Abstract
Sclerotinia sclerotiorum populations from tropical agricultural zones have been suggested to be more variable compared to those from temperate zones. However, no data were available comparing populations from both zones using the same set of markers. In this study, we compared S. sclerotiorum populations from the United States of America (USA, temperate) and southeast Brazil (tropical) using the frequency of mycelial compatibility groups (MCGs) and 13 microsatellite (SSR) markers. Populations were sourced from diseased plants within leguminous crops in New York, USA (NY; n = 78 isolates), and Minas Gerais State, Brazil (MG; n = 109). Twenty MCGs were identified in NY and 14 were previously reported in MG. The effective number of genotypes based on Hill’s number of order 0, which corresponded to the number of multilocus genotypes (MLGs) were 22 (95% CI = 15.6–28.4) and 24 (95% CI = 18.9–29.1) in NY and MG, respectively. Clonal fractions of MLGs were 71.8% (NY) and 78.0% (MG). The effective number of genotypes based on Hill’s number of orders 1 and 2 in NY were 8.9 (95% CI = 5.2–12.6) and 4.4 (95% CI = 2.6–6.1), respectively. For MG these indices were 11.4 (95% CI = 8.7–14.1) and 7.1 (95% CI = 5.1–9.0), respectively. There were no significant differences of allelic richness, private allelic richness, gene diversity, effective number of alleles and genotype evenness between the NY and MG populations. The populations were differentiated, with 29% of total variance attributed to differences between them and G''ST and Jost’s D indices higher than 0.50. Cluster analysis revealed dissimilarity higher than 80% among most MLGs from both populations. Different alleles segregated in the populations but both had similar levels of genotypic variability.
Highlights
Sclerotinia sclerotiorum is amongst the most devastating and recalcitrant plant pathogens that infect a broad range of hosts and may lead to substantial crop losses [1,2,3]
Using the same set of markers and proper analytical tools for comparisons, the objective of this study was to compare the diversity of two populations of S. sclerotiorum: one from a temperate zone in the United States of America (USA) and another from a tropical zone in Brazil using SSR markers and frequency of mycelial compatibility groups (MCGs) data
The clonal fraction in MG (87.2%) was higher than in the NY population (74.4%). This finding is consistent with earlier estimates of MCG diversity in S. sclerotiorum populations
Summary
Sclerotinia sclerotiorum is amongst the most devastating and recalcitrant plant pathogens that infect a broad range of hosts and may lead to substantial crop losses [1,2,3]. Most of the RFLP-based studies depicted a clonal genetic structure in North American populations from Canada [5,6,7,8] or from North Carolina [9] and Washington State [10] in the United States of America (USA). These findings are consistent with the homothallic nature of the pathogen that reproduces predominantly by self-fertilization or by production of somatic resting structures called sclerotia [11]. The use of different sets of genetic markers in the published studies masks reliable comparisons
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