Biology and Ecology of Phytophthora Citricola in Native Plant Communities Affected by Mining

Total Page:16

File Type:pdf, Size:1020Kb

Biology and Ecology of Phytophthora Citricola in Native Plant Communities Affected by Mining M 188: Biology and ecology of Phytophthora citricola in native plant communities affected by mining. Felicity Bunny Dr Bryan Shearer July 1995 . '' Acknowledgements This work was funded by Mineralsand Energy Research Institute of Western Australia. Facilities were provided by the Department of Conservation and Land Management. Thanks go to the many people who provided assistance with this project, especially; Alcoaof Australia Limited for help with the section on distribution of Phytophthora citricola in the northemjarrah forest, Giles Hardy foradvice and encouragement, Sue Broughton, Carla Wilkinson, Brendan Smithand Joanne Robinson for technical assistance. Summary .................................................................................................................................................... l Management recommendations. ................................................................................................................. 2 Section l. Distribution of Phytophthora citrico/a on soil surface and at depth in the northern jarrah forest....................................................... ......................................................................................... 4 Abstract ........................................................................................................................... 4 Introduction.......................................................... ........................................................... 4 Materials and Methods................................... ................................................................. 5 Results....... ....................................................................................................................... 6 Discussion....................................................................................................................... 11 Section 2. Differentiation of local isolates of Phytophthora citrico/a into subgroups basedon isozyme analysis, morphology andcultural characteristics, andvariability in pathogenicity.. ...................... 14 Abstract.................................... ....................................................................................... 14 Introduction....................................................................................................... .............. 14 2. l lsozyme analysis ..................................................................................................................... 15 Materials and methods................................................................... .................................. 15 Results ............................................................................................................................. 18 Discussion ....................................................................................................................... 20 2.2 Cultural variationbetween isolates of Phytophthora citrico/a .................................................. 21 Introduction.............................. ....................................................................................... 2 l Materials and methods........................................................... .......................................... 22 Results............................................................................................................................. 22 Discussion ....................................................................................................................... 23 2.3 Variability in sporangiaand oospore dimensions between electrophoretic types of Phytophthora citricola. ................................................................................................................. 24 Introduction......................... ............................................................................................ 24 Materials and methods..................................................................................................... 24 Results ............................................................................................................................. 25 Discussion ....................................................................................................................... 26 2.4 Variability in pathogenicity of isolates of Phytophthora citrico/a on jarra11 (Eucalyptus marginala) clones. ................................................................................................. ... 29 Introduction......................... ............................................................................................ 29 Materials and methods............................... ...................................................................... 29 Results ............................................................................................................................. 30 Discussion ............................................................................... ....................................... 3 l 2.5 Effect of phosphonate amendment of media on in vitro growth of Phytophthora citricola . ................................................................................................................. 32 Introduction ..................................................................................................................... 32 2.5.1 Effectof amendment of media with 10 ppm phosphonate on isolates of SG 1 and SG 2 ........................................................................................................... ........... 