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 Fusarium graminearum species complex (FGSC), reduces cereal yields and causes substantial economic losses globally. In China, Fusarium asiaticum 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 F. asiaticum 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 F. asiaticum mutants and identifies FaSDHC2-A83V as a key resistance marker, aiding monitoring and sustainable FHB management.