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

Peanut root rot (PRR) is a prevalent and destructive plant disease attributed to <i>Fusarium solani</i>. Pydiflumetofen (Pyd) is a succinate dehydrogenase inhibitor (SDHI) with antifungal activity against <i>F. solani</i>, yet its resistance mechanism has been inadequately explored. In this study, the EC₅₀ values for Pyd against 93 <i>F. solani</i> 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 <i>FsSdhC1</i>^A82V, <i>FsSdhC2</i>^L76M, <i>FsSdhC2</i>^L135V, <i>FsSdhC2</i>^F137L, and <i>FsSdhC2</i>^F147L, were identified in the PR mutants. However, molecular docking analysis indicated that only <i>FsSdhC1</i>^A82V and <i>FsSdhC2</i>^L135V could influence the sensitivity of <i>F. solani</i> to Pyd. These findings help evaluate <i>F. solani</i>'s resistance to Pyd and guide future PRR management with this fungicide.