LAUSR

Fusarium crown rot (FCR) caused by Fusarium pseudograminearum is one of the most important diseases impacting wheat production in the Huanghuai region, the most important wheat-growing region of China. The current study found that the SDHI fungicide pydiflumetofen, which was recently developed by Syngenta Crop Protection, provided effective control of 67 wild-type F. pseudograminearum isolates in artificial culture (PDA), with an average EC50 value of 0.060 ± 0.0098 μg/mL (SE). Further investigation revealed that the risk of fungicide resistance in pydiflumetofen was not especially high. Four F. pseudograminearum mutants generated by repeated exposure to pydiflumetofen under the laboratory conditions indicated that pydiflumetofen resistance was associated with fitness penalties. Mutants exhibited significantly (p < 0.05) reduced sporulation in mung bean broth, as well as significantly (p < 0.05) reduced pathogenicity in wheat seedlings. Sequence analysis indicated that the observed pydiflumetofen resistance of the mutants was likely associated with amino acid changes in the different subunits of the succinate dehydrogenase target protein, including R18L and V160M substitutions in the FpSdhA sequence, as well as D69V, D147G, S199S, and C257R in FpSdhB, and W78R in FpSdhC. This study found no evidence of cross-resistance between pydiflumetofen and the alternative fungicides tebuconazole, fludioxonil, carbendazim, or fluazinam, which all have distinct modes of action and could therefore be used in combination or rotation with pydiflumetofen to reduce the risk of resistance emerging in the field. Taken together, these results indicate that pydiflumetofen has potential as a novel fungicide for the control of FCR caused by F. pseudograminearum, and could therefore be of great significance to ensuring high and stable wheat yields in China.