Genetic and pathogenic variability among Sclerotinia sclerotiorum isolates of rapeseed-mustard

Sclerotinia sclerotiorum causing stem rot is emerging as a serious problem for cultivation of rapeseed-mustard with its appearance in larger proportions. For this study, a total of forty-eight isolates were collected from rapeseed-mustard growing felds of Punjab and adjoining states. Mycelial compatibility studies revealed that 10.4% pairings among isolates from nearby areas were compatible whereas incompatibility was among those from far away regions. Genetic variability studies using SSR primers divided the isolates into four major groups. Based on these, eight representative isolates from different groups were selected for further testing pathogenic variability; which was assessed on introgression lines of Brassica juncea, derived from hybridization with wild crucifers. Results revealed that isolate SsAm was most aggressive whereas SsMk was the least aggressive. Diferences observed in pathogenicity and other characters amongst the isolates advocate the role of pathogen population structure for better and Efficient screening of germplasm and identifying reliable sources of resistance.