33 Materials and methods..................................................................................................... 33 Results................................................................ ............................................................. 33 Discussion ....................................................................................................................... 33 2.5.2 In vitro effect of 15, 30 and 50 ppm phosphonate on isolates of Phytophthora citricola of SG l and SG 2 ......................................................................... 35 Materials and methods................................................... .................................................. 35 Results...................................... ....................................................................................... 35 Discussion ....................................................................................................................... 36 3. Seasonal effect of soil temperature and moisture on survival of different propagules of Phytophthora citricola at two field sites ................ ........... ........ ........................... ........ .. .......... ..... ........... ... 37 Abstract .... ... ................................... ... .... ... ............ ... .. .. ... ... ... .... ..... ... .............. ..... ... .... .... 3 7 Introduction ..... ... ................ ..................... ... ..... ..... .. ... ..... ... ................. ............ ... ... .. .. ... .... 3 7 Materials and methods ...... .. ............... ....... ...... ........... .... ...... ........................................... 38 Results ............. .... ..... .. .................... .. .... .... .. .. .... .. ... ..................... ..... ...... ... ............. ...... .... 43 Discussion ...... ..... ......... .. ... .... ... .......... .. ... .... ....... ..... , ..... ..... .... ..... ... .................... ... ...... .... 57 4. Production of oospores by Phy tophthora citricola in two field soils ... ........ ....... ...... .... ... ................ ...... .... 63 Abstract .... .. .... .... ... ................. ... .... ....... .... .......... .. ..... .... .. ............ ,._. .. ... ..... .. .. ..... .... ..... .. .. 63 Introduction ....... ..... ... .... ... .. .... .. .. ... ............. ...... .. ..... ........ ... ............. : .. .......... ... .......... ..... 63 Materials and methods .......... ... .... ....... ..................................... ... ...... ... ... .. ... .... .. ... ... .. ..... 63 Results .... ....... ...... ...... ..... .. .. ..... .... ..... ..... ......... ... ...... .... ....... .... .. .............. ..... .... .... ...... ...... 64 Discussion .... ........ ... .. .................................. ..... .. .. ........ ... ............. ... ..... .. ................... .... .. 65 5. In vivo effects of phosphonate on Phytophthora citricola isolates of SG l and SG 2 ........ ........ .... .. .. ... .... 67 Abstract .. .. ..... .. ......... ........... ... ... .... ... .... ... ... ... ...... .. .... .. ... ........ ... .. ........ ... .. ... .... ..... .. ......... 67 Introduction ......................................... .. .. ... .. .... .................... ... ... .... ................ ....... ..... ... .. 67 Materials and methods .......... ... ...................... .... ... ... ....... ............. .... ..... .. ... .... ... .. .. ........ .. 67 Results ..... ... .... .. .. .... .... ... ............ ............ ...... .. .. ........ ... ..... ............ .. .... .... ..... ... ... ....... ........ 68 Discussion .... ........................................................................... .............. .... ...................... 71 Table 4.2. Numbers of oospores produced in two soils at Moore River and Dwellingup by four Phytophthora citricola isolates ... ............ ... .. ....... ..................... .... ..... .. ...............
Recommended publications
  • Phytophthora Plurivora T. Jung & T. I. Burgess and Other Phytophthora Species Causing Important Diseases of Ericaceous Plant
    Plant Protect. Sci. Vol. 47, 2011, No. 1: 13–19 Phytophthora plurivora T. Jung & T. I. Burgess and other Phytophthora Species Causing Important Diseases of Ericaceous Plants in the Czech Republic Marcela MRÁZKOVÁ1, Karel ČERNÝ1, Michal TOMšovsKÝ 2 and Veronika STRNADOVÁ1 1Silva Tarouca Research Institute for Landscape and Ornamental Gardening, Průhonice, Czech Republic; 2Mendel University in Brno, Brno, Czech Republic Abstract Mrázková M., Černý K., Tomšovský M., Strnadová V. (2011): Phytophthora plurivora T. Jung & T. I. Burgess and other Phytophthora species causing important diseases of ericaceous plants in the Czech Republic. Plant Protect. Sci., 47: 13–19. Ornamental nurseries, garden centres, public gardens and urban greenery in the Czech Republic were surveyed in 2006–2009 for the presence of Phytophthora spp. and the diseases they cause on ericaceous plants. Diseased plants such as Rhododendron spp., Pieris floribunda, Vaccinium sp., and Azalea sp. showed various symptoms including leaf spot, shoot blight, twig lesions or stem, root and collar rot. Nearly 140 Phytophthora isolates were collected from symptomatic plants in different areas of the country. Of the Phytophthora spp. on ericaceous plants or in their surroundings, P. plurivora appeared to be the most common species. Herein, we focus on the most frequently occurring species, P. plurivora, and describe its morpho-physiological and pathogenicity features and confirm its identity based on ITS sequences of rDNA. In addition, we give a list of other Phytophthora spp. including P. cactorum, P. cambivora, P. cinnamomi, P. citrophthora, P. megasperma, P. multivora, P. ramorum, and P. gonapodyides that we identified on the basis of their cultural and morphological characteristics and DNA sequences.
