Resistance detection of Fusarium graminearum species complex to pydiflumetofen in Anhui Province and biological characteristics of resistant populations

In order to document the resistance of Fusarium graminearum species complex (FGSC), which causes Fusarium head blight (FHB) of wheat, to the fungicide pydiflumetofen, a total of 6900 FGSC isolates were collected from 10 cities of Anhui Province in 2024 and used for the resistance detection by using 5 μg/mL pydiflumetofen as the discriminative dosage. The mutant genotypes, toxigenic chemotypes, fitness and cross-resistance of the sensitive and resistant populations to other commonly used fungicides such as fluopyram, carbendazim, tebuconazole and phenamacril were determined. The results indicated that the resistance frequency was 0.43%, and all resistant isolates possessed an A83V mutation in the succinate dehydrogenase C₁ subunit (SdhC₁). The toxigenic chemotypes of field resistant isolates were all NIV type. The pathogenicity of sensitive isolates seemed to be stronger than that of resistant isolates, while there was little difference between the two populations in hyphal growth rate and conidial production. There was positive cross-resistance between pydiflumetofen and fluopyram, but no cross-resistance between pydiflumetofen and other fungicides, such as carbendazim, tebuconazole or phenamacril. The study suggested that resistance of FGSC to pydiflumetofen has emerged in some major wheat-producing areas of Anhui Province. It could be speculated that long-term exclusive use of pydiflumetofen for FHB control may pose a high risk of resistance development, and the results of this study may provide guidance on the management of pydiflumetofen resistance and its appropriate use.