A83V Mutation in FaSDHC2 Confers High Field Resistance to Pydiflumetofen and Exhibits Negative Cross-Resistance to Benzovindiflupyr in <i>Fusarium asiaticum</i>

Fusarium head blight (FHB), primarily caused by the <i>Fusarium graminearum</i> species complex (FGSC), reduces cereal yields and causes substantial economic losses globally. In China, <i>Fusarium asiaticum</i> is the predominant FGSC species, causing yield losses and deoxynivalenol contamination. Pydiflumetofen, a succinate dehydrogenase inhibitor, was widely used in China for FHB control. Among 5176 field isolates collected in 2023 from Hubei, Anhui, and Jiangsu provinces, five pydiflumetofen-resistant <i>F. asiaticum</i> isolates were identified. These isolates exhibited reduced sporulation and virulence. Site-directed mutagenesis confirmed that the FaSDHC2-A83V substitution conferred high resistance while impairing sporulation. No cross-resistance occurred with pyraclostrobin, phenamacril, or tebuconazole, but strong positive cross-resistance was observed with fluopyram and enpyracymid, and negative cross-resistance with benzovindiflupyr, a novel finding with potential implications for agricultural and clinical antifungal strategies. This study reports the first field-derived pydiflumetofen-resistant <i>F. asiaticum</i> mutants and identifies FaSDHC2-A83V as a key resistance marker, aiding monitoring and sustainable FHB management.