    [Show full text]
  • Detection and Quantification of Phytophthora Species Which Are
    Eur. J. For. Path. 29 (1999) 169–188 © 1999 Blackwell Wissenschafts-Verlag, Berlin ISSN 0300–1237 Detection and quantification of Phytophthora species which are associated with root-rot diseases in European deciduous forests by species-specific polymerase chain reaction 1 2 3 3 4 By R. SCHUBERT *, G. BAHNWEG *, J. NECHWATAL ,T.JUNG ,D.E.L.COOKE , 4 1 2 2 J. M. DUNCAN ,G.MU¨LLER-STARCK ,C.LANGEBARTELS ,H.SANDERMANN JR and 3 W. OßWALD 1Faculty of Forest Sciences, Section of Forest Genetics, Ludwig-Maximilians-University Munich, Am Hochanger 13, D-85354 Freising, Germany (R. Schubert for correspondence); 2GSF-National Research Center for Environment and Health, Institute of Biochemical Plant Pathology, Ingoldsta¨dter Landstr. 1, D-85764 Neuherberg, Germany; 3Faculty of Forest Sciences, Institute of Forest Botany, Phytopathology, Ludwig-Maximilians- University Munich, Am Hochanger 13, D-85354 Freising, Germany; 4Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK Summary Oligonucleotide primers were developed for the polymerase chain reaction (PCR)-based detection of selected Phytophthora species which are known to cause root-rot diseases in European forest trees. The primer pair CITR1/CITR2, complementing both internal transcribed spacer regions of the riboso- mal RNA genes, gave a 711 bp amplicon with Phytophthora citricola. The Phytophthora cambivora specific primer pair CAMB3/CAMB4, producing a 1105 bp amplicon, as well as the Phytophthora quercina specific primer pair QUERC1/QUERC2, producing a 842 bp amplicon, were derived from randomly amplified polymorphic DNA (RAPD)-fragments presented in this paper. All three primer pairs revealed no undesirable cross-reaction with a diverse test collection of isolates including other Phytophthora species, Pythium, Xerocomus, Hebeloma, Russula, and Armillaria.
    [Show full text]
  • Seasonal Fluctuations in the Extent of Colonization of Avocado Plants by the Stem Canker Pathogen Phytophthora Citricola
    J. AMER. SOC. HORT. SCI. 120(2): 157–162. 1995. Seasonal Fluctuations in the Extent of Colonization of Avocado Plants by the Stem Canker Pathogen Phytophthora citricola Zeinah A. El-Hamalawi and John A. Menge Department of Plant Pathology, University of California, Riverside, CA 92521 Additional index words. Persea americana, amino acids, total soluble carbohydrates Abstract. At monthly intervals, plants and stem cuttings of avocado (Persea americana Miller) ‘Hass’ grafted on ‘Barr Duke’ rootstock and ‘Topa Topa’ growing in a lathhouse were wounded and inoculated with the stem canker pathogen, Phytophthora citricola Sawada. The seasonal changes (measured monthly) in the extent of colonization of the avocado plants by P. citricola followed a periodic pattern, with two peaks of colonization during an annual growth cycle. Concentration of free amino acids and total soluble carbohydrates in the plant tissues followed a periodic pattern with two peaks similar to that of canker growth. Months were significantly different for canker size, free amino acids, and total soluble carbohydrates of the bark tissues. The extent of colonization was highest during May-June, after the first vegetative flush, and during November-December, after the second vegetative flush. Total free amino acids of the hark tissue was highly correlated with canker size (r = 0.89). Although the total soluble carbohydrate of the bark tissue was also elevated during the periods of canker development, it showed lower positive correlation (r = 0.45) with canker size. Plants were relatively resistant to colonization through March-April, during the first vegetative flush, and through August-September, during the second vegetative flush.
