Vegetative Compatibility Groups in Colletotrichum coccodes Subpopulations from Australia and Genetic Links with Subpopulations from Europe/Israel and North America

Vegetative compatibility of 94 isolates of Colletotrichum coccodes from Australia originating from potato, soil, and a weed (Solanum esuriale) was tested using nitrate-nonutilizing (nit) mutants. Isolates distributed to six vegetative compatibility groups (VCGs), five of them multimember (24.5, 23.4, 13.8, 12.8, and 7.5% distribution) and only one composed of two isolates (2.1%); 15.9% of them were not assigned to any of the VCGs. Aggressiveness of 51 isolates representing all six VCGs was tested by mature green tomato bioassay: isolates assigned to AUS-VCG-4 were the most aggressive and those in AUS-VCG-3 the least (P < 0.05). Isolates from warmer climates and lower latitudes were more aggressive (P < 0.05). In addition, we report for the first time complementations between isolates from Australia (AUS); North America (NA); and Israel, The Netherlands, Scotland, France, Germany (EU/I). Isolates assigned to AUS-VCG-4 anastomosed with isolates assigned to EU/I-VCG-7 and NA-VCG-5 (which also anastomosed with each other). Isolates assigned to EU/I-VCG-6 anastomosed with isolates assigned to NA-VCG-2 and isolates assigned to AUS-VCG-2 anastomosed with isolates assigned to EU/I-VCG-2. The linkage between subpopulations could result from the limited exchange of seed tubers among continents, or could be due to, for instance, gene flow, selection, or a limited number of polymorphic vegetative incompatibility genes.

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Vegetative Compatibility Groups in Colletotrichum coccodes, the Causal Agent of Black Dot on Potato

Phytopathology ◽

10.1094/phyto.2002.92.8.827 ◽

2002 ◽

Vol 92 (8) ◽

pp. 827-832 ◽

Cited By ~ 41

Author(s):

N. Nitzan ◽

M. Hazanovsky ◽

M. Tal ◽

L. Tsror(Lahkim)

Keyword(s):

Genetic Diversity ◽

The Netherlands ◽

Economic Importance ◽

Vegetative Compatibility ◽

Colletotrichum Coccodes ◽

Black Dot ◽

Vegetative Compatibility Groups ◽

Nit Mutants ◽

Pathogenicity Tests ◽

Self Compatibility

Black dot of potato, caused by Colletotrichum coccodes, is a disease of growing economic importance, but the degree of genetic diversity and pathogenic differentiation among isolates is unknown. Using nitrate auxotrophic (Nit) mutants, we characterized vegetative compatibility groups (VCG) diversity for C. coccodes for 110 isolates originating from Israel, The Netherlands, and France. We recovered frequencies of nit1 and NitM mutant classes at 38.5 and 7.2%, respectively, and selected 12 isolates as tester isolates. Using these testers, we defined four multimember VCGs at 7.3, 35.5, 20.0, and 10.0% frequency in this sample. Thirty isolates (27.3% of all tested isolates) could not be assigned to any of the major groups, and showed only self-compatibility. The frequency of recovery of Nit mutant sectors was highest in isolates from VCG4, with 50.9 and 13.6% recovery for nit1 and NitM, respectively. However, we did not detect differences in the frequency of mutant classes among the three countries of origin. In pathogenicity tests, isolates from VCG3 were the most aggressive to potato, as expressed by high stem colonization levels and sclerotia density on root and crown. These results suggest that there is significant VCG diversity in this species and that this VCG diversity may be correlated with pathogenic characteristics or specialization.

