These perature, especially at night, relatively weeds are very common in Venezuela low, between 18 and 28°C. In Brazil, rain- fields.

89 Figure 1. Symptoms induced by SphaceJia sorghi in sorghum panicles.

Figure 2. Droplets of the sugary exudation in sorghum panicle.

90 Figure 3. Droplets of the sugary exudation and powdery crust of dried drops on foliar surface.

The sugary exudation and the sphace­ line cells which, together, exhibit a white, lial tissue filling the ovary were observed creamy color; with short conidiophores in in the above mentioned host plants. Typi­ dense palisades, bearing phialidic co­ cal sclerotia, curved as a little horn (= er­ nidiogenous cells in which conidia are got in French), from which the perfect produced (Figures 4 and 5). Conidia are stage of the fungus would arise, were very abundant, slimy, oblong, elliptical, never found. Thus, the ascogenous forms slightly constricted at the middle, hyaline, were not observed in Venezuela. guttulate, 15-19 (m long and 4-5 (m wide at the base and at the apex (Figure 6). Pathogen The sugary exudate and the sphacelial Microscopic examination of cross sec­ stroma are colonized by Cerebella andro­ tions of infected ovaries revealed the pogonis Ces. which seems to inhibit scle­ presence of fungal structures whose char­ rotium development and therefore the acteristics are similar to the ones de­ sexual stage formation. C. andropogonis scribed by various authors for the fungus is easily recognized for its blackish brown S. sorghi (Bandyopadhyay et al. 1990, colored conidiophores in dense palisades 1996, Fredericksen et al. 1991). of velvet-like appearance, forming char­ acteristic C'onvolutions like those on the Infected ovaries are almost entirely surface at the brain mass (hence the name filled with a stromatic, not very compact, Cerebella) (Figures 7 and 8) (Langdon convoluted mass formed by angular hya- 1955, Tarr 1962).

91 Figure 4. Cross section of an ovary infected by SphaceJia sorghi, showing stroma with conidio­ ph ores in palisade.

Figure 5. SphaceJia sorghi. Stroma with conidiophores, conidiogenous cells and conidia.

92 Figure 6. Conidia of SphaceJia sorghi.

Samples of inflorescences of culti­ mental samples from Africa, Asia or vated and wild sorghum sugary exuda­ South America. tions, were sent to Professor P. G. Mantle, Imperial College, University of London, b. Conidial dispersion by strong air who confirmed the presence of sphacelial movements from adjacent countries fructifications and typical sugars of the such as Brazil and Colombia, as it sexual stage of C/aviceps africana Fre­ happens with rust uredospores. deriksen, Mantle and de Milliano, and the c. C. africana might have been present lack of well developed sclerotia. The ab­ in Venezuela for some years in host sence of sclerotia reduces the risk of tox­ icity of false grains. plants, and remained unnoticed, un­ til the particular environmental con­ Disease Introduction ditions of 1996 favored inoculum pressure thereby producing the epi­ The possible explanations for the pres­ phytotic. ence of the disease in Venezuela, are as Primary Infection follows: In Venezuela, it can be assumed that in a. Introduction ofthe fungus with com­ the absence of ascospores, primary infec­ mercial grain sorghum imported for tion originates from conidia from wild animal consumption, or with experi- hosts or volunteer sorghum plants grow-

93 Figure 7. Cerebella andropogonis growing on the S. sorghi honeydew. -,

Figure 8. Cerebella andropogonis on inflorescence of Panicum maximum infected with S. sorghi.

94 ing along field borders or roadsides. Co­ • Eliminating all wild hosts, espe­ nidia may also come from the sugary cially P. maximum and wild sor­ powdery crust on panicles or infested dfr ghum plants present in the field or bris left in the field after harvest. Conidia in nearby areas. may remain viable for several months and • Changing the male:female propor­ then spread by wind, insects, birds, ani­ tion to increase the male lines to en­ mals and farm implements (Bandyopadh­ hance the pollen quantity and yay et. al. 1996). thereby obtaining a higher fertiliza­ tion and a lower infection. Seeds from diseased fields may carry • Obtaining a better synchronization of the male and female flowering, the sugary exudate along with the fungus with the respective study of the ex­ mycelium and conidia leading to reduced act cycle and line development. germination, and increased predisposi­ • Using healthy parental seeds to rfr tion to seedling diseases (McLaren 1993). duce primary inoculum. • Reducing tillers by increasing plant Considerations about Control popUlation in the female lines and eliminating, ifpossible, the suckers The use of resistant hybrids is the first before flowering. option to control ergot. However, resis­ • A very important measure is to pro­ tant male sterile lines are not available. In tect the fields with an appropriate most countries, work is directed towards fungicide, with three applications the selection of these lines, in places (every 5 to 6 days) starting just bef­ where environmental conditions favor­ ore anthesis. Spray droplets must able to the disease are naturally present. be evenly distributed over the Germplasm can also be tested by inocu­ whole panicles. lating the panicles by spraying an aqueous sugary suspension prior to pollination Grain Production (Futrell & Webster 1966). In grain sorghum fields, the disease is As long as resistant material is not normally less severe than in seed produc­ available, other control options may be tion due to self-pollination. Protective considered for managing the disease. The fungicides are not recommended due to precautions can be summarized as fol­ its high cost, but an economic study on lows: cost-benefit ratio is required. Defensive strategies are more pertinent. These are: Hybrid seed production: • Eliminating all possible wild hosts • Sowing in appropriate periods of the pathogen from the field and avoiding high humidity and low neighboring areas before sowing. temperatures during flowering pfr • Eliminating volunteer sorghum riod. plants, especially if infected. • Moving seed production to drier ar­ • Assuring that the seeds are healthy, eas with low relative humidity. coming from pathogen free areas. An appropriate seed treatment fun-

95 gicide should be applied if any ways that will allow us to coexist with this doubt exist. disease. Diseases such as downy mildew and maize mosaic of corn, the bacterial According to Brazilian investigations blight of sesame and the white leaf of rice carried out in 1995 and 1996 (Odvody are examples ofthis evolution and adapta­ 1996), the "Triazole" family can satisfac­ tion. torily control the disease. Commercial products such a Tilt® (Ciba-Geigy), Foli­ References cur® and Baytan® (Bayer) are all used in Bandyopadhyay, R., Mughogho, L. K., Manohar, concentrations around 0.5-1 L ha. S. K. and Satyanarayana, M. V. 1990. Stroma development, honeydew formation and conid­ Baytan was. more effective, but it is ial production in C/aviceps sorghi. Phytopa­ toxic at the indicated level. Seed treat­ thology 80:812-818. Bandyopadhyay, R., Frederickson, D. E., ment can eliminate the conidia that can be McLaren, N. W. and Odvody, G. N. 1996. Er­ present in the sugary exudation dried on got, A global threat to sorghum. International Sorghum and Millets Newsletter 37:1-32. the grains. Campbell, W. P. 1959. Inhibition of starch forma­ tion by C/avieeps purpurea. Phytopathology Final Consideration 49:451-452. Frederickson, D. E., Mantle, P. G. and de Milliano. W. A. 1. 1991. C/avieeps afrieana sp- nov.; the Ergot, honeydew or sugary disease of distinctive ergot pathogen of sorghum in Africa. sorghum, is a disease that can disseminate Mycological Research 95:1101-1107. quickly by means of wind, animals and Futrell, M. C. and Webster, O. 1. 1966. Host range and epidemiology of the Sorghum ergot organ­ seeds, reaching long distances and ism. Plant Disease Reporter. 50:828-831. spreading in vast areas. It perpetuates in Langdon, R.F. 1955. The genus Cerebella. Myco­ debris, grains and a variety of host plants. logical PaperNo. 61. Kew, Surrey, UK: Com­ monwealth Mycological Institute. 18 pp. The control measures listed above must McLaren, N. W. 1993. Effect of sugary disease be studied and assessed for each circum­ exudates on germination, seedling development stance since some are difficult to follow, and predisposition to seedling diseases of sor­ ghum (Sorghum bieolor) South African Journal such as the elimination of wild sorghum of Plant and Soil. 10: 12-16. plants. As the disease is present in most Odvody, G. 1996. Chemical control of Clavieeps seed producing areas of Venezuela, care afrieana on grain sorghum. Texas A & M Uni­ versity, Mimeograph. 5 pp. (Limited distribu­ should be taken in selecting fields for seed tion) multiplication. Tarr, S. A. 1. 1962. Diseases of Sorghum, Sudan Grass and Broom Corn. Kew, Surrey, U.K: Commonwealth Mycological Institute. 380 pp. As happens with most diseases, an evo­ lution will take place in which we find

96 Cereal Ergots in Uruguay

Maya S. Pineiro

Ergot alkaloids produced by Claviceps or from the weed grasses making the ra­ on forage grasses (tall fescue, ryegrass) tion unsuitable for animal feed. and cereal grains are widespread in Uru­ guay. Local climatic conditions are ideal In response to increasing ergot infec­ for sclerotia development and germina­ tion resulting in large animal health and tion, dissemination of ascospores, and in­ economic losses, the Uruguayan authori­ fection. The weather and agronomic prac­ ties, in 1986, issued regulations establish­ tices make sclerotia as important propa­ ing limits. These set a maximum value of gules. The presence of ergot in cereals is 0.03% (0.03 g of ergot sclerotia per 100 g quite common. Most of it is attributed to of animal feed) or 450 ng g"1 oftotal alka­ admixture of grains with ryegrass. An­ loids for all species, with the exception of nual rye grass is a common weed, which feed for sows, rabbits and chinchillas dur­ invades cultivated lands in Uruguay. In ing lactation and pregnancy, where there these wild grasses, infection by Claviceps is a zero tolerance. These regulatory lim­ purpurea, Pithomyces chartarum, its take into account a daily dose of 59 ).lg Claviceps spp, etc. is very common and kg-I of alkaloids as the maximum permis­ the fungi are widely distributed in our sible intake without having toxic effects fields. Annual ryegrass seeds infected in dairy cows. This is a very strict stan­ with fungal endophytes or C. purpurea dard, comparable to Canada's 0.05% for ergot sclerotia very often become compo­ their highest grade rye, and 0.01 % for ex­ nents of feed. Other species such as C. port wheat. paspa/i and Ustilago paraguaiensis also affect cattle, producing nervous disor­ Even when applying commercial grad­ ders. ing systems and the 1986 regulations, pre­ cautions had to be taken as toxic levels Contamination with ergot occurs in all passed into the grains because alkaloid cereal grains, bran and other cereal by­ values higher than those permitted could products and feed. Feed components of­ not be detected by routine grain quality ten include mixtures of third grade laboratories. Determination of ergot scle­ screenings, which have weed grass seeds rotial tissue was not possible once mix­ and ergot sclerotia. Low-grade categories tures were milled. Up to 1993, ergot was of cereals, such as barley, wheat, rye, may detected mainly by microscopic counts of contain ergot bodies from the cereal itself sclerotia or ergot bodies and sporadically by colorimetric assays, pigment content and biological trials.

Human toxicosis has not been detected Maya s. Pineiro, Head, Mycotoxin Department, Laboratorio Tec­ after the enforcement of the ergot regula­ nologico del Uruguay (LATU) Ave.ltalia 6201, Montevideo CP tions, grain sanitary limits and trade con­ 11500, Uruguay trol, but animal cases are endemic. Since

97 1992, ergot toxicity syndromes and field of these alkaloids in samples of our main outbreaks have been on the rise in cattle, cereals and animal feeds. sheep, swine, horses and poultry. These local animal toxic signs include: poor In 1993-1995, a pilot study monitoring weight gains, abortions and reproductive mycotoxin contamination in food and problems, agalactia, staggers in heifers, feeds, including ergot alkaloids was con­ summer hyperthermia, heat stress, pe­ ducted by LATV with FAO's financial ripheral necrosis and gangrene, nervous assistance (Pifieiro et al. 1996). Ergot al­ disorders, convulsions and other clinical kaloids were detected in 26% of the feed manifestations of vasopressor action of samples at levels above the legal allow­ ergot alkaloids. All members of the fam­ ance. The major pharmacologically ac­ ily Clavicipitaceae are capable of produc­ tive ergot alkaloids analyzed were ergota­ ing ergot alkaloids and should be suspect mine, ergocristine, ergocornine, and in these toxic cases. In addition ender alpha-ergokryptine. Since then, we have phytic fungi can also be found in pasture routinely determined these ergot alka­ grasses and can be toxic to animals. loids in our laboratory (Pifieiro et al. 1995). Analyses were by liquid chroma­ Cereal grains are very susceptible to er­ tography using a 5-)lm Hypersil C 18 col­ got infection. During the last decade, im­ umn (100 x 4.6 mm), with an isocratic provement in agricultural practices, miH­ Hewlett Packard 1050 system with fluer ing techniques and grading .have elimi­ rescence detector (Scott and Lawrence nated the potential risk of widespread 1980, Ware et al. 1986). human outbreaks of ergotism. Howev~r the chronic effects of ingesting low levels Sugary disease of sorghum has not of ergot alkaloids over long periods and been overtly observed in Uruguayan the animal cases detected locally led us to fields although cases have been sus­ investigate the actual levels of ergot alka­ pected. The results presented here on er­ loids present in our commonly consumed got alkaloid levels and incidence refer to cereals and feeds. In Uruguay, rye grass sorghum and mixed feed, where sorghum was considered the major source of ergot was a large part of the feed components infection although there was no conclu­ used. sive alkaloid data. At Laboratorio Tec­ nol6gico del Uruguay (LATV) we have As combined toxicities of alkaloids been monitoring animal case studies for may be a more insidious detriment to both ergot alkaloid levels in the feed and com­ livestock and human health than the indi­ ponents used, as well as in all suspected vidual compounds; the results of our stud­ toxic cereals since 1993. ies have been expressed as total ergot al­ kaloids. Our data presented pertains to Our first objective was to compare, de­ samples originating from feed involved in velop or adapt and standardize analytical toxic cases or from suspected contami­ methods for chromatographic identifica­ nated grains. tion and quantification of four major ergot alkaloids. The principal aim, however, Out of 177 total samples analyzed was to evaluate the levels and incidence since 1993 (Table 1), 109 samples had de-

98 Table 1. Level of total ergot alkaloids in 177 cereal-based products in Uruguay

No. product samples <6 5-150 151-450 451-700 701-1000 1001_2000 2001-3000 >3000 Sorghum & mixed feed 105 42 11 22 15 5 8 0 2 Bran & wheat based feed 41 16 9 9 I I 2 I 2 Oats I I 0 0 0 0 0 0 0 Wheat & Flour 17 5 2 2 3 I 4 0 0 Rice & by products 9 3 0 4 I I 0 0 0 Corn 2 I 0 I 0 0 0 0 0 Barley 2 0 0 0 0 I I 0 0

Total ]:lOsitive samples 109 >ngg-1 Total positive samples 49 >450 ng g"l Total samples 177 tectable values (detection limit 6 ng g-I) and flour (4.5%), bran and wheat based for total ergot alkaloids. Ergotamine was feed (3.9%), for a total of27.7% samples the major alkaloid present in all cases. Of over legal allowances. all samples, 49 surpassed the legal limit of 450 ng g-I. Levels varied from 3000 ng g-I for total alkaloids (Table 2). culties. However, good preventive meas­ The percentage of total positive samples ures based on mycological identification; above the detection limit was 61.9%. alkaloid detection and quantification; High levels of alkaloids, with values pasture, silage and feed handling can r~ above 1001 ng g-I to >3000 ng g"\ were duce toxic levels, improving sanitary and found in sorghum and mixed feed, bran economic aspects considerably. and by products and wheat. Such high al­ kaloid content was detected in 5.6% sor­ As general recommendations, reduc­ ghum and mixed feed samples_ tion in ergot contamination is possible by clearing wild grasses near cultivated Of the samples exceeding regulations, fields; sowing cereal varieties less sus­ sorghum and mixed feed represented the ceptible to ergot; rotation with non-hosts; largest part (16.9%), followed by wheat post harvest removal of sclerotia; and deep plowing. From the industry point of Table 2. Percent samples of various cereal view, segregation, density, sieves, sepa­ products (total 177) with alkaloid lev­ rators, flotation, milling, etc can remove els below or above the tolerance level over 80% of ergot. (450 ng go!) in Uruguay. Product <450 >450 ogg-l ogg-l The data presented here should raise Sorghum & mixed feed 42.0 16.9 awareness ofthe possibility of toxicity by Bran & wheat based feed 19.2 3.9 the consumption of ergot contaminated Oats 0.6 0.0 Wheat & flour 5.1 4.5 cereals on a daily basis by humans as well Rice & by-products 3.9 1.1 as animals. It would assist in evaluating Corn 1.1 0.0 Barley 00 11 health risks from intake of ergot alkaloids Sub Totals 719 275 and setting and enforcing appropriate standards.

99 Acknowledgement tamination in Uruguayan food and feeds. Natural Toxins 4:242-245. Pineiro, M. S., Silva, G., and Gonzalez, S. 1995. The author appreciates the review of Deteccion e identificacion de alcaloides del er­ this manuscript by Dr Peter M. Scott, got en alimentos y raciones. Page 89 in Abstract of VII Jornadas Cientificas de la Sociedad Uru­ Health Canada, Food Research Division, guaya de Biociencias, 28-30 April 1995, Pir­ Health Protection Branch, Ottawa; Dr iapolis, Uruguay. Marc Savard, Agriculture and Agrifood Scott, P. M. and, Lawrence, G. A. 1980. Analysis of ergot alkaloids in flour. Journal of Agricul­ Canada, Research Branch, Ottawa; and ture and Food Chemistry 28:1258-1261. Michael Stack, CFSAN, FDA, Washing­ Ware, G. M., Carman, A. S., Francis, o. 1., and ton, D.C. Kuan, S. S. 1986. Liquid chromatographic de­ termination of ergot alkaloids in wheat. Journal ofthe Association of Official Analytical Chem­ References ists 69:697-699. Pifteiro, M. S., Dawson, R., and Costarrica M. L. 1996. Monitoring program for mycotoxin con-

100 Sorghum Ergot in Mexico

J. H. Torres-Montalvo and N. Montes-Garcia

Abstract

Grain sorghum is one ofthe three most important crops in Mexico and its production is now threatened by ergot, which was first observed in February, 1997. Initial ergot in­ festation coveredparts ofthe states ofTamaulipas, Veracruz, and San Luis Potosi. As of May, 1997, ergot was present in northern Tamaulipas, and the states of Sinaloa, Nayarit, Jalisco, and Colima. The seed industry is attempting to reduce the impact ofeF­ got in seed production fields by applying triazole fungicides. More information is needed about chemicals, rates ofapplication, and phytotoxicity. INIFAP is conducting research in different areas to control the disease. Monitoring is being done to evaluate the spread and the severity ofergot. Chemical control and host plant resistance are prj. ority research areas. Regulatory measures have been applied to prevent the dissemina­ tion of CJaviceps africana.

Grain sorghum [Sorghum bicolor (L.) The main production areas are northern Moench] has increased in economic im­ and central Mexico in the states of Ta­ portance in Mexico during the last four maulipas, Sinaloa, Guanajuato, Michoa­ decades. Its adoption by farmers has been can and Jalisco (Fig. 1), where 87% ofthe so successful that it was considered the total grain is harvested (SAGAR 1996). second green revolution (DeWalt and The highest yields in the world have been Barkin 1985). This success was due to its achieved in the state of Guanajuato (19 t I high yield, wide adaptation to the differ­ ha- ). ent ecological conditions in Mexico, drought tolerance, and to the demand of Mexico is the fifth largest producer of the grain by the feed industry. Another grain sorghum in the world following the important factor was the availability of US, India, China, and Nigeria. In spite of hybrids that are used in 95% of the pnr this large production, Mexico imports 3.5 duction area. million t of sorghum grain annually which is equivalent to 45% of the total grain rt>­ Today, grain sorghum is the third most quired by the industry. This makes Mex­ important crop in the country sown in 1.4 ico the largest sorghum grain importer in million ha. More than 4.2 million tons of the world. grain is produced per year (F AO 1996). Many diverse factors limit grain yield including drought, soil salinity, pests and diseases. It was estimated that diseases • J. H. Torres-Montalvo, National Research Institute for Forestry, Agriculture and Livestock (INIPAF), Mexico, present address: are responsible for 10-15 % of crop losses Dept. of Plant Pathology and Microbiology, Texas A&M Univer­ in Mexico (Narro et al. 1992). Ergot sity, College Station, TX, USA.; and N. Montes-Garcia, INPAF, Apartado Postal 172, Rio Bravo, Tamaulipas, Mexico. 'Corre­ (caused by Claviceps africana), a poten­ sponding author. tially devastating disease of sorghum,

101 1. Sinaloa 2. Tamaulipas 3. Jalisco 4. Guanajuato 5. Michocan

Figure 1. Main grain sorghum producing areas in Mexico. was first observed in Mexico in February lipas and the neighboring states of 1997. Our paper presents the evolutionary Veracruz and San Luis Potosi, ergot was status of ergot in Mexico. found in commercial fields, seed produc­ tion fields, and nurseries with A-lines, R­ Initial Spread of the Disease lines, grain hybrids, and forage sorghums. Moist conditions persisted after the flow During the first week of February ering stage and saprophytes such as Cere­ 1997, the ergot epidemic spread to and bella sp. were observed. Ergot was also within Mexico. Ergot was initially o~ reported infecting johnson grass [Sor­ served in several sorghum fields in the ghum halepense (L.) Pers.] throughout states ofTam au lipas, San Luis Potosi, and the area and several plants of pearl millet Veracruz (Fig. 2). In Tamaulipas, the [Pennisetum glaucum (L.) R. Br.] under main sorghum producing state, infested high inoculum pressure in a winter grow­ plants were reported in the central and out nursery in southern Tamaulipas esta~ southern part of the state. In central Ta­ Ii shed by the Texas Department of Agri­ maulipas, ergot was observed in ratoon culture (IDA). crops and volunteer plants that flowered at the end of January. In southern Tamau-

102 Up to Feb '97 • Up to May '97

Figure 2 .. Spread ofsorghum ergot in Mexico.

The highest incidence of infection was sclerotia morphology, amount of secon­ reported in the sorghum male-sterile lines dary conidiation (Frederickson et al. and the forage sorghums. Some commer­ 1989, Frederickson et al. 1991), and the cial hybrids with various levels of male­ fact that this species was the causal agent sterility, believed to be caused by the sen­ in other countries of the Western Hemi­ sitivity of the plant to temperatures below sphere (Reis et al. 1996). Studies on alka­ 12°e during pollen formation also had a loid content are being conducted to con­ high incidence of ergot. Lack of pollen firm this identification. most likely contributed to colonization of the ovary by spores ofe. africana. Micro­ Continued Dissemination of Ergot sporogenesis is the developmental stage that is most susceptible to adverse envi­ There are two sorghum growing sea­ ronmental conditions (Manjarrez­ sons per year in northern Tamaulipas, Sandoval et al. 1989). during which 90-95% of the state's grain is produced. During the main season, sor­ Initially, ergot failed to move further ghum is sown throughout the month of north because host plants in this area su:t: February and during the first 8 days of fered freeze damage during the month of March (Herrera and Betancourt 1981); January (Fig. 3). The causal agent was however, the farmers usually sow sor­ identified as Claviceps africana, based on ghum from January to late March,

103 40....------.,..100 ;C

~ 354---~~--~~~~~~---4~~~== m o 80 nr ~ 30 !:t. ~ 25~~~--+r~--1~+_--r_r_--~~----~ (lj ::J 60 :c 20+~~·r,-+-r-W~~ 10r.... . i c: ~ 15~1'"~--; ,,--' -\0:1'/'''-/ 40 3 0.. E 10 Q) \.1 1 MaxRH 20 ~ I- 5 -1--'--:1-'_\_! _\;....1 ------Max Temp r.,","!1\""'~,,,,",, Min Temp 1 / o ~I I I I I I I I I rrrrrrrrrrrrrr 0 C C C c ..c ..c ~ '- '- ~ '- '- ~ >- ro ro ro ro Q) Q) ro ro ro ttl 0- 0- 0- ro '"")'"")'"")'"")LL.LL. :E :E :E :E « « « :E ~OOOOo 0r- o 0 0 0 0 0 ('t') ('I') ~ C\I ('t') 0 ~ C\I ~ C\I 0 ~ C\I ~

Figure 3. Maximum and minimum temperatures COC), and maximum relative humidity (%) in northern Tamaulipas, 1997, Rio Bravo, Mexico. depending on availability ofthe soil mois­ rility in some commercial fields and 2) ture. multiple planting dates have resulted in florets blooming over extended periods of After the first appearance of ergot, it time which contributes to availability of was expected that incidence would be less plant host to the fungal spores. Some in northern Tamaulipas during the main farmers had sown during the first week of growing season since sorghum usually January and others were still sowing in flowers during April-May. This is based May. The first observations suggests dif:. on historic climatic data, which suggests ferences in susceptibility to ergot among that temperature and relative humidity at different hybrids but more research is this time interval are not conducive for needed before definite conclusions can be development of ergot. However, the 1997 made. Up to 80% incidence and 40% se­ growing season was unique. Two factors verity were recorded in some commercial have contributed to the continued spread hybrids, particularly those that flowered of ergot: 1) the environmental conditions in late March and early April. were favorable for development of the disease as cool temperatures and high Besides the above listed factors, john­ relative humidity have been present most son grass is an endemic weed in the area ofthe season (Fig. 3) including tempera­ where estimates of more than 40 000 ha tures below 12°C that caused pollen ste- are infested in northern Tamaulipas

104 (Rosales 1994). This dramatically in­ creased considerably. In 1995 less than creases the risk of ergot incidence in sor­ 1% ofthe sorghum seed was produced in ghum fields, because johnson grass could Northern Tamaulipas [National Service act as an alternate host when sorghum flo­ of Inspection and Certification of Seeds rets are not available. (SNICS) 1996]. The remaining seed was imported and primarily from the United Ergot was observed in the Pacific re­ States. Eight seed companies and one gion in the states of Sinaloa, Nayarit, Jal­ farmer organization produced 22 differ­ isco, and Colima (Fig. 2), and was ofhigh ent hybrids on more than 2 000 hectares in incidence in production fields and re­ 1997 (SNICS 1997). Advantages for seed search nurseries that flowered in April production in this region are: favorable and May. As on May, 1997, ergot has not environmental conditions for production been reported in the Bajio, which is the of good quality seed, highly mechanized second largest sorghum production area farms, acceptable yields, a short split be­ in Mexico and comprises the states of tween flowering for both parents, con­ Guanajuato and Michoacan. The first sor­ stant winds that favor pollination, ade­ ghum fields will not initiate flowering un­ quate infrastructure for seed processing, til late June. There is a high risk that ergot availability of labor for rogueing the will be present in the Bajio because envi­ fields, availability of irrigation, and a ronmental conditions would be nearly large local market (Williams-Alanis and ideal for ergot development. Torres-Montalvo 1988).

Impact of Ergot on Seed Production After the first report of ergot in Me~­ ico, the seed industry was shocked at the Besides grain sorghum, northern Ta­ implications that this disease carried for maulipas is also the main sorghum seed seed trade and the fact that ergot primarily production area in Mexico. Most hybrid affects the male sterile-lines in the pro­ seed was produced in this region in the duction ofF1 hybrids, particularly ifthere 1980's (Table 1); however, due to in­ is poor pollination by the restorer lines creased costs, seed production has de- (Bandyopadhyay et al. 1996).

Table 1. Sorghum seed produced in Mexico, 1988-95. Year Area Seed Neededl Seed Produced Surplus or Yield (113) (t) (1) Defjcir (1 ha-I) 1988 17160 42790 73816 113.0 2.6 1989 9247 37312 17323 117.0 1.9 1990 10716 42146 21016 41.0 2.0 1991 5834 33206 9809 63.0 1.7 1992 5543 32072 9980 31.0 1.8 1993 946 21404 1333 47.0 1.4 1994 308 20652 309 6.S 1.0 1995 2213 35031 3754 0.9 1.7

Source: National Service of Inspection and Certification of Seeds (SNICS) IHybrid seed needed for commercial use the following year. 2For the growing season the following year.

105 During a disease survey in early May ing to evaluate incidence and severity of 1997, ergot was not observed in the seed ergot. production fields blooming although in­ oculum was present because infected Studies on preventive chemical control plants were found in nearby commercial are being conducted using both systemic fields that had flowered in April. and contact fungicides. Time of applica­ tion, chemicals, rates, and methods of ap­ Seed companies are using chemical plication are some of the variables under control to prevent ergot by applying tria­ study. Chemical seed treatments are also zole fungicides based on the success in being conducted. Management practices Brazil (Ferreira et al. 1996). Adequate such as planting dates, temperature ef:. equipment for ground application of fects on fertility and viability of sorghum chemicals is not available and, therefore, pollen, and identification of alternate aerial applications are being used. Propi­ hosts are being evaluated. conazole (Tilt~ or tebuconazole (Folu­ cur®) have been sprayed 2-3 times by the Host plant resistance is the most eco­ seed companies. Rates varied from 250 to nomical and logical control strategy if 1 500 ml of chemical (250 g ajo L- ). The sources ofresistance are available. All pa­ cost of three sprays is estimated at US rental lines and hybrids of !NIFAP are 1 $625 ha- , including the cost ofthe chemi­ currently being evaluated. Resistance, cal and aerial applications. Most applica­ when identified, needs to be incorporated tions were done during blooming. Seed into elite sorghum germplasm. Other re­ producers are concerned with possible search projects include studies on toxicol­ phytotoxic effects offungicides on the pa­ ogy, biology of the pathogen, and DNA rental lines when applied during the flow­ marker assisted selection. ering stage sprayed twice before the plants began to bloom. The first applica­ Scientists from !NIFAP and Texas tion was at the 50% flag leaf stage, and the A&M University conducted a meeting in second 5-6 days later. The efficiency of April 1997, to plan and implement col­ aerial applications to control the possible laborate research in areas of mutual inter­ presence of ergot and phytotoxicity are est. Chemical control and monitoring the being evaluated. spread of ergot in Mexico and Texas were of the greatest concerns. Research Regulation When ergot was first reported in Mex­ ico, the National Research Institute for Sanidad Vegetal, the phytosanitary Forestry, Agriculture and Livestock (INI­ agency in Mexico imposed an emergency F AP) immediately initiated a comprehen­ plan to control the spread of ergot to other sive program to control the disease. The regions of the country. The objective of first priority was to determine the extent this plan was to diagnose, prevent, control ofthe disease. A research team, primarily and eradicate sorghum ergot (SAGAR, from the Rio Bravo Experimental Station, Diario Oficial de la Federaci6n, 1997). conducted regional and national monitor- These measures included incineration of

106 fields with more than 50% incidence, lim­ press. INIFAP is also producing technical ited the sale of infected grain to areas articles. where sorghum is not produced, and dis­ infecting of equipment used in infested Acknowledgments fields with 5% NaCI. The first author thanks Dr. Clint Magill After the announcement of this plan, and the USAID grant No. PCE-5063-A- other regulations have been made public. 00-2045-00 "Solutions to some livestock, The measures can be divided into three ar­ poultry and plant health production prob­ eas: management of infected grain, in­ lems that are of concern to free trade be­ spection and management ofseed produc­ tween Mexico and the United States" for tion fields and storage facilities, and pro­ sponsoring the expenses to travel to dif. hibit impqrtation of infected grain and/or ferent locations in Mexico to collect data seed. These measures were reviewed by and for funding to participate in the Con­ the responsible regulatory agency which ference in Brazil. also cooperates with scientists and the sorghum industry to obtain information to References regulate the movement of contaminated Bandyopadhyay, R., Frederikson, D. E., McLaren, grain/seed and to approve use ofthe effec­ N. W., and Odvody, G.N. 1996. Ergot, a global tive fungicides needed to control ergot. threat to sorghum. International Sorghum and Millets Newsletter 37:1-32. DeWalt, B.R., and Barkin, D. 1985. EI sorgo y la Education crisis alimentaria mexicana. Pages 153-167 in EI sorgo en sistemas de produccion en america Sorghum producers, extension special­ latina (C.P. Paul, and B.R. De Walt, eds.). EI Batan, Mexico: Centro Internacional de Mejo­ ists, and the sorghum industry will need ramiento de Maiz y Trigo. additional research to provide answers on FAO. 1996. Production Year Book 1995. 49:84- 85. Rome, Italy: FAO. ergot and effective methods for control. Ferreira, A S., Pinto, N. F. 1. A, and Casela, C. R. They need to be informed of problems 1996. A valiacao de Fungicidas para 0 controloe and methods to reduce the impact of the de ergot ou doenca acucarada (Claviceps afri­ cana) em sorgho. Pesquisa em andemento 14.4 malady. Several seminars, meetings and pp. conferences were organized by different Frederickson, D. E., Mantle, P. G., and de MiJliano, agencies to provide information about er­ W. A. J. 1989. Secondary conidiation of Sphacelia sorghi on sorghum, a novel factor in got to producers, the private sector, and the epidemiology of ergot disease. Mycological institutions involved in the sorghum in­ Research 93:497-502. dustry. Frederickson, D. E., Mantle, P. G., and de MiJliano, W. A 1. 1991. Claviceps africana sp-nov.; the distinctive ergot pathogen of sorghum in Africa. Information is vitally needed in Span­ Mycological Research 95:1101-1107. ish. The bulletin "Ergot - A global dis­ Herrera, A., and Betancourt, A 1981. Fecha op­ tima de siembra en sorgo. Folleto Tecnico No. ease threat to sorghum" produced by the 1. Campo Agricola Experimental Rio Bravo. Sorghum Improvement Conference of INIA 16 pp. North America (SICNA) and the Interna­ Manjarrez-Sandoval, P., Gonzalez-Hernandez, V. A, Mendoza-Onofre, L. E., and Engleman M. tional Crops Research Institute for the 1989. Drought stress effects on the grain yield Semi-Arid Tropics (ICRISA T), was and panicle development of sorghum. Canadian translated into Spanish and is now in Journal of Plant Sciences 69:631-641.