    [Show full text]
  • Tolerance Mechanism in Hybrid Citrus Rootstock Progenies Against Phytophthora Nicotianae Breda De Haan
    Indian Journal of Experimental Biology Vol. 59, March 2021, pp. 202-213 Tolerance mechanism in hybrid citrus rootstock progenies against Phytophthora nicotianae Breda de Haan Prashant Kalal1, RM Sharma1*, AK Dubey1, Deeba Kamil2, Lekshmy S3, Amrender Kumar4 & OP Awasthi1 Division of 1Fruits & Horticultural Technology; 2Plant Pathology; 3Plant Physiology; and 4AKM Unit, ICAR-Indian Agricultural Research Institute, New Delhi-110 012, India Received 27 August 2019; revised 20 November 2020 Phytophthora species is the major threat for world citrus industry in general, and for India, in particular due to commercial use of susceptible rootstocks. The resistant gene possessed by Poncirus genus may be of immense use, if transferred in a well acclimatized citrus species which can have good impact on fruit size of scion varieties. Being a soil borne problem, development of resistant/tolerant rootstock(s) is the most eco-friendly solution to combat with this deadly disease. The present study was conducted during 2016 to understand the tolerance mechanism in the intergeneric hybrids of citrus rootstocks against Phytophthora nicotianae. The materials of study consisted of 30 hybrids, ten each of Pummelo (P) × Troyer (T), Pummelo (P) × Sacaton (S) and Pummelo (P) × Trifoliate orange (TO) were tested against the inoculation of P. nicotianae, taking Pummelo, Troyer and Citrumelo as control treatments. Of the total hybrid progenies, only six hybrids (P × TO-103, P × TO- 112, P × S-117, P × S-119, P × T-125 and P × T-130) expressed resistance against P. nicotianae on the basis of lesion length (nil or <2.5 cm). Of the tested hybrids, P x S-117 had the highest photosynthetic rate (A) (8.12 µmol m-1s-1) followed by P × TO-112 and P × S-119.
    [Show full text]
  • Of Phytophthora for More Accurate Morphological-Molecular Identification: the Importance of Types and Authenticated Specimens
    Abstracts: 5 th IUFRO Phytophthoras in Forests and Natural Ecosystems Auckland and Rotorua, New Zealand, 7-12 March 2010 Refined systematics (taxonomy, nomenclature and phylogenetics) of Phytophthora for more accurate morphological-molecular identification: The importance of types and authenticated specimens. Z. Gloria Abad 1, and Michael C. Coffey 2 1 USDA-APHIS-PPQ-RIPPS-MOLECULAR DIAGNOSTICS LABORATORY,Beltsville, Maryland, USA, 20705 2 WORLD PHYTOPHTHORA GENETIC RESOURCE COLLECTION, Department of Plant Pathology and Microbiology, University of California, Riverside, California, USA, 92521 Phytophthora with 98 species, is an ecologically important genus that has been well-studied. Although considerable advances in molecular systematics have been made there is still confusion in recognizing new species and difficulty in identifying described species. This is due in part to the number of sequences in GenBank that are from misidentified cultures or that are poorly annotated. Species complexes for P. capsici , P. citricola , P. cryptogea , P. dreschleri , P. megasperma , and others have been named due to the difficulties to identify the sensu stricto or extype clusters. The position of the extypes suggests the presence of few to several distinct species in each complex. Establishing a database of sequences from accurately identified material is vital so that others can use that tool to make correct molecular identifications. Ex types define the species so sequences from those isolates should be the primary reference in the database. The World Phytophthora Genetic Resource Collection (WPC) is a valuable biological resource containing many ex types and has been extensively used in the Phytophthora Database (PD) which is a web-based source of genotypic and phenotypic data for the international community.