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Population biology of the chestnut blight fungus, Cryphonectria parasitica

Canadian Journal of Botany ◽

10.1139/b95-261 ◽

1995 ◽

Vol 73 (S1) ◽

pp. 311-319 ◽

Cited By ~ 50

Author(s):

Michael G. Milgroom

Keyword(s):

Gene Flow ◽

North America ◽

Population Biology ◽

Random Mating ◽

Cryphonectria Parasitica ◽

Vegetative Compatibility ◽

Chestnut Blight ◽

Vegetative Compatibility Groups ◽

Chestnut Blight Fungus ◽

Endothia Parasitica

Interest in the population biology of the chestnut blight fungus Cryphonectria parasitica has been motivated largely by the potential for biological control of chestnut blight with fungal viruses that cause hypovirulence. Earlier studies gave valuable insights into the correlation between diversity of vegetative compatibility groups and transmission of hypovirulence viruses. However, inferences about evolutionary processes affecting populations were not possible because vegetative compatibility groups are not genetically defined. Using restriction fragment length polymorphism markers, however, progress has been made in studying the origin of C. parasitica in North America, gene flow among populations, dispersal within populations, and recombination and the mating system. Cryphonectria parasitica populations in North America are genetically more similar to populations in Japan than in China, which is consistent with previous speculations that this fungus was introduced from Japan. Populations in China and Japan are quite different, suggesting little or no gene flow between these areas. Restricted gene flow and genetic drift are probably the dominant evolutionary forces shaping North American populations, with approximately 20% of gene diversity due to differences among populations (GST = 0.20). Two populations of C. parasitica in Michigan and one population in Italy are primarily clonal in structure. In contrast, sexual reproduction appears to be common in populations in eastern North America, although most of these populations deviate significantly from random mating. Deviations from random mating are most likely due to self-fertilization (uniparental inbreeding), restricted dispersal of male gametes, and mating between individuals that are more closely related genetically than would be expected by chance (biparental inbreeding). Aggregations of similar genotypes in space suggest that populations of C. parasitica may be structured into genetic neighborhoods by restricted dispersal. Future research efforts in this system will explore isolation by distance and address questions of hypovirulence virus coevolution with its fungal host. Key words: Cryphonectria parasitica, Endothia parasitica, chestnut blight, genetic neighbourhoods, inbreeding.

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Reassessment of Vegetative Compatibility of Sclerotinia homoeocarpa Using Nitrate-Nonutilizing Mutants

Phytopathology ◽

10.1094/phyto-98-1-0108 ◽

2008 ◽

Vol 98 (1) ◽

pp. 108-114 ◽

Cited By ~ 16

Author(s):

Y.-K. Jo ◽

S. W. Chang ◽

J. Rees ◽

G. Jung

Keyword(s):

Minimal Medium ◽

The United States ◽

Vegetative Compatibility ◽

Complete Medium ◽

Sclerotinia Homoeocarpa ◽

Hyphal Fusion ◽

Vegetative Compatibility Groups ◽

Nit Mutants ◽

Mutant Phenotypes ◽

First Time

Nitrate-nonutilizing (nit) mutants were recovered for the first time from 21 isolates of Sclerotinia homoeocarpa collected in the United States. Mutants were selected from shredded mycelium of each isolate when cultured on water agar medium amended with 4% (wt/vol) potassium chlorate. The mutants could be classified into three phenotypes: nit1, nit3, and NitM, based on their growth on minimal medium (Czapek solution agar) supplemented with NaNO2 or hypoxanthine. Complementary heterokaryons were observed in pairings between different phenotypes of nit mutants derived from compatible isolates, but not in self-fusions or pairings between incompatible isolates. The vigor of prototrophic growth varied with isolates and mutant phenotypes. Strong and continuous heterokaryons, as well as weak and spontaneous ones, formed depending on pairings of nit mutants. Stable heterokaryons between compatible isolates, but apoptotic reactions between incompatible isolates, were observed immediately after hyphal fusion under the epifluorescence microscope. The 21 isolates used in this study, which were previously assigned into 11 different vegetative compatibility groups (VCGs) based on the formation of a barrage zone at the contact site of paired isolates on complete medium (potato dextrose agar), were regrouped into five VCGs based on heterokaryon formation between nit mutants on minimal medium.

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Vegetative Compatibility Groups and Parasexual Segregation in Colletotrichum acutatum Isolates Infecting Different Hosts

Phytopathology ◽

10.1094/phyto-12-10-0327 ◽

2011 ◽

Vol 101 (8) ◽

pp. 923-928 ◽

Cited By ~ 11

Author(s):

Claudinéia Conationi da Silva Franco ◽

Juliane Rocha de Sant' Anna ◽

Lúcia Jacovozzi Rosada ◽

Edilson Nobuyoshi Kaneshima ◽

José Renato Stangarlin ◽

...