107 Narro, J., Betancourt, V. A, and Aguirre, 1. 1. 1992. ergot disease, caused by a pathogen diagnosed Sorghum diseases in Mexico. Pages 75-84 in as C/aviceps africana. Plant Disease 80:463. Sorghum and millets diseases: a second world Rosales, E. 1994. Control del zacate johnson en review, W. A 1. de Milliano, R. A Frederiksen, maiz. Folleto Tecnico No. 15. Campo Experi­ and G. D. Bengston (eds). Patancheru 502 324 mental Rio Bravo. INIF AP. 8 pp. Andhra Pradesh, India: International Crops Re­ Secretaria de Agricultura, Ganaderia y Desarrollo search Institute for the Semi-Arid Tropics. Rural (SAGAR). 1996. Anuario Estadistico. National Service ofInspection and Certification of DGPA Mexico D.F. Seeds (SNICS). 1996. Produccion de semilla Secretaria de Agricultura, Ganaderia y Desarrollo certificada de sorgo. Estadisticas 1988-1995. Rural (SAGAR). 1997. Diario Oficial de la Fed­ SNICS-SAGAR. Mexico D.F. eraci6n. Pages 53-54. Abril 7 de 1997 National Service ofInspection and Certification of Williams-Alanis, H. and Torres-Montalvo, H. Seeds (SNICS). 1997 Produccion de semilla 1988. Produccion de semilla de sorgo. Pages certificada de sorgo. Estadisticas 1997. SNICS­ 22-45 in Produccion y manejo de semillas, H SAGAR. Matamoros, Mexico Castillo. ed. Matamoros, Mexico: PIFSV Press. Reis, E. M., Mantle, P. G., and Hassan, H. A G. 1996. First report in the Americas of sorghum

108 Session IV - Ergot Biology

Session President - R.A. Frederiksen

109 DNA Comparisons and Alkaloid Toxicity of the Ergot Fungi - A Contribution to Ergot Phylogeny Sylvie Paioutova

Abstract

The RAPD patterns ofClaviceps purpurea revealed great variability even among the isolates from the same plant and head Two groups were found, based on the relatedness oftheir RAPD patterns as well as on the presence or absence ofan EcoRI restriction site in the 5. 8S rDNA. One ofthem (EcoRI+) predominated on the cereals and grasses from open habitats whereas the other (EcoRI-) preferred glycophytic hosts. Unlike e. pur­ purea, the RAPD patterns ofe.fusiformis, e. paspa/i and e. gigantea did not show intra--species variability. The DNA sequence comparison ofITS spacers and the 5.8S rDNA region from 12 Claviceps species revealed the existence of two distinct groups: Group1-e. viridis, e. africana, e.gigantea, Clavicepssp. exSorghum, Clavicepssp. ex Panicum maximum, e. phalaridis and e. citrina and Group 2-e. purpurea, e. sul­ cata, e. fusiformis, e. grohii and e. paspa/i.

Both Claviceps sp., e. citrin a, e. phalaridis and e. paspa/i shared a deletion in the ITS1 region, e. phalaridis and e. citrin a exhibited another deletion in the ITS2 region, about 30 bp long. The missing regions were also found in the outgroup species Fusar­ ium sambucinum suggesting their older phylogenetic origin.

The alkaloids in sclerotia and shaken cultures ofe. gigantea were analyzed The e. gigantea pathway leads from dihydro-chanoclavine throughfestuclavine and dihydro­ lysergol to dihydrolysergic acid The occurrence ofdihydroergosine, the only dihydro­ genated peptide alkaloid known from the phylogenetically related species e. africana indicates that in e. africana a similar pathway could be operating.

The Position of Claviceps the family Clavicipitaceae. The family is among Hypocreales placed in the order Hypocreales, but in the fifties, doubts concerning the morphol­ The evolution and to some extent the ogy ofthe conidiogenous stroma led some taxonomy ofthe parasitic fungi belonging mycologists to transfer it into Xylariales to the genus Claviceps are influenced by (Luttrell 1951). Another mycologists their host plants-grasses, rushes and erected the order Clavicipitales (Gau­ sedges. The genus Claviceps belongs in mann 1952). Recently, molecular taxon­ omy was used to solve the relationships among different members ofHypocreales

Sylvie Paloutova, Senior Researcher, Institute of Microbiology, Czech and the original placement of monophy­ Academy of Sciences, VideAska 1083, 14220 Prague, Czech Republic letic Clavicipitaceae into this order was confirmed. The molecular phylogenies

111 also show that the genus Claviceps was grasses from open habitats (Figure 1). the flrst group derived from the common EcoR- group consisted of30% ofisolates ancestor line, then Epichloe/Neotypho­ and seems to prefer the glycophytic hosts, dium followed by Atkinsonella and last like Molinia, Agrostis, Poa annua, Cala­ clade contains species of Balansia and magrostis, but was also found on Festuca Myriogenospora (Spatafora and Black­ rubra and Dactylis sp. In this group, there well 1993, Rehner and Samuels 1995, are two basic RAPD patterns with the Glenn et al. 1996). These results contra­ primer 257. dict the formerly held hypothesis about Balansia being the most primitive clavi­ After conflrming the stability of flnger­ cipitoid group. print patterns during the asexual propaga­ tion ofthe isolates, experiments were car- The Intraspecific Variation of C. purpurea

The undoubtedly most widespread er­ got is the type species C. purpurea that Eco RI+ Eco RI- colonizes all pooid and arundinoid kb grasses and also occurs on chloridoids and rarely on panicoids. This wide host spectrum led many mycologists to search for varieties or races based on host prefer­ ences. Indeed, several groupings were de­ scribed during this century, but when compared they differ, e.g., Stager's (cf. Campbell 1957) European groups from the groups observed in Japan by Tanda (1979). Campbell (1957) cross­ inoculated the C. purpurea isolates from 37 grasses and found that when quite ag­ gressive methods of artiflcial inoculation were used, no host preferences occurred.

The search for varieties continues us­ ing the methods of DNA flngerprinting in our laboratory and in the group of Prof. 1 2 3 4 A, 8gl1 Tudzynski in Germany. Results were the Figure 1. RAPD banding patterns of C pur­ same in both laboratories (JungehUlsing purea subgroups with the primer 1995). There are at least two groups that 257. I - isolate from Lolium sp., England; 2 - isolate from Fesluca share 1-2 major RAPD bands and we ovina, Czech Rep.; 3 - isolate from Poa annua, Czech. Rep., 4 - isolate from AgrOSlis sp., Belgium. found that they also differ in the presence a - C. purpurea species-specific band of EcoRI conservative restriction site in b - Eco RI+ group-specific band c - Eco RI- group-specific band the 5.8S rDNA. EcoRI+ group (70 % of A - type of pattern found in 16 Eco RI- isolates isolates) was found on cereals and the B - type of pattern found in 2 EcoRl- isolates

112 ried out to look at mutation and rei sola­ with equal chromosome number but une­ tion, variability through comparing the qual chromosome size was possible, but isolates from different florets on the same each isolate from the progeny had differ­ flower head, different heads from the ent karyotype due to translocations during same plant, different plants at the same lo­ meiosis. Translocations during the sexual cality and from different species of this cycle were the major source of RAPD locality. Pattern differences were found variability. Chromosomal polymor­ even among isolates from the same head phisms were observed among the isolates (Figure 2) that confirm multiple infection from the same place, year and host spe­ steps. cies, probably due to chromosomal rear­ rangements. JungehUlsing, from Tudzynski' s group, found that the chromosome To find out ifthe RAPD polymorphism number in C. purpurea isolates is variable variability of C. purpurea was reflected (3 - 6) and that their size ranges from 1.8 also in other genome parts, the rDNA re­ to 7 Mh. She confirmed that the sexual gions containing ITS spacers and 5.8 crossing (by double infection) of parents rDNA from the strain C. purpurea P695/S

Species-specific RAPD (206)

africana fusiform

II

II

citrina phalaridis grohii viridis gigantea paspali

II

II Figure 2. The RAPD variability ofthe field isolates from Lolium.

113 (Schumann et al. 1982), isolated probably GAM 12885 and 109 differed from the from European cereals, and from C. pur­ European P695/S each in the 5 and 6 posi­ purea, isolated in our laboratory from tions, respectively. They varied in the sclerotia onPhalaris sp. collected in Aus­ ITS 1 spacer, but none were common tralia, were sequenced. These sequences whereas the difference between them was were compared to two American C. pur­ in 10 positions ofITSl. GAM 12885 also purea sequences: isolate GAM 12885 lacked the conservative EcoRI restriction collected on Dactylis glomeratanear Ath­ site located in the 5.8S rDNA sequence ens, Georgia, USA (Glenn and Bacon which documents that EcoRI+ and 1996, sequence U57669 in GenBank) and EcoRI- group exists also in America. isolate 109 from Festuca arundinacea, Lexington, Kentucky (Schardl et al. The Variability of other 1991). Claviceps species

The European and Australian isolate DNA fingerprinting of nine Claviceps differed only in a single base out of 556 species was performed by RAPD tech­ localized in ITS2. The American isolates nique with primer 206 (TCAA-

Head 3 Head 8 Plant 1 Plant 2

Figure 3. Species-specific RAPD with the primer 206.

114 CAATGTCGGCCTCCGT) (Figure 3). Chloridoideae, according to the geer Unlike C. purpurea, different isolates of graphical distribution, acquired C4 pher C. paspa/i and C. fusiformis exhibited tosynthesis and expanded before the very low RAPD pattern variability. The breakup of the Pangea (Middle Creta­ patterns ofthree Mexican C. gigantea iso­ ceous), the greatest number of species be­ lates were identical and also C. africana ing concentrated in South Africa. isolates from Bolivia and Australia did not differ. It may be argued that C. afri­ Part of the Panicoideae (the tribe Pani­ cana is spreading too rapidly to develop ceae) acquired C4 photosynthesis shortly genome differences among distant iser before South America was separated from lates. The patterns with the primer 206 the rest of Gondwana (Late Cretaceous). were markedly species-specific and this In isolated South America, Paniceae could enable the identification of sphace­ grasses became dominant. C3 photosyn­ lial stages once the teleomorph RAPD thesis was retained in apparently more was determined. The RAPD pattern was primitive shade loving species (Opli~ used as the first criterion for excluding the menus, lcnanthus, and partially Panicum) possibility that the newly discovered er­ whereas C4 species colonized open habi­ got from D. spicata (c. citrina) is C. pur­ tats of tropical and subtropical zones purea (Paloutova et al. 1998). (some species of Panicum, Paspa/um, Cenchrus, Brachiaria, Pennisetum). The Claviceps Phylogeny In southern Asia, the Andropogoneae Langdon (1952, 1954) presented the (Sorghum, Zea, Saccharum, Bothri­ first outline of Claviceps evolution. Its ochloa, Imperata) developed from some main course is connected with the evolu­ C4 ancestor and rapidly occupied savanna tion of grasses and the global climatic habitats and dry open woodlands. It is as­ changes, so that brief outline of grass ever sumed that this occurred some 25-30 mil­ lution will be given here: lion years ago (mya). Andropogonoid species form 30-40% of all grass species Grass Evolution in India and Africa. The transfer of An­ dropogoneae to America occurred proba­ Brown and Smith (1972) and Jones bly via southern Europe, before their (1991) summarize the evolution of separation in Tertiary and they reached grasses. Grasses probably appeared dur­ Australia via island chains. ing the Jurassic period (Mesozoic), in the wet tropics. The subfamilies Phareae, Pooidae subfamily retained C3 photer Centothecae and Arundinoidae (C3) are synthesis, as C4 does not present any ad­ presumed to be the most primitive. De­ vantage in a cooler climate. It expanded scendants of early arundinoids are the mainly into the Northern Hemisphere. subfamilies Chloridoidae and Panicoi­ The Southern Hemisphere does not sup­ deae that developed C4 photosynthetic port its climatic needs except in New Zea­ pathways and thus acquired competitive land, southern South America and Aus­ advantage in warmer regions. tralia.

1J5 The grass phylogenies derived from chloridoid-specialized species known so plastid as well as nuclear DNA sequences far are C. cynodontis (Cynodon), C. yana­ show two main groups: In the PACC gawaensis (Zoysia), and C. cinerea (Hi­ group (Panicoids, Arundinoids Chlori­ laria) and we added a new species, C. ci­ doids and Centothecae), chloridoids and Irina, found in Central Mexico on Dis­ arundinoids are sister groups to the ances­ tichlis spicatawhich was described in our tor of panicoids, which correlates well laboratory (PaIoutova et al. 1998). Also with the theory based on the geographical the occurrence of C. purpurea on chlori­ distribution of grass subfamilies. The doids was documented (Campbell 1957, group BOP contains Bambusa-Oryza and Gray et al. 1990). Pooids (Mathews and Sharrock 1996). The pooid ergot is represented by C. Ergot Distribution purpurea with Laurasian distribution and parasitic/endophytic C. phalaridis en­ The global distribution of Claviceps demic to Australia. Both species colonize species is influenced by the presence of arundinoid species like Danthonia and the grass hosts and also by the human fac­ have a wide host spectrum, although C. tor. With the exception ofBrazil and West purpurea is considered as an advanced India atthe end ofthe 19th century (Moller species and C. phalaridis a more primi­ 1901, Hennings 1899), the information tive one. C. litoralis occurs on northern concerning the occurrence oftropical for­ Japanese islands, and Sakhalin, on Ely­ est ergots is very scarce. As far as I know, mus and Hordeum (Kawatani 1944). no primitive ergot with an undifferenti­ Some mycologists, however, doubt its' ated sclerotium has been found in an Afri­ species status and consider it a variety of can tropical forest. However, this could C. purpurea. C. grohn, C. cyperi and C. be also explained by the periodical nigricans that colonize sedges of the changes of climate in Africa that led to ex­ North temperate regions bear some mor­ tinction of original rain forests. The best phologic and metabolic similarity to C. information about geographical and host purpurea (Mower and Hancock 1975) distribution is available for the ergots that colonize cereals and pasture grasses In the genus Claviceps, the panicoid (Langdon 1952). species prevail. The most primitive spe­ cies, C. orthocladae which is found on The distribution of ergot species Centothecae and C. flavella and C. dia­ throughout the world has several interest­ dema (undifferentiated sclerotium en­ ing features. First, there is a striking dit: compassing the flower parts, germination ference in the number of ergot species directly on the host) which are found on colonizing the main subfamilies of POR­ panicoids, occur only in the South Amer­ ceae. The colonization of chloridoid, ica tropics, whereas none have been arundinoid and pooid hosts is somewhat found in wet tropical and subtropical for­ obscured by the vast occurrence ofC. pur­ ests of Africa 'and South Asia. None ofthe purea, but in fact ergot occurrence out­ South America ergots were found in other side panicoids is as rare as its' occurrence regions except for C. paspali that was on cyperaceous hosts. The only

116 spread by human influence. They evolved shows two highly supported distinct as a separate group. In contrast, several groups: species are found both in Africa and India and some also in Australia, so that the or~ 1. C. viridis, C africana, C. gigantea, C. gin of these species is obscured by a rela­ phalaridis, Claviceps sp. ex Sorghum and tively recent exchange. No colonization Panicum and C. citrina of arundinoid grasses was observed in panicoid ergots. 2. C. purpurea, C. sulcata, C. fusiformis, C. grohii and C. paspaJi Claviceps Phylogenetic Tree The more basal species C. phalaridis, Following the study of ergot distribu­ Claviceps sp. ex Sorghum and Panicum, tion and grass evolution, the species for C. citrina and also C. paspaJi from the phylogenetic analysis based on the com­ second group shared a marked deletion in parison of internal transcribed spacers the ITS 1 region, C. phalaridis and C. ci­ ITS1, 2 and 5.8S rDNA were collected. trina exhibited another deletion in the Four species (Table 1) were obtained ITS2 region, about 30 bp long. These de­ from the collections, while the remaining letions were found not only in the Fusar­ eight were isolated in our laboratory. ium outgroup but to some extent also in another two sequences of nectriaceous The aligned DNA sequences were ana­ fungi that we tested as suitable outgroup lyzed by the neighbor-joining method species and could be interpreted as a contained in Puzzle (Strimmer and von primitive character. Haeseler 1996) and MEGA packages (Kumar et al. 1994). Fusarium sam­ A schematic restriction map of the se­ bucinum sequence X65477 from Gen­ quences and the position of deletions are Bank (O'Donnell 1992) was used as an shown on Figure 4. As the tree was made outgroup species. The tree (Figure 3) only from one quarter of known Claviceps species, the relationships are

Table 1. Characterization of ergot species used in phylogeny tree. Species Host Origin Alkaloids C.purpurea Pooidae Europe, America clavines, ergopeptides Arundinoidae Africa, Australia C. fosiformis Pennisetum, Cenchrus Africa clavines C. sulcata Brachiaria Africa + C. grohii Carex Canada + C nafivali Paypalum South America c1avines lysergamides c.'viridis Oplismenus India, Japan C. aJricana Sorghum Africa dihydroergosine C. gigantea Zea Mexico dihydroclavines dihydrolysergamide C. phalaridis Pooidae Australia Arundinoidae Claviceps sp. Sorghum Japan unknown Claviceps sp. Panicum maximum Paraguay unknown C. citrina Distichlis Mexico

117 C• Vln• 'd' IS 86 _rL C. africana 64 73 I 89 C. gigantea 81 C. phalaridis Claviceps sp. (Sorghum) _ Claviceps sp. (Panicum maximum) r-- C. citrina

~. C. paspali C. grohii

~ C. sulcata 93 "78 C. pUIJlurea 7"51 ~ C. fusiformis Fusarium

Figure 4. Neighbor joining tree for 12 Claviceps species. The gamma distances were computed according to Jukes and Cantor algorithm, parameter a=0.32, with pairwise deletion option con­ tained in the MEGA software. NJ tree was constructed with 500x bootstrap. The branch support BCL values (higher than 50%) are shown on the respective branches. far from absolute. However, they confirm The second branch is quite puzzling. the existence of two main groups and the Advanced cold resistant species distrib­ close relationship of South American spe­ uted on the Northern Hemisphere and cies to the ergot ancestors. The Claviceps found on pooids and/or sedges are united tree corresponds to some extent to the with African savanna species strictly scheme of grass evolution published by bound to panicoid hosts. What is even Mathews and Sharrock (1996). The first more striking is the similarity of DNA se­ group corresponds to the grasses of quences in this group-at least 97% PACC clade. C. phalaridis probably de­ among the most distant C. purpurea and veloped on arundinoids and survived in C. grohii that speak for the relatively re­ Australia because its pooid hosts were not cent evolution. Rehner and Samuels colonized by C. purpurea. The grouping (1995) observed 95.6% identity in 960 bp ofMexican andropogonoid parasite C. gi­ fragment of 28S rDNA of C. purpurea gantea with two Sorghum parasites from and C.fusiformis. Africa confirms that the andropogonoids took their ergots with them during their The first ergot species probably ap­ radiation from South Asia. peared on the predecessors of PACC grasses in the warm and humid climate of

118 the South America region of former Gon­ fusiformis (agro-, elymo- and chanoclav­ dwana. This hypothesis is supported not in e), C. paspa/i (clavines and lysergic only by the geographic distribution and acid amides), C. gigantea (dihydroclav­ molecular phylogeny of contemporary ines) (for review see Flieger et al. 1997). primitive Claviceps species but also by The peptide alkaloid dihydroergosine is the lack of primitive tropical forest ergot the main component in C. africana and species in Africa. traces of agroclavine were found in C. sorghi (Mantle 1968). Tanaka and Main spreading of ergot proceeded to­ Sugawa (1952) detected peptide alka­ gether with the expansion of panicoid loids, ergometrine and agroclavine in species. The change in world climate on sclerotia of C. imperatae. Porter et al. the Cretaceous-Tertiary boundary led to (1974) detected ergometrine-related alka­ reduction of tropical forests and increase loids in ergotized Cynodon dactylon, but in open grassy habitats. The ergot specia­ the ergot species was not identified. Taber tion then continued independently on all and Vining (1960) found alkaloids in sub­ continents of the former Gondwana. The merged cultures of C. maximensis and an ergots of the first group probably origi­ ergot from Zizania sp. nate from this event. The exchange among African and Indian species was In his descriptions of new Japanese er­ enabled at the same time as the spreading got species (Tanda 1981, 1991) only as­ of andropogonoid grasses in the Oligo­ sayed alkaloids in sclerotia using blue cene. coloration with vanUrk's reagent and their toxicity to mice. Some positive col­ The contemporary ergots ofthe second orimetric reaction was found only in C. group occurring in the colder climatic re­ bothriochloae (Tanda 1991). In C. yana­ gions and semi-arid Africa probably gawaensis, however, the mice toxicity evolved relatively recently to fill the eco­ was observed despite the absence of logical niches available which required measurable alkaloids (Tanda 1981), sug­ the adaptation to survive low tempera­ gesting the presence of other toxic secon­ tures and/or dryness. Where their ances­ dary metabolites. tors came from is unclear and more spe­ cies from these regions should be ana­ An indirect proof of alkaloid produc­ lyzed. Tentatively we speculate about a tion by C. cinerea was the occurrence of Laurasian origin and relatively recent abortions in cattle grazing Hilaria mutica, transfer to Africa. colonized by this ergot in North Mexico (Zenteno-Zevada 1958). Alkaloids of Different C/aviceps species In our laboratory we study the alkaloid content of different Claviceps species as Until now, the qualitative analysis of well as the intraspecific variation in alka­ alkaloid content has been made in only loids of C. purpurea. The type of alka­ seven species of the 43 described, these loids produced could also help in the elu­ being C. purpurea (peptide alkaloids of cidation of relatedness amongst species. the ergotamine or ergotoxine group), C.

119 C. gigantea Flieger, M., Sedmera, P., and Novak, 1. 1991. Deg­ radation products of ergot alkaloids. Journal of Natural Products 54:390-395. We analyzed the alkaloids produced in Flieger, M., Wurst, M., and Shelby, R. 1997. Ergot sclerotia as well as shaken cultures of C. alkaloids - sources, structures and analytical methods. Folia Microbiologica (Prague). 42:3- gigantea. Dihydroderivatives of the com­ 30. pound known from the usual clavine­ Frederickson, D. E., Mantle, P. G., and de MiIliano, lysergic acid pathway were found, sug­ W. A 1. 1991. Claviceps africana sp-nov.; the distinctive ergot pathogen of sorghum in Africa. gesting that C. gigantea alkaloid biosyn­ Mycological Research 95:1101-1107. thesis leads from dihydrochanoclavine Giiumrum, E. A 1952. The Fungi, New York, Haf­ through festuclavine and dihydrolysergol ner Publishing Co. Glenn, A E., Bacon, C. W., Price, R., and Hanlin, to dihydrolysergic acid. The precursor of R. T. 1996. Molecular phylogeny of A crem 0- this pathway is not known. It is interesting nium and its taxonomic implications. Mycolo­ that dihydroergosine, the only dihydro­ gia 88:369-383. Gray, A 1., Drury, M., and Raybould, A F. 1990. genated peptide alkaloid known, is pro­ Spartina and the ergot fungus Claviceps pur­ duced by the related species C. africana purea - a singular contest? Pages 63-79in (Mantle 1968, Frederickson et al. 1991). Pests, Pathogens and Plant Communities, 1. J. Burdon and S. R. Leather, eds. Oxford: Black­ This indicates that in C. africana, a simi­ well Scientific Publications. lar pathway is operating. Hennings, P. 1899. Xylariodiscus nov. gen. und einige neue brasilianische Ascomycetes E. Ule' schen Herbars. Hedwigia, Beibl. 38: 63-65. Other Claviceps species Jones,C. A 1991. C4 grasses and cereals: growth, development and stress response. Pages 39-54. Our preliminary analyses show that al­ New York, Chichester, Brisbane, Toronto, Sin­ gapore: John Wiley. kaloids are present in the shaken cultures Jungehulsing, U. 1995. Genomanalyse bei ofC. grohiiandC. sulcata. Walker (1957, Claviceps purpurea. Bibliotheca Mycologica 1970) found no alkaloids in C. phalaridis 161, Berlin, Stuttgart: 1. Cramer. Kawatani, T. 1944. Clavicipiti species nova para­ sclerotia. This interesting ergot species is sitica ad Elymum mollem Trin. Bulletin of the noted by its endophytism on pooid and National Institute of Hygienical Science (Ja­ arundinoid grasses in Australia. We ana­ pan). 65:81-83. Krajicek, A, Trtik, B., Spacil, J., Sedmera, P., lyzed the sclerotia and cultures in our Vokoun, J., and Rehacek, Z. 1979. Hydroxyer­ laboratory on HPLC enabling the detec­ gotamine, a new ergot alkaloid. Collection of tion of alkaloids on the ppm level and the Czech Chemical Communications 44:2255- 2260. preliminary results confirmed their ab­ Kumar, S., Tamura K., and Nei, M. 1994. sence as well as the presence of group of MEGA:Molecular Evolutionary Genetics unknown metabolites. We obtained, after Analysis software for microcomputers. CA­ BIOS 10:189-191. the analysis, sclerotia of a new species of Langdon, R. F. N. 1952. Studies on ergot. PhD Mexican ergot C. citrina from D. spicata. Thesis, University of Queensland, Australia. Langdon, R. F. N. 1954. The origin and differentia­ tion of Claviceps species. University of References Queensland Papers: Botany 3:61-68. Lehmann, P. F., Lin, D., and Lasker, B. A 1992. Brown, W. V., and Smith, B. N. 1912. ~rass evolu­ Genotypic identification and characterization tion and the Kranz syndrome, C 3/C 2 ratios and of species and strains within the genus Candida continental drift. Nature 239:345-346. using random amplified polymorphic DNA Campbell, W. P. 1957. Studies of ergot infection in Journal of Clinical Microbiology 30:3249- gramineous hosts. Canadian Journal of Botany. 3254. 35:315-320. Lin W. N. C. H., and Ramstad, E. 1967. Enzymol­ ogy of ergot alkaloid biosynthesis. part III. 10-

120 Hydroxyelymoclavine, an intermediate in the logenetic relationships of nonpathogenic grass peroxidase conversion of elymoclavine to pen­ mycosymbionts and clavicipitaceous plant niclavine and isopenniclavine. Lloydia 30:202- pathogens. Plant System and Evolution. 208. 178:27-41. Linhartova-Bumbova, R., Flieger, M., Sedmera, Schumann, B., Erge, D., Maier, W., and Groger, D. P., ZimaJ. 1991. New aspects of submerged fer­ 1982. A new strain of C. purpurea accumulat­ mentation of Claviceps paspali. Applied Mi­ ing tetracyclic clavine alkaloids. Planta Medica crobiology and Biotechnology. 45:11-14. Luttrell, E. S. 1951. Taxonomy ofPyrenomycetes. Spatafora, 1. W., and Blackwell, M. 1993. Molecu­ University of Missouri Studies 24:1-120. lar systematics of unitunicate perithecial asco­ Mantle, P.G. 1968b. Studies on Sphacelia sorghi mycetes: The Clavicipitales-Hypocreales McRae, an ergot of Sorghum vulgare Pers. An­ connection. Mycologia 85:912-922. nals of Applied Biology 62:443-449. Strimmer, K. and von Haeseler, A. 1996. Quartet Mathews, S., and Sharrock, R. A. 1996. The phyto­ puzzling: a quartet maximum likelihood chrome gene family in grasses (Poaceae): A method for reconstructing tree topologies. Mo­ phylogeny and evidence that grasses have a sub­ lecular and Biological Evolution 13:964-969. set of the loci found in dicot angiosperms. Mo­ Taber, W. A. and Vining, L. C. 1960. A comparison lecular and Biological Evolution 13: 1141- of isolates of Claviceps spp. for the ability to 1150. grow and to produce alkaloids on certain nutri­ Moller, A. 1901. Phycomyceten und Askomyceten ents. Canadian Journal of Microbiology 6:355- von Brasil. Pages 1-319 in Botanische Mitthei­ 365. lungen aus den Tropen 9, A. F. W. Schimper, Tanaka, K. and Sugawa, T. 1952. Journal of the ed. Jena, Germany: G. Fischer Verlag. Pharmaceutical Society (Japan) 72:616-620. Mower, R. L and Hancock, 1. G. 1975. Sugar com­ Tanda, S. 1979. Mycological studies on the ergot in position of ergot honeydews. Canadian J oumal Japan 9. Distinct variety of Claviceps purpurea of Botany 53:2813-2825. Tul. on P halaris arundinacea L. and P. arundi­ O'Donnell, K. 1992. Ribosomal DNA internal tran­ nacea var. picta L. Tokyo Nogyo Daigaku scribed spacers are highly divergent in the phy­ 24:79-95. topathogenic ascomycete Fusarium Tanda, S. 1981. Mycological studies on the ergot in sambucinum (Gibberella pulicaris). Current Japan 20. Claviceps yanagawaensis Togashi Genetics 22:213-220. parasitic on Zoysia japonica Steud. Tokyo pazutova, S., FucikovsIcy, L., Leyva-Mir, S. G., Nogyo Daigaku 26:193-199. and Flieger, M. 1998. Claviceps citrina sp. Tanda, S. 1991. Mycological studies on ergot in Ja­ nov.; a parasite of halophytic grass Distichlis pan 26. A new ergot, Claviceps bothriochloae spicata from central Mexico. Mycological Re­ parasitic on Bothriochloa parviflora. Tokyo search. 102:850-854. Nogyo Daigaku 36:36-42. Porter, J. K., Bacon, C. W., and Robbins, 1. D. Walker, 1. 1970. Systemic fungal parasite of 1974. Major alkaloids of a Claviceps isolated Phalaris tuberosa in Australia. Search 1:81-83. from toxic Bermuda grass. Agricultural and Walker, 1. 1957. A new species of Claviceps on Food Chemistry 22:838-841. Phalaris tuberosa L. Proceedings of the Lin­ Rehner, S. A., and Samuels, G. 1. 1995. Molecular nean Society of the New South Wales 82:322- systematics of the Hypocreales: a teleomorph 327. gene phylogeny and the status of their ana­ Zevada-Zenteno, M. 1958. Estudios sobre hongos morphs. Canadian 10urnal ofBotany 73 Supple­ parasitos de Gramineas de la republica Mexi­ ment: S816-S823. cana. Pages 501-519. in II. Memorios del Schardl, C. L., Liu, J. S., White, J. F., Finkel, R. A., Primer Congreso Nacional de Entomologia y An, Z., and Siegel, M. R. 1991. Molecular phy- Fitopatologia, Chapingo 1958.

