Genetic diversity and pathogenicity differentiation of Sclerotinia sclerotiorum on rapeseed (Brassica napus L.) in Anhui Province, China

The pathogenicity of 47 isolates of Sclerotinia sclerotiorum from oilseed rape (Brassica napus L.) in Anhui, China, was tested by detached leaf inoculation using the susceptible rape cultivar Wanyou-14. All isolates were pathogenic to the cultivar and could be grouped into 3 categories based on the lesion length on the leaves tested: weak pathogenicity type, intermediate pathogenicity type, and strong pathogenicity type. This suggested that there was differentiation in the pathogenicity among the strains tested of S. sclerotiorum. Additionally, the intraspecific DNA polymorphisms among 47 strains of S. sclerotiorum were investigated by screening 40 pairs of inter-simple sequence repeat (ISSR) primers. Unweighted pair-group method with arithmetic average cluster analysis of these ISSR data distinguished all strains from each other and revealed considerable genetic variability among them. These strains were classified into 7 clusters according to their branching in the dendrogram, and partial correlation was observed between the genetic polymorphisms and the pathogenicity of S. sclerotiorum strains.