Pest management science · 2026
Baseline sensitivity to the SDHI fungicide pydiflumetofen and resistance mechanisms in Fusarium oxysporum, one of the causal agents of soybean root rot in China.
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Cai Yuanyuan, Liu Yu, Li Zhaorui, Chen Xi, Lv Liang, Liu Xili, Miao Jianqiang
Аннотация
BACKGROUND: Soybean root rot (SRR) is a devastating disease that severely reduces yield and quality in China, with Fusarium oxysporum recognized as one of the most prevalent causal agents. Pydiflumetofen, a new-generation succinate dehydrogenase inhibitor (SDHI) fungicide, exhibits potent efficacy against Fusarium spp. However, the resistance risk and underlying mechanisms of the SRR pathogen to pydiflumetofen remain largely unexplored.
RESULTS: Baseline sensitivity was determined using 104 isolates collected from five major soybean-producing provinces. The half-maximal effective concentration (EC50) values ranged from 0.0106 to 0.1068 μg mL-1, with a mean of 0.0437 ± 0.0187 μg mL-1. The unimodal frequency distribution indicated no naturally occurring resistant subpopulations in the field. Through fungicide-directed laboratory selection, 12 resistant mutants were obtained, showing resistance factors (RFs) between 82.70 and 7136.98. Phenotypic characterization revealed divergent fitness costs among mutants. Sequence analysis identified two point mutations: A83V in FoSdhC₁ and D133N mutation in FoSdhD. Site-directed mutagenesis via homologous recombination confirmed the causal relationship between these mutations and pydiflumetofen resistance. The A83V mutation conferred high-level resistance (RF > 100), while the D133N mutation conferred moderate-level resistance (RF between 10 and 100). Cross-resistance assays showed positive cross-resistance with cyclobutrifluram, but no cross-resistance with difenoconazole, fludioxonil, carbendazim, or pyraclostrobin.
CONCLUSION: The resistance risk of F. oxysporum to pydiflumetofen is categorized as moderate overall. The FoSdhC₁A83V mutation confers high-level resistance, and the FoSdhDD133N mutation confers moderate-level resistance. The established baseline provides a critical reference for field resistance monitoring, and these findings support the rational use of pydiflumetofen and the development of resistance management strategies. © 2026 Society of Chemical Industry.
RESULTS: Baseline sensitivity was determined using 104 isolates collected from five major soybean-producing provinces. The half-maximal effective concentration (EC50) values ranged from 0.0106 to 0.1068 μg mL-1, with a mean of 0.0437 ± 0.0187 μg mL-1. The unimodal frequency distribution indicated no naturally occurring resistant subpopulations in the field. Through fungicide-directed laboratory selection, 12 resistant mutants were obtained, showing resistance factors (RFs) between 82.70 and 7136.98. Phenotypic characterization revealed divergent fitness costs among mutants. Sequence analysis identified two point mutations: A83V in FoSdhC₁ and D133N mutation in FoSdhD. Site-directed mutagenesis via homologous recombination confirmed the causal relationship between these mutations and pydiflumetofen resistance. The A83V mutation conferred high-level resistance (RF > 100), while the D133N mutation conferred moderate-level resistance (RF between 10 and 100). Cross-resistance assays showed positive cross-resistance with cyclobutrifluram, but no cross-resistance with difenoconazole, fludioxonil, carbendazim, or pyraclostrobin.
CONCLUSION: The resistance risk of F. oxysporum to pydiflumetofen is categorized as moderate overall. The FoSdhC₁A83V mutation confers high-level resistance, and the FoSdhDD133N mutation confers moderate-level resistance. The established baseline provides a critical reference for field resistance monitoring, and these findings support the rational use of pydiflumetofen and the development of resistance management strategies. © 2026 Society of Chemical Industry.