121 Host x Pathogen x Environment Interaction in Sorghum Ergot Disease

N. W. McLaren

Abstract

Weather is a primary determinant ofergot incidence and severity. Low pre-jlowering temperatures predispose florets to infection by reducing pollen viability. Reducedpol len viability extends the susceptible periodfor infection, which is from flower opening and early anthesis to pollination andfertilization. Genotypes differ in the extent ofpre disposition and hybrids with cold tolerance and an ability to produce viable pollen de­ spite reduced temperatures have been identified Similarly, weather during early anthe­ sis affects ergot severity. Optimum disease occurs at 19°C and high humidity with little or no infection at temperatures exceeding 28°C. Secondary sporulation and sclerotium development are also affected by prevailing weather conditions. The relationship be­ tween weather and disease can be used to modify production practices to reduce the risk ofencountering ergotfavorable conditions. Planning offlowering dates based on long­ or medium-term weather data for a specific locality has proved successful in reducing the risk of ergot in South Africa. Selection ofgerm plasm under ergot-favorable condi­ tions has yielded more resistant lines and hybrids which, when grown commercially, re­ duce the risk of the disease.

Numerous examples of discontinuities tolerance levels, in particular, requires between optimum conditions for growth quantification so as to determine the of a plant and the growth and pathogenic crossover points at which host or patho­ development of disease causal organisms gen acquire the respective advantage of have been described. Optimizing growing prevailing environmental conditions. conditions for the host plant by means of management practices can result in con­ Host predisposition is defined as the comitant sub-optimal conditions for tendency of nongenetic factors, acting pathogen development and visa versa. prior to infection, to affect a plant's sus­ Implementation of control strategies ceptibility to disease (Yarwood 1959). based on such discontinuities, however, Predisposition of male-normal sorghum requires a thorough knowledge of both [Sorghum bicolor (L.) Moench] to infec­ host and pathogen responses to their rt>­ tion by Claviceps africana Frederickson, spective environments. Variation in host Mantle & de Milliano has been a major area for research at the Agricultural Rt>­ search Council's - Grain Crops Institute in South Africa (McLaren 1992, McLaren N. W. McLaren. ARC - Grain Crops Institute. Private Bag X1251. and Wehner 1992, McLaren 1997). Potchefstroom. 2520, Republic of South Africa. A voiding predisposing environmental conditions and identifying hybrids and

122 lines tolerant to predisposing factors has activity increases. In vitro studies have in­ formed the basis of ergot research and dicated the optimum temperature for ger­ control. Similarly, consideration of envi­ mination and growth ofthe pathogen to be ronmental factors which favor pathogen 19-20°C (Bandyopadhyay et al. 1996, growth, infection and dispersal have led Frederickson 1990, McLaren, unpub­ to changes in production practices so as to lished (Figure 1)). No or limited growth reduce the risk of conditions favorable for was recorded above 30°C. the pathogen during the critical stage of plant development. In this paper, empha­ Cool (19± 1°C), wet, cloudy weather sis will be on these two aspects ofthe host during early anthesis favors rapid devel­ x pathogen x environment interaction. opment and spread ofthe disease (Sunda­ ram 1971). Kulkarni (1942) reported Disease Favorable Environment most severe infections within tht:, range of 21 to 31°C when humidity was high. Most Ergot is a disease of unfertilized ova­ damage occurred in fields, which flow­ ries. The critical period for infection of ered during the cooler periods. Frederick­ sorghum by the ergot pathogen is from son (1994) found that ergot severities flower opening and the onset of anthesis were significantly higher at 20°C and until effective pollination and fertiliza­ 25°C than at 30°C. At 30°C, ergot severi­ tion make pistils escape or resist further ties of 0.9% were recorded, as opposed to infection (Futrell and Webster 1965, 26% at 20°C and 14% at 25°C. The latent Sangitrao 1982, Musabyimana et al. period for infection was also significantly 1995). Infection occurs primarily through shorter at lower temperatures. the stigma, and infection hyphae essen­ tially follow the same path as the pollen Cloudiness during anthesis promotes tube (Frederickson and Mantle 1988). In­ disease development (Anahosur and Patil fection or fertilization depends on envi­ 1982), probably due to delayed anther de­ ronmental conditions, which determine hiscence and pollen deposition and activ­ whether infection hyphae or pollen tubes ity under these conditions (Quinby 1958). obtain the competitive advantage for the Futrell and Webster (1966) reported that ovary. Under optimum daily tempera­ near 100% RH for 24 h during early flow­ tures for host development (>28°C) and ering was optimal for infection of a male­ night temperatures> 17°C (depending on sterile line. Sangitrao and Bade (1979) host adaptation) pollen germinates within believed that when humidity is high, rain­ 30 min and fertilization occurs within 2 to fall is not essential for ergot development. 12 h (Stephens and Quinby 1934, Anahosur and Patil (1982) concluded that Artchwager and McGuire 1949). In con­ temperatures of 19 to 21°C with 67-84% trast, at similar temperatures conidia re­ RH following panicle emergence, were quire 8 to 12 hours for germination on the sufficient for infection in male-sterile sor­ stigma and 36-48 hours to reach the ovary ghum. (Sangitrao 1982, Frederickson and Man­ tle 1988, Frederickson 1990). At cooler The above-mentioned conditions are temperatures pollen release and growth similar to those defined by McLaren and become retarded. Conversely, pathogen

123 30 I~M.OO l i 20 ~ 10

o w-______~ ______~ ______~~ ____~~ 16 20 24 28 32

Temperature r C)

Figure 1. Effect of temperature on germination ofClaviceps africana macroconidia on water agar after 12 h.

Wehner (1990), who determined the opti­ could increase the risk of ergot infection. mum temperature for disease develop­ In controlled pollination frequency trials ment at 19.5°C and the upper maximum they found a strong correlation (r = 0.87) limit at 28°C above which disease sever­ between the percentage of unpollinated ity was negligible (Figure 2). They, too, florets and ergot infection. found an inverse relationship with humid­ ity, maximum disease tending to occur at Downes and Marshall (1971) demon­ high humidity. In their studies, however, strated that night temperatures of 13°C or they recorded a strongly negative inter­ less during meiosis could induce male ste­ correlation between daily maximum tem­ rility in sorghum. Brooking (1976) esti­ perature and rainfall (r = 0.71), and sun­ mated the critical stage for cold induced shine hours (r = 0.86), and suggested that sterility to be 2 to 3 weeks prior to anthe­ maximum temperature was a suitable in­ sis. The greatest temperature sensitivity dicator of disease favorable conditions was during the late archesporial ceII­ under South African conditions. pollen mother cell development period, up to the leptotene stage of meiosis. Once Predisposition meiosis progressed beyond leptotene, ste­ rility was not induced. Development from Futrell and Webster (1965) suggested microspore release through to fertiliza­ that any factor that prolongs the period tion was particularly insensitive to pro­ from flower opening until fertilization longed night temperature treatment. In-

124 ro~------~

60 • (Y+1 )=EXP(1.014I.o.02tlP-5.868)

~ ~ ~ ~ ~ ~ ~ ~ M Mean dally maximum temperature r C} (days 1 to 4 after pollen shed)

Figure 2. Relationship between ergot severity and mean daily minimum temperature at Potchefstroom 1986/87; 1987/88; 1988/89 and Kempton Park 1988/89 in plots not sub­ jected to preflowering cold stress (>16°C) (McLaren and Wehner 1990). florescences showing low temperature­ McLaren and Wehner (1992) demon­ induced sterility developed anthers that strated the relationship between cold­ were exserted normally at anthesis but induced sterility and ergot susceptibility. were only partially dehiscent. Pollen In field trials with male-normal sorghum grains in these anthers at anthesis were hybrids, night temperatures

125 100 (a) (b) ...... I _ " . • • fPAN8564 •• 0.8 • 80 I Y=OO.48X·1.54X'-322.54 ,. i R'=O.75 i I· !!! PAN 6479 .S! iY=8.50X.a3.D2 'j 0.6 60 7 ~-u; \ ~ R'-O.82 I ~CD . 16 I 'fI, rn i • il .\ CD 0.4 \ tn 40 I W~ • PAN 8479:SAF , IYa2.D2-O.10X ~ ,i I R"-O.83 ,. 0.2 .\ 20 PAN 8584:SAF \ ~ • IY-o.01X" -O.42X+3.45 • ~ R'-O.93 , ,. ' .. 0 0 6 8 12 16 20 6 8 12 16 20 Minimum temperature Minimum temperature (' C) rC)

Figure 3. Relationship between mean minimum temperature (23-27 days pre-flowering) and ergot severity in two sorghum hybrids expressed as a ratio of ergot development in a male ster­ ile line (a) and seed set (b).

got incidence and seed set were inversely a quantitative response and not a qualit&­ correlated (r = -0.92). Hybrids differed in tive one occurring below some critical their ability to tolerate preflowering cold tern perature. stress, with PAN8564 maintaining seed set and ergot resistance until 12°C. In Molefe (1975) reported ergot in Bot­ contrast, a progressive increase in sterility swana in panicles that flowered when hu­ and concomitant increase in ergot was re­ midity was high, minimum temperature corded in P AN84 79. This result is similar was 14°C, and maximum temperature to cold-induced sterility recorded by was 27°C. The low minimum temperature Brooking (1979), who suggested that the may have been a predisposition factor fa­ linear response of some genotypes to tem­ voring disease development. Similarly, perature reduction indicate that sterility is Sangitrao and Bade (1979) found mini-

126 mum daily temperatures of 13 to 18°C potentials (Figure 4). Conversely, those and 76 to 84% RH most favorable for er­ with low cold tolerance and hence low got development. pollen viability (P22/96; P AN 8494 ) were more predisposed to infection and yielded Studies carried out by McLaren (un­ high disease severities despite low ergot published) using experimental hybrids potentials. Pepper and Prine (1972) showed that those with cold tolerance in shaded sorghum with black plastic fabric relation to the production ofviable pollen (25% light) and found two critical periods (determined by an iodine starch test) were that adversely affected grain yield com­ able to escape disease despite high ergot ponents. One of these was from the pre-

100~------~~------,

~8494 P22·96 80 yoO.mx'.... Ya3..1,ax D.1M • 11'00.17 80 •

40

...... "': .. • ...... • , • P39-96 ..

••• ... -•. 80 . • • 60 • ,... .. 40 YoO.D02X 11'00..

20

Ergot potenllal

Figure 4. Relationship between ergot potential and observed ergot severity and concomitant changes in pollen viability in experimental sorghum hybrids.

127 boot vegetative stage when the last leaf nightfall, coinciding with a sharp rise in was just visible above the whorl, to full RH and fall in temperature. Secondary panicle expansion or 50% anthesis (ap­ sporulation did not occur following sev­ proximately 2 weeks preceding anthesis). eral hot days in succession. Shading during these times resulted in re­ duced numbers of seeds per panicle. Low The effect of temperature on germina­ radiation-induced sterility may, there­ tion of sclerotia has received limited at­ fore, be an additional factor to be consid­ tention due to difficulties obtaining suffi­ ered in ergot epidemiology and may ex­ ciently high germination frequencies. plain significant increases in ergot sever­ Frederickson (1990) obtained 5% germi­ ity during prolonged cloudy weather. nation in e. africana after 16 weeks of in­ cubation in sterile sand at temperatures Inoculum Production ranging from 4 to 28°C and subsequently, 10% after 4 weeks at diurnal oscillations Bandyopadhyay et al. (1990) showed of 10 to 28°C. Mantle (1968) incubated that temperature and relative humidity af sclerotia of a Nigerian isolate at 24, 27 fected honeydew formation and spore and 30°C, achieving initial germination production, but not sphacelia develop­ after 4 weeks at 27°C. ment. Temperatures from 14-28°C com­ bined with RH above 90% for 12-16 h Germination of sclerotia of e. sorghi day· I favored conidial production and was achieved after 5 weeks incubation on hence pathogen spread. In contrast, at 28- moist sand at 24°C (Frederickson et al. 35°C andRH <90% for 22 h day·1 sphace­ 1991). Sangitrao (1982) found that scle­ lia developed into sclerotia and honeydew rotia ofe. sorghi germinated at 5 to 55°C, and spore production were suppressed. with20to 30°C being the optimum range. Manzarpour (1985) found that most co­ nidia germinated to form microconidia at EnVIronmental effects may be secon­ 24-30°C, whereas at higher temperatures dary by way of their effects on sapro­ they germinated by forming a hyphal phytes that affect sclerotial development. germ tube. Sclerotia develop poorly in a rainy season due to the growth of Cerebella sp. which Frederickson et al. (1993) demon­ suppresses their development, whereas strated how rapid, epidemic development dry weather after infection allowed for­ of e. africana could result from secon­ mation ofless contaminated, mature scle­ dary sporulation of the pathogen. They rotia (Futrell and Webster 1966). Sangi­ considered secondary sporulation to be trao et al. (1979) found that molds on scle­ the primary epidemiological agent within rotia under wet conditions result in the their experimental area. Secondary sporu­ elongated outer portion of the sclerotia lation is most profuse at 28/23°C, fol­ becoming thin and papery and ultimately lowed by 24114°C and least at 35/28°C weathering. They also found that the por­ (Bandyopadhyay et al. 1990). Frederick­ tion of the sclerotia protected by glumes son et al. (1989, 1993) studied diurnal pat­ does not weather and suggested that this terns of secondary conidia concentrations and found the greatest occurrence at

128 plays an important role in the perpetua­ South Africa results in low risk of ergot­ tion of the pathogen. favorable disease conditions.

Implications of the Host x Pathogen x Predicting Disease Severity Environment Interaction in Disease Control McLaren and Flett (in press) developed a model to predict ergot severity (sensu The purpose of disease control is to McLaren, 1992) based on weather vari­ prevent disease damage from exceeding ables as follows: the level at which profit or required yield is diminished. A number of management Y=(aXl ) +EXP(bX2_+cX 2 +d) + strategies have been employed to exploit (e*X3) (Eq. 1) the host x pathogen x environment rela­ tionships to control ergot and reduce the where Y =expected mean ergot severity risk of yield losses. Xl=mean minimum temperature (0C), Sowing Dates 23-27 days before flowering

In India, early sowing which ensures X2=mean daily maximum temperature that sorghum flowers during the warmer (0C), 1-5 days after flowering and drier part of the growing season re­ duces the risk of ergot (Singh 1964, Desai X3=mean daily maximum humidity et al. 1979, Sangitrao et al. 1979, Anaho­ (0C), 1-5 days after flowering. sur and PatilI982). Early flowering crops are also less likely to be subjected to low and a, b, c, d and e are regression coeffi­ temperatures during microsporogenesis cients. and thus escape being predisposed to in­ fection. McLaren (1996) used the criteria The model was calibrated to predict er­ maximum daily temperature of 28°e got potential i.e., expected ergot severity (temperature above which disease inci­ in a sorghum nursery with a broad genetic dence is minimal) and 12°e minimum base subjected to artificial inoculation temperature (temperature below which (inoculum sprayed at weekly intervals total sterility or maximum predisposition with a spore suspension in water adjusted occurs) to identify high- and low-risk to ca. 104 spores mrl). Application of the flowering periods, based on long- and model during the 1996/97 season yielded medium-term weather data for various a high "index of agreement" (Wilcox production areas in South Africa (Figure 1982) (d = 0.846, Table 1). These results 5). Also indicated in Figure 5 are pre­ indicate that ergot severity can be accu­ dicted ergot severities based on weather rately predicted based on maximum and variables during flowering (McLaren and minimum temperature and maximum Flett in press) using methodology indi­ relative humidity during critical phases of cated below (Equation 1). Generally, host development. The model will, how­ flowering before the end of January in ever, need to be recalibrated for specific germplasm, applications and risk analysis

129 ~------~~

Expected ergot severity 50 50

40 40

...... ;.Risk;,;.· .;.,;d.....;.--l...... High iniaction 30 30

i1J. '.,. ,.' ... -... -.,. .. 20 20

.' ...... _.. • • I'>.. minimum temperature r C) _::::'':~ ___ ...• _... ~ ... :::C.. _::::t,:u~~'1.'''~••••••••• _ ••••••••••••••••••• - •••••• 10 . Riskd •... •• ...o"il 10 LaN...... High "\0...... ~ padsposiition •••• ' ...... , . o o 20 10 1 20 10 30 10 20 10 20 January February March April

Figure 5. Example ofthe use of long-term maximum and minimum temperatures for the estima­ tion of high and low risk ergot periods (Bethlehem, South Africa). Expected ergot sever­ ity is calculated according to Equation 1 (see text).

Table 1. Observed and predicted ergot severities associated with flowering dates at two localities in South Africa during 1997 illustrating the accuracy of ergot prediction based on weather variables. Maximlim Minimum Maximum Observed ergot Predicted ergot ElmJlcring date localiljl temperatllre (DC) temperatllre (DC) RH (O&,) s~eriljl (Ot.) s=riljl (Ot.) 17 February Potchefstroom 32.4 17.6 76.2 7.3 7.7 18 February Bethlehem 30.2 15.8 93.6 16.5 24.9 25 February Bethlehem 23.0 16.0 96.0 31.1 36.4 4 March Potchefstroom 25.2 16.8 91.8 34.3 29.7 10 March Potchefstroom 23.8 16.2 87.2 40.1 31.6 14 March Bethlehem 21.3 13.6 97.0 58.6 45.6 17 March Potchefstroom 23.8 17.5 86.2 29.3 27.0 25 March Beth1ehem 123 121 26 Q 613 485 Index of agreement (Wilcox) 282 d=Q 846

130 ofvarious flowering dates or seed produc­ Similar responses are reflected in Figure tion localities. If applied to natural epi­ 4. demics, an inoculum algorithm will need to be developed. The model is currently McLaren (1992) used regression being used effectively in the evaluation of analyses to quantify resistance of sor­ lines and cultivars for ergot resistance ghum genotypes to ergot. Sowing nurser­ (McLaren 1992; Figure 4), but no doubt ies at two locations over a range of sowing could be adapted and applied elsewhere, dates created temperature gradients. At notably to determine the need for fungi­ flowering individual heads were marked cide applications. with the date of anthesis and artificial in­ oculation. Ten heads of each genotype Germplasm Evaluation for Resistance were inoculated on 3 to 4 different dates at each location. Visual estimations of per­ Sundaram (1980) suggested that in or­ centage infected florets head- l were made der to compare ergot severities in breed­ and these values were used to calculate ing lines, particularly those differing in the mean ergot severity associated with maturities, sowing dates must be adjusted each inoculation date for each genotype. so that plants will flower and can be in­ An index of ergot-favorable conditions oculated at the same time. In most semi­ was determined as the mean disease inci­ arid regions climatic cycles are unpredict­ dence over all genotypes associated with able and synchronous flowering in de­ a specific flowering date. This was sired climatic conditions is virtually im­ termed the disease potential, or expected possible. Furthermore, temperature varia­ disease severity associated with a specific tions ofrelatively small magnitude before flowering date. More recently, the above flowering and during the first 5 days after model (Equation 1) which determines er­ pollen shed significantly affect ergot inci­ got potential based on weather variables dence (McLaren and Wehner 1990, has been applied. 1992). This, together with natural varia­ tion in flowering dates both within and Non-linear regression analysis, using across sorghum genotypes, has resulted in the model Y=axb (where Y=observed dis­ inaccurate comparison of ergot inci­ ease incidence, x=disease potential, and a dences. The extent to which the differ­ and b are regression coefficients) was ences in disease incidences reflect the used to determine the relationship be­ host genotype, or the result of differences tween ergot potential associated with dij: in climate associated with differing flow ferent inoculation dates and observed dis­ ering dates, is questioned. ease incidence within genotypes. Regres­ sion lines could be classified into three McLaren (1997) demonstrated varia­ categories; those linearly related to dis­ tion in production of viable pollen in sor­ ease potential, those highly susceptible ghum lines subsequent to pre-flowering (even at low disease potentials) and those cold stress. Whereas most lines yielded with various degrees of resistance despite <40% viable pollen with a pre-flowering increasing disease potentials (Figure 4). temperature <14°C, some selections Genotypes in the latter group differed yielded in excess of 70% viable pollen.

131 with respect to resistance breakdown significantly increased with increased ni­ points. Rearrangement of the regression trogen applications. Potassium decreased model also enabled the subsequent rate of disease incidence. Phosphorus did not af­ resistance breakdown at any point to be fect disease incidence but stimulated hon­ calculated. An advantage of this method eydew secretion. Chinnadurai (1972) was that ergot severity in sorghum geno­ found that trace elements affected growth types that flowered at different times and sporulation of C. sorghi. Lack of could be statistically compared. manganese caused the most reduction in mycelial growth, iron was essential for Conclusions sporulation and molybdenum was inhibi­ tory to both growth and sporulation. Simi­ Weather during early anthesis and dur­ lar results have been recorded with ergot ing meiosis prior to flowering are the pri­ caused by C. purpurea and C. fusiformis . mary determinants of ergot severity. The Herbicides have also been observed to response of sorghum to weather differs promote infection of rye grass by C. pur­ according to tolerance of pre-flowering purea (Macek and Milevoj 1978). Thus, cold stress and flowering behavior during although many aspects of the host x anthesis. These factors have become ma­ pathogen x environment interaction have jor selection criteria in the development been studied and exploited in disease con­ of hybrids and varieties with ergot resis­ trol, further studies of the relationships tance in South Africa. However, detailed may yield improved disease control studies of mechanisms of escape resis­ strategies which will reduce the risk of, tance in the host x pathogen x environ­ and losses due to ergot. ment relationship are still required. Brooking (1976) stated that pre­ References flowering low temperatures do not affect Anahosur, K.H., and Patil, H.S.1982.Effect of date female sterility. Personal observations in of sowing on the incidence of ergot of sor­ fields in South Africa suggest that studies ghum.1ndian Phytopathology 35:507-509. on cold-induced female sterility or re­ Artschwager, E., and McGuire, R.C. 1949. Cytol­ ogy of reproduction in Sorghum vulgare. Jour­ duced male x female compatibility under nal of Agricultural Research 78:659-673. cold stress are warranted. Similarly, stud­ Bandyopadhyay, R., Frederickson, D.E., McLaren, ies on a wide range of germ plasm are re­ N.W., and Odvody, G.N. 1996. Ergot, a global threat to sorghum. International Sorghum and quired to determine the limits ofpredispo­ Millets Newsletter 37:1-32. sition. Currently, 12°C is the lowesttoler­ Bandyopadhyay, R., Mughogho, L.K., Manohar, ance limit recorded to date (McLaren and S.K., and Satyanarayana, M.V. 1990. Stroma development, honeydew formation, and conid­ Wehner 1992). The possibility of select­ ial production in Clavieeps sorghi. Phytopa­ ing for lower temperature tolerance needs thology 80:812-818. investigation. Brooking,I.R. 1976. Male sterility in Sorghum hi­ color (L.) Moench induced by low night tem­ perature. 1. Timing of the stage of sensitivity. Other environmental factors, which Australian Journal of Plant Physiology 3:589- may significantly affect ergot incidence 596. Brooking, 1.R. 1979. Male sterility in Sorghum bi­ and severity, have been largely ignored. color (L.) Moench induced by low night tem­ Chinnadurai (1971) found that the inci­ perature. II. Genotypic differences in dence of ergot of sorghum in India was

132 sensitivity. Australian Journal of Plant Physiol­ Mantle, P.G. 1968. Studies on Sphaeelia sorghi ogy 6:143-147. McRae, and ergot ofSorghum vulgare Pers. An­ Chinnadurai, G. 1971. The role of fertilizers on the nals of Applied Biology 62:4~3-449. incidence of sugary disease of sorghum. Tropi­ Manzarpour, A. 1985. Aspects of metabolism and cal Agriculture (Trinidad) 48 :51-53. physiology in Clavieeps. Diploma thesis, Impe­ Chinnadurai, G. 1972. Effect of certain trace ele­ rial College, University of London, UK. ments on the growth and sporulation ofSphaee­ McLaren, N.W. 1992. QuantifYing resistance of lia sorghi. Indian Phytopathology 25: 599-600. sorghum genotypes to the sugary disease patho­ Desai, K.B., Joshi, H.U., Kikani, B.K., and gen (Clavieeps afrieana). Plant Disease Rajkule, P.N. 1979. Effect of seeding date on 76:986-988. sugary disease appearance. Sorghum Newslet­ McLaren, N.W. 1996. Components ofresistance of ter 22:110-111. sorghum to ergot. Page 41 in Abstracts of the Downes, R. W., and Marshall, D.R. 1971. Low tem­ Plant Breeding Symposium presented by the perature induced male sterility in Sorghum hi­ ARC-Grain Crops Institute and South African color. Australian Journal of Experimental Plant Breeders' Association, 19-21 Mar 1996, Agriculture and Animal Husbandry 11 :352- South Africa. 356. McLaren, N.W. 1997. Changes in pollen viability Frederickson, D.E. 1990. Ergot disease of sor­ and concomitant increase in the incidence of ghum. PhD thesis, University ofLondon (Impe­ sorghum ergot with flowering date and implica­ rial College), London, UK. 217 pp. tions in selection for escape resistance. Journal Frederickson, D.E. 1994. Effect of temperature on of Phytopathology 145 :261-265 ergot infection and pollination. Page 2 in ICRI­ McLaren, N.W., and Flett, B.C. Use of weather SAT Southern and Eastern Africa Regional variables to quantifY sorghum ergot potential in Program Annual Report 1993. Bulawayo, Zim­ South Africa. Plant Disease (In press). babwe: SADC (Southern African Development McLaren, N.W., and Wehner, F.C. 1990. Relation­ Community)IICRISAT (International Crops ship between climatic variables during early Research Institute for the Semi-Arid Tropics) flowering of sorghum and the incidence of sug­ Sorghum and Millet Improvement Program. ary disease caused by Sphaeelia sorghi. Journal Frederickson, D.E., and Mantle, P.G. 1988. The of Phytopathology 130:82-88. path of infection of sorghum by Clavieeps sor­ McLaren, N.W., and Wehner, F.C. 1992. Preflow­ ghi. Physiological and Molecular Plant Pathol­ ering low temperature predisposition of sor­ ogy 33:221-234. ghum to sugary disease (CJavieeps afrieana). Frederickson, D.E., Mantle, P.G., and de Milliano, Journal of Phytopathology 135:328-334. W.AJ. 1989. Secondary conidiation ofSphaee­ Molefe, T.1. 1975. Occurrence of ergot on sor­ lia sorghi on sorghum, a novel factor in the epi­ ghum in Botswana. Plant Disease Reporter demiology of ergot disease. Mycological 59:751-753. Research 93:497-502. Musabyimana, T., Sehene, C., and Bandyopadh­ Frederickson, D.E., Mantle, P.G., and de Milliano, yay, R. 1995. Ergot resistance in sorghum in re­ W.A.J. 1991. Clavieeps afrieana sp-nov., the lation to flowering, inoculation technique and distinctive ergot pathogen of sorghum in Africa. disease development. Plant Pathology 44:109- Mycological Research 95:1101-1107. 115. Frederickson, D.E., Mantle, P.G., and de Milliano, Pepper, G.E., and Prine, G.M. 1972. Low light in­ W.AJ. 1993. Windbome spread of ergot dis­ tensity effects on grain sorghum at different ease (Clavieeps afrieana) in sorghum Alines in stages of growth. Crop Science 12:590-593. Zimbabwe. Plant Pathology 42:368-377. Quinby, J.R. 1958. Grain sorghum production in Futrell, M.C., and Webster, 0.1.1965. Ergot infec­ Texas. Texas Agricultural Experiment Station tion and sterility in grain sorghum. Plant Dis­ Bulletin No. 912. College Station, Texas, USA: ease Reporter 49:680-683. Texas A & M University. Futrell, M.C., and Webster, O.J. 1966. Host range Sangitrao, C.S. 1982. Studies on ergot disease of and epidemiology of the sorghum ergot organ­ sorghum in Vidarbha. Ph.D. thesis, Punjabrao ism. Plant Disease Reporter 50:828-831. Krishi Vidyapeeth, Akola, India, 212 pp. Kulkarni, G.S. 1942. Ergot in India. Current Sci­ Sangitrao, C.S., Taley, Y.M, and Moghe, P.C. ence 11 :246. 1979a. Effect ofplanting date on the appearance Macek, J., and Milevoj, 1. 1978. The influence of of sugary disease. Sorghum Newsletter 22: 111. some herbicides on the change of sensitivity of Sangitrao, C.S., and Bade, G.H. 1979. Meteoro­ rye to Clavieeps purpurea Tu!. Abstracts ofpa­ logical factors associated with honey dew de­ pers, 3rd International Congress of Plant Pa­ velopment and sclorotial stage in sorghum thology, Munich, 1978. ergot. Sorghum Newsletter 22: 107-108.

133 Singh, P. 1964. Sugary disease of sorghum. Pages ceedings of the International Workshop on Sor­ 29-33 in Progress report ofthe Accelerated Hy­ ghum Diseases, 11-15 Dec 1978, ICRISAT, brid Sorghum Project and the Millet Improve­ Hyderabad, India. Patancheru, Andhra Pradesh ment Programme. New Dehli, India: Indian 502 324, India: International Crops Research Council of Agricultural Research. 81 pp. Institute for the Semi-Arid Tropics. Stephens, J.C., and Quinby, J.R. 1934. Anthesis, Wilcox, C.J. 1982. Some comments on the evalua­ pollination, and fertilization of sorghum. Jour­ tion of model performance. Bulletin American nal of Agricultural Research 49:123-136. Metero10gica1 Society 63: 103 9-1313. Sundaram, N.V. 1971. Possible resistance to sug­ Yarwood, C.E. 1959. Predisposition. Pages 521- ary disease in sorghum. Indian Journal of Ge­ 562 in P1antPath010gy Vol. 1 J.G. Horsfall, and netics and Plant Breeding 31 :383-387. A.E. Dimond, eds. New York, USA:Academic Sundaram, N.V. 1980. Sorghum ergot. Pages 377- Press. 379 in Sorghum diseases: a world review. Pro-

134 The Lifecycle, Spread and Survival of the Sorghum Ergot Pathogens

Debbie. E. Frederickson

Abstract

Knowledge ofthe biology ofa pathogen, as described in its lifecycle, enables the ef fective targeting of control measures. The lifecycles ofthe three sorghum ergot patho­ gens are compared to the lifecycle ofClaviceps purpurea and to one another. The rapid build-up ofdisease in the field is attributed to the polycyclic nature ofthe asexual stage. Windborne secondary conidia ofClaviceps africanaJormed under high relative humi~ ity in the field, are the chiefmeans ofspread of ergot in Zimbabwe. Experiments show that the secondary conidia can travel at least up to 300 m and that even a small initial concentration of10 secondary conidia per cubic meter ofair is enough to start an epi­ demic. Later in the epidemic concentrations may reach as high as 350 per cubic meter. In unprotectedA-lines in Zimbabwe all 38 rows ofa 30 meter plot became infected after 1 cycle ofhoneydew production. Although severities declined rapidly from source, only 2 more cycles were required to eliminate obvious disease gradients so that more uniform final severities of50-70% were obtained Overall apparent disease rates (r) reached O. 2 per unit per day in A-lines, varying between 0.14 and 0.29 in individual A-lines and reaching as high as 0.58 in single plots ofsome A-lines. These values compare well to those obtained in epidemics ofthe potato late blight and wheat stem rust pathogens. At the end ofthe crop season, with the cessation ofrains and the maturity ofthe crop, conid­ ial production ceases. The pathogens have to survive between crops in someform. Per­ ennation of the sorghum ergot pathogens as conidia on seed and crop debris or in sphacelia or sclerotia may be possible. The perfect stages of the 3 pathogens are con­ trasted and it is suggested that the teleomorph ofe. africana does not play a major role in survival or dissemination. Alternate hosts such as otherSorghum species are proba­ bly much more important in perennation, survival and spread than are any other grasses. Reports of alternate hosts in the literature are corifusing and contradictory.

