JOURNAL OF AGRICULTURAL SCIENCE IN FINLAND Maataloustieteellinen A ikakauskirja Vol. 56: 175—182, 1984

Bipolaris sorokiniana on seed in Finland

AARNE KURPPA Department of Plant Pathology, University of Helsinki, SF-00710 HELSINKI 71, Finland

Abstract. Bipolaris sorokiniana is reported as a common in commercially grown barley seed in Finland with possible economic importance. In 1974, when 200 samples of barley seed were surveyed the fungus was identified in 60 per cent of samples. The three fol- lowing years the incidence was 19, 29 and 38 %. The mean per cent seeds infected was 3.8, 1.3, 1.2 and 1.9 respectively. The highest recorded individual % was 92. The most severely infected cultivar was Paavo each year. In most cases only the seed cover was invaded by the fungus but also infection in the embryo and the cell leyers surrounding it was observed. Such severely infected seeds did not germinate or the seedlings were readily infected after germina- tion. B. sorokiniana was less frequent in the western parts of the country. Field experiments in 1972—1979 confirmed the same varietal susceptibility which was found by the survey of commercial samples of barley seed. High rainfall and relative humidity in July and August were the main factors associated with increased seed infection incidence.

Introduction ceptible crop is readily infected by the fungus which is able to overwinter in the soil even in Bipolaris sorokiniana (Sacc. ex Sorok.) cool climate and because many wild grasses Shoem. (syn. Helminthosporium sativum act as an inoculum reservoir (Jorgensen Pamm., King & Bakke), perfect state Coch- 1974, Whittle 1977). The diseases the fun- liobolus sativus (Ito & Kurib.) Dastur has gus causes are a seedling blight, a foot and a cosmopolitan distribution on many grasses root rot, foliar disease, headblight and and and causes serious disease and kernel blight (Anderson & Banttari 1976). economic losses in spring barley and wheat Up to 15 % of yield losses have been recently particularly in warm temperate areas (Spra- reported (Whittle & Richardson 1978). que 1950, Anderson & Banttari 1976). In re- There is no earlier information as to when cent years the fungus has become more fre- the fungus became common in Finland, but quent in North Western Europe (Jorgensen in North Western Europe it happened during 1974, Mäkelä 1975, Whittle 1977). The sus- the 1950 s and 1960 s (de Tempe 1964, Jorgen-

Index words: Bipolaris sorokiniana, Hetminslhosporium sativum, salivas, common root rot; barley, seed infection

175 Fig. 1. A barley seed sample cv. Paavo with very high Fig. 2. A seed half with severe embryo infection by the incidence of Bipolaris sorokiniana after 5 days of incu- fungus after 4 days of incubation. bation in a petri dish.

sen 1969, Hewett 1975). A later report of mined for possible embryo infection. The Kurppa (1982) assumes the fungus gaining seeds were cut into two halves and one half still increasing importance as a pathogen of was placed in a petri dish as described above spring barley in Finland. and the other half was discarded. One hun- dred seeds were examined per a sample. The seed halves were observed after three of Materials and methods days incubation for the localization of the site of During the years 1972 to 1979, 11—l9 infection. During the short incubation time spring barley cultivars grown in field experi- no growth from the seed cover could reach ments at the University Farm at Viikki were the embryo area, but any fungal growth examined each year for the presense of Bipo- within the embryo could be easily seen. laris sorokiniana. Experimental seed samples Preliminary tests of seed infection inci- from North Savo Experimental Station, dence included a treatment with 1 % Na- Maaninka were examined during 1972 and hypochloride solution. Comparison of test 1973. 649 commercial samples of spring bar- results with and without this treatment ley, including those most commonly sown showed no significant differences and the were taken from those seed lots received treatment was discontinued. annually at the State Seed Testing Institute, The weather conditions during the rese- Helsinki for testing for purity and germina- arch period: tion. The growing seasons 1972—1975 were Representative sub-samples of 100 seeds warmer and seasons 1976—1978 cooler than were placed in petri dishes (diameter 14 cm), average. The temperature during the 1979 50 each on wet filter paper and cotton filter. season was near average. Summers in 1973 The dishes were incubated at 20—22°C for and 1975 were very dry and 1976, 1977 and six days and then examined for fungal 1979 were abnormally rainy. The precipita- growth. B. sorokiniana could be readily tion during late summer 1974 was also high identified with a stereo microscope at the (Anon 1972—1979). magnification of 12 to 50 times if it was pre- sent seeds. in germinating Results The fungi belonging to the other genera were also recorded. The seed lots with high The incidences of Bipolaris sorokiniana in incidence of seed infection were further exa- spring barley seed varied marketly during the

