Pharmacological characteristics of the novel fungicide pyrisoxazole against Sclerotinia sclerotiorum.

Pyrisoxazole is a pyridine compound of demethylation inhibitor fungicides. In this study, baseline sensitivity of Sclerotinia sclerotiorum to pyrisoxazole was determined using 166 strains from the oilseed rape fields in 2014, 2015 and 2016. The EC50 values for mycelial growth inhibition ranged from 0.0214 to 0.5443 μg mL-1, with a mean EC50 value of 0.2329 ± 0.1048 μg mL-1 and were normally distributed. The EC50 values had no significant difference among three populations from 2014, 2015, and 2016. There was no correlation with sensitivity between pyrisoxazole and carbendazim or iprodione. After treated with pyrisoxazole, we observed increased cell membrane permeability, and decreased exopolysaccharide and oxalic acid production, which can contribute to reduced virulence of S. sclerotiorum and lead to failure of disease infection. Protective and curative activity tests showed that pyrisoxazole exhibited excellent protective and curative activity against S. sclerotiorum in oilseed rape, and protective activity was better than curative activity. Compared with the currently used fungicides, pyrisoxazole not only exhibited excellent control efficacy on Sclerotinia stem rot, but also dramatically reduced the doses of fungicides in the field trials. Overall, these data provide more references for revealing pharmacological effect of pyrisoxazole against S. sclerotiorum and managing Sclerotinia stem rot on oilseed rape caused by benzimidazole- and dicarboximide-resistant populations.