Three distinct species of Claviceps ano (1991), the pathogen of Africa, Aus­ have been described as pathogens of sor­ tralia, the Americas and Thailand and Ja­ ghum: 1) Claviceps sorghi Kulkarni, Se­ pan; 3) Claviceps species also of Japan, shadri and Hegde (1976) as found in India the formal description to be published by and other parts of Asia; 2) Claviceps afri­ Tsukiboshi (personal communication). cana Frederickson, Mantle and de Milli- The life-cyc1e(s) ofthe three pathogens is the culmination of their strategies for spread and survival and is important for considerations on disease control. Debbie. E. Frederickson, 32, Berrington Rd., Norwich, NR6 6PH, U.K.

135 Claviceps species are important ovary F or the sorghum ergot pathogens, the pathogens of cereal crops and grasses. best starting point is with the portion of Therefore one tum of the lifecycle de­ the lifecycle that is most well defined and pends upon the success of host infection studied, and well proven i.e. the imperfect at a quite specific crop stage i.e. the ovary stage. The most observant of us would, in at flowering, and of subsequent perenna­ the field, first notice e. africana infec­ tion in the absence of the host between tions as sphacelia emerging from between cropping seasons. The lifecycle ofe. pur­ host glumes at about 6 days post­ purea, found in any text book of plant pa­ infection. More usually, for all 3 of the thology, is the most familiar, and the best sorghum ergot pathogens, we see the hon­ investigated and substantiated of all the eydew at about 7 days post-infection, ergot pathogens. Because of this, the life­ dripping from infected florets. This early cycle tends to be rather over emphasized honeydew is usually initially thin, trans­ as a yardstick for sorghum ergots. Whilst parent and devoid of spores, becoming providing a useful model for the lifecycle progressively more sticky, colored of sorghum ergot pathogens, it should honey-yellow to brown or pinkish and only be used as a analogy because of im­ opaque with conidia. Alternatively hon­ portant differences in pathology. The life­ eydew may remain of thin viscosity and cycle ofe. purpurea is as follows: e. pur­ droplets of honeydew may become super­ purea, a pathogen of rye, wheat and bar­ ficially white at the surface, even where ley in temperate climes, overwinters as honeydew drips onto soil. This feature, sclerotia in seed or on the ground. In the secondary conidiation, is characteristic of spring, sclerotia germinate producing nu­ natural C. africana infections. It may oc­ merous stomata with capitulae. Each peri­ cur less readily with C. sorghi but never thecium bears many asci containing the with C. species. When honeydew has this ascospores, constituting the primary in­ characteristic the oblong to oval macroco­ oculum. Infection of host stigmas by nidia at the surface have germinated to windborne ascospores results in the inva­ produce secondary conidia. Smeared on a sion ofthe ovary by fungal hyphae and de­ slide, or viewed with Cryo-SEM, the velopment of the fungal sphacelium. characteristic pear-shaped secondary About a week later honeydew, containing spores, borne on long sterigma-like pro­ millions of infectious conidia, is pro­ cesses, can be recognized. This phenome­ duced. Dissemination of honeydew to un­ non would not be expected by analogy infected flowers by insects and rain en­ with e. purpurea. ables further disease spread. By the time honeydew secretion ceases, the pur­ In one season epiphytotics of disease ple/black, hard, elongate sclerotia are may quickly occur under favorable very obvious on the infected spike. Scle­ weather conditions, when conidia are rotia are dislodged at around harvest and transmitted to uninfected flowers and fall to the ground or become mixed with later maturing tillers i.e. this part of the seed, remaining dormant overwinter, and cycle of infection, asexual spore produc­ so the cycle is completed. tion, infection, is polycylic. e. purpurea conidia are disseminated by rainsplash

136 and insects (Ingold 1971, Moreno et al. To put the potential for spread ofC. af­ 1970), leading to limited disease develop­ ricana in perspective, in one experiment ment (epidemics are very unusual). Co­ with C. africana in Zimbabwe (Freder­ nidia of C. sorghi are also disseminated ickson et al. 1993) a central plot of sor­ by rainsplash for limited distances (BaIr ghum was inoculated and began to pro­ dyopadhyay et al. 1991) but there is no vide inoculum (secondary conidia) to sur­ evidence of insect transmission. Instead, rounding A-line plots at 11 days post­ the secondary conidia introduce a new, inoculation. Nine days later (day 20) the and highly significant, dimension to the first outbreaks were visible in surround­ lifecycle: secondary conidia become air­ ing plots. By day 26, still within 1 cycle, borne and are dispersed by wind. The infection was fairly well distributed over presence of secondary conidia in air and the entire experimental area. Represented their relationship with infection has been graphically, the overall rate of disease investigated for the pathogen, C. afri­ spread, measured as apparent infection cana, under natural conditions in Zim­ rate (r) (Van der Plank 1963) reached 0.2 babwe during several crop seasons (Fre­ per unit per day. Individual values for dif­ derickson et al. 1989, 1993). Their pres­ ferent A-lines ranged from 0.14 to 0.29, ence in air shows a diurnal pattern, their with values as high as 0.48 and 0.58 in in­ concentration gradually increasing dividual plots. These rates compare fa­ throughout the day to reach a peak around vorably to those measured in epidemics of nightfall, concurrent with the rise in rela­ the two quite devastating pathogens, po­ tive humidity. This may reduce desicca­ tato late blight (Phytopthora infestans), tion of the thin-walled, hyaline spores. and wheat stem rust (Puccinia gram in is Initial low incidences and severities of er­ trifici). Fo~ potato blight r, 0.42, in a got follow low concentrations of 101m3 Ihr highly susceptible cultivar and 0.11 in a secondary conidia in air, and disease less susceptible cultivar. The wheat stem build-up to high severity follows higher rust pathogen achieved r, 0.41 (Van der concentrations of up to 350/m3/hr (Fre­ Plank 1963). Claviceps africana is clearly derickson et al. 1989, 1993). Frederick­ in the same league. son et al. (1993) detected secondary co­ nidia at 15 m from source; Frederickson Towards the end ofthe crop season, the (unpublished) trapped secondary conidia dormant tissue is sclerotial, rather than at 30 m from source and secondary co­ sphacelial. Spore production ceases and a nidia can probably travel much further, by more resilient, solid body is found in the inference from the presence of infections floral cavity. C. sorghi and C. species up to 300 m away in adjacent fields (Fre­ sclerotia are usually quite visible as eloIr derickson et al. 1993). Secondary gate structures protruding from infected conidiation probably accounts for the ra­ florets. However the true sclerotia of C. pidity with which even small initial infeo­ africana are almost entirely enclosed tions give rise to large scale epiphytotics within the host glumes because parasitic in C. africana and to outbreaks in areas bodies of this species are smaller and glo­ previously unplanted to sorghum. bose in shape. Anything visible will a~ most certainly represent the sphacelial

137 part of the structure. Sclerotia are held but only a few ofthese matured to produce quite firmly in the floral cavity and are not asci. C. sorghi sclerotial germination oc­ likely to be dislodged easily. Pathogens curs only slightly more readily but with will thus only remain in the field at har­ more consistency. Both Sangitrao (1982) vest in the form of sphacelia or sclerotia and Frederickson et al. (1991) obtained ( containing conidia) in discarded, iIr germination of sclerotia in the tempera­ fected panicles, honeydew on discarded ture range of 20-30°C after 5 weeks in panicles and other trash, and honeydew moist sand. Ascosporic infection byC. af­ on the soil surface. Threshing may cause ricana in Africa is probably extremely the mixing of sphacelia and sclerotia with rare in nature, in fact there is no evidence seed; harvested seed may be coated with for the natural occurrence of the sexual honeydew. stage at all. The role of airborne dispersal by ascospores has been assumed by the Therefore the number of options for secondary conidia at another stage in the perennation may be manifold. However lifecycle altogether and secondary co­ most are as yet unproven as generating vi­ nidia may also be involved in perenna­ able primary inoculum in the new season. tion. The most usual assumption by analogy to C. purpurea is that ascosporic infection In Africa, many researchers have rou­ must play the major role. Ascosporic in­ tinely used C. africana conidia from pani­ fection by C. purpurea is common in na­ cles, sphacelia and sclerotia, stored at ture and has been used repeatedly by re­ "winter" room temperatures, as inoculum searchers to initiate infections in wheat in infection experiments 9-10 months experiments (Mantle & Shaw 1976). Ger­ later (Futrell & Webster 1966, Mower et mination of sclerotia and ascosporic in­ al. 1973, Frederickson et al. 1991, 1993). fection, occur readily, simply by burying Initial severities following from the re­ sclerotia from the previous season in pots peated spraying of such inoculum onto of soil between plants. Tsukiboshi (per­ panicles are very low, usually only a few sonal communication) also reports the sphacelia result. However a small initial 50% germination of C. species sclerotia source is sufficient to start an epiphytotic, after 1 month incubation in moist sand. as shown earlier. In nature viable conidia However sclerotia of C. sorghi and C. af­ remaining after winter would have to ricana are not so compliant. After many reach flowering panicles from ground unsuccessful attempts, Frederickson et al. level, whether as honeydew on soil, trash (1991) finally achieved germination ofC. or seeds, or associated with sphacelia or africana sclerotia in vitro. After 1 month, sclerotia. Germination ofmacroconidia to 10% of sclerotia, previously maintained form airborne secondary conidia may per­ at winter room temperatures (20-25°C) at mit this and merits investigation, as does Matopos, Zimbabwe, germinated when the survival of conidia on all these vehi­ incubated in pots at the ambient outdoor cles. temperatures of the growing season (10- 28°C). After 6 weeks, 80% had germi­ One final possibility for perennation is nated to produce stromata with capitulae, the involvement ofalternate hosts. The al-

138 ternate host could be involved at two pos­ spread and survival. Clearly if we hope to sible stages. Primary inoculum may infect exploit our knowledge of ergot pathogen an earlier- maturing host and the resultant biology to effect control, there are still sphacelial honeydew could infect later­ many questions to be addressed, and gaps maturing sorghum. This is the usual situa­ in our knowledge ofthe lifecyc1e to close, tion for e. purpurea in England Black­ before we can do so. grass (Alopecurus myosuroides) is in­ fected by e. purpurea ascospores in ad­ References vance of wheat anthesis (Mantle & Shaw Bandyopadhyay, R., Mughogho, L. K. and 1976) and the honeydew subsequently in­ Sharma, H. C. 1991. Source of primary inocu­ fects wheat. Secondly, honeydew from lum and spread of ergot. Pages 24-25 in Cereals sorghum could infect the alternate host, Program Annual Report, 1990. Patancheru 502 324, India: International Crops Research Insti­ which could then act as a reservoir of in­ tute for the Semi-Arid Tropics. (Limited distri­ fection. The continual flowering of Sor­ bution). ghum halapense in Australia (Ryley, per­ Boon-long, T. 1992. Sorghum diseases in Thai­ land. Pages 41-43 in Sorghum and Millets Dis­ sonal communication) would seem to per­ eases, a Second World Review. W. A. J. de mit the latter. Most tests for alternate Milliano, R. A. Frederiksen, and G. D. Beng­ hosts have at best been host range tests, ston (eds). Patancheru 502 324,Andhra Pradesh, International Crops Research Institute involving the inoculation of putative al­ for the Semi-Arid Tropics. ternate host with honeydew from sor­ Chinnadurai, G. and Govindaswamy, C. V. 1971. ghum or vice versa to prove susceptibil­ Host range of the sorghum sugary disease pathogen. Madras Agricultural Journal 58:600- ity. The literature presents a confusing ar­ 603. ray of examples, for many species have Frederickson, D. E. 1990. Ergot disease of sor­ been investigated with conflicting results. ghum. PhD thesis, University of London (Impe­ rial College), London, U.K. 217 pp. For example Panicum maximum was Frederickson, D. E., Mantle, P. G. and de Milliano, positive as an alternate host ofe. ajricana W. A. J. 1989. Secondary conidiation of in Thailand (Boon-long 1992) but not of Sphacelia sorghi on sorghum, a novel factor in the epidemiology of ergot disease. Mycological e. ajricana in Zimbabwe (Frederickson Research 93:497-502. 1990). The only consistent involvement Frederickson, D. E., Mantle, P. G. and de Milliano, appears to be with wild sorghum species W. A. 1. 1991. Claviceps africana sp-nov.; the distinctive ergot pathogen of sorghum in Africa. as alternate hosts, and possibly pearl mil­ Mycological Research 95:1101-1107. let (Pennisetum glaucum). Caution is Frederickson, D. E., Mantle, P. G. and de Milliano, needed for many ergot species naturally W. A. 1. 1993. Windborne spread of ergot dis­ ease (Claviceps africana) in sorghum A-lines in infect wild grasses (Loveless 1964) and Zimbabwe. Plant Pathology 42:368-377. so honeydew on a grass alone is not evi­ Frederickson, D. E. and Mantle, P. G. 1996. Pearl dence for infection by the sorghum ergot millet as an alternate host of the sorghum ergot pathogen, Claviceps africana. International pathogens, even if adjacent to the sor­ Sorghum and Millets Newsletter 37:83-85. ghum field. Conidial characteristics must Futrell, M. C. and Webster, O. 1. 1966. Host range and epidemiology of the sorghum ergot organ­ be measured (Loveless 1964) and Koch's ism. Plant Disease Reporter 50:828-831. postulates attempted. Ingold, C. T. (Ed) 1971. Fungal Spores, their Lib­ eration and Dispersal. Oxford, UK. Clarendon Press. The lifecycle ofan organism represents Kulkarni, B.P.G., Seshadri, V.S. and Hegde, R.K. a summary of its biological strategy for 1976. The perfect stage of Sphacelia sorghi

139 McRae. Mysore Journal ofAgricultural Science Moreno, R, Pedrson, V.D. and Schulz, J.T. 1970. 10:286-289. Transmission of Claviceps purpurea (fr.) co­ Loveless, A.R 1964. Use ofthe honeydew state in nidia by the cabbage looper moth Trichoplusia the identification of ergot species. Transactions ni (Hubner). Proceedings of the North Dakota ofthe British Mycological Society 47:205-213. Academy of Science 24:11-14. Mantle, P.G. and Shaw, S. 1976. Role of ascospore Sangitrao, C.S. 1982. Studies on ergot disease of production by Claviceps purpurea in aetiology sorghum in Vidarbha. PhD thesis, submitted of ergot disease in male sterile wheat. Transac­ Punjabrao Krishi Vidyapeeth, Akola, India, 212 tions of the British Mycological Society 67: 17- pages. 22. Van der Plank, J. E. 1963. Plant Diseases: Epi­ Mower, RL., Gray, G.R, and Ballou, C.E. 1973. demic and Control. New York and London: Sugars from Sphacelia sorghi honeydew. Car­ Academic Press. bohydrate Research 27: 119-134.

140 Putative Control of Ergot Disease Epidemics in Hybrid Sorghum Production through the Inhibition of Secondary Sporulation by C/aviceps africana.

RA.G. Hassan, P.G. Mantle and N.W. McLaren

Abstract

A strategy is proposedfor limiting epidemics ofergot disease in the production ofFJ hybr..id sorghum seed Certain sweet sorghums inhibit the secondary sporulation which occurs on exuded ergot honeydew by supplying the parasite with excess sucrose which is transformed to uniquefree oligosaccharides with spore-germination inhibitingprope~ ties. Therefore the strategy seeks to incorporate a sweet character into A lines for hybrid seed production to restrict secondary disease spread

The African ergot pathogen of sor­ to be a strong nutritional preference for ghum, Claviceps africana and its ana­ the glucose moiety of sucrose, as opposed morph Sphacelia sorghi, can cause sig­ to the fructose. Iffructose is as growth in­ nificant economic losses in the produc­ hibitory in all ergot fungi as it is in the best tion of F J hybrid seed. Recent spread of studied example, Claviceps purpurea, it the pathogen in the Americas and Austra­ is readily understood how the pathogen lia has focused attention on control meas­ has developed a means of glucose release ures. which at the same time avoids creating in­ creased concentration of free fructose. Assuming that secondary sporulation Hence, the fructofuranosidase of C. pur­ of Sphacelia sorghi macrospores in vivo purea provides an ideal way of making is the most important factor in creating glucose available for respiration and as a epidemics of ergot disease in sorghum source of biosynthetic carbon skeletons. (Frederickson et al. 1989), it is necessary It does so by forming a series of oligosac­ to consider two particular biological fea­ chari des, first by transfer of a fructose tures. residue to a sucrose molecule and then by addition of further fructose units and glu­ The first is probably common to all er­ cose is thereby obtained as a free mono­ got fungi, and concerns the way in which saccharide. These oligosaccharides might each pathogen utilizes the sucrose sup­ temporarily inhibit germination of spores plied by the host plant in phloem translo­ while they are embedded in honeydew. cate to the diseased ovaries. There seems Indeed any such inhibition might only be advantageous to the fungus since there is no point in germination occurring until conidia in much diluted honeydew are H.A.G. Hassan and P.G. Mantle, Biochemistry Departmen~ Imperial Col­ lege of Science, Technology and Medicine, London SW7 2AY. UK.; N.W. transferred to other uninfected flowers by McLaren, ARC - Grain Crops Institute, Private Bag X1251, Potchefstroom, 2520, Republic of South Africa. rainsplash or head to head contact in hu-

141 mid conditions. Therefore, no special of secondary sporulation in vivo might properties have been ascribed to the oli­ change (reduce) if a sweet stem sorghum gosaccharides; they just apparently pro­ were the host in which the pathogen had vide a convenient way of maintaining a access to more abundant sucrose. This, low molar concentration of unwanted therefore, is the origin of our first­ fructose. declared strategy to utilize a sweet sor­ ghum character in the A-line ofF] hybrid The second biological feature is the sorghum seed production (Hassan et al. differential parasitic behavior expressed 1995). The most that could initially have by the sphacelial stages of the sorghum been expected in terms ofmechanism was ergot pathogens of India (S. sorghi) and that this honeydew would contain a Africa (c. africana). TheirS. sorghi ana­ higher than usual concentration of un­ morphs are mycologically so similar that transformed sucrose which, by an os­ it is impractical to differentiate them by motic effect, might suppress secondary microscopic examination of the spore­ sporulation. laden honeydew. Nevertheless, they are genotypically distinct in so far as, for ex­ The first step in testing the feasibility ample, when allowed to develop parasiti­ of this strategy was to explore responses cally on the same male-sterile sorghum of sweet sorghum accessions under field host, the honeydew from C. africana pro­ conditions in South Africa. In two succes­ duced abundant secondary sporulation sive years (1994-1995), this was whereas none was evident on the honey­ achieved, though with great difficulty due dew from C. sorghi (Frederickson et al. to the widespread prevailing droughts in 1991). Further parasitic development of Southern Africa. Several sweet sorghums the mycelia allows organization of mor­ were selected which consistently failed to phologically distinctive sclerotia and the support overt secondary sporulation on accumulation of dihydrogenated ergot al­ the honeydew exuded from infected flo­ kaloids (notably dihydroergosine) only in rets, particularly during warm dry condi­ C. africana. Subsequently, there may be tions. the elaboration of the distinctly different teleomorphs, though this may be ex­ As an indication of what is meant by tremely difficult to achieve with C. afri­ sweetness in sorghum in the flowering cana in experimental conditions and there stage, analysis in April 1997 of juice is uncertainty concerning the extent to squeezed from the last internode of acces­ which this occurs naturally. Conse­ sions grown in South Africa frequently quently, to make a rather simple combina­ contained at least 10% sugar, mainly in tion of these two features was the most the form of sucrose. How this related to prudent (Frederickson et al. 1991) in at­ the concentration of phloem translocates tempting to explain why secondary sporu­ available to the pathogen is unclear, but lation was so much more evident in vivo the analysis at least indicates liberal avail­ in infections of sorghum by C. africana. ability of sugar. However, it did allow the initially plausi­ ble deduction that the extent ofexpression

142 Concomitantly, the sugars in honey­ yielded only fructose. Similarly, a disac­ dew exuded from infected grain sor­ charide also appeared to be composed ghums and from sweet sorghums were only offructose. Fast atom bombardment studied in greater depth than had been mass spectrometry of peracetylated and previously attempted (Frederickson permethylated trisaccharide gave data 1990). It gradually became clear that the consistent with a constitution of three oligosaccharides arising from C. africa­ hexoses. The deduced tri-fructose, occur­ na 's parasitism ofsorghum were not iden­ ring naturally through the ergot fungus's tical to those produced in an analogous enzymology, was likely to be constructed way by C. purpurea parasitising rye or by the 2-1 or 2-6 linkages that are the op­ wheat, the latter having been elucidated to tions characteristic of the inulin or levan considerable depth of enzymology (Dick­ series of oligofructosides, respectively. erson 1972). Nor did the sorghum ergot The inulin series are typically derived by honeydew oligosaccharides readily partial hydrolysis of storage carbohydrate match the complex saccharides described polymers (of the order of ~ 50 fructose by Mower et al. (1973) for the same or­ residues) of some Compositae plants (e.g. ganism (Frederickson et al. 1991) ob­ Jerusalem Artichoke [Helianthus sp.], tained from Nigeria. It was therefore de­ chicory [Cichorium sp.] and Dahlia tube­ cided to explore C. africana honeydew rosa). Levan oligosaccharides may simi­ from sorghum without any preconceived larly be obtained by partial hydrolysis of expectations except that whatever occurs fructosans obtained from some grasses or must be derived enzymologically from arising from the fermentation utilization the sucrose supplied to the pathogen by of sucrose by certain bacteria (e.g. Serra­ the host in leaked phloem translocate. tia sp.). Since mass spectrometry could Preparative descending paper chromatog­ not distinguish between 2-1 and 2-6 link­ raphy was the primary separation tech­ ages between fructose units, and also that nique adopted since glucose, fructose and obtaining purified honeydew sugars in sucrose can readily be resolved, and in­ >20 mg amounts was feasible, a nuclear creasing polymerization of saccharides magnetic resonance spectroscopy ap­ progressively retards migration rates on proach was adopted. Subsequently, litera­ paper in the propan-l-ol:ethyl ace­ ture showed that in recent years helpful tate:water (7: 1 :2) solvent system em­ l3C data on small, mainly inulo-, oligo­ ployed. Subsequently, preparative high saccharides was published. Conse­ voltage paper electrophoresis was advan­ quently, our attention was also directed to tageous in further resolving mixtures obtaining our own model inulobiose and which co-chromatographed in paper par­ inulotriose purified by the same method­ tition chromatography methodology. ology as used for ergot honeydew con­ stituents, which were subjected to the Acid hydrolysis, in conditions that effI­ same NMR instrumentation for data ac­ ciently cleave the glucose-fructose bond quisition and analysis. in sucrose, showed that the most abundant honeydew oligosaccharide, chroma­ A striking feature of the principal tri­ tographing typically as a trisaccharide, saccharide (tri-fructose) revealed by

143 NMR spectroscopy was its homogeneity, seen in the recent epidemics in South after isolation only by descending paper America, and particularly in a Bolivian chromatography, indicated by 9 strong isolate used to infect male sterile grain l3C resonances. This was in contrast both sorghum in London in 1996. to the extreme complexity of resonances seen in inulotriose obtained by partial Analysis ofthe honeydew exuded from acid hydrolysis of inulin and purified certain sweet stem sorghums infected similarly and also to the relative comple~ with C. africana in experimental agricul­ ity even after further high voltage electro­ tural field conditions, but not supporting phoresis. It was quite clear that the ergot secondary sporulation, showed that rather sugar was not ofthe inulin series. Correla­ high concentrations of levantriose accu­ tions ofl3C and IHNMR data have led to a mulate and are maintained even in humid firm conclusion that the C. africana tri­ conditions. fructose is levantriose, which previously was known only as a laboratory com­ Logically it follows that the failure to pound and was never found as a free natu­ support secondary sporulation was conse­ ral product. Further, the levantriose in quent on transformation of the sucrose­ thin films of potato dextrose agar was richer phloem trans locate in these particu­ found to inhibit germination of macro­ lar sweet sorghums to the biologically­ spores, applied to the surface, completely active levantriose. This sugar is not at 2% w/v and almost completely at 1%. widely fungitoxic since it did not inhibit Such concentrations are readily achieved germination of conidia of two plant in the honeydew exuded from infected pathogenic Penicillia (P. digitatum andP. florets of certain sweet sorghums. expansum) even at a concentration of2%.

There is, therefore, the unexpected sce­ An exploitable bjochemical mecha­ nario that the African sorghum ergot nism is therefore available in certain pathogen predominantly transforms the sweet sorghums, and the use of a sweet hosts' sucrose to a potentially toxic un­ character in the male-sterile A-line in FI usual fructoside which on grain sorghum hybrid seed production is proposed as a only accumulates in rather low amounts feasible strategy to suppress ergot disease in honeydew and therefore permits the epidemic development. profuse secondary sporulation that is so characteristic of honeydew exudate and The strategy relies on the persistent ex­ that poses such a potent factor in epidemic pression of the particular, and rather un­ development. The reason why honeydew usual, enzymology in C. africana. So far from infected grain sorghum is so dilute our experience with the pathogen on its with respect to sugars is that the metabolic spread northwards through South Amer­ demands of the large sphacelium, which ica shows a consistent pattern of typical C. africana produces, nearly exhausts the oligosaccharides in honeydew, even to plant's phloem translocate. The vigor in the extent that the composition has in ef­ producing a large parasitic sphacelium is fect taxonomic value in disease diagnosis notably evident in the sorghum infections and was invoked as a complementary

144 character when the pathogen was recently dominant pure grain sorghum genome of first encountered in Brazil (Reis et al. the B line. If fertility is not efficiently re­ 1996). . stored persistent expression of the sweet character may be desirable. The first step in this experimental con­ struction of agronomically suitable A Amplification of the biochemical lines, expressing a sweet character during mechanisms tentatively perceived for C. 1-2 weeks after flowering when suppres­ africana in producing oligosaccharides sion of secondary sporulation on honey­ which can inhibit secondary sporulation dew is epidemiologically most important, is currently in progress in London, with is to demonstrate that male sterile forms strong indication already that the disac­ of our selected sweet sorghums will be­ charide is levanbiose, again recognized have similarly to these fertile forms with for the first time that this small fructoside respect to suppression of secondary spo­ occurs as a free natural product. It will be rulation. Construction of male steriles is important to define at least two more of currently in progress in South Africa and, the minor oligosaccharides and to show provided that they come up to expecta­ whether or not they are biologically active tions, the challenge will be to introduce concerning secondary sporulation. In any appropriate sweet character expression case it is already clear that C. africana has into sorghums that are agronomically rather unique mechanisms for sucrose suitable to act as A lines in F) hybrid seed utilization which are especially efficient production systems. It will still be desir­ in making virtually all the glucose com­ able to achieve efficient pollination as ponent available for nutrition and con­ rapidly as possible from the B line. N ever­ signing the fructose into fructosans, that theless, primary foci of disease due to er­ for the purpose of F) hybrid seed produc­ got may arise in some florets ofthe A line tion can be exploited with long-term cost but these foci should not then function as benefit both to the seed producers and to sources of further windborne inoculum the farmer in the semi-arid tropics._ causing epidemic development. It may of course be prudent to destroy B line plants References immediately after pollen shedding in case Dickerson, AG. 1972. A P-D-fructofuranosidase they develop their own foci for disease from Claviceps purpurea. Biochemical Journal spread, though this may be of minor im­ 129:263-272. portance if the B line is efficiently self­ Frederickson, D.E., Mantle, P.G. and de Milliano, W.A.J. 1989. Secondary conidiation ofSphace­ pollinated. lia sorghi on sorghum, a novel factor in the epi­ demiology of ergot disease. Mycological Ergot disease causes most seed losses Research 93:497-502. Frederickson, D.E. 1990. Ergot disease of sor­ in male sterile sorghums and therefore ghum. PhD thesis, University of London, (Im­ persistence of the sweet character expres­ perial College), London, UK. 217 pp. sion in the F) hybrid need not be an objec­ Frederickson, D.E., Mantle, P.G. and de Milliano, W.AJ. 1991. Claviceps africana sp-nov.; the tive, especially if restored fertility has distinctive ergot pathogen of sorghum in Africa. been efficient. The sweet character in the Mycological Research 95:1101-1107. A line could therefore be recessive to a Hassan, H.AG., Mantle, P.G. and McLaren, N.W. 1995. A strategy for constraining ergot disease

145 epidemics in Fl Hybrid sorghum production in Reis, E.M., Mantle, P. G. and Hassan, H.A. G. 1996. Proceedings XIII International Plant Protection First report in the Americas of sorghum ergot Congress. The Hague. July, 1995. Abstract 677. disease, caused by a pathogen diagnosed as Claviceps africana. Plant Disease. 80:463. Mower, R.L., Gray, G.R. and Ballou, C.E. 1973. Sugars from Sphacelia sorghi. Carbohydrate Research 27:119-134.

146 Session V - Ergot Management Strategies

Session President - Ranajit Bandyopadbyay

147 Host Plant Resistance: Sorghum Ergot

J.A. Dahlberg

Abstract

Sorghum [Sorghum bicolor (L.) Moench] is the fifth most important cereal crop in the world In 1995, sorghum ergot caused by Claviceps africana was first reported in the Americas. Since then it has moved to cover the hemisphere. Fungicides have become the short-term solutionfor control, but treatment is expensive. Host-plant resistance of fers a possible solution to limiting ergot and reducing the costs ofseed production. B& cause ofits unique life history with sorghum, sterile plants and any plant that has prob­ lems with sterility is vulnerable to the disease. Disease management strategies include three basic approaches; 1) escape in space and/or time, 2) accommodation to the patho­ gen (tolerance), and 3) confrontation (use ofphysical or chemical defenses, including both antibiosis and nonpreference resistance). Each has limitations based on our lim­ ited knowledge of the sorghum-ergot relationship.