    [Show full text]
  • Abstracts of Presentations at the 1989 Annual Meeting of the American Phytopathological Society
    Abstracts of Presentations at the 1989 Annual Meeting of The American Phytopathological Society August 20-24, 1989 Richmond Marriott Hotel and Richmond Convention Centre Richmond, Virginia The number above an abstract corresponds to its designation in the program of the 1989 APS Annual Meeting in Richmond, VA, August 20-24. If a presentation was not given at the meeting, the abstract is not printed among the following pages. The index to authors begins on page 1224. 1 lated peanut leaf and disease proportions are generated for early leafspot, late leaf spot, both leafspots mixed or peanut INFLUENCE OF TILLAGE SYSTEMS ON THE INCIDENCE AND SPATIAL PAT- rust. Pre-testing, drill and practice, and post-testing sessions TERN OF TAN SPOT OF WHEAT. Wolgang Schuh, Department of Plant were conducted in a 1-hr time period for introductory plant Pathology, The Pennsylvania State University, University Park, pathology students. Twenty of 22 students significantly improved PA 16802. their ability to estimate disease proportions of late leaf spot (random lesion sizes) as measured by (i) a higher coefficient of The incidence and spatial pattern of Pyrenophora tritici- determination relating the actual proportion (X) to the esti- repentis was assessed at four locations (two conventional & two mated value (Y) and/or (ii) a regression coefficient (slope) conservation tillage) two times during 1987 and three times which was closer to 1.0 in post-tests compared to pre-tests. during 1988. Tan Spot was detected earlier in 1988 and had a higher final disease incidence in both years under conservation tillage. Spatial pattern analysis, using Morisita's index of 4 dispersion, revealed a shift from clumped to random distribu- EFFECTS OF MAIZE INTERCROPS ON ANGULAR LEAF SPOT OF BEANS.
    [Show full text]
  • Re-Evaluation of Phytophthora Citricola Isolates from Multiple Woody Hosts in Europe and North America Reveals a New Species, Phytophthora Plurivora Sp
    Persoonia 22, 2009: 95–110 www.persoonia.org RESEARCH ARTICLE doi:10.3767/003158509X442612 Re-evaluation of Phytophthora citricola isolates from multiple woody hosts in Europe and North America reveals a new species, Phytophthora plurivora sp. nov. T. Jung1,2, T.I. Burgess1 Key words Abstract During large-scale surveys for soilborne Phytophthora species in forests and semi-natural stands and nurseries in Europe during the last decade, homothallic Phytophthora isolates with paragynous antheridia, semi- beech papillate persistent sporangia and a growth optimum around 25 °C which did not form catenulate hyphal swellings, citricola were recovered from 39 host species in 16 families. Based on their morphological and physiological characters and decline the similarity of their ITS DNA sequences with P. citricola as designated on GenBank, these isolates were routinely dieback identified as P. citricola. In this study DNA sequence data from the internal transcribed spacer regions (ITS1 and forest ITS2) and 5.8S gene of the rRNA operon, the mitochondrial cox1 and -tubulin genes were used in combination with multivora β morphological and physiological characteristics to characterise these isolates and compare them to the ex-type and nursery the authentic type isolates of P. citricola, and two other taxa of the P. citricola complex, P. citricola I and the recently oak described P. multivora. Due to their unique combination of morphological, physiological and molecular characters phylogeny these semipapillate homothallic isolates are described here as a new species, P. plurivora sp. nov. Article info Received: 5 February 2009; Accepted: 26 March 2009; Published: 14 April 2009. INTRODUCTION dieback, respectively (Fig.
    [Show full text]
  • Major and Emerging Fungal Diseases of Citrus in the Mediterranean Region Mediterranean Region
    Provisional chapter Chapter 1 Major and Emerging Fungal Diseases of Citrus in the Major and Emerging Fungal Diseases of Citrus in the Mediterranean Region Mediterranean Region Khaled Khanchouch, Antonella Pane, Ali KhaledChriki and Khanchouch, Santa Olga Antonella Cacciola Pane, Ali Chriki and Santa Olga Cacciola Additional information is available at the end of the chapter Additional information is available at the end of the chapter http://dx.doi.org/10.5772/66943 Abstract This chapter deals with major endemic and emerging fungal diseases of citrus as well as with exotic fungal pathogens potentially harmful for citrus industry in the Mediterranean region, with particular emphasis on diseases reported in Italy and Maghreb countries. The aim is to provide an update of both the taxonomy of the causal agents and their ecology based on a molecular approach, as a preliminary step towards developing or upgrading integrated and sustainable disease management strategies. Potential or actual problems related to the intensification of new plantings, introduction of new citrus cul- tivars and substitution of sour orange with other rootstocks, globalization of commerce and climate changes are discussed. Fungal pathogens causing vascular, foliar, fruit, trunk and root diseases in commercial citrus orchards are reported, including Plenodomus tra- cheiphilus, Colletotrichum spp., Alternaria spp., Mycosphaerellaceae, Botryosphaeriaceae, Guignardia citricarpa and lignicolous basidiomycetes. Diseases caused by Phytophthora spp. (oomycetes) are also included as these pathogens have many biological, ecological and epidemiological features in common with the true fungi (eumycetes). Keywords: Plenodomus tracheiphilus, Colletotrichum spp., Alternaria spp., greasy spot, Mycosphaerellaceae, Botryosphaeriaceae, Guignardia citricarpa, Basidiomycetes, Phytophthora spp 1. Introduction Citrus are among the ten most important crops in terms of total fruit yield worldwide and rank first in international fruit trade in terms of value.