Keyword(s):

Genetic Variability ◽

Vegetative Compatibility ◽

Colletotrichum Acutatum ◽

Diploid Strain ◽

Alternative Source ◽

Parasexual Cycle ◽

Wild Isolate ◽

Vegetative Compatibility Groups ◽

Nit Mutants ◽

First Time

Heterokaryosis is an important mechanism which provides genetic variability increase in filamentous fungi. In order to assess the diversity of vegetative compatibility reactions existing among Colletotrichum acutatum isolates derived from different hosts, complementary nit mutants of each isolate were obtained and paired in all possible combinations. Vegetative compatibility groups (VCG) were identified among the isolates according to their ability to form viable heterokaryons. Seven VCGs were identified among the isolates, one of which contained isolates from different hosts. VCGs 2 and 6 contained two and three members, respectively; VCG-3 contained four members, and four VCGs (1, 4, 5, and 7) contained a single one. This study shows, for the first time, the isolation and the parasexual segregation of a heterozygous diploid sector derived from the heterokaryon formed with nit mutants from VCG-6. Diploid, named DE-3, showed nit+ phenotype and growth rate similar to the parental wild isolate. When inoculated in the presence of the haploidizing agent benomyl, the diploid strain produced parasexual haploid segregants exhibiting the nit phenotypes of the crossed mutants. Since viable heterokaryons and diploid may be formed among vegetative compatible isolates of C. acutatum, this study suggests that the parasexual cycle may be an alternative source of genetic variability in C. acutatum isolates.

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Additional Vegetative Compatibility Groups in Colletotrichum coccodes Subpopulations from Europe and Israel

Plant Disease ◽

10.1094/pdis-91-7-0805 ◽

2007 ◽

Vol 91 (7) ◽

pp. 805-808 ◽

Cited By ~ 12

Author(s):

S. Shcolnick ◽

A. Dinoor ◽

L. Tsror (Lahkim)

Keyword(s):

The Netherlands ◽

Vegetative Compatibility ◽

Northern Europe ◽

Colletotrichum Coccodes ◽

Tuber Quality ◽

Potato Tubers ◽

Black Dot ◽

Damage Potential ◽

Vegetative Compatibility Groups ◽

Accurate Evaluation

Potato black dot, caused by Colletotrichum coccodes, damages tuber quality and may reduce yield. In previous work, four multimember vegetative compatibility groups (VCGs) have been reported. The objectives of the current study were to characterize a population of C. coccodes comprised of isolates from Israel and Northern Europe (EU/I) using VCG, and to assess the correlation between VCGs and aggressiveness of isolates on potato. A composite of 176 isolates was collected from symptomatic tissues of potato tubers or stems. A total of 6 (3.4%) isolates were characterized in VCG1; 29 (16.5%), 32 (18.2%), and 7 (4.0%) in VCG 2, 3, and 4, respectively; and 7 (4.0%), 9 (5.1%), 48 (27.3%), and 15 (8.5%) in the newly defined VCG 5, 6, 7, and 8, respectively. Twenty-three isolates (13%) were not assigned to any of the VCGs. Two of the VCGs had a specific geographical distribution: the 9 isolates assigned to VCG6 originated from The Netherlands, and 34 of 38 isolates assigned to VCG7 were from Scotland. Aggressiveness of isolates of a given VCG was examined on potato. VCGs 5 and 6 were comprised of the most aggressive isolates, and VCG1 of the least aggressive. These results could facilitate a more accurate evaluation of damage potential that may be caused by this pathogen.