176 —1979. 1979 0 0 2.4 1972 0 3 2.4 during 1978 Viikki 1977 2 1 2.5 Farm, cultivars 1976 0 1 0 0.3 University Six-row 1975 0 0 0 0.0 at 02444 1974 14 17 11.6

experiments 1973 0 0 0— 0 0.0 field 1972 16 12 14 24.5 from infected cultivars seeds Cultivar Etu Hja-673 Pomo Suvi Tammi Teemu Vigdis barley cent Per Fig. 3. The regional distribution of the seed samples. spring 2 2 3.7 See Table 3. 1979

different 1978 2 5.3 research period 1972—1979. In certain years of the fungus was widespread occuring with yield 0 1.5 high levels in susceptible cultivars. Overall 1977 figures for seed infection show the fungus grain

in 1 was common but associating with certain 1976 0 0.4 cultivars. In the seed samples from field ex- cultivars periments at University Farm, Helsinki Viik- 1975 0 0 0.0 ki, the fungus was very common in 1972 and Two-row 1974 but did not occur at all in 1973 and sorokiniana 00442 1975. From low to moderate incidences were experiments. 0 Bipolaris 1974 12 4.8 recorded in the following years (Table 1). in ______During dry seasons the infection status of the of not 0 0 0 0.0 sowing seed did not have any effect on the 1973 0— infection incidence of new grain yield, but cultivar during moist seasons the crop grown from 2 occurence = 1972 26 20 16 29 18.6 infected seed served as an important source 0000356 The for spore liberation for secondary infection. 1. Fungal growth in individual seeds was Ingrid mostly superficial and the fungal hyphae had Table Cultivar Aapo Arvo Birgitta Eva— Gunilla Kajsa Karri Mari Yearly mean 177 only invaded the seed coat. In 1972 severe in- barley crop by Mäkelä (1971, 1972, 1975) fection of embryos or the surrounding layers and barley seed by Kurppa (1975) show deci- was detected in many cultivars, particularly cively the incidence of the fungus in barley in cvs Paavo, Mari and Birgitta. The highest in- Finland. dividual percentage of embryo infection was The infection incidence was clearly asso- recorded with cv. Paavo at 32 %. The other ciated with certain cultivars as also reported common fungus species recorded each year by de Tempe(l964), Kietreiber (1973, 1974) with the survey were Alternaria sp., Cepha- and Whittle (1977). The true susceptibility losporium sp., Cladosporium sp. and Uloc- to seed borne infection is related to the inva- ladium sp.. Also Fusarium species were com- sion to the seed by the fungus as reported by mon after rainy late growing seasons like Anderson and Banttari (1976). Superficial 1972 and 1974. A survey of spring barley cul- invasion is effectively controlled by the use tivars at North Savo Experimental Station, of mercurial seed treatment but infection in Maaninka 1972 revealed the following inci- the embryo or the surrounding cell leyers is dence of B. sorokiniana in seed samples (%): not controlled. Balder 10, Etu 13, Karri 9, Lise 0, Mari 10, Differences in the disease incidence and Paavo 8, Pirkka 0, Pomo 31, Olli 0, Otra 6 fungal incidence have also been reported and Vigdis 19. Severe infection of the between areas and years by Jorgensen embryo was detected with the cvs Porno and (1969) and Kietreiber (1973, 1974) and these %. Vigdis with an incidence of 10 The fol- are strongly related to the weather conditions lowing summer the mean percent infected as shown by Couture and Sutton (1977). seeds of cv. Vigdis was 60.0. The higher incidence in central part of the According to surveys of commercial sam- country rather than in the coast area is asso- ples of spring barley in 1974—1977 B. soro- ciated to higher relative humidity and after- kiniana was a common and widespread fun- noon showers which are more frequent out- gus throughout the country, wherever barley side the coast area during the critical period is grown (Table 2). In 1974, when the fungus of seed ripening. was exceptionally common, several samples No regional differences in disease inci- with high incidence of seed infection were re- dence could be found associated to sowing corded. Differences in the incidence were seed because commercially distributed seed is also found between the cultivars. Each year mainly used for sowing. Seed dressing to the highest levels occurred in cv. Paavo. All control the pathogen is increasingly impor- these samples with high B. sorokiniana inci- tant because it also helps to prevent the accu- dence were also severely infected in the mulation of the fungus as a destructive soil embryos. borne pathogen. This is particularly true Clear differences in incidence between after rainy growing seasons. geographic areas could not be found, but it The most important factor in seed infec- seems obvious that fungus is less frequent in tion is the location of the fungus in the seed, Western and South Western parts of the either in the seed coat or in the embryo. country (Turku and Pori and Vaasa coun- ties) (table 3).

