Resistance to the SDHI Fungicide Pydiflumetofen in Fusarium solani: Risk Assessment and Resistance-Related Point Mutation in FsSdhC Gene

Peanut root rot (PRR) is a prevalent and destructive plant disease attributed to Fusarium solani. Pydiflumetofen (Pyd) is a succinate dehydrogenase inhibitor (SDHI) with antifungal activity against F. solani, yet its resistance mechanism has been inadequately explored. In this study, the EC₅₀ values for Pyd against 93 F. solani strains ranged from 0.0095 to 0.3815 μg/mL, with all strains displaying a minimal inhibitory concentration (MIC) of ≤1 μg/mL. Four Pyd-resistant (PR) mutants were obtained, exhibiting stable resistance levels and comparable fitness to their parental strains in terms of mycelia growth, hyphal tip morphology, asexual reproduction, and virulence assessment. Five-point mutations, including FsSdhC1^A82V, FsSdhC2^L76M, FsSdhC2^L135V, FsSdhC2^F137L, and FsSdhC2^F147L, were identified in the PR mutants. However, molecular docking analysis indicated that only FsSdhC1^A82V and FsSdhC2^L135V could influence the sensitivity of F. solani to Pyd. These findings help evaluate F. solani's resistance to Pyd and guide future PRR management with this fungicide.