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Vegetative Compatibility Groups and Aggressiveness of North American Isolates of Colletotrichum coccodes, the Causal Agent of Potato Black Dot

Plant Disease ◽

10.1094/pd-90-1287 ◽

2006 ◽

Vol 90 (10) ◽

pp. 1287-1292 ◽

Cited By ~ 25

Author(s):

N. Nitzan ◽

L. Tsror (Lahkim) ◽

D. A. Johnson

Keyword(s):

North American ◽

Average Frequency ◽

Vegetative Compatibility ◽

Colletotrichum Coccodes ◽

North American Population ◽

Black Dot ◽

Vegetative Compatibility Groups ◽

The North ◽

Nit Mutants ◽

Compatibility Group

The vegetative compatibility of 123 isolates of Colletotrichum coccodes from North America (United States and Canada) originating from potato, tomato, pepper, and mint was tested using nitrate-nonutilizing (nit) mutants. The North American isolates did not anastomose with previously selected European/Israeli vegetative compatibility group (VCG) testers; therefore, eight isolates were selected as VCG testers for the North American population. The 123 isolates distributed to seven VCGs at 1.6, 1.6, 4.0, 8.1, 13.8, 19.5, and 36.6%, with 14.6% of the isolates not assigned to any of the seven VCGs. Among the North American (NA)-VCGs, the average frequency of the nit1/nit3 nit mutants was lower (P < 0.05) for isolates belonging to NA-VCG1 than for isolates belonging to the NA-VCGs 2, 3, and 5. In contrast, the frequency of NitM nit mutants did not vary (P > 0.05) among the NA-VCGs and was collectively 5.14%. The results also indicated significant (P < 0.05) differences among NA-VCGs and European/Israeli (EU/I)-VCGs regarding the frequency of nit mutants. The aggressiveness trials of the North American isolates to potato indicated that plants infected with isolates belonging to NA-VCG2 and NA-VCG5 had more (P < 0.05) sclerotia on the roots and crowns than plants infected with isolates belonging to NA-VCGs 1 and 3. The plants infected with isolates belonging to NA-VCG2 had sclerotia formed higher (P < 0.05) up the stem than the plants infected with isolates belonging to NA-VCGs 1, 3, or 5. The plants infected with isolates assigned to NA-VCG2 had more (P < 0.05) infected progeny tubers than the plants infected with isolates belonging to NA-VCGs 1, 3, or 5; and the plants infected with isolates belonging to NA-VCGs 1, 2, and 5 yielded fewer (P < 0.05) potato tubers than the noninoculated control plants. A naming system for the population of C. coccodes based on the continent source of the population, the VCG number, and the isolate's code was suggested.

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Genetics of Gibberella fujikuroi. VIII. Vegetative compatibility groups

Canadian Journal of Botany ◽

10.1139/b86-019 ◽

1986 ◽

Vol 64 (1) ◽

pp. 117-121 ◽

Cited By ~ 13

Author(s):

Gurmel S. Sidhu

Keyword(s):

Fusarium Moniliforme ◽

Vegetative Compatibility ◽

Gibberella Fujikuroi ◽

Vegetative Incompatibility ◽

Vegetative Compatibility Groups ◽

Pathogenicity Genes ◽

Mating Group ◽

Nit Mutants ◽

Independent Segregation ◽

Group A

Gibberella fujikuroi (anamorph Fusarium moniliforme) mating group A isolates from corn and sorghum were categorized into different vegetative compatibility groups, using nit mutants (mutants unable to reduce nitrate or chlorate) to observe heterokaryosis among the compatible isolates. Vegetative incompatibility seems to be widespread in nature in this fungus and is controlled by nuclear genes called het or vic genes. A total of nine het genes were estimated for G. fujikuroi mating group A. Based on the independent segregation of nine het genes, 512 vegetative compatibility groups may be present in nature. However, only 13 vegetative compatibility groups were identified among conidial isolates recovered from Nebraska. The frequency of individual vegetative compatibility groups in a disease complex may be useful for monitoring pathogenicity genes in this fungus.