    [Show full text]
  • Diversity and Management of Phytophthora in Southeast Asia
    Diversity and Management of Phytophthora in Southeast Asia Editors: André Drenth and David I. Guest Australian Centre for International Agricultural Research Canberra 2004 Diversity and Management of Phytophthora in Southeast Asia Edited by André Drenth and David I. Guest ACIAR Monograph 114 (printed version published in 2004) The Australian Centre for International Agricultural Research (ACIAR) was established in June 1982 by an Act of the Australian Parliament. Its mandate is to help identify agricultural problems in developing countries and to commission collaborative research between Australian and developing country researchers in fields where Australia has a special research competence. Where trade names are used this constitutes neither endorsement of nor discrimination against any product by the Centre. ACIAR MONOGRAPH SERIES This peer-reviewed series contains the results of original research supported by ACIAR, or material deemed relevant to ACIAR’s research objectives. The series is distributed internationally, with an emphasis on developing countries. © Australian Centre for International Agricultural Research, GPO Box 1571, Canberra, ACT 2601, Australia Drenth, A. and Guest, D.I., ed. 2004. Diversity and management of Phytophthora in Southeast Asia. ACIAR Monograph No. 114, 238p. ISBN 1 86320 405 9 (print) 1 86320 406 7 (online) Technical editing, design and layout: Clarus Design, Canberra, Australia Printing: BPA Print Group Pty Ltd, Melbourne, Australia Diversity and Management of Phytophthora in Southeast Asia Edited by André Drenth and David I. Guest ACIAR Monograph 114 (printed version published in 2004) Foreword The genus Phytophthora is one of the most important plant pathogens worldwide, and many economically important crop species in Southeast Asia, such as rubber, cocoa, durian, jackfruit, papaya, taro, coconut, pepper, potato, plantation forestry, and citrus are susceptible.
    [Show full text]
  • Stress Physiology of Phytophthora-Canker Pathogens in Landscape Trees: Impacts, Mechanisms, and Mitigation Through Biochar Amendment
    Stress Physiology of Phytophthora-canker Pathogens in Landscape Trees: impacts, mechanisms, and mitigation through biochar amendment Drew Carson Zwart A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy University of Washington 2012 Reading Committee: Soo-Hyung Kim, Chair Robert Edmonds Kelby Fite Program Authorized to Offer Degree: School of Environmental and Forest Sciences i University of Washington Abstract Stress Physiology of Phytophthora-canker Pathogens in Landscape Trees: impacts, mechanisms, and mitigation through biochar amendment Drew Carson Zwart Chair of Supervisory Committee: Dr. Soo-Hyung Kim School of Environmental and Forest Sciences Soil-amendment with biochar is thought to confer multiple benefits to plants including induction of systemic resistance to plant pathogens. Pathogens in the genus Phytophthora cause damaging diseases of woody species throughout the world. The objectives of the experiments described in the following chapters were to determine 1) what are the physiological impacts of stem cankers caused by Phytophthora cactorum in Acer rubrum seedlings, 2) if biochar amendment induces resistance to canker causing Phytophthora pathogens and how this resistance is related to the amount of biochar amendment in two common landscape tree species: Quercus rubra (L.) and Acer rubrum (L.), and 3), how does biochar improve resistance against stem lesions. Inoculation of A. rubrum seedlings with P. cactorum resulted in a dramatic and sustained reduction in carbon assimilation rates and stomatal conductance, and a temporary reduction in photosynthetic efficiency compared to non-inoculated control plants. Foliar starch levels did not ii support the hypothesis that the reduction of photosynthesis was the result of reduced carbohydrate transport and subsequent feedback inhibition.