Sorghum [Sorghum bicolor (L.) growing the material in the summer in the Moench] ergot, identified as Claviceps United States. Breeder's seed that is africana, was first reported in the imported into the U.S. is being treated Americas in mid-1995 in Brazil (Reis et with selected fungicides as a precaution. al. 1996). Since that time, 33% of the Breeding programs will have additional countries in the Americas and the costs in fungicide treatment to minimize Caribbean have had confirmed reports of ergot in the field and reduce the chances ergot. The disease has moved of seed contamination. approximately 8000 km (5000 miles) in two years. Crisis exemptions are being sought and granted to spray the systemic In the spring of 1997, ergot was propiconazole Ti1t® on nurseries and reported in Puerto Rico, Jamaica, the production fields this summer. These Dominican Republic, and Mexico emergency exemptions are defined by the including several winter nursery sites Animal and Plant Health Inspection utilized by the U.S. Sorghum Industry. Service (APHIS) of the United States The economic impact of this disease was Government as; "Emergency Exemp­ felt immediately. Several research tions. The authority given to the programs have lost a full breeding cycle Environmental Protection Agency (EPA) due to a primarily self-imposed ban on to exempt a State or Federal agency from the requirements ofFIFRA, if emergency conditions exist. There are four types of emergency exemptions which may be J.A. Dahlberg, USDA-ARS-TARS, 2200 Ave. Pedro Albizu-Campos, Suite 201, MayagOez, PR 00680-5470. used based on the following circumstances: (l) Crisis. An exemption

149 requested if the time available from This will involve host-plant resistance discovery or prediction of a pest outbreak and perhaps the use of specialized is insufficient for a pesticide to be biotechnology to achieve this goal. registered for the particular use. (2) Specific. An exemption requested if a Host-Plant Resistance pest outbreak has or is about to occur, and no pesticide is registered and readily Host-plant resistance has been available or no other appropriate method recognized by farmers for several of control is available to eradicate or thousand years. Early farmers used control the pest. (3) Quarantine. An deliberate human selections as a means of exemption requested if significant selecting specific heads or panicles for economic or health problems will occur planting in the next generation. Selections without the use ofthe pesticide. (4) Public were based on larger heads, larger seed, Health. An exemption to control a pest more seed, better seed, and more than that will cause a significant risk to human likely, disease free panicles. This type of health" (APHIS 1995). selection pressure created populations that became an array of deliberately Cost estimates have run from chosen components. It may still be rich in approximately $30.00 per acre for variation because cultivators of treatment using Tilt with an overall traditional agriculture have an projected cost of$2.00-3.00 for every bag appreciation for mixtures, but the of hybrid seed produced. Ergot has also mixtures will conform to whatever an been reported in Australia, and they are individual selector chooses. The total projecting increased costs of $20.00 potential range of variation will be Australian dollars for each 25 kg bag of fragmented into landrace populations or seed with an increased cost of $4.0 primitive cultivars (Harlan 1975). million Australian dollars annually to the Individual plant characteristics and the industry. Brazil is also experimenting physical and chemical structure of these with several different applications of plant popUlations would, therefore, systemic fungicides such as Tilt, directly and indirectly affect the evolution triadimenol (Bayfidan®), and tebuco­ and ecology of plant pathogens and the nazole (Folicur®) for use in control of ability ofthe plant population to deal with ergot in hybrid seed production fields. them (Fritz and Simms 1992).

Because of ergot's sudden appearance This co-evolution of plants with their in the America's, short term strategies in respective pathogens was eloquently this region have been limited to research stated by Flor (1955, 1956) in what has on fungicidal treatments. However, given become known as the gene-for-gene the overall cost, both financially and hypothesis. Simply stated, genes in a host environmentally, of using chemicals as plant that control susceptibility or the main control strategy, resistant resistance have a corresponding gene in cultivars seem to be a practical and the pathogen that determines avirulence economical form of control for the future. or virulence. This interaction determines whether or not the disease will be

150 expressed in the host (Fehr 1987). Several The sorghum head is a panicle authors and books have discussed the consisting of a central axis with whorls of gene-for-gene hypothesis and its effects main branches, each with secondary and on breeding for plant resistance and the sometimes tertiary branching. The length mechanisms involved (Bagga and Boone ofthe rachis branches permits a variety of 1968, Ellingboe 1981, Fritig and Legrand panicle shapes and sizes. The branches 1993, Fritz and Simms 1992, Jacobs and carry the racemes of the spikelet (Figure Parlevliet 1993, Johnson and Jellis 1992, 1). The panicle emerges from the flag leaf Martin et al. 1993, Michelmore 1995, sheath, or boot. Toxopeus 1956). From these discussions, three basic strategies for disease As sorghum flowers undergo anthesis, management in host-plant resistance have spikelets form at the apices of the rachis developed; 1) escape in space and/or branches. Spikelets come in pairs on the time, 2) accommodation to the pathogen racemes with one being sessile and fertile (tolerance), and 3) confrontation (use of and the other being pedicelled and sterile. physical or chemical defenses, including Each sessile spikelet contains one fertile both antibiosis and nonpreference and one sterile floret. Anthesis occurs resistance) (Kennedy and Barbour 1992). early in the morning and proceeds from the apex to the bottom of the panicle over These disease management strategies a six-to-nine day period, depending on the have the potential for the development of environment, size of the panicle, and the plants that are better adapted to handling variety. Sorghum flowers open as a result outbreaks of ergot in the future. However, of the lodicules swelling and forcing the in order to understand how these glumes apart (Doggett 1988). The strategies might be used and developed, it stigmas emerge and the papillae fluff out. is essential that one understands some of Stigmas generally extend beyond the the basic morphology involved in glumes which close after one to four susceptibility of sorghum to ergot and hours (Stephens and Quinby 1934). ergot's own life history. Stigmas may be receptive to pollen one to two days pre-flowering and may be The Sorghum Plant and Ergot receptive for up to a week after flowering. Jaster (1985) reported that under certain Sorghum is a robust and genetically environmental conditions, stigmas may variable plant. Most sorghums are be viable up to 12 days after 100% photoperiod sensitive and days to anthesis. flowering range from 36 to 199 days. It has strong stems and ranges in height Seeds begin to appear shortly after from less than 1 m to greater than 4 m. flowering. Physiological maturity, Stems are juicy or dry, sweet or bitter. recognized by the development of the Leaves are arranged alternately and have black-layer, occurs between 25-55 days prominent midveins and parallel lateral after flowering. Seed is normally veins. Long, overlapping leaf sheaths are harvested 10-20 days after black-layer attached at the nodes. formation when seed moisture content is

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.c

o·4 11

Figure 1. The inflorescence and spikelets of sorghum. (1) parts of the panicle: a, internode of rhachis; b, node with branches; c, branch with several racemes. (2) Raceme: a, node; b, internode; c, sessile spikelet; d, pedicel; e, pedicelJed spikele~; f, terminal pedicelJed spikelets; g, awns. (3) Upper glume: a, keel; b, incurved margin. (4) Lower glume: a, keel; b, keel-wing; c, minute tooth terminating keel, (5) Lower lemma: a, nerves. (6) Up­ per lemma: a, nerves; b, awn. (7) Palea. (8) Lodicules. (9) Flower: a, ovary; b, stigmas; c, anthers. (10) Grain: a, hilum. (11) Grain: a, embryo mark; b, lateral lines. (Snowden 1936). roughly 15%. Seeds are made up of compounds, which separates the primarily three major components: the endosperm from the pericarp. endosperm, embryo, and pericarp. Associated with the seeds of many Because the life and disease cycle of sorghum cultivars is a specialized layer ergot will and has been discussed called the testa, composed of phenolic extensively in this conference, discussion

152 on ergot will be limited to its life cycle and et al. 1996). The focus on plant-host its potential interactions with sorghum. resistance must therefore revolve around The life cycle of Claviceps africana is the pathogen's interaction with the outlined in Figure 2. It is critical that in its pollinating mechanisms involved in the life cycle non-pollinated stigmas are sorghum plant. present for colonization by either conidia or ascospores of the pathogen. The Potential Strategies for Disease primary site of infection is the stigma, Management in Sorghum although the conidia may also infect through the style and the ovary wall. Once Three basic strategies for disease germinated conidia reach the vascular management in host-plant resistance for .bundles ofthe rachilla, rapid colonization sorghum are available; 1) escape in space of the ovary takes place (Bandyopadhyay and/or time, 2) accommodation to the

Life Cycle of Claviceps africana

Airborne conidia wind ~ Nonpollinated ~stigma Ascospores Conidia on honeydew surface I 5-10 days sClerotia~3~days

Ovaries converted to sphacella high I humidity

Sphacelia produce conidia in honeydew

Figure 2. Life &:yc)e ofsorghum ergot (CJaviceps africana) (after Odvody).

153 pathogen (tolerance), and 3) exist in nature in which interaction confrontation (use of physical or between host plants and pathogens can chemical defenses, including both exist. Disease expression is modifiable antibiosis and nonpreference resistance). through the interaction ofgenes from both In order for these systems to be utilized, the plant population and the pathogen. several programs must be in place to Both individual plants and population and support these strategies. The first step in pathogens survive. Male-sterile the development of these tools are proper populations of sorghum are an artifact of screening and evaluation techniques for our agricultural scheme and are not viable ergot. Bandyopadhyay et al. (1996), in an forms in nature; consequently, genes for excellent review on ergot, outline the resistance and virulence within a male­ research that has taken place in the sterile population would not have development of inoculation methods, evolved. Therefore, genes for resistance screening techniques, evaluation in our germplasm sources may be difficult procedures, and finally sources of to elucidate. This does not preclude, resistance; considering that, lines with however, the use of escape mechanisms significant and stable levels of resistance that might assist in limiting outbreaks of were not available (Bandyopadhyay et al. ergot in the future and the potential of 1996). biotechnology, specifically, transform­ ation as possible tools within our disease To fully implement these options, management strategy. disease management must consider that in sorghum we are dealing with two Escape in Space and/or Time different developmental programs in our breeding strategies; 1) development of In both B/R lines and male-steriles, maintainer and restorer (BIR) lines and 2) manipulation of flowering dates development of male-sterile lines. In B/R (maturity) to allow flowering to occur lines, germplasm accessions that show during optimal pollination and fertility some promise of resistance have been times is one method that can be found within many ofthe collections from incorporated into breeding programs. around the world (for sources of These genes could produce cultivars and resistance, see Bandyopadhyay et al. hybrids that flower at times when weather 1996) and this would be expected if one conditions are unfavorable to ergot accepts the gene-for-gene hypothesis. development. Germplasm is currently available to begin this process. Flowering Landraces or traditional cultivars in sorghum germplasm ranges from 36 to presented populations in which co­ 199 days. This would also require a evolution of the ergot pathogen could thorough understanding of weather evolve and both resistant and virulence conditions throughout the proposed genes could co-exist. Male-sterile lines, developmental stages of sorghum. however, pose a different problem. A major assumption within the gene-for­ Male-steriles have been bred for gene hypothesis is that plant populations prolonged periods of stigma receptivity

154 and this has been important in the hybrid Confrontation seed industry when pollen parents flower (Use ofPhysical or Chemical Defenses, later than females (Frankel and Galum Including both Antibiosis and 1977). De Vries (1971) also reported that Nonpreference Resistance) greater periods of stigma receptivity produced greater seed set. Jaster (1985) Post-fertilization, ultrastructural found significant differences in stigma changes in the gynoecium following receptivity anlOng selected cytoplasmic pollination, prevent ergot hyphae from genetic male steriles. Greater periods of infecting the ovary along the same stigma receptivity could also possibly pathways (Bandyopadhyay et al. 1996). lead to greater susceptibility to ergot and In BIR lines, several strategies can be we might have to begin developmental employed to enhance sorghum's ability to programs to produce female lines with confront ergot. Mechanisms that enhance shorter periods of stigma receptivity. This pollen shed, pollen fertility and is one area of research that requires fertilization can be used. McLaren and further funding and evaluation. Again, Wehner (1992) found the preflowering germplasm exists to meet this challenge. cold stress was highly correlated to ergot incidence. Bandyopadhyay and Reddy Accommodation to the Pathogen (1991), using different B-lines arrived at (Tolerance) basically the same conclusions. Both studies relate to fertility issues interacting This strategy may be the most difficult with environmental conditions. Lansac et to implement, especially on large scale al. (1994) looked at pollen viability and production and hybrid seed production germination and found that sorghum areas. Unfortunately, even small numbers pollen was similar to other Gramineae of infected panicles may be enough to species in that it was desiccation sensitive completely contaminate production seed and lost viability during drying. Further given the mechanical harvesting that is research is needed to evaluate the used in such operations. Harvesters could potential of this mechanism as a viable act as efficient spreaders of honeydew tool in our disease management strategy. onto harvested seed. In order for tolerance Dr. Keith Schertz (personal communi­ to be an effective tool in our disease cation) indicated that work was done in strategy arsenal, finding accessions that the 1930s on pollen shed by Quinby and would allow for infection and production Stephens (USA) and Rangoswamy of sphacelia in sterile florets in BIR lines, (India), however, little research has been but would then limit the production of carried out since then. honeydew would have to be found within our germplasm collections. Due to the inverse relationship of ergot severity with pollination, screening for resistance to both C. sorghi and C. africana in male-steriles has not shown much promise. Most research in this area has concentrated on AI, A2, A3, and ~ cytoplasmic male-steriles sources and

155 further evaluation of other sources is important in male-sterile lines and the use needed. One promising area of research of biotechnology offers some promise, might be in stigmatic secretions that may albeit in the future. Development of influence spore germination. world-wide screening nurseries, Chinnadurai et al. (1970) found varietal inoculation techniques, and evaluation of differences in stigmatic secretion of such germ plasm resources are required in products as malic acid, succinic acid, order to build the knowledge base that arginine, aspartic acid, tartaric acid, and will allow us to utilize host-plant tyrosine which might be related to spore resistance. This conference and this germination in ergot. Similar results have disease provides us with that opportunity been found in pearl millet (Kannaiyan et to lay the foundation for this world-wide al. 1973). Further research efforts need to effort to combat ergot for the future. be carried out to validate these findings. References Due to the inherent difficulties in APHIS. 1995. APHIS Directive 6901.1, Registra­ finding resistance in male-steriles, tion, use management, and coordination of pes­ biotechnology or more specifically, ticides. U.S. Gov. Print. Office, Washington, transformation may provide a window of D.C. Bagga, H.S. and Boone, D.M. 1968. Inheritance of opportunity in the development of resistance to Venturia inaequalis in crabapples. resistant female lines. Anti-fungal Phytopathology 58: 1183-87. proteins expressed in the stigma, style, Bandyopadhyay,R. and Reddy, B.V.S. 1991. Iden­ tification of ergot resistance in hybrid parents. and ovary might provide a level of Pages 25-26 in Cereals Program annual report resistance in females such that we may be 1990. Patancheru 502 324, Andra Pradesh, In­ able to move away from chemical control dia: International Crops Research Institute of the Semi-Arid Topics. in the field. Transformation is possible in Bandyopadhyay, R., Frederickson, D.E., McLaren, sorghum and testing of anti-fungal N.W., and Odvody, G.N. 1996. Ergot, a global proteins and tissue-specific gene threat to sorghum. International Sorghum and Millets Newsletter 37:1-32. expression will need to be carried out. Chinnadurai, G., Govindaswamy, C.V., and Ra­ makrishnan, K. 1970a. Studies on the effect of Conclusions stigmatic exudates of sorghum on the parasit­ ism of Spacelia sorghi McRae. Phytopatholo­ gische Zeitschrift 69:56-63. Ergot is a serious and costly disease to De Vries, APh. 1971. Flowering biology of wheat, sorghum production, especially in hybrid particularly in view of hybrid seed production-a review. Euphytica 20: 152-70. seed production. Estimated costs for Doggett, H. 1988. Sorghum. 2nd. Edition. Long­ chemical control are high and will man Scientific and Technical, New York, NY, increase production costs for farmers and USA 512 pp. Ellingboe, AH. 1981. Changing concepts in host­ the seed industry. However, host-plant pathogen genetics. Annual Review ofPhytopa­ resistance may help control this disease thology 19:125-43. and eventually reduce costs of Fehr, W.R. 1987. Principles of cultivar develop­ ment, Vol. 1 theory and techniques. New York, production. Germplasm sources exist that USA: Macmillan Pub. Co. 536 pp. may either escape or resist the disease in Flor, H. H. 1955. Host-parasite interaction in rust in B/R lines. Extensive research and flax-its genetics and other implications. Phyto­ pathology 45:680-85. collaboration will be needed to further elucidate mechanisms that will be

156 Flor, H. H. 1956. The complementary genic sys­ Kennedy, G. G. and J. D. Barbour. 1992. Resis­ tems in flax and flax rust. Advances in Genetics. tance variation in natural and managed systems. 8:29-54. Pages 13-41 in Plant resistance to herbivores Frankel, R. and Galun, E. 1977. Pollination mecha­ and pathogens: ecology, evolution, and genetics nisms, reproduction and plant breeding. New R.S. Fritz, and E.L. Simms (eds.). Chicago, York, USA: Springer-Verlag. USA: Univ. of Chicago Press. Fritig, B. and Legrand, M. (eds.) 1993. Mecha­ Lansac, A. R., Sullivan, C. Y., Johnson, B. E., and nisms of plant defense responses. Dordrecht, Lee, K. W. 1994. Viability and germination of The Netherlands: Kluwer Academic Pub. 480 the pollen of sorghum [Sorghum bieolor (L.) pp. Moench]. Annals of Botany 74:27-33. Fritz, R. S. and Simms, E. L. 1992. Ecological ge­ Martin, G. B., Brommonschenkel, S. H., Chun­ netics of plant-pathophage interactions. Pages wongse, J., Frary, A., Ganal, M. W., Spivey, R., 1-9 in Plant resistance to herbivores and patho­ Wu, T., Earle, E. D., and Tanksley, S. D. 1993. gens: ecology, evolution, and genetics (R.S. Map-based cloning of a protein kinase gene Fritz, and E.L. Simms (eds.) Chicago, USA: conferring disease resistance in tomato. Science Univ. of Chicago Press. 26: 1432-36. Fritz, R. S. and Simms, E. L. (eds). 1992. Plant re­ McLaren, N. W. and Wehner, F. C. 1992. Pre­ sistance to herbivores and pathogens: ecology, flowering low temperature predisposition of evolution, and genetics. Chicago, USA: Univ. sorghum to sugary disease (Clavieeps afri­ of Chicago Press. 590 pp. eana). Journal of Phytopathology 135:328-334. Harlan, J. R. 1975b. Crops & Man. American Soci­ Michelmore, R. W. 1995. Isolation of disease resis­ ety of Agronomy, Madison, WI. 295 pp. tance genes from crop plants. Current Opinion Jacobs, Th. and J. E. Parlevliet. (eds.) 1993. Dura­ in Biotechnology 6:145-152. bility of disease resistance. Dordrecht, The Reis, E. M., Mantle, P. G., and Hassan, H. A. G. Netherlands: Kluwer Academic Pub. 375 pp. 1996. First reports in the Americas of sorghum Jaster, J.R. 1985. Analysis of seed set and stigma ergot disease, caused by a pathogen diagnosed receptivity among cytoplasmic male sterile sor­ as Clavieeps afrieana. Plant Disease 80:463. ghum [Sorghum bieolor (L.) Moench] culti­ Snowden, J. D. 1936. The cultivated races of sor­ vars. MS thesis, Texas A & M University, ghum. Adlard & Sons, Ltd. London, UK. 274 College Station, Texas, USA. 62 pp. pp. Johnson, R. and Jellis, G. J. (eds.) 1992. Breeding Stephens, J.C. and Quinby, J.R. 1934. Anthesis, for disease resistance: proceedings of the Inter­ pollination, and fertilization in sorghum. Jour­ national Conference on Breeding for Disease nal of Agricultural Research 49:123-136. Resistance, 16-19 Dec 1991, Newcastle-upon­ Toxopeus, H. J. 1956. Reflections on the origin of Tyre, U. K. Dordrecht, The Netherlands: Klu­ new physiological races in Phytophthora infes­ wer Academic Pub. 205 pp. tans and the breeding for resistance in potatoes. Kannaiyan, J., Vidhyasekaran, P., and Kandas­ Euphytica 5:221-37. wamy, T, K. 1973. Amino acid content ofbajra in relation to disease resistance. Indian Phyto­ pathology 26:358-359.

157 Chemical Control of Sugary Disease of Sorghum (C/aviceps africana) N.F.J. de Almeida Pinto, A. da Silva Ferreira, and C.R. Casela

Abstract

Sugary disease, caused by Claviceps a/ricana, represents a major threat to hybrid seed production in Brazil. Since the disease was observed in 1995, a collaborative re­ search program involving private and public sector has been developedfor control of the disease. This paper reports results of recent trials developed in the EMBRAPA Maize and Sorghum Research Center Experiment Station, in the evaluation offungi­ cides and doses for the control ofsugary disease in seed production fields.

Sugary disease of sorghum, caused by significantly increased seed production. Claviceps africana, has been considered a In vitro studies indicated that Benomyl, major threat to hybrid seed production in Captan, Ziram, Thiram, Vitavax, and Brazil. The disease was observed in Miltox inhibited growth and sporulation Brazil in 1995 and by mid 1996, Brazilian of Sphacelia sorghi. In this paper we scientists, through a collaborative present some of the recent results of research program involving public and fungicide trials performed at the Em brapa private sector, identified two active Experiment Station to evaluate the impact ingredients that were highly effective in of fungicides in the control of sugary the control ofthe disease. disease.

Very few reports are found in the Fungicide trials were divided into three literature regarding the control of C. experiments. In the first trial fungicide africana by fungicides. No fungicidal treatments consisted of four sprays, at activity towards sugary disease was three-day intervals using a backpack reported for the residual action of sprayer, starting at the beginning of benomyl, bitertanol, carbendazim plus anthesis. In all treatments sorghum flusilazole, procymidone, propiconazole, panicles were sprayed so that they were tebuconazole, and triadimenol. On the completely covered by the fungicide. other hand, Dithane M-45, Difolatan, Disease evaluations were based on the Cuman, Carbendazim plus Tridemorph, percentage of infected panicle according Carbendazim plus Thiram, and to a 1 to 5 scale, where 1 = no disease and Thyophanate methyl proved to be 5 = above 50% of disease. Tebuconazole effective in reducing disease severity and was very effective in controlling sugary disease (Table 1). Some toxicity to sorghum seeds was observed as a result of application of Triadimenol, despite its N.F.J. de Almeida Pinto, A. da Silva Ferreira, and C.R. Casela, high efficiency in the control of the CNPMSIEMBRAPA, C.P. lSI, Sete Lagoas, MG, Brazil disease (Table 2).

158 Table 1. Effect offungicides in the control of sugary disease (CJaviceps africana) in a seed produc- tion field ofthe cultivar BR304, Embrapa Corn and Sorghum Research Center, Lagoas, MG, Brazil, 1997.

Dose(ml DP" DPb DP' DSd DS' DSf 1 Treatment a.i. ha-l~ ('Yo) ('Yo~ ('Yo) ('Yo) ('Yo) ('Yo~ NEIg NE2h NE3 Propiconazole 75.0 0.0 4.4 77.3 0.0 1.0 3.2 2 2 Propiconazole 125.0 0.0 0.0 24.6 0.0 0.0 1.2 2 Propiconazole 50.0+ 0.0 7.5 82.9 0.0 1.0 3.2 2 2 Difenoconazole 50.0 Propiconazole 75.0+ 0.0 12.6 73.3 0.0 2.0 4.0 2 2 Difenoconazole 75.0 Tebuconazole 60.0 0.0 2.3 41.1 0.0 0.5 1.2 2 Testemunha 58.9 100.0 100.0 3.0 37.5 65.0 2 4 a=diseased panicles three days after last spraying; b=diseased panicle 14 days after last sprayiny; '=diseased panicle final rating; d=disease severity three days after last sprayinl!; '=disease severity 14 days after last spraying; =disease severity final rating; ~disease grade three days after last spraying; =disease grade 14 days after last spraying; l=disease grade final rat ing.

Table 2. Effect offungicides in the control ofsugary disease (CJaviceps africana) in a seed produc- tion field ofthe cultivar BR304, Embrapa Corn and Sorghum Research Center, Lagoas, MG, Brazil, 1996. a b c d Dose (g or DPl DP2 DSl DS2 Treatment ml ai. ha-l~ (%~ (%~ (%~ (%~ NEl' NE2f Tebuconazole 375 19.8 38.4 2.6 5.0 2 2 Benomyl 750 49.2 86.3 5.0 15.0 2 3 Mancozeb 2400 79.4 100.0 20.7 50.0 4 Triadimenol 250 0.0 0.0 0.0 0.0 I F entin hydroxide 500 Phytotoxic to panicles and leaves Metalaxyl + 960+216 91.4 100.0 21.3 66.7 3 Mancozeb Tiofanato 700 88.9 100.0 21.7 50.0 3 4 Metllico Testemunha 87.2 100.0 58.3 93.3 Tebuconazole 375 57.4 90.1 12.3 15.0 3 3 Tebucenazole 375 30.9 42.5 4.0 5.3 2 2 a=diseased panicles three days after last spraying; b=diseased panicle 14 days after last spraying; '=disease severity three days after last spraying; d=disease severity 14 days after last spraying; '=disease grade three days after last spraying; f=disease grade 14 days af- ter last spraying.

In the second trial, plots were sprayed diseased spikelets and number of sclerotia in a three-spray program at 5-day per 1OOg of seed (Table 3). The third trial intervals. The highest doses of included a 7 -day interval spraying Tebuconazole were the most effective in program for the highest dose of the controlling sugary disease, resulting in combination Propiconazole + increased seed weight and percentage of Difeconazole. The fungicides germination, and a reduced number of Propiconazole, Propiconazole +

159 Table 3. Effect offungicides in the control ofsugary disease (Claviceps africana) in a seed produc- tion field of the cultivar BR304, Embrapa Corn and Sorghum Research Center, Lagoas, MG, Brazil, 1997.

Dose Disease Seed Seed wei~ht No. selerotia (kg or 1 a.i. spikelets weight Germination Vigor panicle- per 100 I 1 Treatment ha- (%} (g 1000- } (%} (%} (g} g of seed Tebueonazole 0.2500 4.33 32.15 a 76.67 a 64.33 abe 11.29 a 2.7 Tebueonazole 0.1250 8.00 30.31 a 78.33 a 63.00 abe 10.55 a 4.3 Tebueonazole 0.0625 12.00 26.63 b 73.00 ab 62.67 abe 8.23 ab 17.7 Propieonazole 0.2500 4.00 26.87 b 76.67 a 67.33 ab 8.13 ab 3.3 Propieonazole 0.1250 10.60 25.87 b 73.67 ab 69.67 a 10.57 a 8.0 Propieonazole 0.0625 12.30 25.62 b 70.00 be 59.67 abe 9.55 a 28.0 Triadimenol 0.2500 0.63 25.46 b 68.33 be 54.33 e 10.84 a 0.3 Triadimenol 0.1250 0.30 26.94 b 69.67 be 58.67 be 8.78 a 0.0 Triadimenol 0.0625 1.00 26.59 b 65.67 e 56.67 be 9.97 a 0.7 Testemunha 57.00 19.37 e 68.33 be 60.00 abe 5.48 b 54.0

l=average values followed by the same letter are indicative of no significant differences at 5% probability (Tukey).

Difeconazole, and Tebuconazole were Khadke, V.D., More, B.B., and Konde, B.K 1979. In vitro evaluation of some fungicides and anti­ effective in controlling the disease (Table biotics for the control of Sphacelia sorghi an in­ 1). citant of sugary disease of sorghum. Pesticides, 22:15-60. Lakshmanan, P., and Mohan, S. 1988. Studies on In all the trials, plots artificially or the effect of various fungicides on Sphacelia naturally inoculated before fungicide sorghi. Pesticides, 22:27. spraying, fungicides did not give McLaren, N. W. 1994. Efficacy of systemic fungi­ cides and timing of preventative sprays in the complete control of disease, indicating control of sugary disease of grain sorghum (Sor­ the non-curative effect of the fungicides. ghum bieolor). South African Journal of Plant Residual fungicide activity was not and Soil, 11:30-33. Mielke, H. 1993. Investigations on the control of enough to protect the crop throughout the ergot. Nachrichtenblatt Deutschen Pflanzen­ flowering period. schutzdienstes, 45:5-6. Pinto, N.FJ.A, Ferreira, AS., and Casela, C.R. 1997. Ergot (Clavieeps afrieana) ou doen~a References a~ucarada do sorgo. Sete Lagoas, MG: EMBRAPA-CNPMS, page 24 in EMBRAPA­ Anahosur, KH. 1979. Chemical control of ergot of CNPMS. Circular Tecnica, 23. sorghum. Indian Phytopathology, 32:487-489. Schultz, T.R., Johnston, WJ., Golob, C.T., and Anahosur, KH. and PatH, H.S. 1982. Effect of date Maguire, J.D. 1993. Control of ergot in Ken­ of sowing on the incidence of ergot of sorghum. tucky bluegrass seed production using fungi­ Indian Phytopathology 35:507-509. cides. Plant Disease, 77:685-687. Cagas, B. 1992. Seed yield and diseases in Ken­ Zgorkiwic, A 1987. Chemical control of ergot tucky after fungicide application. Journal Ap­ (Clavieeps purpurea Tul.) on meadow grass plied Seed Production, 10:11-14. (Poa pratensis L.). Prace Naukove Instytutu Ochrony Roslin, 29: 179-195.

160 Integrated Management of Sugary Disease of Sorghum - Practical Aspects E.M. Reis and M.M. Casa Blum

Abstract

This paper discusses the strategies involved in the control ofsugary disease ofsor­ ghum caused by Claviceps africana. The knowledge ofthe biological cycle ofthe patho­ gen is offundamental importance to establish integrated disease control strategies. The strategies aim to reduce the inoculum at its source. Main inoculum sources are seed in­ oculum, crop residues, sclerotia, and secondary hosts. Disease may be managed through seeding time, pollen management, breeding to increase sugar content in honey­ dew, and chemical protection of the infection court.

