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 FsSdhC1A82V, FsSdhC2L76M, FsSdhC2L135V, FsSdhC2F137L, and FsSdhC2F147L, were identified in the PR mutants. However, molecular docking analysis indicated that only FsSdhC1A82V and FsSdhC2L135V 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.