A Novel Point Mutation (L837F) in Osmosensor-like Histidine Kinase FgOs1 Drives Potent Fludioxonil Resistance in <i>Fusarium graminearum</i>

<i>Fusarium graminearum</i> is a preeminent fungal pathogen exacting a heavy toll on global crop production. Fludioxonil, a highly effective broad-spectrum fungicide, has been extensively deployed to mitigate the devastation wrought by <i>F. graminearum.</i> Nevertheless, the molecular mechanisms of fludioxonil resistance in this pathogen remain largely enigmatic. In this study, we identify a novel point mutation (L837F) in FgOs1 (osmosensor-like histidine kinase), which is located in the HIS_KIN (histidine kinase) domain. Biological assays revealed that the FgOs1^L837F mutation reduced the ability of <i>F</i>. <i>graminearum</i> to adapt to low-temperature stress, osmotic stress, and metal ion stress and also decreased its pathogenicity. Additionally, this mutation did not confer cross-resistance to the fungicides phenamacril, tebuconazole, and carbendazim. To facilitate field monitoring, we employed allele-specific PCR (AS-PCR) to detect FgOs1^L837F point mutation in <i>F</i>. <i>graminearum</i>. This study offers crucial support for fungal disease control and crop protection.