Sugary disease is known also as ergot Damage may be direct or indirect: of sorghum. Nevertheless the common Direct when ovary infection takes place, name that should prevail is sugary disease and seed or kernels are not formed. because long, black, hard sclerotia like Indirect damage results from the sugary spurs are not produced. Diagnosis would secretion or sphacelium on seeds which be facilitated if sugary disease would be may reduce seedling emergence in the used for the disease caused by Claviceps field by stimulating attack by soil fungi or africana Frederickson, Mantle & de from toxins present in the sphacelium. Milliano and ergot for C. sorghi McRae. Nevertheless this has not been confirmed Two distinct pathogens and diseases of in Brazil yet. Direct losses in seed sorghum are involved. production in the 1996 growing season in Brazil were estimated as in excess of one Sugary disease causes damage mainly million dollars. No damage has been in seed production fields. It is known as determined for commercial fields yet. the male sterility disease since any factor that negatively interferes with Integrated Disease Management fertilization predisposes the female of Plant Diseases flower to infection. Infection does not In integrated disease management take place in those florets where (IDM), all available control strategies fertilization occurs. Hence disease is within a unified program are used to keep more important in seed producing fields the harmful organism population than in commercial ones. (pathogens) below the economic damage threshold (EDT) in such a way as to minimize negative side effects on the environment (Anonymous, 1969). To achieve this goal a detailed understanding E.M. Reis and M.M. CasaBlum, Faculdade de Agronomia e Medicina Vet· to the pathogen life cycle is required. erinaria, Univernidade de Passo Fundo, Caixa Postal 611, 99001 • 170, Passo Fundo, RS, Brazil Biological cycle of SphaceJia sorghi

161 McRae (teleomorph Claviceps aj'ricana seed surface lasts for only one month Frederikson, Mantle & de Milliano): (Reis & Blum, unpublished data). McLaren (1993) reported that seed The target of control measures of any washing in seed processing plants might disease should be the causal agent. Hence, improve seedling emergence in the field a detailed knowledge of the biological by lowering sugar and toxic substance cycle of the etiologic agent is concentrations. fundamental. Control strategies aim at interrupting one or more phases ofthe life b) Sclerotia within seeds. The presence cycle in order to impede continuous of sclerotia in sugary disease is abundant. disease development. The life cycle ofS. Sclerotia of C. africana are not soft, long, sorghi is based on information from hard and black like those of the true ergot literature mainly from Africa and India. diseases such as C. purpurea in wheat or rye (Wiese 1977). Thus it is suggested to Main Phases ofthe Life Cycle name them pseudosclerotia or sclerotia­ to be Targeted by IDM are like bodies. The amount of sclerotia produced in infected panicles is very Inoculum sources - The reduction of high. Thus a large number is found among inoculum at its source is the principle on threshed seeds. Little is known about the which strategies are based. biological function of these resting structures in the continuation of the 1) Seeds as source of inoculum: The parasite's life cycle. Germination of C. literature reports that two types of africana sclerotia in the laboratory has inoculum may be present with the seeds. been reported once by Frederickson et al. (1991). No reports of their germination a) Conidia in the honeydew under field conditions have been found in contaminate seeds during harvesting. available literature. Germination, Similar to wheat and rye ergot, formation and release of ascospores, the macroconidia on the seed surface should true structures for air-borne dispersal of not play any role in the pathogen life cycle inoculum, needs investigation. Work (Wiese 1977). The biological function of carried-out in Brazil by commercial conidia is to infect ovaries of unfertilized sorghum seed producing companies has flowers; this is the only known infection demonstrated that the mechanism of seed site for ergot diseases. Hence, no control cleaning and classification allows the should be directed at this inoculum. Since complete removal of sclerotia from inoculum as conidia is in the wrong infested seed lots. Even if they could infection court (seed surface) and unable easily germinate, they would be to cause infection. Additionally, eliminated from seeds by seed processing laboratory experiments have shown that a equipment. seed treatment with captan (75% WP) at concentrations >40 ~g mrl inhibited 2) Sorghum residues as source of spore germination (Reis & Blum, inoculum: Futrell & Webster (1966) unpublished data). It was also shown that reported that S. sorghi may survive in the viability ofthe inoculum as conidia on the

162 dry honeydew in the anamorphic form macroconidia. A summer rotation would (conidia) in infected panicles, which imply that sorghum could be cultivated remain in the soil after harvesting. again after an 18 month period. The Secondary conidia can be released from potential control of sugary disease this inoculum source and carried by wind through crop rotation however is unclear to infect ovaries of sorghum flowers in the taking in to consideration more important next season. Under field conditions and sources of inoculum such as secondary monoculture, the required survival period hosts. would be about 6-7 months. However, research is required to quantify the time Seeding Time ofSorghum in the required to complete decomposition of Americas and Relation to the Pathogen sorghum residues as well as inoculum Survival in its Parasitic Phase viability under southern Brazilian conditions. In Passo Fundo, Rio Grande Table 1 shows the seeding and do SuI State, sclerotia are naturally flowering time ofsorghum throughout the broken down, nearly 98% oftheir weight, Americas. Secondary conidia produced in a 11 month period. The experiment is on sorghum panicles of cultivated plants still in progress and no germination has would ensure inoculum for the whole been detected in any sclerotia kept at the continent. Every month should there be soil surface to simulate no-till farming sorghum at flowering prone for infection and at a depth 10 cm to simulate everywhere. Thus pathogen does not need conventional tillage. Experiments on other alternative mechanism for survival decomposition of naturally infected in the Americas, even sclerotia. panicles and macroconidia viability are being carried-out. Currently, one may Secondary hosts as source of inoculum infer that a single season's crop rotation Secondary hosts can be defined as with a non-susceptible plant species may alternative non-profitable susceptible reduce inoculum in infected panicles species, such as weeds and wild plants. remaining on the soil, both as sclerotia or

Table 1. Seeding and flowering time of sorghum in the Americas. Seedin time Flowerin time Coun 1st Season 2nd Season 1st Season 2nd Season Brazil OctoberlDecember February/March January/February AprillMay Mexico NovemberlDecember March/April April June/July January/March July/August Colombia! March/April September/ May/June November/ Venezuela October December USA March/May June/August Bolivia May/June July/August Argentina OctoberlNovember December/February Honduras August/September May OctoberlNovember October

163 Futrell & Webster (1966) and presented in Table 2. The only infective Bandyopadhyay (1992) reported the inoculum to S. bieolor came from S. following secondary hosts of S. sorghi in halepense in which conidia shape and size Africa and India: Cenehrus eiliaris, C. were similar to S. sorghi. The remaining setigerus, Isehaemium pilosum, Panieum isolates appear to be different and maximum, Pennisetum typhoides, P. possibly are undescribed Sphaeelia orientalis and Sorghum halepense. species, when compared with the Although not being a secondary host, descriptions of Loveless (1964). Futrell & Webster (1966) include maize as a susceptible species. However, field These results suggest that only the observations in Brazil both in species bieolor and halepense and experimental areas and on farms, failed to probably sudanense and vertieiliflorum in reveal any visible symptoms on maize the genus Sorghum should be considered plants growing in close proximity to host of the sorghum sugary disease infected sorghum plants. One may fungus. Among them is Johnson grass an speculate that in Brazil maize is not important species in Brazil. The naturally infected and thus it is not a incidence of this weed in South America susceptible species or inoculum source is particularly high in Argentina while for sorghum. less so in Brazil.

In Brazil, a number of species have Technically, the control of secondary been reported as showing signs of sugary hosts would be recommended to avoid an disease. Conidia of Sphaeelia-like fungi alternative source of inoculum, but this is were measured and inoculated on to a not feasible taking into consideration the male sterile sorghum line. Results are large areas infested by these species,

Table 2. Measurement of SphaceJia spp. macrononidia.

Macroconidia Length Width Mean

Host plant ~m Sorghum hieolor 10.0 - 22.5 x 5.0 - 10.0 14.8 x 7.4 Braehiaria hrizantha 10.0 - 20.0 x 4.5 - 7.5 15.2 x 6.1 Cenehrus sp. 15.0 - 30.0 x 3.7 - 7.5 22.3 x 5.4 Lolium multlflorum 7.5 - 13.8 x 3.0 - 7.5 9.1 x 4.5 Panicum maximum 13.7 -27.5 x 5.5 - 10.5 20.6 x 7.6 Paspalum dilatatum 8.7 - 22.5 x 5.0 - 8.0 15.4 x 6.9 Paspalum guenoarum 10.0 - 23.7 x 3.7 - 7.5 16.2 x 5.2 Pennisetum amerieanim (own inoculum) 10.0 - 18.7 x 4.5 - 8.7 14.8 x 6.8 Pennisetum amerieanum'" 10.5-21.5 x 5.0 - 10.0 15.9 x 7.2 Sorghum halepense * 10.0 - 28.7 x 5.0 - 10.0 17.2 x 7.6 Frederickson, Mantle & deMilIiano (1991) 9.0-17.0 X 5.0 - 8.0

• Sorghum inoculum

164 especially Johnson grass. Besides that, • selection of parents adapted to the there is a need to confirm the production environment in such a way that pol­ of secondary conidia in these plants as len quantity and viability is not at: they are on sorghum according to fected Frederikson et al. (1991). Control of this • management of seeding time to disease will be impossible by the synchronize the flowering of male reduction of the inoculum from these and female lines sources. If secondary conidia are • nitrogen or irrigation may be used in the later flowering line to antici­ abundantly produced and easily pate flowering transported through wind at very large • pollination may be also improved distances, they would be sufficient to by promoting air turbulence by ensure inoculum for a large geographic plane or atomizer area such as a country or a continent • knowledge of the climate of the re­ (Table 2). gion where seed is produced so that sorghum flowers within the tem­ The host range reported in the literature perature range of 20 to 25°C and has not been confirmed for Brazil. The with blowing wind isolated pathogen has been restricted to • improvement of lines for a higher the genus Sorghum, and may b~ a new amount of pollen production, strain or a new species when compared higher viability, larger period of with the literature. More investigation is pollen production should be pur­ needed to prove this hypothesis. From sued with reduced susceptibility of now on, Sorghum hieoior, S. haiepense, these features to environmental S. sudanense and S. vertieili.florum should conditions. be considered as the only host of C. afrieana in Brazil. Other plant species Under field conditions in Brazil should be inoculated under natural commercial hybrids exhibit differences in conditions to test Koch's postulates. disease severity. This may be attributed to better adaptation or to the more efficient Pollen Management pollination that occurs in more resistant lines compared with more susceptible As sugary disease is the result of lines. infection of unfertilized ovaries and flower predisposition is directly related to Genetic Improvement poor pollination, the management of factors involved in pollination may lead A high sugar content of the honeydew to damage reduction. Recommended may suppress germination of measures are: macroconidia and as a consequence reduce the production of secondary • selection of sorghum lines with conidia, the main infecting structures of high pollen production the pathogen. This strategy may be • optimization of the ratio offemale­ achieved by incorporation of the sweet male lines character present in sweet sorghum into the genome of male sterile lines.

165 According to Hassan et al. (1995), Australia. This may be aided by the breeding for resistant cultivars that may continuous cropping of sorghum during be done through the introduction of this all seasons on the continent (Table 1). trait could reduce the rate of spread of the This ensures the presence of inoculum at disease through a seed production (male all times and all places. The presence of sterile) field. Johnson grass may add to this as an important source of inoculum in South Control by Chemical Protection America. These suppositions require ofInfection Courts investigation. At present the only feasible means of controlling the disease in seed While resistance is not available, fields is by fungicide application. fungicides may be used to reduce losses in seed production fields. References

McLaren (1994) and Ferreira et al. Anonymous. 1969. Insect pest management and control Vol. 3. National Academy of Sciences (1996) demonstrated the potential of Publication 1695. Washington, DC 508 pp. triazole fungicides in the control of Bandyopadhyay, R. 1992. Sorghum ergot. Pages sugary disease. In Brazil three 235-244 in Sorghum and millets diseases: A second world review, W. A. J. de Milliano, R. applications are recommended as A. Frederiksen, and G. D. Bengston, eds. Inter­ follows: (a) 250 ml/ha of tebuconazole national Crops Research Institute for the Semi­ (Folicur 200 EC), at the beginning of Arid Tropics. Patancheru, 502-324. Andhra Pradesh, India: International Crops Research flowering when sorghum plants are 80% Institute for the Semi-Arid Tropics. with emerged panicles; (b) 500 ml/ha, 5-6 Ferreira, A.S., Pinto, N.FJ.A., and Casela, C.R. days after the first spray; and (c) 250 1996. A valia9ilo de fungicidas para 0 controloe de ergot ou doen9a a9ucarada (Claviceps afri­ mllha 5-6 days after the second cana) em sorgo. Centro Nacional de Pesquisa application. The use of ground equipment de Milho e Sorgo - CNPMS-EMBRAPA. is recommended using a three nozzle Frederickson, D.E., Mantle, P.G., and de Milliano, W.A.J. 1991. Claviceps africana sp-nov.; the spray boom for each sorghum row. Two distinctive ergot pathogen of sorghum in Africa. spraying jets are directed to the panicle Mycological Research 95:1101-1107. sides and one to its top. Volumes of about Futtrell, M.C., and Webster, 0.1.1966. Host range 1 and epidemiology of the sorghum ergot organ­ 300-400 I ha- have been used for the ism. Plant Disease Reporter 50:828-831. technical control of the disease in seed Hassan, H.A.G., Mantle, P.G., and McLaren, N.W. production fields. No recommendation is 1995. A strategy for constraining ergot disease epidemics in F1 hybrid sorghum production. available yet for disease control in Proceedings XIII International Plant Protection commercial fields. Congress. The Hague, Netherlands. July 1995 (Abstract 677). Loveless, A.R. 1964. Use ofthe honeydew state in Final Remarks the identification of ergot species. Transactions ofthe British Mycological Society, 47 :205-213. The number of secondary conidia McLaren, N. W. 1993. Effect of sugary disease exu­ dates on germination, seedling development produced both in seed production fields and pre-disposition to seedling diseases of sor­ and in commercial ones and their efficient ghum (Sorghum bicolor). South African Jour­ transport by wind to long distances may nal of Plant and Soil 10: 12-16. Weise, M.V. 1977. Compendium of wheat dis­ explain the recent occurrence and rapid eases. The American Phytopathological Soci­ spread ofthis disease in the Americas and ety, S1. Paul, MN pg. 106.

166 Session VI - International Collaboration in Ergot Research - Global Network

Session President - Robert E. Schaffert

167 Role of ICRISAT in Sorghum Ergot Research

R. Bandyopadbyay

Abstract

ICRISAT is currently preparing to operationalize its Medium-Term Plan (MTP) for 1998-2000. One of the key components ofthe MTP is to further intensify participatory approaches in research involving networking and partnerships with National Agricul­ ture Research Systems (NARS), Advanced Research Institutes, the private sector and Nongovernmental Organizations (NGO) to capture complementarities and compara­ tive advantages. Due to funding constraints, ICRISAT has decided to continue sorghum ergot research only with noncore, complementary grants. ICRISAT has experience in ergot research in the Center and through collaborative projects in eastern Africa. ICRJ. SAT can help in the joint development ofa suitable network on sorghum ergot and con­ tribute to it by information exchange, assisting in seeking donor fundingfor collabora­ tive research, and developing International Public Goods such as information on epidf? miology to design disease management strategies, risk assessment modeling and identifying ergot-resistant sorghums. We recommend a collaborative approach with shared responsibilities and devoid ofundue overlapping efforts among interested parI­ ners for achieving the common goal of controlling the disease.

Ninety percent ofthe world's sorghum but not grain in flows. The importance of production area is located in developing sorghum as a feed and forage source in the countries, where it is a staple for millions mixed crop-livestock systems charac­ of the very poorest people, who lack teristic ofthe Semi-Arid Tropics (SAT) is economic access to more expensive gaining momentum. The grain of cereal grains (FAOIICRISAT 1996). sorghum is emerging as a significant Because sorghum is a crop of only the livestock feed in India, and is the major poorest minority, national average figures use of the crop in Latin America and the often do not reflect the large dietary developed world. Feed usage of sorghum intake by these disadvantaged groups. not only improves farm incomes and Over the past two decades, sorghum areas diversifies the enterprise, but also helps in Asia and Latin America have declined, make milk and meat products more although grain yields are increasing to affordable, thus improving the nutrition compensate. Even these yield increases of the poor. may be underestimations due to the increasing areas sown for fodder use, The International Crops Research which are accounted for in area estimates Institute for the Semi-Arid Tropics (ICRISAT) was established in 1972 as the first international research center under the auspices ofthe Consultative Group on R. Bandyopadhyay. International Crop Research Institute for the Semi-Arid Tropic (ICRISAT), Patancheru 502324, Andhra Pradesh, India. International Agricultural Research

169 (CGIAR). The mandate ofICRISAT is as to help the peoples of the SAT to work follows: together to achieve effective practical solutions. ICRISAT's mission is carried • Serve as a world center for the im­ out through strategic partnerships with a provement of grain yield and qual­ wide range of national and local ity of sorghum, millets, chickpea, organizations, in which each partner pigeonpea, and groundnut and act contributes according to its special as a world repository for the genetic expertise and mandate. ICRISAT, as a resources ofthese crops. global center of scientific excellence, • Develop improved farming sys­ contributes broadly applicable tems that will help to increase and international public goods (IPGs), while stabilize agricultural production its regional, national, and local partners through more effective use of natu­ translate these goods into the final ral and human resources in the sea­ products that help improve the lives ofthe sonally dry semi-arid tropics. • Identify constraints to agricultural rural poor in their areas ofresponsibility. development in the semi-arid trop­ ics and evaluate means of alleviat­ Sorghum Diseases in the Medium­ Term Plans (MTP) ofICRISAT ing them through technological and institutional changes. • Assist in the development and The MTP constitutes a statement ofthe transfer oftechnology to the farmer strategic directions and priorities of the through cooperation with national institute. In the past decade, MTPs for and regional research programs, 1989-93 and 1994-97 have been and by sponsoring workshops and operationalized. During the first of these conferences, operating training MTPs, sorghum disease research programs, and assisting extension encompassed grain mold, anthracnose, activities. leaf blight, foliar diseases, downy mildew, long smut and ergot. Due to ICRISA T' s mission statement reads as funding constraints, research on downy follows: through international research mildew, long smut and ergot was dropped and related activities, and in partnership from the core research agenda during the with national agricultural research 1994-97 MTP period. systems (NARS), to contribute to sustainable improvements in the The MTP for the period 1998-2000 is productivity of agriculture in the SAT currently pending approval from the (plus other countries in which ICRISAT's Technical Advisory Committee of the mandate crops have relevance) in ways CGIAR (ICRISA T 1997). This MTP' is that enhance nutrition and well being, not inconsistent with the priorities, especially of low-income people. objectives, goals, and values ofthe past. It may not be surprising that the proposed ICRISAT's expertise in science-based 1998-2000 agenda is evolutionary, rather agriculture development, together with its than revolutionary, since strategic international, apolitical, nOll-profit, and research in close partnership with humanitarian nature, uniquely position it stakeholders requires a long-term

170 approach, and emerges from a wide and Sorghum Ergot Research ongoing consensus-building process. atICRISAT Nevertheless, strong currents of change underlie this evolution, particularly in During the mid-seventies, ergot response to strong donor interests, new research began with resistance screening scientific developments, and the activities in India. This activity was increasing strength of a number ofNARS discontinued after two years since partners. Despite the importance of many resources were needed for research on research opportunities, funding levels other more important diseases at that constrain the extent to which they can be time. Ergot research was initiated again in pursued. ICRISAT determines which 1986 at the request of the NARS in aspects it can afford to address by Ethiopia and Rwanda where the disease dividing the entire research agenda into a was considered important. During 1986- number of specific distinctive topics, and 90, our research objectives were: ranking them in prioritized order. It then pursues as many of the highest priority • study the biology of the pathogen topics as funding will permit. and epidemiology of the disease • determine the role of pollination and fertilization in disease develop­ To achieve objectivity in the process of ment ranking ICRISA T' s priorities, specific • develop methods to screen for ergot criteria were established against which resistance the merits of the suggested topics were • identify sources oflocally-adapted, judged. These included: equity, ergot-resistant germplasm efficiency, internationality, sustain­ ability, new science opportunities, Some of the highlights of our results relevance to NARS priorities and future are as follows: trends, which could change basic assumptions. Based on these criteria and Biology ofthe Pathogen considering the emerging importance of sorghum ergot, ICRISAT has decided to The variation in symptomatology of reinstate ergot research but it can only be the disease as affected by environmental conducted using external (non-core) conditions was described (Bandyo­ funding. Grain mold, anthracnose and padhyay et al. 1990). The occurrence of foliar diseases of sorghum remain on the secondary conidia in the Indian isolate of core agreed agenda. Research on these the pathogen and the unique process of diseases will be conducted at ICRISAT secondary conidiogenesis was reported locations in India, Mali and Kenya in (Bandyopadhyay et al. 1990). The collaboration with NARS and Advanced epidemiological implications of Research Institutes (ARIs). secondary conidia are considerable and the production of easily detachable secondary conidia outside the surface of sticky honeydew matrix suggests that the fungus can be disseminated by wind.

171 Epidemiology soil remained light brown, whereas honeydew that fell on wet soil developed Know ledge of sources ofinoculum that a white fluffy growth. Scanning electron initiate ergot infection in the field, and of microscopy observations showed that the mode and extent of spread of the honeydew that fell on dry soil contained disease is required to devise disease only nongerminated microconidia management strategies. Three embedded in their original viscous graminaceous weeds (Cenchrus ciliaris, matrix. In wet soil, the fluid matrix was Panicum maximum, and Urochlora not evident and microconidia germinated panico ides) were identified as sources of to produce a crop of secondary conidia primary inoculum in the field. Large­ raised above the soil surface. Properly scale field experimentation showed that designed field experiments with caged wind-driven, water splash-dispersed plants (to avoid insects) showed that macroconidia disseminate the disease. secondary conidia from the soil surface Secondary foci appeared to be randomly were wind disseminated and infected the established in down-wind areas. There caged plants. Thus, soilborne secondary were 2-3 infection cycles, each of 6-8 conidia may be an important inoculum days duration, in a flowering season. The source in the field. spatial pattern of infected spikelets changed from a focal to a random pattern Pollination Effects as disease progressed. It is generally believed that pollinated Field experiments also indicated that flowers resist infection and are not the pathogen can be dispersed by wind. colonized by the fungus. Ergot Wind dispersal is primarily due to development by inoculating flowers at secondary conidia produced on the different time intervals before or after surface of honeydew. It is important to pollination was studied. Pollination- and consider that secondary conidia are infection-related events were monitored produced only at high (>90%) relative by fluorescence microscopy. The humidity, and cool temperature (15- fertilization event was related to 20°C); both conditions are also favorable reduction in ergot because the fungus for infection after spore deposition. Thus, failed to grow or grew slowly in pistils the pathogen has ecologically adapted inoculated after fertilization. Similarly, itself to produce a type of conidia pollen tube growth was retarded in (secondary) that has greater possibilities flowers inoculated before pollination. of dissemination (by wind) only when However, a few flowers produced grains conditions for infection are optimal. with the fungus growing at the basal end. It was hypothesized that such grain Although honeydew from infected probably resulted from pistils in which plants usually drips and falls on soil, the infection hyphae and pollen tubes were epidemiological significance of soilborne observed growing simultaneously, each conidia was not known. It was observed succeeding in their respective function - that honeydew that dripped on to dry field colonization and fertilization. Occurrence

172 of ergot-infected grain is a phenomenon the disease in the region. ICRISAT, not reported before. Information on therefore, restructured its ergot research pollination effects was vital for the by conducting all its activities on host development of a screening technique and resistance aspects through two identification of resistance. collaborative projects in Ethiopia and Rwanda. The objectives of the Identification ofErgot Resistance in collaborative projects were to develop a Hybrid Parents resistance screening technique and to identify ergot resistance. Training was an IdentifIcation of ergot-resistant seed integral part ofthe projects. ICRISAT and parents is a priority for the development national program scientists jointly of ergot-resistant hybrids. Variation was planned and conducted all the observed in seed set (20-93%) in hybrid experiments on ergot. Together, scientists parents and hybrids in seasons when night maintained inoculum, inoculated and temperatures were low (9-11°C). Low evaluated panicles, analyzed results and night temperatures are known to planned further experiments. Each year, adversely affect self-pollination and, from 1987 to 1989, an ICRISAT scientist therefore, reduce seed set. Reduction in worked at ergot 'hot spots' in Ethiopia the efficiency of self-pollination and Rwanda together with the national predisposes plants to ergot infection. program counterparts. A plant pathologist Based on these observations, it was from each country spent 3-7 months at hypothesized that self-pollination ICRISAT working on ergot. efficient lines at low temperature are more likely to resist ergot than lines that Through this collaborative research, are not self-pollination efficient. simple and effective artificial inoculation Evaluation of seed parents at low (10°C methods were developed and the night, 25°C day) and normal (15°C night, importance of inoculation demonstrated 25°C day) temperatures in controlled in resistance screening. A field screening environment growth chambers proved the technique was developed that has been hypothesis and assisted in the suitably used by both national programs identification of ergot-resistant seed to identify locally adapted, ergot-resistant parents. sorghum lines (Tegegne et al. 1994, Musabyimana et al. 1995). Ethiopian and Collaborative Research on Rwandan scientists have exchanged Sorghum Ergot in Eastern Africa ergot-resistant lines and shared these with scientists in southern Africa, Kenya, and In eastern Africa there was a sorghum India where ergot is also an important research network with an Advisory problem. Committee to determine research priorities. This committee considered The impact of the collaborative ergot a priority disease and recommended projects has been the development of that scientists in Ethiopia and Rwanda, expertise and materials that are of where ergot is a serious problem, should immediate benefit to the national collaborate with ICRISA T on research on

173 programs because the research was deliberate strategy encouraging the conducted at national research stations emergence of alternative suppliers. This using plant materials and physical strategy is embodied by the development facilities available to the national of enabling technologies that will programs. The Ethiopian and Rwandan increase the attractiveness of investments national programs now conduct ergot by other groups in ergot research. By research independently. developing prototypes that can be finalized for release by NARS and Dimensions of ICRISAT's Role ultimately generate a profit for the private sector, ICRISA T can help strengthen Comparative Advantages national and development capacities, and and Partnerships phase out its own role in final product development. Profits from technologies Within its agreed agenda, ICRISAT can be reinvested in research, leading to will only engage in research that sustainable research and development by generates benefits, such as IPGs, widely alternative supplies. ICRISAT, NARIs, across its mandate region. ARls, and the private sector have always Internationality was a specific criterion maintained close working relationships. considered during prioritization of Clearly each partner has comparative research topics, and local or sub-regional advantages that result in the whole being relevance was a reason that the priority far more effective than its individual for ergot research was lowered. Outside parts. As different partners mature and the agreed agenda, ICRISAT will evolve, their roles may need to change so continue to engage in projects focused on that complementarity is maintained. national priorities using bilaterally targeted local funds. These national During the MTP period, ICRISAT will projects often provide the CGIAR with seek opportunities to outsource parts ofits opportunities to identify and deliver the research agenda where this can provide benefits ofIPGs (e.g., germplasm) which clear increases in efficiency while would otherwise not have been possible. maintaining a satisfactory standard of quality. However, an operational The emerging capacity of some definition of outsourcing in relation to the National Agricultural Research Institutes research agenda needs clarification. (NARIs), networks, regional ICRISA T sees little comparative organizations, private sector entities, and advantage in engaging in a strict other alternative suppliers of research subcontracting mode of research; other goods, makes it possible for ICRISAT to institutions could handle the mechanics of refocus its own limited reSOl>1rces towards such transactions equally well. Instead, other opportunities. For ergot research, ICRISAT sees value in extending the several research entities have strength breadth and depth of its research work that can be captured imaginatively through cost-effective joint efforts with through collaborative research. To further NARS, ARls, and other organizations. advance the devolution of parts of its ICRISA T's commitment to greater research agenda, ICRISAT will pursue a

174 inclusiveness blends nicely with this promises to substantially strengthen outsourcing strategy, since closer NARS capacity to provide the full partnerships in research provide a spectrum of outputs required to achieve framework in which an increasing share sustainable agricultural development in of the joint agenda can be outsourced to their countries. These partnerships are partners, simultaneously accomplishing now organically embedded in ICRISAT's important training and technology research agenda. dissemination functions as well. Mechanisms for these outsourcing modes Information Exchange include visiting scientist positions, studentships, networking, j oint proposal The availability of information is development and marketing. For widely recognized as being a key factor in example, the SADC/SMIP/ICRISAT the achievement of sustainable self­ project provided facilities for the Ph.D. sufficiency in developing countries. research of D.E. Frederickson that Recent enhancements in information provided several key IPGs on ergot that technology have generated opportunities have relevance worldwide (Frederickson for the exchange of information on a scale 1990). that was previously impractical. ICRISA T is dedicated to making Developing Human information relating to its mandated areas Resources ofNARS Partners ofinterest as widely available as possible.

The NARS fora have given visibility Following the outbreak of ergot and support to a fundamental shift that has epidemics in Brazil and Australia, been underway over recent years in the ICRISA T, and the Sorghum and Millet modality through which ICRISAT (and Improvement Conference of North other CGIAR Centers) provide assistance America (SICNA) collaborated in in the development of national scientific making information on the disease resources. This shift involves a transition available rapidly. A review article on from a conventional training-course ergot was commissioned from scientists mode, towards full research partnerships with expertise on the disease in South formed around joint priorities. Through Africa, Zimbabwe, India and ICRISAT these partnerships NARS colleagues gain for publication in the International experience in all stages of an active Sorghum and Millets Newsletter (ISMN). research program, including priority An extensive review article was setting, project planning and proposal published (Bandyopadhyay et al. 1996) development, fund seeking, project on an urgent basis to make it available at execution, review and impact assessment. the International Sorghum and Millet Advanced skill sets are needed to carry Improvement Conference, Lubbock. A out these partnerships, including selected bibliography on sorghum ergot scientific creativity, flexibility, was also published in the ISMN. A color innovativeness, and the ability to flier with pertinent information on the communicate the value and relevance of disease was inserted in the ISMN with the research. The development of these skills

175 review. The flier has been distributed to continues to foster the development ofthe sorghum growers, seed industry, following networks: researchers and policy makers. It was also put on the home page (www.cgiar.orgl • CLAN (Cereals and Legumes Asia ICRISAT) of ICRISAT in the World Network) Wide Web for easy accessibility. It is now • WCASRN/ROCARS (West and being translated into Spanish and Central African Sorghum Research Portuguese. The flier was produced by Network) ICRISAT with funding from National • WCAMRNIROCAFREMI (West Grain Sorghum Producers (Abernathy, and Central African Millet Re­ search Network) TX) and SICNA, and is an example ofthe • SMIP (Sorghum and Millets Im­ importance of collaboration in achieving provement Program) in southern shared goals. Africa • CLAIS (Commission Latinoameri­ Continued communication of results cana de Investigadores en Sorgo) through the ISMN, other publications, and through meetings and conferences Networks are ideal for building bridges such as this one in Brazil will facilitate the among countries, regions and institutions. dissemination of the most recent This attribute contributes strongly to information. The current and future ICRISA T' s target ofInclusiveness during capability of communication through e­ the MTP period. An emerging trend is the mail and the Web (e.g., www.ars­ increased participation of such "non­ grin.gov/ars/SoAtlantic/Mayaguez/sorgh traditional" NARS such as NGOs, private umhtml) will vastly increase the global sector organizations, and farmer ability to communicate and exchange cooperatives that are becoming important information on ergot. These agents of technology delivery over time. communication modes have been Another trend is the increased phenomenally successful just within the participation in network partnerships of past year. ARIs that can contribute the basic research components needed to solve Networks recalcitrant problems.

Networks are essential for interlinking ICRISAT's ultimate objective is to ICRISAT, NARS, and ARIs. They help networks become fully NARS­ provide cost-efficient mechanisms for driven, and self-sustaining. In its catalytic joint research, technology ~nd and convening roles, ICRISAT continues information exchange, and strengthenmg to seek increased NARS-to-NARS NARS capacities. They build technology and information exchange, collaboration, capitalizing on the helping achieve regional self-sufficiency. complementary strengths of institutions For example, CLAIS can seek to increase around the world. Enabled by regionally Brazil's role in the exchange of ergot targeted donor support, ICRISA T management technology in Latin America. By reducing the dependence of

176 NARS on ICRISAT for direct support and joint appointments with ARIs to enhance finished technologies, ICRISAT will be complementarities and enable strong able to more fully focus on its global and outputs. In the current scenario of strategic responsibilities as its continuing constrained funding opportunities, a contribution to network objectives. collaborative approach with shared responsibilities is more likely to succeed Conclusions than individual overlapping efforts.

With past experience on collaborative References research on sorghum ergot and information exchange, ICRISAT is well Bandyopadhyay, R., Frederickson, D. E., McLaren, N. W., and Odvody, G.N. 1996. Er­ placed to foster and participate in got, a global threat to sorghum. International collaborative research in a global, Sorghum and Millets Newsletter 37:1-32. Bandyopadhyay, R., Mughogho, L. K., Manohar, regional or bilateral framework. S.K., and Satyanarayana, M. V. 1990. Stroma ICRISAT can collaborate with national development, honeydew formation, and conid­ partners and ARIs in seeking regional and ial production in Claviceps sorghi. Phytopa­ thology 80:812-818. bilateral funds for collaborative projects F AOIICRISAT (Food and Agriculture Organiza­ in which NARS have greater research tion of the United States/ International Crops involvement than ICRISAT. We can Research Institute for the Semi-Arid Tropics). 1996. The world sorghum and millet econo­ assist in exploring possible interest from mies: facts, trends and outlook. Viale delle Ter­ non-traditional donor sources, such as mie di Caracalla, 00100 Rome, Italy, and developing-world governments, the Patancheru 502 324, Andhra Pradesh, India: F AOIICRISAT. 68 pp. private sector, philanthropists, charitable Frederickson, D. E. 1990. Ergot disease of sor­ organizations, foundation support and ghum. PhD thesis, University of London, (Im­ others. ICRISAT with its excellent perial College) London, UK. 217 pp. ICRISAT (International Crops Research Institute environmental control and field facilities for the Semi-Arid Tropics). 1997. Shaping a and germ plasm can participate in research food secure future: ICRISAT's Medium-Term to deliver such IPGs as information on Plan 1998-2000. Patancheru 502 324, Andhra Pradesh, India: ICRISAT. 17 pp. (Limited dis­ epidemiology, risk-assessment modeling, tribution). and screening for cold-tolerance and Musabyimana, T., Sehene, C., and Bandyopadh­ ergot resistance. yay, R. 1995. Ergot resistance in sorghum in re­ lation to flowering, inoculation technique and disease development. Plant Pathology 44: 109- In such projects, ICRISAT would 115. cultivate the use of visiting scientist, Tegegne, G., Bandyopadhyay, R., Mulatu, T., and Kebede, Y. 1994. Screening for ergot resistance personnel exchanges, secondments, and in sorghum. Plant Disease 78:873-876.