Acknowledgements. The State Seed Testing Institute is acknowledged for providing research material. Spe- Discussion cial thanks are due toprofessor Eeva Tapio and Dr. Kai- ho Mäkelä for the support and good advice they have These surveys and other earlier observa- given me in my work. I also wish to thank Dr. Randall tions of Bipolaris sorokiniana occuring in Kelley for linguistic revision of the English text.

178 1977 2 4 10 7 58 4 8 6 6 21 3 9

% recorded 1976 4 35 6 8 2 3 0 4

0 highest 11 3 2 2 2 1 12 individual 1975 14 1345 The 1974 27 6 7 92 9 10 9 63 11 12 22

1977 0.0 1.6 0.8 1.1 17.4 1.7 1.1 2.7 3.8 3.0 0.8 1.5 1.9 seeds 1976 0.0 1.0 0.8 0.2 12.8 1.2 1.6 1.2 0.0 0.8 0.0 0.7 1.2 —1977. cent 1974 infected 0.0 0.1 0.1 1.3 Per 1975 2.7 11.8 0.4 0.2 0.3 0.8 0.2 0.9 0.0 during 1974 4.6 4.0 1.0 47.4 1.1 3.2 4.4 34.0 2.1 2.6 9.7 3.8 yearly examined 1977 23.0 56.0 20.0 41.2 100.0 55.6 27.8 75.0 100.0 50.0 25.0 33.3 38.0 barley samples 1976 0.0 25.0 27.0 11.0 67.0 37.5 55.6 60.0 0.0 44.4 0.0 28.6 28.9 spring cent infected 1975 0.0 25.0 13.0 7.0 88.0 21.4 11.1 20.0 50.0 16.7 15.8 0.0 19.0 of Per samples 1974 63.7 100.0 38.0 100.0 48.0 85.7 100.0 100.0 66.7 70.0 66.7 60.0 commercial 1977 13 9 25 34 5 9 18 4 4 0 10 4 9 0 150 in samples 1976 6 4 33 54 6 16 25 5 3 0 9 4 7 173 of 2 4 8 30 8 14 18 10 0 0 4 6 19 10 sorokiniana Number examined 1975 126 Bipolaris 1974 0 H 3 59 5 23 21 18 0 2 0 18 37 3 200 ofoccurence and The cvs cvs cent 2. number samples per samples infected Eero Etu Hja-673 Otra Paavo Pirkka Pomo Suvi Teemu Birgitta Eva Ingrid Karri Mari Yearly Table Cultivar Six-row Two-row of examined Mean of seeds 179 Table 3. The regional occurence of Bipolaris sorokiniana in Finland during the growing seasons 1974—1977 as determined by a survey of commercial samples of spring barley.

Number of samples examined Per cent samples infected County 1 1974 1975 1976 1977 1974 1975 1976 1977 1 Turku and Pori 57 43 72 63 62.6 20.9 26.4 23.8 2 Uusimaa 31 24 31 15 62.5 16.7 45.2 46.7 3 Kymi 27 11 24 13 66.7 18.2 29.2 84.6 4 Häme 30 15 6 20 65.9 13.3 16.6 35.0 5 Mikkeli 11 1 1 2 71.4 (100.0) (100.0) (50.0) 6 Vaasa 22 20 27 26 43.5 10.0 11.1 34.6 7 Central Finland 6 0 5 8 83.3 60.0 62.5 8 Kuopio 13 5 5 3 76.9 20.0 40.0 66.7 9 Northern Karelia 2 0 0 0 (0.0) 10 Oulu 17 2 0 (100.0) 42.8 (50.0) Total number of samples examined 200 126 173 150

Mean per cent samples infected 63.0 19.0 28.9 38.0 1 See fig. 3.

References

Anderson. W.H. & Banttari, E.E. 1976. The effect of Kurppa,A. 1975. Ohran tyvi- ja lehtilaikku yleistyvä Bipolaris sorokiniana on yield, kernel weight and piilevä kasvitauti. Käytännön Maamies 1975, 7: kernel discoloration in six-row spring barleys. PI. Dis. 20—21.

