A Novel Point Mutation M460I in Histidine Kinase FgOs1\nConfers High Resistance to Fludioxonil in Fusarium\ngraminearum

Fusarium\nhead blight (FHB), caused by Fusarium graminearum, severely impacts global wheat production, reducing both the yield\nand quality. In China, fludioxonil, a phenylpyrrole fungicide, is\nused for managing FHB. This study assessed fludioxonil activity against\n120 F. graminearum strains collected\nfrom Hubei, Zhejiang, and Jiangsu in 2024, revealing an average EC<sub>50</sub> value of 0.0273 ± 0.0062 μg/mL. We obtained two\nresistant mutants through chemical taming and discovered a novel point\nmutation of FgOs1-M460I. Site-directed mutagenesis confirmed that\nthe FgOs1-M460I mutation greatly reduced fludioxonil sensitivity,\nwith an EC<sub>50</sub> value greater than 100 μg/mL. These\nmutants also displayed reduced sexual and asexual reproduction and\nlower virulence and accumulated less glycerol under fludioxonil and\nosmotic stress compared to sensitive strain. The resistant mutants\nshowed no cross-resistance with carbendazim, tebuconazole, phenamacril,\npyraclostrobin, or pydiflumetofen. Thus, we conclude that the FgOs1-M460I\nsubstitution regulates fludioxonil resistance and plays a role in\nasexual reproduction, sexual reproduction, and pathogenicity.