Sclerotinia sclerotiorum (Lib.) de Bary is a necrotrophic fungal pathogen with a broad host range and a worldwide distribution.Boscalid belongs to the class of succinate dehydrogenase inhibitors (SDHIs) and exhibits a broad-spectrum antifungal activity on various crops.Numerous studies have indicated that mutations in highly conserved amino acid residues located in succinate dehydrogenase (SDH) complex are responsible for SDHI resistance in various fungi and bacteria.In S.sclerotiorum, boscalid resistance has been detected in one field isolate with a mutation H134R in SDHD gene.In this study, however, a new point mutation A11V (GCA to GTA) in SDHB gene has been detected in S.sclerotiorum boscalid resistant (BR) isolates.To confirm whether the mutation in SDHB confers resistance to boscalid, SDHB gene in the sensitive isolate was replaced by that from the BR mutants.Gene replacement mutant exhibited significant resistance to boscalid.Interestingly, the BR mutants lacked the ability to produce sclerotia.These results indicated that the mutation A11V in SDHB gene conferred resistance of S.sclerotiorum to boscalid and indirectly regulated sclerotial development