Phenotypic and genotypic characterization of single isolate-derived monoascospore strains of Sclerotinia sclerotiorum from common bean

White mold is a highly destructive disease caused by Sclerotinia sclerotiorum, a polyphagous fungus that infects several hosts including common bean grown that is widely cultivated in Brazil. The pathogenic populations are known to exhibit genetic variability but studies rarely used single ascospore-derived strains. In this study, 12 monoascospore strains originated from a same isolate (UFLA 54), but from different apothecia, were compared among them and with the mother strain with regards: days to first sclerotium formation, mycelial growth rate mycelial compatibility groups, microsatellite markers and mating type locus (MAT1–1 and MAT1–2). Their pathogenicity was assessed on three common bean lines. Cluster analysis of growth rates data separated UFLA 54 from all monoascospore strains, which shared same alleles in the microsatellite locus. Inversion of MAT1–1 region was found for both UFLA 54 and half of monoascospore strains. Aggressiveness of the monoascospore strains was not consistent across common bean lines. Our study reveals significant variability of S. sclerotiorum at the single isolate level.