Risk assessment and resistant mechanism of Fusarium graminearum to fluopyram

Fusarium head blight (FHB), caused by the Fusarium graminearum species complex, poses a significant threat to global wheat production and human health due to its high virulence and the ability to produce harmful secondary metabolites. Although various fungicides have been extensively used to control FHB, there is a critical need for more comprehensive information on the resistance of F. graminearum to fluopyram in China. This study evaluated the sensitivity of F. graminearum strains collected from five distinct regions to fluopyram. The EC₅₀ values for fluopyram ranged from 1.20 to 6.42 μg/mL, with an average value of 3.30 μg/mL. Additionally, fluopyram-resistant mutants were generated in the laboratory by chemical taming, with a resistance frequency of 8.3 × 10-^-3. Furthermore, no significant differences were observed in conidiation, growth rate, and temperature sensitivity between the resistant mutants and the parental strains. It was also determined that fluopyram exhibits positive cross-resistance with pydiflumetofen but no cross-resistance with carbendazim, tebuconazole, and pyraclostrobin. The mutations associated with fluopyram resistance in F. graminearum were identified as SDHB-H248L, SDHC2-A83V, and SDHC2-R86K. Based on these findings, the risk of resistance development in F. graminearum to fluopyram was assessed as moderate. Additionally, it was found that the combination of prothioconazole and fluopyram is more effective than their individual use in field trials. Considering the role of fluopyram in inhibiting DON produced by F. graminearum, it is recommended that fluopyram be used in conjunction with other highly effective fungicides to control FHB, thereby achieving both disease control and mycotoxin reduction.