177 The Role of the International Sorghum and Millet Collaborative Research Program on Management of Claviceps africana in Sorghum

Richard A. Frederiksen and John M. Yohe

INTSORMIL has a team of researchers visited the nurseries in Brazil in 1996 and from the U.S. and developing countries proposed collaborative programs of with interest in collaborative research on research in areas of host reaction to diseases of importance to sorghum with disease. These initiatives were thought to an emphasis on those constraints that are be preemptive. Additionally, this global most important. Consequently, conference on sorghum ergot was INTSORMIL has a mandate to address proposed by INTSORMIL scientists and the problems associated with ergot. has been jointly sponsored by However, there are far too many INTSORMIL. This conference was constraints worldwide to address all of needed because at the time there were them simultaneously, with equal vigor. many questions being asked regarding The network of sorghum workers in ergot and the implications that this Africa, Asia, and Latin America gives disease will have on the industry where INTSORMIL an opportunity to outline sorghum is grown under intensive existing information and focus these production through the use of hybrids. limited resources in the most efficient Currently, there is a cooperative initiative manner as well as to derive resources with Mexico to monitor the spread of from other agencies and donors for CZaviceps african a as it moves additional support. While it may appear northward. Presently, ergot is that a delay in response to ergot has approximately 50 km north of the occurred, the facts dictate differently. Mexican border. This represents the INTSORMIL scientists were informed of extent of the distribution of the pathogen ergot being present in Brazil shortly after before crossing the Wild Horse Desert of it was noted there. Discussions among Southern Texas. This is a region ofnearly interested parties were initiated and some 100 km of range land with limited crop commercial firms made decisions as to production separating the Rio Grande how to handle seed stocks from nurseries Valley from the upper coastal plains of in Brazil, and later movement of seed Texas. Appearance of ergot in this region from other Latin American countries would indicate that the pathogen has the where ergot had been reported. ability to move over greater distances and INTSORMIL and ICRISAT scientists would present even a greater threat to sorghum production. In fact the pathogen continues to move and as of October 7, 1997, was found in Nebraska. Richard A. Frederiksen, Professor, Department of Plant Pathology and Mi­ crobiology, Texas A&M Univelllity, College Station, TX 77843-2132 and John M. Yohe, Program Director, INTSORMll., 113 Biochemistry Hall, University of Nebraska, Lincoln, NE 68583-0748

178 INTSORMIL researchers now have control. Disease management through more scientists interested in the host resistance, chemical controls, and management of ergot. For example, other strategies are all important. Control feeding trials involving animals in of ergot in seed production fields using Mexico and Texas are planned, as are fungicides will hopefully only be a studies on the presence of secondary temporary arrangement. Eventually, metabolites following ergot honeydew ergot, like most other diseases of encrusting on sorghum grain. These sorghum, will be controlled through a studies, while critical in determining the management system that relies less on importance of ergot, are not essential for pesticides and more on natural host control. INTSORMIL, ICRISAT, and protection. INTSORMIL can provide the International scientists can bring the scientific expertise to make this possible. necessary individuals together to work on

179 The Role of USDA in Research o~ Sorghum Ergot

J. A. Dahlberg

The United States Department of was based primarily on the fact of ergot's Agriculture (USDA)* is made up of 17 rapid spread in the Americas and the fact agencies, each with various that ergot was becoming established in responsibilities and duties as they relate to the continental U.S. as a result of natural American Agriculture. The two major spread by airborne spores. APHIS agencies that will deal with ergot are the continues to monitor the spread of the Animal and Plant Health Inspection disease and will continue to be updated on Service (APHIS) and the Agricultural progress made in the control of the Research Service (ARS). APHIS's role in disease via the NPAG and various other American Agriculture is to provide organizations working on ergot. leadership in securing the health and care of animals and plants and improving The ARS will playa major role in the productivity and competitiveness in National effort to gather information and agriculture, thereby contributing to the develop research on ergot. The ARS is the national economy and the public health of in-house research arm of the USDA and our citizens. To carry out this mission, its' mission is to "provide access to APHIS guards U.S. borders against agricultural information and develop new foreign agricultural pests and diseases, knowledge and technology needed to searches for and monitors agricultural solve technical agricultural problems of diseases and pests, takes emergency broad scope and high national priority, to action if a foreign pest or disease ensure adequate availability of high­ threatens the U.S., facilitates agricultural quality, safe food and other agricultural exports through scientifically based products, to meet the nutritional needs of sanitary and phytosanitary standards, and the American consumer, to sustain a ensures the safety of genetically viable and competitive food and engineered plants and other products of agricultural economy, to enhance quality agricultural biotechnology. On March 10, oflife and economic opportunity for rural 1997 aNew Pest Advisory Group citizens and society as a whole, and to (NPAG) was formed to discuss issues and maintain a quality environment and make recommendation concerning ergot. natural resource base." The ARS From this meeting, APHIS recommended currently plays a strong role concerning that no regulation should be introduced research activities on ergot by that would affect the movement of maintaining and updating a World Wide sorghum into the country. This decision WebHomepage dealing with ergot (http://www.ars-grin.gov /ars/ SoAtlantic/ Mayaguez/ s orgh umn ews .htm I), lA. Dahlberg, USDA-ARS-TARS, 2200 Ave. Pedro Albizu·Campos, Suit. releasing research dollars ($100,000 this 201, MayagOez, PR 00680-5470 past year) for study of the disease, and

180 evaluating reported resistant sources of conditions for screening of exotic exotic germplasm at our Tropical accessions and the development of Agricultural Research Station, located in improved sources of germplasm for Mayagfiez, Puerto Rico. Two major disease resistance. Plans of action research facilities are gearing up to do include; 1) evaluation of reported sources further research on ergot; our research of resistance, 2) crossing of these facility at Fort Detrick, Maryland, USA, accessions to A3 cytoplasmic sources to and our site in Mayagfiez. These two sites evaluate them in a male-sterile have already collaborated on evaluating background, 3) evaluate other sources of fungicide treatments of honeydew cytoplasmic sterility, 4) enhancement of infected seed and have published their these sources of resistance into improved findings on the Web site. Most seed genetic backgrounds, and 5) develop companies and State and Local regulatory markers for study of genetic variability of agencies to ensure the safe movement of ergot found within the Americas. research seed into the United States have Through collaborative efforts and approved these recommendations for use. contacts, such as this conference, the Our Fort Detrick facility offers state-of­ USDA looks forward to working with the the-art lab facilities for importation of worldwide sorghum scientific exotic diseases and pests for study and community to strengthen our focus on evaluation, and current plans of action research areas in which we can excel to include; 1) development of molecular provide additional research and methods for species identification, 2) information in our effort to safeguard direct morphological comparison of the sorghum from ergot in the future. different species under the same environmental conditions, and 3) 'Much of the general information on determination of environmental factors the agencies within the USDA was taken that influence the formation and viability from their respective Homepages on the of sclerotia. Our Mayagfiez facility World Wide Web(http://www.usda.gov). provides excellent environmental

181 Sorghum Ergot in Australia

Malcolm Ryley and Bob Henzell

The Australian Grain (Stenodiplosis sorghicola [Coquillett]) Sorghum Industry late in the growing season. The optimum planting period in central Queensland is Grain sorghum is a major component late December to mid February, while on of farming systems in north east Australia the Darling Downs in southern due to the dominance of summer rainfall, Queensland, October is the preferred its vital contribution to management of time. Further south in New South Wales many soilborne diseases, and in providing the optimum planting time is in late stubble cover for erosion control. October and November. Consequently, Between 400,000 ha and 600,000 ha are most sorghum crops are flowering during grown annually, with production varying hot weather (maximum daily from approximately 500,000 t to 1.5 temperatures >28°C) when the risk from million t, depending mainly on seasonal ergot should be very low. However, some conditions. Australia is among the top 10 late-planted crops may still be flowering producers in the World, but well behind in April, when temperatures are the United States, India, Mexico and considerably lower than in mid-season. China. Approximately 70% ofthe crop is Ratoon cropping, a practice in which seed grown in central and southern is harvested from the previous season's Queensland, with the remainder in regrowth, is conducted by some growers northern New South Wales (Figure 1). in central Queensland but it is considered The grain is used exclusively for to be an opportunistic practice in response stockfeed, particularly poultry, beef to good rainfall in spring. cattle, pigs and dairy cattle and none is used for direct human consumption. The Australian Seed Industry, Stockfeed usage in Australia increased Parent Seed Production and from 340,000 t in 1985-86 to 1.1 million t Breeders' Nurseries in 1995-96, with a consequential decrease in the volume exported. Four seed companies (Pacific Seeds/Advanta, Pioneer Hi-bred, Grainco In Australia, planting times are and Hylan Seeds) produce 5,000-6,000 t influenced mainly by the availability of of planting hybrid seed annually, with adequate soil moisture for germination about 60% being commercial grain seed. and also by considerations of frosting and Most is produced during the summer potential damage from sorghum midge months (planted between October and late November) under irrigation in the Macquarie Valley of central New South Wales and in the Murrumbidgee Malcolm Ryley, Queensland Department ofPrimary Industries, PO Box 102, Irrigation Area in southern New South Toowoomba, Queensland 4350, Australia; Bob Henzell, Hermitage Re­ search Station, Warwick, Queensland 4370, Australia. Wales, and a small quantity is produced

]82 150 0 E ,. .. Grain :.. ; sorghum

• Seed production Nurseriesl parent seed D* Ergot recorded 200S NORTHERN 200 S TERRITORY QUEENSLAND

WESTERN I J AUSTRALIA ~ . - . - . - . - . - . - . - . - . - ..- . - . - . ~

SOUTH

300 S AUSTRALIA l:;:;) ...... 30 0 S ... ~:

~ NEW SOUTH WALE J ·-..... 6 · ......

130 0 E 140 0 E 1500 E 1600 E

Figure 1. Commercial sorghum production areas, seed production areas, breeders' nurseries and parent seed production blocks, and distribution of CJaviceps africana in Australia, 1996- 1997. near the New South Wales-Queensland situations when there has been a shortfall border. Some winter production is in summer production (Figure 1). conducted in irrigation areas on the Ord River, Western Australia, the Burdekin Breeders' nurseries and parent seed River on the northern Queensland coast, production blocks are often conducted at and at Lakeland Downs in northern the same site. Pacific Seeds/Advanta Queensland, but mainly for short plants two nurseries at Gatton in southern daylength cultivars and in emergency Queensland, the first planted in early September ( flowering in December) and

]83 the other in late January (flowering in late 5% in the R-lines were found in both grain March-April). Some basic seed is and forage sorghum blocks. A white produced at the Ord River in winter. waxy coating covered entire panicles and Pioneer Hi-bred conducts 2 summer white deposits of dried honeydew were nurseries at Wyreema, near Toowoomba evident on the plant parts and on the in southern Queensland which generally ground below the affected panicles. is cooler and has lower humidity during Honeydew, ranging from translucent the summer and early autumn months through opaque to honey-yellow and than Gatton. One is planted in mid finally white, exuded from spikelets. The October and.the other in late November. honeydew contained 3 types of hyaline, A winter nursery and grow-out blocks for thin-walled, aseptate conidia. Macro­ hybrids and inbreds are planted in the conidia were oblong, rounded at both Burdekin area in early April. Grainco ends, often constricted in the median conducts parent seed production/ region, 10-20 ~m x 5-S ~m; secondary nurseries in summer at Cambooya and in conidia were narrowly obovoid-clavate, winter at Bowen on the northern 11-17 ~m x 5.5-S.0 ~m, with a short Queensland coast. Hylan conducts their ~piculus at the base; and microconidia parent seed production in the Burnett were spherical and 2-3 ~m in diameter. district, approximately 120 krn north of Oval-spherical sclerotia, 3.5-5.0 ~m x Toowoomba. The Queensland Depart­ 2.0-2.5 ~m, which were protruding ment of Primary Industries (DPI) between the glumes of many spikelets breeding program has summer nurseries were collected at the same site 14 days at Hermitage (planted October), Gatton later. A tentative identification of (planted late November), Biloela planted Claviceps africana Frederikson, Mantle September and January) Research and de Milliano (Frederikson et al. 1991) Stations and a winter nursery at Ayr was confirmed by Dr. P. Mantle, Imperial Research Station in northern Queensland, College of Science, Technology and planted in early April. Medicine, London.

The Outbreak of Sorghum Ergot Two days after the first report, ergot had been found in other nurseries and in Sorghum ergot was first identified in forage sorghum crops within a 10 krn Australia on April 26, 1996 on a specimen radius. Quarantine notifications which which had been presented to the Plant prohibited the movement of produce and Pathology group at the DPI, Toowoomba also restricted some farming activities (Ryley et al. 1996). The ergot sample had were placed on 3 properties (including 2 been collected from a research farm at research stations). Within 1 week, ergot Gatton. Quarantine authorities in DPI and had been found over an area of in the Australian Quarantine Inspection approximately 16,000 km2 during Service (AQIS) were immediately surveys of forage and grain sorghum notified, and a strategy for further short­ crops in southern Queensland. Most term action was developed. The site was records were on forage sorghum, which visited the following day and infection tends to flower unevenly often resulting levels of 100% in A-lines, but only about

184 in poor pollination, and on late-flowering Namoi Valley of northern New South tillers in grain sorghum crops. Quarantine Wales, and in hybrid seed production restrictions on the 3 properties were lifted blocks in the Macquarie Valley of central when it was realised that the disease was New South Wales, about 600 km not restricted to a small geographic area. southwest of the previously known A DPI sorghum ergot task force southern limit of the disease. In early consisting of quarantine, plant pathology 1997 the pathogen was reported on and management personnel was set up to Sorghum almum Parodi, a common weed coordinate surveys, to provide in central Queensland.Secondary conidia information to growers, seed companies, have been implicated in the spread of advisers and the general public, and to sorghum ergot in Africa (Frederickson et liaise with authorities in other Australian al. 1989, 1993) and Brazil (Bandyo­ states. padhyay et al.1996) and they undoubtedly contributed to the spread of the pathogen Current Distribution of in southern Queensland. Weather Sorghum Ergot conditions in southern Queensland before and immediately after the first detection One month after the intial sighting of of C. afrieana were ideal for infection, sorghum ergot in Australia, the disease disease development and dispersal of had been found on forage sorghum secondary conidia. At Gatton between [Sorghum hieolor (L.) Moench, Sorghum May 1 and May 6, 1996 there were 6 sudanense (piper) Staph and S.hieolor x consecutive days with rainfall above 20 S. sudanense], on late flowering grain mm, maximum daily temperatures below sorghum tillers, and on johnson grass 25°C and strong easterly to south-easterly Sorghum halepense (L.) Pers. over an winds. The outbreaks in New South 2 area ofnearly 70,000 km in southern and Wales may also have been the result of central Queensland, and on forage infection by secondary conidia. However sorghum on the Atherton Tableland, there is no conclusive evidence that north Queensland approximately 1,400 sorghum ergot spread rapidly from a km north of Gatton. Within another 2 single focus (Gatton) or possibly 2 foci months it had been found on forage (Gatton and northern Queensland) in sorghum or in nurseries and parent seed Australia in mid 1996. It is possible that blocks at several localities near the coast sorghum ergot had been present in between the southern and northern Australia for a number of years at very outbreaks. In early August the disease low levels due to drought conditions. was identified at Lakeland Downs, some 160km north of the Atherton Tablelands, Identity of the Causal Agent which is now the northernmost known limit of ergot in Australia. Between The morphology of the conidia and/or October, 1996 and May, 1997, ergot has sclerotia of most of the isolates collected been reported at many localities within from grain sorghum, forage sorghums the known area of distribution. In and S. halepense were identical to the February, 1997 the disease was recorded original isolate from Gatton. Cross in forage sorghum crossing blocks in the inoculation studies using macroconidia

185 Table 1. Morphol gy of conidia in collections from northern Queensland, May, 1996. . nfjoj('nnn . , .ne~je.

macro conidia length (~m) 10-20 12.6-14.8 9-19 12.1-14.1 width (~m) 5-8 7.0-7.1 4-5.5 4.6-5.0 secondary conidia length (~m) 11-17 13.8-15.4 9-14 10.5-12.0 wifith ';,m) Ii_I! Ii "'1_71 4_" " 47_4 () lRange of dimensions of conidia from 50 collections 2Range of means of 50 collections.

from S. hieolor and S. halepense also mm long and 2.0-4.0 mm wide with a conftrmed that the latter was a host of C. rough surface. The second type were afrieana. However some collections from cylindrical, with longitudinal grooves in forage sorghums differed from C. the smooth basal portion, 5.0-S.0 mm afrieana. A careful examination of long and 1.S-2.5 mm wide. Although the macro conidia and secondary conidia sclerotia were similar in some respects to (produced in vitro) from individual those described for C. sorghi spikelets in the same panicles in a (Frederickson et al. 1991; Bandyo­ collection from north Queensland (May, padhyay et al. 1996) they should not be 1996) revealed that most spikelets were assigned to that species at present, infected by C. afrieana, but on the pending further study. remainder the conidium morphology did not resemble that species. The Considerable variation in the macroconidia ofthis taxon were similar in morphology (particularly dimensions) of length to those of C. afrieana, but were both conidia and sclerotia have been consistently narrower, while the reported (Bandyopadhyay et al. 1996; secondary conidia were shorter and present report) which may be a reflection narrower than C. afrieana (Table 1). ofthe influences ofenvironmental factors According to Frederickson et al. (1991) and the hosts. There is an urgent need to macroconidia of Clavieeps sorghi are reexamine the taxonomy of Clavieeps narrower (4-6 /lm) than those of C. taxa which infect Sorghum species. This afrieana (5-S /lm) as are macroconidia of reassessment must be conducted using as the north Queensland isolates. These and many traditional characteristics as other differences (such as conidium shape possible, as well as new molecular and sterigma dimensions) suggest that the techniques such as RFLPs and RAPDs. species may be C.sorghi. Insights into the genetic relationships between isolates from different countries Two distinct types of sclerotia were and within countries and into the role of found in inflorescences of forage sexual reproduction in the life cycle can sorghum at a locality on the Darling also be obtained from such molecular Downs (west of Toowoomba) in June, studies. 1996. The ftrst type, typical of those described for C. afrieana ( Frederickson et al. 1991) were oval-spherical, 4.0-5.5

186 Losses in Commercial Grain Crops Despite the small losses experienced in and Forage Sorghums the commercial grain industry the potential for serious losses remains. It is In the 1996 and 1997 seasons losses in apparent that there is abundant inoculum grain sorghum crops have been extremely present for most of the year to initiate an low. In 1996 most commercial grain epidemic. In 1996 ergot was recorded crops in southern and central Queensland from April-July and again from October had flowered before the disease was onwards in central and southern discovered and it was only late flowering Queensland. Some hosts, particularly tillers which were infected, with infection forage sorghums, S. almum and S. levels <5%. The low temperatures at this halepense appear to be particularly time of year (particularly night susceptible and can be considered to be temperatures) and the uneven flowering very important sources of inoculum when of the tillers, hence poor pollination and commercial grain crops are flowering. fertilisation, were ideal for ergot The roles of other sources of inoculum, infection. Some harvesting difficulties such as ascospores from germinating due to honeydew were experienced in sclerotia, conidia in honeydew on fallen southern Queensland in late flowering inflorescences and conidia in locules of crops, but direct yield losses were immf

187 Losses in nurseries and parent seed incidence was approximately 5% in grain production blocks have been far more sorghum lines and 50% in forage severe. At the site of the initial recording sorghum lines despite having been in April, 1996, infection levels of 100% sprayed twice a week for 4 weeks with were experienced in A-lines and Folicur at 0.5L1ha. At this same site approximately 5% in R-lines across all spraying lines which flowered a month nurseries. As a consequence, no AxB or later with this fungicide on a 4 day cycle hybrid crosses were harvested. Losses of resulted in approximately 85% control. In approximately 30% were experienced in another nursery, lines which flowered an experimental hybrid seed production during an overcast, wet and cool period in block on the northern Queensland coast in late January-early February and which August-September, 1996. An unexpected were not sprayed were heavily infected outbreak was recorded in A-lines in (50% in A-lines and <5% in R-lines). The breeders' nurseries at Gatton in September 1996-planted nursery at December, 1996. Examination ofweather Biloela was the only DPI nursery infected data indicated that approximately 8 and with ergot in 1996-97. High levels of 17 days before symptoms were noticed infection occurred in A-lines which there were 2 days with maximum flowered in late November, when the risk temperatures <27°C, mInImUm from ergot should have been low due to temperatures <15°C and rainfall of >5 high temperatures expected at that time. mm. Between these two periods the maximum daily temperatures were Consequences and Control >30°C. It is apparent that temperatures in Commercial Grain Crops following infection have little influence on disease development. However losses Consequences. Apart from the were negligible in single rows of A-lines potential direct yield losses associated but were higher in multiple rows. with ergot, there are other consequences Attempts to manage the infection with of sorghum ergot which have, and will, aerial applications (by both helicopter and impact on the Australian sorghum plane) of Folicur at 0.5 L ha-I proved industry. Seed costs will undoubtedly ineffective. A second nursery at Gatton, increase due to the increased costs with lines flowering between late March associated with management of ergot in and early May, a higher risk period due to seed production blocks. The Seed low temperatures than in December­ Industry estimates that given the worst­ January, was not sprayed with Folicur and case scenario the cost of a 25 kg bag of had negligible infection. seed could increase by AUS $20 (AUS $ 0.77 = 1 US $). The outbreak in Australia Nurseries are also conducted by seed has export trade implications, particularly companies on the eastern Darling Downs, to countries which demand a nil tolerance which is generally cooler and less humid to ergot sclerotia. A 0.3% tolerance to than the Gatton district due to its ergot sclerotia has been set for the elevation. In one nursery where breeding domestic stockfeed market, and the lines flowered in January, 1997, ergot impact ofthis limit on the availability and price of lotfeed sorghum grain is

188 unknown. Before the 1996-97 season warning system for fungicide application confidence by some growers in grain in seed production blocks. sorghum was lowered due to uncertainty in the potential damage which ergot was Consequences and Control in likely to cause, but that confidence had Seed Production and Nurseries been partly restored towards the end of the season in which losses have been Consequences. Although direct yield negligible. The presence of ergot has also losses from ergot in seed production reduced the flexibility ofplanting times in blocks have been moderate to date, the an attempt to avoid the high risk period at potential for significant losses remains. A the end of the season (crops flowering in crop failure due to ergot could have April-early May). serious consequences not only for the supply of adequate planting seed for the Control. The following recom­ Australian plantings, but also for the seed mendations have been made to growers to company which has the failure, due to a minimise losses from ergot - (i) planting loss in market share. The effect will also times should be selected to ensure that flow on to domestic production levels. crops flower during the low risk period Serious losses in nurseries and parent (January-March), (ii) crops should be seed blocks can result in loss of important well managed to ensure even flowering, breeding material and impact on the and (iii) if necessary kill late-flowering development and release ofnew cultivars. tillers with herbicides to minimise Seed companies have faced extra potential harvesting problems. To assist production costs such as labour for growers in the selection of planting times handling contaminated seed lots, costs a climatic risk analysis has been associated with interstate quarantine conducted for selected localities in requirements, purchase of specialised Australia. A set of climatic parameters, spraying equipment and fungicides. based on overseas research results, was There has also been a loss in flexibility in used to interrogate long-term weather planting times and locations, and in the data, reSUlting in a prediction of the future new production areas may have to number of infection events which had be sourced. o<:;curred over the past 30 years. The analysis indicated that crops flowering Control. At present, ergot can be early (before December) or late (after considered to be endemic in Queensland March) in the season were at greatest risk. and most of New South Wales, and only The climatic parameters used in this southern New South Wales and the Ord model are being modified to more closely River Irrigation Area can be classed as reflect the field situation. For example, being ergot-free. As mentioned before, experience in Queensland has shown that ergot has been found in the seed infection can occur without rain; production area in central New South prolonged heavy dew at night is Wales, but not in southern New South apparently sufficient for infection. Other Wales. Selection of planting times and models have the potential for use as a localities which are likely to result in the smallest losses can be made with the aid

189 of a climatic model, but even 1 or 2 days apparent that losses will vary from year to of un seas only cool wet weather can result year. in significant losses. Measures designed to minimise the risks of introducing ergot Acknowledgements into ergot-free areas, such as grading, fungicide seed dressings such as thiram, The authors wish to thank officers of washing of honeydew-contaminated the Queensland Department of Primary seed, are being practised. Improved Industries and personnel of pollen management through alterations in Pacific/Advanta, Pioneer Hi-bred, male:female ratios has also been Grainco and Hylan Seeds for their recognised by seed companies. However, assistance in collection of ergot fungicides applied during flowering will specimens and provision of information remain the major management tool. for this paper. Particular thanks is given to Permits have been granted for emergency Dr. John Alcorn who provided data on use of tebuconazole, triadimenol and collections from northern Queensland procymidone in nurseries and seed and to those who proofread the production blocks, and the first 2 manuscript. fungicides are currently being used routinely. However, there still needs to be References considerable research on aspects of Bandyopadhyay, R., Frederickson, D.E., McLaren, application including nozzle type, water N.W., and Odvody, G.N. 1996. Ergot, a Global rates and the relative efficacy ofaerial and Threat to Sorghum. International Sorghum and ground application. Fungicides with Millets Newsletter 37:1-32. Frederickson, D.E., Mantle, P.G., and de Milliano, eradicant activity need to be identified to W.A.J. 1989. Secondary conidiation ofSphace­ enable applications after conditions lia sorghi on sorghum, a novel factor in the epi­ suitable for infection have occurred, as do demiology of ergot disease. Mycological Research 93:497-502. fungicides with residual activity to reduce Frederickson, D.E., Mantle, P.G., and de Milliano, the numbers of applications. W.A.J. 1991. Claviceps africana sp-nov.; the distinctive ergot pathogen of sorghum in Africa. Mycological Research 95:1101-1107. The Future Frederickson, D.E., Mantle, P.G., and de Milliano, W.A.J. 1993. Windborne spread of ergot dis­ Sorghum ergot has had little direct ease (Claviceps africana) in sorghum A-lines in Zimbabwe. Plant Pathology 42:368-377. impact on grain sorghum production in Ryley, MJ., Alcorn, J.L., Kochman, J.K., Kong, Australia, but the seed industry has been G.A., and Thompson, S.M. 1996. Ergot on Sor­ seriously affected by the disease. The ghum spp. in Australia. Australasian Plant Pa­ thology 25:214. potential for epidemics both in seed production and commercial grain production exists, and although low risk times and localities can be identified, only short periods of unseasonal weather are needed for ergot epidemics. It is impossible to predict the long-term impact of ergot in Australia, but it is

190 Global Conference on Ergot of Sorghum

Recommendations Report

Participants ofthe Global Conference web sites and other sources of er­ on Ergot of Sorghum met in plenary got information accessible by sessions and in work groups to make computer or other means. general and specific recommendations • Develop a mechanism for posting for collaboration and networking with the of the most recent sorghum ergot overall goal of developing sustainable control or management informa­ control strategies for sorghum ergots. tion on the ergot web site. • Develop an e-mail directory of in­ I. General Recommendations dividuals specifying sorghum ergot expertise or interest and post the di­ rectory on the ergot web site and Establish an International Steering disseminate through other appro­ Committee to serve and assist in priate means. An initial listing coordinating sorghum ergot research should include attendees of this activities and communication within the conference. international community. In response to • Develop international working this recommendation the following groups to target specific sorghum International Steering Committee ergot research projects. Members, as shown in the table below, • Maintain and promote collabora­ were selected. tion and integration of sorghum er­ got research between the public and Responsibilities of the private sectors of the sorghum re­ International Steering Committee search and production industry. • Promote funding for integrated re­ • Maintain and expand the World search and development for the Wide Web site for dissemination sustainable control of ergot in sor­ of information on ergot of sorghum ghum. including links to other pertinent

Year of Il\bm" rnnnt,."

~andyopadhyay, Ranajit 2002 ICRISAT India ~asela, Carlos Roberto 2002 Embrapa Milho e Sorgo Brazil !Dahlberg, Jeff 2001 USDA USA !MantIe, Peter George 2000 Imperial College of Science UK !Maunder, Bruce 2000 NGSP USA !McLaren, Neal W. 2001 Grain Crops Institute SAfrica Pdvody, Gary (Chairman) 2002 TexasA&M USA !Ribas, Paulo 2000 Agroceres Brazil iRyley, Malcolm J. 2001 QLD Dept of Primary Ind. Australia

191 n. Recommendations for Research Sclerotia should not be used as a Strategies in the Area of Genetic phytosanitary restriction measure Resources because sclerotia and sclerotium­ like material pose little risk for initi­ • Evaluate sources of resistance (re­ ating disease compared to external ported in the literature) by utilizing airborne inoculum. sorghum germplasm available within national and international collections (Jeff Dahlberg, USDA Sclerotia, sclerotium-like material, and Ranajit Bandyopadhyay, ICRI­ and honeydew encrusted seed pose SATwere elected to coordinate this the same qualitative risk concerning effort). epidemiology of sorghum ergot • Develop and distribute a standard caused by Clavieeps afrieana be­ methodology for evaluation of ge­ cause sclerotial germination is low netic resources. and there is no evidence for sexual­ • Develop and distribute information ity from isolates in the Americas. about standard inoculation tech­ niques. Seed intended for planting should be • Evaluate the role of different sor­ treated with an appropriate fungi­ ghum cytoplasms and fertility on cide (e.g. captan or thiram) that infection. completely eliminates inoculum of • Evaluate alternate sources of cyto­ the ergot pathogen on the seed sur­ plasmic male sterility for resistance face. to ergot • Develop standardized screening Host Range of C/avieeps africana techniques for pollen fertility, pol­ len shed, fertilization, and seed set. Sorghum bieolor, S. bieolor subspe­ • Evaluate tillering ability in germ­ plasm collections of both B, A, and cies bie%r, S. halepense, and other R lines. sorghum species are recognized as • Ten sites were identified as possi­ hosts for C. afrieana. Other (re­ ble locations for initial screening of ported) secondary hosts will be rec­ accessions reported by ICRISAT ognized only after Koch's postulates and others as ergot-resistant have been demonstrated under natu­ sources. ral conditions. Zea mays is not a host Argentina India of sorghum ergot under natural con­ Australia Mexico ditions. Brazil Puerto Rico Ethiopia South Africa Honduras United States Chemical Control

III. Recommendations for Control Development of improved chemical and Management Strategies control methodology is needed, es­ pecially for ergot control in hybrid Phytosanitary Issues seed production.

In areas where sorghum ergot exists:

192 Risk of strains of C. ajricana toler­ global locations. The ergot web ant to triazole fungicides should be page may be the primary means to assumed and there must be a proac­ accomplish this goal. tive effort to identify alternate fungi­ cides with a different mode of ac­ Pollen Management tion. The critical importance of pollina­ Exercise restraint in the indiscrimi­ tion/fertilization events as the pri­ nate use of fungicides to minimize mary ergot escape mechanism for the risk of developing fungicide­ sorghum indicate a need for more re­ resistant strains. search in this area. These should in­ clude studies on host:pathogen:en­ Alternate Control Strategies vironment interactions affecting sorghum pollination/fertilization Alternate control strategies need to and further development and refine­ be developed to both minimize the ment of pollen management strate­ need for chemical control and maxi­ gies. Knowledge in these areas may mize its effectiveness. also provide a basis for the develop­ ment of sustainable host plant resis­ Biological Research tance.