    [Show full text]
  • Phytophthora Nicotianae Breda De Haan Induced Stress Changes in Citrus Rootstock Genotypes
    Indian Journal of Experimental Biology Vol. 57, April 2019, pp. 248-258 Phytophthora nicotianae Breda de Haan induced stress changes in citrus rootstock genotypes Kuldeep Singh1, RM Sharma1*, AK Dubey1, Deeba Kamil2, Lekshmy S3, OP Awasthi1 & GK Jha4 Division of 1Fruits & Horticultural Technology; 2Plant Pathology; 3Plant Physiology; and 4Agricultural Economics, ICAR-Indian Agricultural Research Institute, New Delhi (India) Received 15 May 2017; revised 15 February 2018 Phytophthora spp. are the most serious threat to citrus industry worldwide. Being a soil borne problem, use of tolerant rootstocks is the most ecofriendly approach to manage the deadly diseases caused by this fungus. Here, we assessed the reaction of eight citrus rootstock genotypes including sour orange, Troyer citrange and six variants of C. jambhiri Lush. viz., RLC-5, RLC-6, RLC-7, Grambiri, rough lemon and Italian rough lemon against the inoculation of Phytophthora nicotianae. Inoculation of P. nicotianae infected the feeder roots of tested rootstocks to varying degree, expressing higher disease incidence (81.25%) and number of infected feeder roots (54.25-60.62%) depending on the rootstock. Troyer citrange and sour orange proved most tolerant rootstocks against the inoculated fungus. Phytophthora inoculation tended to increase - the levels of reactive oxygen species (H2O2 and O2 ), antioxidant enzymes (catalase, peroxidase, glutathione reductase, superoxide dismutase and β-1,3-glucanase) and protein content. However, it significantly reduced the levels of macro- (N, P, K Ca and Mg) and micro- (Cu and Zn) nutrients, although the extent of variation was rootstock specific. Overall, Troyer citrange and sour orange expressed the lowest variation in the levels of ROS, peroxidase (POX), superoxide dismutase (SOD) and β-1,3-glucanase, protein and nutrient contents, while rough lemon proved most strongly affected.
    [Show full text]
  • Citrus and Avocado Pests and Dieseases
    AvocadoAvocado ProblemProblem DiagnosisDiagnosis CommonCommon PestsPests andand DiseasesDiseases Gary S. Bender Farm Advisor U. C. Cooperative Extension Text from the UC California Master Gardener Handbook Pub. 3382 Pages 609-613 Supplemental text by Dr. Gary Bender Pictures from ipm.ucdavis.edu, Dr. Joe Morse and Dr. Mark Hoddle (UC Riverside), and Dr. Gary Bender (UC Cooperative Extension San Diego County) The Most Common Avocado Diseases • Avocado Root Rot (Phytophthora cinnamomi) • Avocado Trunk Canker (Phytophthora citricola) • Oak Root Fungus (Armillaria mellea) • Sun Blotch Viroid • Black Streak • Dothierella Canker Small pale green, wilted leaves. Sparse foliage. New growth absent. Small branches die back at the top of tree allowing other branches to become sunburned. Small fibrous feeder roots absent or, if present, blackened, brittle, dead • Diagnosis: Avocado root rot (Phytophthora cinnamomi) This is a fungus with more than 1000 hosts • Attacks small feeder roots. The most serious avocado disease in California. Fungus thrives in excess soil moisture (over-irrigation and poor drainage). • Attacks trees of any size or age. Absence of feeder roots prevents moisture uptake so the soil under diseased trees stays wet even though tree appears wilted. IPM treatment plan • Fungus can spread on contaminated nursery stock, water in contact with infested soil, shoes and cultivation equipment. Fungus can spread on anything that moves soil, including horses hooves, ladders and bins. • Use only clean nursery stock and replant with only resistant clonal rootstocks. The most effective rootstock currently is ‘Dusa’. Chemical Treatment • For mature trees that are diseased, the best treatment appears to be trunk injection with a registered fungicidal buffered phosphorous acid.
    [Show full text]