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Genetic Variability of Cercospora coffeicola from Organic and Conventional Coffee Plantings, Characterized by Vegetative Compatibility

Phytopathology ◽

10.1094/phyto-98-11-1205 ◽

2008 ◽

Vol 98 (11) ◽

pp. 1205-1211 ◽

Cited By ~ 6

Author(s):

R. B. Martins ◽

L. A. Maffia ◽

E. S. G. Mizubuti

Keyword(s):

Genetic Variability ◽

Production Systems ◽

Diversity Index ◽

Vegetative Compatibility ◽

Cercospora Leaf Spot ◽

Vegetative Compatibility Groups ◽

Nit Mutants ◽

Geographical Regions ◽

Minas Gerais State ◽

Cercospora Coffeicola

Cercospora leaf spot is a destructive fungal disease that has become a threat to the coffee industry in Brazil. Nevertheless, little is known about populations of its causal agent, Cercospora coffeicola. We evaluated the potential of using nitrogen-nonutilizing (nit) mutants and vegetative compatibility groups (VCGs) to characterize the genetic variability of the C. coffeicola population associated with coffee plantings in Minas Gerais state (MG), Brazil. A total of 90 monosporic isolates were obtained from samples collected according to a hierarchical sampling scheme: (i) state geographical regions (Sul, Mata, and Triângulo), and (ii) production systems (conventional and organic). Nit mutants were obtained and 28 VCGs were identified. The 10 largest VCGs included 72.31% of all isolates, whereas each of the remaining 18 VCGs included 1.54% of the isolates. Isolates of the largest VCGs were found in the three regions sampled. Based on the frequencies of VCGs at each sampled level, we estimated the Shannon diversity index, as well as its richness and evenness components. Genetic variability was high at all hierarchical levels, and a high number of VCGs was found in populations of C. coffeicola associated with both conventional and organic coffee plantings.

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Genetic Variability in the Potato Pathogen Colletotrichum coccodes as Determined by Amplified Fragment Length Polymorphism and Vegetative Compatibility Group Analyses

Phytopathology ◽

10.1094/phyto-96-1097 ◽

2006 ◽

Vol 96 (10) ◽

pp. 1097-1107 ◽

Cited By ~ 17

Author(s):

Larry J. Heilmann ◽

Nadav Nitzan ◽

Dennis A. Johnson ◽

Julie S. Pasche ◽

Curt Doetkott ◽

...

Keyword(s):

Length Polymorphism ◽

Fragment Length ◽

Fragment Length Polymorphism ◽

Amplified Fragment Length Polymorphism ◽

Vegetative Compatibility ◽

Colletotrichum Coccodes ◽

Aflp Analysis ◽

Aflp Data ◽

Bootstrap Analysis ◽

Nit Mutants

Amplified fragment length polymorphism (AFLP) using three primer sets was used to characterize 211 Colletotrichum coccodes isolates from North America, 112 of which were assigned to six vegetative compatibility groups (VCGs) using nitrate nonutilizing (nit) mutants. These isolates clustered into five corresponding groups by unweighted pairgroup method with arithmetic means-based cluster analysis of AFLP banding patterns. Isolates of C. coccodes belonging to NA-VCG1 and NA-VCG3 were closely related, as were isolates belonging to NA-VCG2 and NA-VCG5. Based on bootstrap analysis of AFLP data, the two isolates originally assigned to NA-VCG4 clustered with isolates belonging to NA-VCG2 and NA-VCG5. C. coccodes isolates that clustered with two isolates belonging to NA-VCG6 were the most diverged from other groups, including seven isolates collected from hosts other than potato. As opposed to the bootstrap analysis, a quadratic discriminant analysis (QDA) of AFLP data correctly categorized the two isolates of NA-VCG4. Furthermore, in isolates where VCG determinations had been made, this model correctly classified isolates of all VCGs. QDA classifications were identical to those made by the bootstrap analysis, with the exception of VCG4. Overall, classifications made by the QDA model were strongly correlated (r = 0.970, P < 0.001) to the VCGs assigned by traditional methods. All 99 C. coccodes isolates evaluated only by AFLP also were subjected to QDA, leading to the assignment of a presumptive VCG for each isolate. No isolates of VCG4 or VCG6 were identified by QDA within this population. Symptoms of black dot developed in plants inoculated with isolates collected from both potato and non-potato hosts. However, total yield was not significantly reduced by infection with non-potato isolates. The lack of any additional groups identified by AFLP analysis may be an indicator of a limited level of genetic variation among North American C. coccodes isolates. AFLP is a much more efficient technique for subspecific characterization in C. coccodes than VCG analysis utilizing nit mutants and will provide an effective means by which the population biology of this pathogen can be further investigated worldwide.

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