Detection and characterization of carbendazim resistance in Sclerotinia sclerotiorum isolates from oilseed rape in Anhui Province of China

Stem rot caused by Sclerotinia sclerotiorum is a devastating disease of oilseed rape (Brassica napus) in Anhui Province of China. The fungicide carbendazim (methyl benzimidazole-2-yl carbamate; MBC) has been used to control this fungal disease since the 1980s. In the present study, 74 isolates of S. sclerotiorum from 13 regions of Anhui were collected, and the sensitivities of these isolates to MBC were examined to monitor fungicide resistance. We found that 22 of the 74 isolates showed resistance to MBC, indicating that S. sclerotiorum has developed resistance in parts of Anhui Province. PCR assays and DNA sequence analysis showed that isolates with high MBC resistance had a point mutation at position 198 in the β-tubulin gene that caused a glutamic acid-to-alanine change in the protein. The β-tubulin gene in low-resistance isolates did not have the mutation. These results indicate that the mutation in β-tubulin gene may be associated with high MBC resistance in S. sclerotiorum. The present study also found no correlation between MBC resistance and pathogenicity of S. sclerotiorum isolates, suggesting that the pathogenicity of S. sclerotiorum isolates on oilseed rape did not vary with MBC resistance status.