Reptr, 60: 754—758. —, 1982. Sienituhoja siemenviljassa. Pellervo 1982, 8: Anon. 1972—1979. Kuukausikatsauksia Suomen sää- 30—31. oloihin. Touko-elokuu 1972—1979. Ilmatieteen lai- Mäkelä, K. 1971. Some graminicolous species of Hel- tos. minthosporium in Finland. Karstenia 12: 5—35. Couture, L. & Sutton, J.C. 1978. Relation of weather —, 1972. Leaf spot fungi on barley in Finland, Acta variables and host factors to incidence of airborne Agr. Fenn. 124; 1 —23. spores of Bipolaris sorokiniana. Can. J. Bot. 56: —, 1975. Occurence of Helminthosporium species on 2162—2170. cereals in Finland in 1971—1973. J. Sci. Agric. Soc. Hewett, P.D, 1975. A health survey of seed barley. PI. Finl. 47; 181—217. Path. 24: 229—232. Spraque, R. 1950. Diseases of cereals and grasses in Jorgensen, J. 1969. Species of Fusarium and Hel- North America. 538 p. New York. minthosporium on seed of barley grown in Denmark Tempe, J.de. 1964. Helminthosporium spp. seeds of during 1965—1967. Acta Agric. Scand. 19; 92—98. in wheat, barley, and . Proc. Int. Seed Test. —, 1974. Occurence and importance of seed borne ino- Assoc. 29: 117—140. culum of Cochliobolus sativus on barley in Denmark. Acta Agric. Scand. 24: 49—54. Whittle, A.M. 1977. Cochliobolus sativus on barley in Kietreiber, M. 1973. Tätßer 1972. Geshundheits- Scotland. PI. Path. 26: 67—74. zustand der Saatgutproben. Jb. 1972 Bundesanst. —, & Richardson, M.J. 1978. Yield losses caused by Pflßau. Samenpruf. Wien, 59—73. Cochliobolus sativus on Clermont barley. Phytopath. Z. 91: 238—256. —, 1974. Tätßer 1973. Geshundheitszustand der Saat- gutproben. Jb. 1973 Bundesanst. Pflßau. Samen- pruf. Wien, 65 —78. Ms received June 29, 1984

180 SELOSTUS

Bipolaris sorokiniana-sienen esiintyminen ohran siementavarassa Suomessa

Aarne Kurppa Helsingin yliopiston kasvipatologian laitos, 00710 Helsinki 71

Bipolaris sorokiniana (syn. Helminthosporium sati- heutti siemenen itämättömyyden tai oraan sairastumisen vum, koteloaste Cochliobolus sativus) todettiin yleiseksi heti itämisen jälkeen. ja potentiaalisesti haitalliseksi sieneksi ohran siementa- Vuosina 1972—1979 tutkittujen kenttäkokeiden sato- varassa vuosina 1972—1979 Helsingin yliopiston kasvi- näytteiden tulokset tukivat otannalla saatuja tuloksia. patologian laitoksella suoritetuissa tutkimuksissa. Vuo- Koska sieni infektoi jyväsadon sekundäärisesti tuulen sina 1974—1977 tutkittiin 649 siementavaraksi tarkoi- mukana leviävien kuromien välityksellä, sen runsaus tettua ohraerää, joista sienen tartuttamiksi todettiin ai- siemenissä kytkeytyi erityisesti heinä- ja elokuun sade- kajärjestyksessä 60, 19, 29 ja 38 %. Infektoituneita jy- määriin, suhteelliseen ilmankosteuteen ja myös kasvus- viä oli vastaavasti keskimäärin 3.8, 1.3, 1.2 ja 1.9 % tojen lakoisuuteen. Erityisen kuivissa olosuhteissa sieni tutkituista. Lajikkeiden välillä oli selviä alttiuseroja, ei infektoinut kypsyvää jyväsatoa lainkaan. Paavo oli infektoitunein kaikkina vuosina ja yleisesti Sienen todellinen merkitys siemenlevintäisenä taudin- viljelty Otra tervein. Selviä eroja kaksi- ja monitahois- aiheuttajana riippuu jyvien infektoituneisuusasteesta; ten lajikkeiden alttiudessa ei todettu. Sientä esiintyi onko sieni vain siemenkuoressa, vaiko myös alkiossa. maan länsiosissa jonkinverran vähemmän kuin muu- Pelkän siemenkuoritartunnan saanut kylvösiemen voi- alla. daan puhdistaa tehokkaasti taudinaiheuttajasta eloho- B. sorokiniana esiintyi useimmiten rihmastona sie- peapitoisella valmisteella peittaamalla. Toimenpide ra- raenkuoressa, mutta monissa tapauksissa se oli infektoi- joittaa osaltaan myös sienen lisääntyvää haitallisuutta nut myös alkion ja sen läheiset solukerrokset, mikä ai- maalevintäisenä taudinaiheuttajana.

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