The Identification of a Limited Number of Vegetative Compatibility Groups within Isolates of Sclerotinia homoeocarpa Infecting Poa spp. and Agrostis palustris from Temperate Climates

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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Genetic Analysis of Fungicide-Resistant Sclerotinia homoeocarpa Isolates from Tennessee and Northern Mississippi

Plant Disease ◽

10.1094/pdis-92-1-0083 ◽

2008 ◽

Vol 92 (1) ◽

pp. 83-90 ◽

Cited By ~ 11

Author(s):

R. E. DeVries ◽

R. N. Trigiano ◽

M. T. Windham ◽

A. S. Windham ◽

J. C. Sorochan ◽

...

Keyword(s):

Fungicide Resistance ◽

Molecular Data ◽

Vegetative Compatibility ◽

Internal Transcribed Spacers ◽

Sclerotinia Homoeocarpa ◽

Vegetative Compatibility Group ◽

Arithmetic Means ◽

Putting Greens ◽

Vegetative Compatibility Groups ◽

Compatibility Group

Sclerotinia homoeocarpa is the causal agent of dollar spot disease that reduces the uniformity and aesthetic value of golf putting greens. Fungicide-resistant isolates of S. homoeocarpa were collected from putting greens at 10 locations across Tennessee and northern Mississippi. Genetic diversity among the 60 isolates was investigated using vegetative compatibility, conserved gene sequences, and amplified fragment length polymorphism (AFLP). Six tester strains were paired with Tennessee and northern Mississippi isolates on potato dextrose agar. Some of the 60 isolates were delineated into vegetative compatibility groups, but fungicide resistance could not be associated with a particular vegetative compatibility group. Genetic similarities of isolates at the vegetative compatibility level could be attributed to founder effects. Sequencing the regions of CAD, EF1-α, β-tubulin, and internal transcribed spacers revealed 100% homology among isolates. Capillary gel electrophoresis and analysis of AFLP fragments indicated 86 to 100% similarity between the isolates. Vegetative compatibility and molecular data indicate that the populations of the pathogen are clonal. Isolates did not cluster according to fungicide resistance during unweighted pair group with arithmetic means analysis, but did appear to cluster according to vegetative compatibility group and location. Although associations could not be made between molecular markers and fungicide resistance, links between vegetative compatibility and AFLP markers may provide a foundation from which other studies could be performed.

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Vegetative Compatibility and Seasonal Variation Among Isolates of Sclerotinia homoeocarpa

Plant Disease ◽

10.1094/pdis.2001.85.4.377 ◽

2001 ◽

Vol 85 (4) ◽

pp. 377-381 ◽

Cited By ~ 21

Author(s):

J. F. Powell ◽

J. M. Vargas

Keyword(s):

United States ◽

Seasonal Variation ◽

Single Species ◽

Vegetative Compatibility ◽

Sclerotinia Homoeocarpa ◽

Dollar Spot ◽

Vegetative Compatibility Groups ◽

Seasonal Epidemics ◽

Northern United States ◽

Multiple Species

Dollar spot of amenity turf, caused by Sclerotinia homoeocarpa, occurs in two seasonal epidemics in the northern United States, one from May to late July and a second from mid-August through October. It is not known whether these seasonal epidemics are the result of multiple species or due to seasonal variation within a single species. Isolates of S. homoeocarpa were collected from dollar spot lesions obtained from golf courses in Michigan, Illinois, and Wisconsin. Vegetative compatibility reactions between isolates identified six vegetative compatibility groups (VCGs) among more than 1,300 isolates collected from the eight locations. Most VCGs were present throughout the season, but one was generally recovered only in the late epidemic. Sequences of the nuclear ribosomal internal transcribed spacer 1 (ITS1) were identical among VCGs, indicating that the VCGs represent a single species. The results of this study suggest that the seasonal dollar spot epidemics observed in the northern United States are caused by a single species.

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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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Vegetative Compatibility Groups of Fusarium oxysporum f. sp. lactucae from Lettuce

Plant Disease ◽

10.1094/pd-89-0237 ◽

2005 ◽

Vol 89 (3) ◽

pp. 237-240 ◽

Cited By ~ 23

Author(s):

Matias Pasquali ◽

Flavia Dematheis ◽

Giovanna Gilardi ◽

Maria Lodovica Gullino ◽

Angelo Garibaldi

Keyword(s):

Fusarium Oxysporum ◽

Genetic Relatedness ◽

The United States ◽

Vegetative Compatibility ◽

Vegetative Compatibility Group ◽

Vegetative Compatibility Groups ◽

Compatibility Group ◽

Race 1

Fusarium oxysporum f. sp. lactucae, the causal agent of Fusarium wilt of lettuce, has been reported in three continents in the last 10 years. Forty-seven isolates obtained from infected plants and seed in Italy, the United States, Japan, and Taiwan were evaluated for pathogenicity and vegetative compatibility. Chlorate-resistant, nitrate-nonutilizing mutants were used to determine genetic relatedness among isolates from different locations. Using the vegetative compatibility group (VCG) approach, all Italian and American isolates, type 2 Taiwanese isolates, and a Japanese race 1 were assigned to the major VCG 0300. Taiwanese isolates type 1 were assigned to VCG 0301. The hypothesis that propagules of Fusarium oxysporum f. sp. lactucae that caused epidemics on lettuce in 2001-02 in Italian fields might have spread via import and use of contaminated seeds is discussed.

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