Research is needed on several as­ IV. Recommendations for pects ofthe biology ofthe Claviceps the Biology of Sorghum Ergot spp. attacking sorghum (see section IV). As new scientific knowledge is • Continue research on sclerotia or gained it should be incorporated into sclerotia-like bodies and determine current and projected ergot control functions ofthese bodies in the dis­ and management strategies. ease and life cycle of sorghum er­ got. Epidemiology • Determine the dispersal of asexual inoculum, vis-a-vis rates, spatial, temporal and any other aspects af­ Encourage further development of fecting dissemination of the patho­ disease prediction models for ergot gen. with regional calibration and inter­ • Expand, apply, and validate disease active capabilities to aid in ergot model in other geographic areas. management decisions including • Use multidisciplinary approaches fungicide application. to toxicological studies in feeding trials of ergot contaminated sor­ Monitoring of sorghum ergot ghum. • Determine the role(s) of sapro­ A mechanism is needed to provide phytic fungi in: toxins, synergisms, for the rapid sharing of information biocontrol and other interactions of concerning the spread, distribution ergot with other microorganisms. and severity of ergot across different

193 • Determine the host range ofthe sor­ forming sorghum for resistance to ghum ergot pathogens and influ­ ergot. ence of different hosts on the pro­ • Utilize molecular level approaches duction of toxic alkaloids. for evaluation of pathogen popula­ tion biology. V. Recommendations for Molecular • Increase the use of fingerprinting Approaches to the Study of technologies in determining rela­ Sorghum Ergot tions among ergot collections for species and other taxonomic rela­ • Evaluate the suggestion of using tions. fertility/incompatibility genetic • Determine the potential of trans­ mechanisms as genes for trans- forming sorghum to express anti­ fungal proteins at infection sites.

194 Participant List Participant List

Aguirre, Julio 1. Andreoli, Claudinei Campo Experimental Rio Bravo (INIF AP) Emhrapa Milho e Sorgo Apartado Postal # 172 Caixa Postal 151 Rio Bravo, TAM 88900 357001-970 Sete Lagoas, MG Mexico Brazil Phone: 893-4-10-45 Phone: 55-31-779-1136 Fax: 893-4-60-20 Fax: 55-31-779-1088 E-Mail: [email protected] E-Mail: [email protected]

Ajudarte Neto, Fernando Antoniali, Antonio F. Zeneca Sementes Ltda. Semeali - Sementes Antoniali Ltda. Rod. Anhanguera kIn 296 Rod. Marechal Rondon Km 523-CP. 428 14140-000 Carvinhos, SP Birigui, SP Brazil Brazil Phone: 55-16-651-1521 Phone: 55-18-642-3129 Fax: 55-16-651-1321 Fax: 55-18-642-3129

Alves, Claudio Vilarinho Azevedo, Jollo Tito Cargill Agricola Emhrapa Milho e Sorgo Rod. MG 181, kIn 07 Caixa Postal 151 Capinopolis, MG 35701-970 Sete Lagoas, MG Brazil Brazil Phone: 55-34-263-1588 Phone: 55-031-779-1000 Fax: 55-34-263-1063 Fax: 55-031-779-1088

Alves, Elcio Oliveira Bandyopadhyay, Ranajit Pioneer Sementes, Ltda. ICRISAT Caixa Postal 104 Patancheru P.O., A.P. 502 324 75510-180 Itumhiara, GO India Brazil Phone: 91-40-596161 Phone: 55-62-431-7789 Fax: 91-40-241239 Fax: 55-62-431-7789 E-Mail: [email protected] E-Mail: [email protected] Barhara, Joadir Santana Alves, Sergio Jose Ministerio da Agricultura IAPAR Alameda Anihal Molina, SIN Rod. Celso Garcia kIn 375 - Cx. Postal 481 Varzea Grande, MT Londrina, PR Brazil Brazil Phone: 55-65-685-1030 Phone: 55-43-326-1525 Fax: 55-65-685-1887 Fax: 55-43-326-7868 Barros, Didio Gazzinelli Andrade, GJayds A. Emhrapa Milho e Sorgo Bolsista-Emhrapa Milho e Sorgo Caixa Postal 151 R. Zequinha Vilela, 305 35701-970 Sete Lagoas, MG Lavras,MG Brazil Brazil Phone: 55-31-779-1068 Phone: 55-35-821-2477 Fax: 55-31-779-1088 E-Mail: [email protected]

197 Boardman. Nathan Chessa, Alberto Crosbyton Seed Co. Pioneer P.O. Box 429 Pueyrredon 971-2600 Venado Tuerto Crosbyton, TX 79322 Argentina USA Phone: 54-462-32700 Phone: 806-675-2308 Fax: 54-462-20349 Fax: 806-675-2407 E-Mail: [email protected]

Boguadi, Maria Mazzorello F. Claflin, Larry E. Ministerio da Agricultura Dept. Plant Pathology, Esplanda dos Ministerios, Sala 431-B Throckmorton Hall Brasilia, DF Kansas State University Brazil Manhattan, KS 66506-5502 Phone: 55-61-218-2330 USA . Phone: 913-532-1369 Bolafios, Jose Fax: 913-532-5692 Semillas Hibridas Pioneer S.A. E-Mail: [email protected] P.O. Box 31561 Cali Costa, Luana Mahe Colombia Bolsista Embrapa Milho e Sorgo Phone: 57-2-669-6855 Caixa Postal 151 Fax: 57-2-669-6907 35701-970 Sete Lagoas, MG Brazil Bressan, Wellington Phone: 55-31-779-1179 Embrapa Milho e Sorgo Fax: 55-31-779-1088 Caixa Postal 151 E-Mail: [email protected] 357001-970 Sete Lagoas, MG Brazil Cruz, Jose Carlos Phone: 55-31-779-1101 Embrapa Milho e Sorgo Fax: 55-31-779-1088 Caixa Postal 151 E-Mail: [email protected] 35701-970 Sete Lagoas, MG Brazil Campos, Mario Silva Phone: 55-31-779-1061 Sementes Agroceres SfA Fax: 55-31-779-1088 Caixa Postal 41 [email protected] 86400-000 Jacarezinho, PR Brazil Cunha, J 0110 Marcos Phone: 55-43-734-4584 Embrapa Sementes Basicas Fax: 55-43-734-4584 Rod. MG 424 Km 65 35001-970 Sete Lagoas Casela, Carlos Roberto Brazil Embrapa Milho e Sorgo Phone: 55-31-779-1130 Caixa Postal 151 Fax: 55-31-779-1131 35701-970 Sete Lagoas, MG Brazil Dahlberg, Jeff Phone: 55-31-779-1104 USDA-ARS-TARS Fax: 55-31-779-1088 Box 70 - PR 00681 E-Mail: [email protected] Mayaguez, Puerto Rico USA Phone: 787-831-3435 Fax: 787-831-3386 E-Mail: [email protected]

198 Dion. Paulo Eduardo Franceschet, Rafael A Zeneca Sementes Ltda. Sementes Agroceres S/A Rod. Anhanguera km 296 Rua 23 Q 18 Lote 1 14140-000 Carvinhos, SP Santa Helena de Goias, GO Brazil Brazil Phone: 55-16-651-1521 Phone: 55-62-641-1679 Fax: 55-16-651-1321 Fax: 55-62-641-1959

Dolezal, William Frederickson, Debra Pioneer HI-Bred International U. of Zimbabwe/ Biological Sciences 7300NW 62nd Ave - P.O. Box 1004 Matopos NES Station P KS 137 Johnston, IA 50131-1004 Harare USA Zimbabwe Phone: 515-270-5986 Phone: 263-4-303211 Fax:: 515-253-2149 [email protected] E-Mail: [email protected] Frederiksen, Richard A Dona, Antonio Donizete Dept Plant Pathology Semeali - Sementes Antoniali Ltda. Texas A & M University Rod. Marechal Rondon Km 523-Cpostal 428 College Station, TX 77843 Birigui, SP USA Brazil Phone: 409-845-1227 Phone: 55-18-642-3129 Fax: 409-845-6483 Fax: 55-18-642-3129 E-Mail: [email protected]

Faria, Luiz Antonio L. Frias, Gustavo A Embrapa Sementes Basicas Sanidad Vegetal, Mexico Rod. MG 424 Km 65 GMO Perez Valenzuela 127, Del Carmen 35001-970 Sete Lagoas Coxoacan Brazil Mexico, DF Phone: 55-31-779-1130 Phone: 52-5-54-6467 Fax: 55-31-779-1131 Fax: 52-5-54-6467

Fernandes, Celso Dornelas Garcia, Joiio Carlos Embrapa Gado de Corte Embrapa Milho e Sorgo Rod. BR 262 km 04 Caixa Postal 151 79106-000 Campo Grande, MS 35701-970 Sete Lagoas, MG Brazil Brazil Phone: 55-67-768-2075 Phone: 55-31-779-1150 Fax: 55-67-763-2245 Fax: 55-31-779-1088 E-Mail: [email protected] E-Mail: [email protected]

Ferreira, Alexandre S. Giorda, Laura Embrapa Milho e Sorgo EEAINTA Manfredi Exp. Sta. Caixa Postal 151 5988 Manfredi, Cordoba 35701-970 Sete Lagoas, MG Argentina Brazil Phone: 54 - 572 - 93058 Phone: 55-31-779-11 04 Fax: 54 - 572 -93061 Fax: 55-31-779-1088 E-Mail: emanfi"[email protected] E-Mail: [email protected]

199 Gomez. Cesar Ruiz Hassan, Hanadi Abdel G. Sementes Valle S/A Imperial College of Science CRA 34 14-156-ACOPI-YUMBO Department of Biochemistry Cali-Valle London SW7 1LU Colombia UK Phone: 57-2-664-4900 Phone: 44-171·589·5111· ext 55206 Fax: 57-2-664-4899 Fax: 44·171·225·0960 E-Mail: [email protected] E-Mail: [email protected]

Gomez, Francisco Huertas, Carlos Alberto Escuela Agricola Panamericana ICA - Sanidad Vegetal Zamorano Honduras· Apdo 93 Calle 37 nO 8·43 piso 4 Tegucigalpa Bogota Honduras Colombia Phone: 504·76-6231 Phone: 57·1·288·4128 Fax: 504·76·6232 E·Mail: [email protected] Huettel, Robin N. USDA CSREESIPAPPP Gonzalez, Carlos A Agribox·2220, 701 D Street, SW Novartis de Colombia Washington, DC 20250 Autopista Yumbo Km 5 USA Cali Phone: 204·401·580 Colombia Fax: 202-401·6869 Phone: 57·2·665·3166 E-Mail: [email protected] Fax: 57-2·664·8408 Indira, Sunkara Grainco Seeds National Research Center for Sorghum PO Box 136 Rajendranagar Toowoomba, QLD Hyderabad·500 030 A.P. Australia India Phone: 61-76·358·000 Phone: 91·40-245225 Fax: 61·76·353·334 Fax: 91·40·246378 E·Mail: [email protected] Hare, Brian Pacific Seeds PTY Ltda Isakeit, Tom PO Box 337 Texas A&M Research & Extension Center Toowoomba, Queensland 4350 2401 East Highway 83 Australia Weslaco, TX 78596 Phone: 61·76·902666 USA Fax: 61·76-301·063 Phone: 210· 968·5581 Fax: 210· 969·5639 Hart, Terry E·Mail: t·[email protected] Triumph Seed Co. Inc. P.O. Box 1050 Kaula, Godwin M. Ralls, TX 79357 Mt Makulu Res. Stn USA PlBag 7 Phone: 806·253·2584 Chilanga Fax: 806·253·2820 Zambia Phone: 26001 278001 Fax: 260·01·27893 E·Mail: [email protected]

200 Klink. Urubatan Palhares Lopes, Antonio Delphino Zeneca Sementes Ltda. Ministerio da Agricultura Rod. Anhanguera kIn 296 Av. Raja Gabaglia, 245-Bairro Cidade Jardim 14140-000 Carvinhos, SP 30380-980 Belo Horizonte, MG Brazil Brazil Phone: 55-16-651-1521 Phone: 55-31-292-2511 Fax: 55-16-651-1321 E-Mail: 55-31-275-2262

Kolmer, John Luders, Martin L. ASTA NOV ARTIS Seeds Argentina Suite 570 South/601 13th, ST, NW CC25 (2605) Santa Isabel Washington, DC 20250 Santa Fe USA Argentina Phone: 202-638-3128 Phone: 54-462-27680 Fax: 202-638-3171 Fax: 54-462-25964

Kubicek, Quentin B. Lust, Tim USDA!APHIS Plant Protection & Quarantine National Grain Sorghum Producers 4700 River Road Box 530 Riverdale, MD 20737 Abernathy, TX 79311 USA USA Phone: 301-734-5865 Phone: 806-298-4501 Fax: 301-734-8669 Fax: 806-298-4234 E-Mail: [email protected] E-Mail: [email protected]

Labarta, Marcelo D. Malaguti, Gino Instituto Nacional de Sementes (INASE) National Center of Agronomic Research Paseo Col6n 922 30 nO 63 CENIAP-Av. L. RuizPineda24-P.O. Box4690 Capital Federal - Bs As El Limon - Maracay 210 1 Argentina Venezuela Phone: 54-1-349-2433 Phone: 58-43-831004 Fax: 54-1-349-2417 Fax: 58-43-330949 E-Mail: [email protected] E-Mail: [email protected]

Leonard, Lee Mantle, Peter George Cargill Inc Imperial College of Science RR2 Box 82 Department of Biochemistry Lockney, TX 79241 London SW7 2AY USA UK Phone: 806-652-3301 Phone: 44-181-594-5245 Fax: 806-652-3807 Fax: 44-181-225-0960 E-Mail: [email protected] E-Mail: [email protected]

Lima, Jose Saltorio Mantovani, Evandro C. Cargill Embrapa Milho e Sorgo R. Jacarezinho, 1121 Caixa Postal 151 Andira, PR 357001-970 Sete Lagoas, MG Brazil Brazil Phone: 55-43-733-3535 Phone: 55-31-779-1105 Fax: 55-43-733-2415 Fax: 55-31-779-1088 E-Mail: [email protected]

201 Martinez-Soriano, Juan P. Mitidieri, Francisco J. Mexican Society for Plant Pathology Zeneca Sementes LTDA. CINVESTAV Irapuato Rod. Anhanguera Km 296 Apdo. postal 629-Irapuato Cravinhos, SP Mexico Brazil E-Mail: [email protected] Phone: 55-16-651-1521 Fax: 55-16-651-1321 Maunder, Bruce National Grain Sorghum Producers Mollero, Djalma Leme 4511 9th ST Zeneca Sementes Ltda. Lubbock,1J{79416 Rod. Anhanguera km 296 USA 14140-000 Carvinhos, SP Phone: 806-763-3336 Brazil Fax: 806-762-0825 Phone: 55-16-651-1521 E-Mail: [email protected] Fax: 55-16-651-1321

McLaren, Neal W. Moraes, Maria Heloisa D. ARC-Grain Crops Institute ESALQIUSP Private Bag X1251 A v. Padua Dias, 11 -CP 09 Potchefstroom 2520 13418-900 Piracicaba, SP South Africa Brazil Phone: 27-18-2996346 Phone: 55-19-429-4100 or 4195 Fax: 27-18-2947146 E-Mail: [email protected] E-Mail: [email protected] Moran, Jorge Luis Meirelles, Marcio Menezes Escuela Agricola Panamericana Marangaru Sementes Ltda. P.O. Box 93 Av. Visconde do Rio Branco, 25 Tegucigalpa Jardin6polis, SP Honduras Brazil Phone: 504-766231 Phone: 55-16~628-4421 Fax: 504-766 232 Fax: 55-16-628-4421 E-Mail: [email protected]

Mendes, Dilza Coelho Moreira, Joao Eduardo Dept da Defesa Agropecm\rialBahia DFNCE Av. Ademar de Barros 976 Ondina Rua Jorge DunnA, 1703 40170-110 Salvador, Bahia Fortaleza, CE Brazil Brazil Phone: 55-71-237-0152 Phone: 55-85-281-6046 Fax: 55-71-237-0012 Fax: 55-85-281-5700

Miranda, Joao E.C. Mottana, Gracieti Viscarra Embrapa Milho e Sorgo UFS C Ciencia e Tecnologia de Alimentos Caixa Postal 151 C.P. 476, Itacoorubi 357001-970 Sete Lagoas, MG 88034-001 Florian6polis, SC Brazil Brazil Phone: 55-31-779-1076 Phone: 55-48-234-4888 Fax: 55-31-779-1088 Fax: 55-48-331-9943 E-Mail: [email protected]

202 Mtisi. Esther Nider, Fabio Plant Protection Research Institute Dekalb Argentina SA Box CY 550 Causeway C. Correo 25 Harare Salto, Provo of Buenos Aires Zimbabwe Argentina Phone: 263-4-704531 ext. 2078 Phone: 54-474-30485/86 Fax: 263-4-728316 Fax: 54-474-30541 E-Mail: [email protected]. Mukuru, Samwiri Z. starte1.com.ar ICRISAT c/o James Baira, P.O.Box 8111 Nogueira, Sonia Regina Kampala, Uganda UFLA Kenya Rua Chagas D6ria, 248/apt" 04 Phone: 256-41-344244 ext 5000 Lavras,MG Fax: 256-41-257869 Brazil E-Mail: [email protected] Phone: 55-35-821-9330 Fax: 55-35-829-1283 Narvaez, Dario Kansas State University Nowell, David Plant Pathology Dept Pannar Research Department 4026 Throckmorton hall P.O. Box 19 Manhattan, Kansas 66506 Grey town 3250 USA South Africa Phone: 913-532-2415 E-Mail: [email protected] Fax: 913-532-5692 E-Mail: [email protected] Odvody, Gary Texas A & M Research and Extension Center Netto, Dea Alecia M. Rt. 2 Box 589 Embrapa Milho e Sorgo Corpus Christi, TX 78410 Caixa Postal 151 USA 35701-970 Sete Lagoas, MG Phone: 512-265-9205 Brazil Fax: 512-265-9434 Phone: 55-31-779-1140 E-Mail: [email protected] Fax: 55-31-779-1088 E-Mail: [email protected] Oliveira, Christiane Abreu Bolsista Embrapa Milho e Sorgo Nicodemo, Alexandre G. R Lassance Cunha, 227/603 Centro Zeneca Sementes LTDA. Sete Lagoas, MG Rod. MG 122 km 159 Brazil 39440-000 Janauba, MG Phone: 55-31-771-4016 Brazil E-Mail: [email protected] Phone: 55-38-821-1938 Fax: 55-38-821-1799 Palmeira, Elita Maria Leite Ministerio da Agricultura Nicoli, Amantino Martins Av. Hildebrando de Gois, 150 - Ribeira Embrapa Sementes Basicas Natal,RN Rod. MG 424 Km 65 Brazil 35001-970 Sete Lagoas Phone: 55-84-221-1749 Brazil Fax: 55-84-2211740 Phone: 55-31-779-1130 Fax: 55-31-779-1131

203 Pazeto, Lindomar D. Pozar, Gilberto Sementes Demefertil Cargill Av. Floriano Peixoto, 3828 Sitio Sao Joao, sin, CP 6553 B. Geraldo 38406-279 Uberlandia, MG 13082-970 Campinas SP Brazil Brazil Phone: 55-34-212-1422 Prates, Helio pazoutova, Sylvie Embrapa Milho e Sorgo Institute of Microbiology CAS Caixa Postal 151 Biskupcova 12 357001-970 Sete Lagoas, MG Prague 3 Brazil Czech Republic Phone: 55-31-779-1057 Phone: 4202-475-2332 Fax: 55-31-779-.1088 Fax: 4202-471-5743 E-Mail: [email protected] E-Mail: [email protected] Prezotto, Leonir J. Pereira F, Isarael A Sementes Agroceres SI A Embrapa Milho e Sorgo Rod. Km 03-Clube Recreativo Caixa Postal 151 Santa Helena de Goias, GO 35701-970 Sete Lagoas, MG Brazil Brazil Phone: 55-62-614-1067 Phone: 55-31-779-1152 Fax: 55-31-779-1088 Reddy, Belum E-Mail: [email protected] ICRISAT Patancheru P.O., AP. 502324 Perkins, James India Dekalb Genetics Phone: 91-40-596161 3100 Sycamoere Road Fax: 91-40-241239 Dekalb, II 60115 E-Mail: [email protected] USA Phone: 815-758-9524 Reis, Erlei Melo Fax: 815-758-4106 UFPF-Faculdade de Agronomia E-Mail: [email protected] Caixa Postal 567 99001-970 Passo Fundo, RS Pineiro, Maya Brazil Technological Laboratory ofUruguay-LATU Mycotoxin Department Resende, Ivan Carvalho Montevideo Sementes Agroceres S/A Uruguay Rod. MGT 154 - Caixa Postal 81 Phone: 59-8-261-3724 Capinopolis, MG E-Mail: [email protected] Brazil Phone: 55-34-263-1677 Pinto, Nicesio F.J. de A Fax: 55-34-263-1904 Embrapa Milho e Sorgo Caixa Postal 151 Ribas, Paulo Motta 35701-970 Sete Lagoas, MG Sementes Agroceres S/A Brazil Rod. MGT 154 - Caixa Postal 81 Phone: 55-31-779-1093 Capinopolis, MG Fax: 55-31-779-1088 Brazil E-Mail: [email protected] Phone: 55-34-263-1677 Fax: 55-34-263-1904

204 Ribeiro. Celso A. Pinto Roman, Hector A. Zeneca Sementes Ltda. Cargill Hybrid Seeds Rod. MG-188 km 158,5 Cpostal230 Rt. 23, Box 557 Paracatu, MG Pontiac, IL, 61764 Brazil USA Phone: 55-61-672-6377 Phone: 815-844-3128 Fax: 55-61-672-6377 Fax: 815-844-3156 E-Mail: [email protected] Riccelli, Mauricio Himeca Rooney, Bill Apartado Postal 236 Texas A&M University Maracay, 2101-A Dept. of Soil & Crop Sciences Venezuela College Station, TX 77843-2474 Phone: 58-44-461334 USA Fax: 58-44-461334 Phone: 409-845-2151 E-Mail: [email protected] Fax: 409-862-1931 E-Mail: [email protected] Rocha, Vilson Antonio Sementes Agroceres SI A Rosinha, Raul Os6rio Fda. Agroceres Embrapa Sementes Basicas Santa Cruz das Palmeiras, SP Rod. MG 424 Km 65 Brazil 35001-970 Sete Lagoas Phone: 55-19-672-2424 Brazil Fax: 55-19-672-2525 Phone: 55-31-779-1130 Fax: 55-31-779-1131 Rodrigues, Delmo Diogo E-Mail: [email protected] Cargill Caixa Postal 6553 Ryley, Malcolm John 13082-970 Campinas SP Queensland Department of Primary Industries Brazil PO Box 102 Phone: 55-19-239-1381 Toowoomba, QLD 4350 Fax: 55-19-239-4396 Australia E-Mail: delmo_ diogoJodrigues@ Phone: 61 76881319 cargill. com Fax: 61-76-881-199 E-Mail: [email protected] Rodrigues, Jose Avelino S. Embrapa Milho e Sorgo Salas, Fernando Ornelas Caixa Postal 151 Gobierno del Estado de Nayarit 357001-970 Sete Lagoas, MG Tepic - Av. Mexico # 38 rute Brazil Nayarit Phone: 55-31-779-1075 Mexico Fax: 55-31-779-1088 Phone: 321-20063 E-Mail: [email protected] Fax: 321-23554

Rodriguez, Jesus Vizcaino Salgado, Luiz Eduardo V. Semillas Hibridas, S.A. de C. V. Pioneer (Dekalb Mexico) R. Marques Povoa, 1044/31 Av. Hidalgo N° 23756° Piso Brazil Guadalajara, Jalisco 44690 Phone: 55-34-977-4737 Mexico Phone: 91-3-616-9850 Fax: 91-3-797-0044

205 Sangitrao, Chandrakant S. Santos, Jose Alves Filho ICRISAT - Department of Plant Pathology .DFAIMS Punjabrao Krishi Vidyapeeth/Krishi Nagar Rua D. Aquino, 2696 Maharashtra 444 104 Campo Grande, MS India Brazil Phone: 91~724-26320 Phone: 55-67-725-7100 Fax: 91-724-58219 Santos PO, Laerte F. Sans, Luiz Marcelo Aguiar Naterra Nac. Sementes Coml. Imp. Ltda. Embrapa Milho e Sorgo Rua Simao Alvares, 1001 - Casa 6 Caixa Postal 151 05417-030 Sao Paulo, SP 35701-970 Sete Lagoas, MG Brazil Brazil Phone: 55-11-211-5649 Phone: 55-31-779-1149 Fax: 55-11-816-3263 Fax: 55-31-779-1088 E-Mail: [email protected] E-Mail: [email protected] Santos, Ugo Mar~al Santana, Evandro B. Sementes Agroceres Sf A Sementes Ribeiral Ltda. Rua 104, nO 1101 Av. Arlindo Porto 439 Capin6polis, MG 38700~000 Patos de Minas, MG Brazil Brazil Phone: 55-34-263-1755 Phone: 55-34-823-1400 Fax: 55-34-263-1779 Fax: 55-34-823-1400 Scaranari, Ciro Santos, Claudia C. Ferreira Embrapa SPSB Bolsista Embrapa Milho e Sorgo Av. Anchieta, 173 Conj. 41142 Caixa Postal 151 13015-100 Campinas, SP 35701-970 Sete Lagoas, MG Brazil Brazil Phone: 55-19-232-1955 Phone: 55-31-779-1000 Fax: 55-19-232-1707 Fax: 55-31-779-1088 E-Mail: [email protected] E-Mail: [email protected] Schaffert, Robert E. Santos F, Edgar Embrapa Milho e Sorgo Ministerio da Agricultura Caixa Postal 151 Largo dos Aflitos - Edif. Ceres Brazil Salvador, BA Phone: 55-31-779-1076 Brazil Fax: 55-31-779-1088 Phone: 55-71-320-7420 E-Mail: [email protected]

Santos, Fredolino G. Scheidl, Guillermo Heriberto Embrapa Milho e Sorgo Dekalb Argentina S.A. Caixa Postal 151 C. Correo 25 35701-970 Sete Lagoas, MG SaIto, Provo of Buenos Aires Brazil Argentina Phone: 55-31-779-1069 Phone: 54-474-30485 or 30486 Fax: 55-31-779-1088 Fax: 54-474-30541 E-Mail: [email protected] E-Mail: [email protected]. startel. com. ar

206 Scussel. ViI des Maria Silva, Luiz Claudio UPS C Ciencia e Tecnologia de Alimentos Sementes Agroeeres Sf A C.P. 476, Itacoorubi Rod. Dionisio Bartolotti, Ian 0,5 -CP 9 88034-001 Florian6polis, SC Santa Cruz das Palmeiras, SP Brazil Brazil Phone: 55-48-234-4888 Phone: 55-19-672-2424 Fax: 55-48-331-9943 Fax: 55-19-672-2525 E-Mail: [email protected] Silva, Sidiney Senetiner, Alberto Carlos Sementes Agroceres SfA QEACA R. 104, nO 1101 Merced 1425 Capin6polis, MG 2700 Pergamino, Bs. As. Brazil Argentina Phone: 55-34-263-1755 Phone: 54-1-477-20798 Fax: 55-34-263-1976 Fax: 54-1-477-20798 Soferini, Otavio B. Silva, Arnaldo Ferreira Braskalb Embrapa Milho e Sorgo Brazil Caixa Postal 151 35701-970 Sete Lagoas, MG Souza, Jorge Luiz R. Brazil Zeneca Sementes Ltda. Phone: 55-31-779-1062 Rod. Anhanguera Ian 296 Fax: 55-31-779-1088 14140-000 Carvinhos, SP Brazil Silva, Herberte Pereira Phone: 55-16-651-1521 Zeneca Sementes Ltda. Fax: 55-16-651-1321 Rod. Anhanguera Ian 296 14140-000 Carvinhos, SP Stack, James P. Brazil University ofNebraskalSCREC Phone: 55-16-651-1521 Box 66 Fax: 55-16-651-1321 Clay Center, Nebraska 68933 USA Silva, Jose Antonio Phone: 402-762-4435 SFFVIDFAIGO Fax: 402-762-4422 Pra9a Cinira, 100 Centro E-Mail: [email protected]!.edu Goiania, GO Brazil Stem, Eduardo Phone: 55-62-225-5421 Semillas Papalotla Fax: 55-62-224-6444 Miguel Angel de Quevedo N°126-2 Chimalistac Silva, Jose Pereira Mexico City, DF 01050 Naterra Nac. Sementes Com!. Imp. Ltda. Mexico Rua Simao Alvares, 1001 - Casa 6 05417-030 Sao Paulo, SP Suarez, Jorge E. Brazil ICA Colombia Phone: 55-11-211-5649 A.A. 7984 Fax: 55-11-816-3263 Santafe de Bogota E-Mail: [email protected] Colombia Phone: 57-1-2-881753 E-Mail: [email protected]

207 Swann. Bill Waquil, J. Magid Pacific Seeds/Advanta Seed Organization Embrapa Milho e Sorgo PO Box 337 Caixa Postal 151 Toowoomba, Queensland. 4350 357001-970 Sete Lagoas, MG Australia Brazil Phone: 61-76-902-666 Phone: 55-31-779-1097 Fax: 61-76-301-063 Fax: 55-31-779-1088 E-Mail: [email protected] E-Mail: [email protected]

Toews,Doug Williams, Hector Alanis International Seeds, Inc. Compo Exp. Rio Bravo P.O. Box 168 INIFAP Halsey, OR 97348 Apdo Postal 172 USA Rio Bravo Phone: 541-369-2251 Mexico Fax: 541-369-2640 E-Mail: [email protected]

Torres-Montalvo, Heriberto Yohe, John M. TexasA&M University of Nebraska 301 Ball St#1109 INTSORMIL College Station TX 77840 113 Biochemistry Hall USA Lincoln, NE 68583-0748 Phone: 409-845-8182 USA Fax: 409-845-6483 Phone: 402-472-6032 E-Mail: [email protected] Fax: 402-472-7978 E-Mail: [email protected] Tupekar, Prakash N. Maharashtra Hybrid Seeds Co. Ltd. Zago, Claudio Prates 4th. Fl. Resham Bhavan 78 Veer Nariman Rd. Sementes Agroceres S/A Mumbai, Maharasthra 400 020 Rod. MGT 154 - Caixa Postal 81 India Capin6polis, MG Phone: 91-22-2049497 Brazil Fax: 91-22-2047871 Phone: 55-34-263-1677 E-Mail: [email protected] Fax: 55-34-263-1904

Vacaro, Eloy L. Zorrilla, Hugo Agropecmiria Oeste Ltda. (Agroeste) Pioneer HI-Bred Sorghum Research R: Antonio Vacaro 130, Bairro Aeroporto 1724 Hayes Dr. 89820-000 Xanxere, SC Manhattan, KS 66502 Brazil USA Phone: 55-49-433-2011 Phone: 913-537-5100 Fax: 55-49-433-2089 Fax: 913-537-4560 E-Mail: [email protected] Viana, Antonio C. Embrapa Milho e Sorgo Caixa Postal 151 357001-970 Sete Lagoas, MG Brazil Phone: 55-31-779-1186 Fax: 55-31-779-1088 E-Mail: [email protected]

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