Inhibitory Activity of Pydiflumetofen Against Fusarium spp. and Its Potential for Controlling Soybean Root Rot

ABSTRACT

Soybean root rot is a globally prevalent soil‐borne disease that threatens soybean production, with Fusarium species being the most prominent cause of substantial losses worldwide. Pydiflumetofen and fluopyram are both new‐generation succinate dehydrogenase inhibitors (SDHIs) with great potential for controlling diseases caused by Fusarium spp. However, little is known about their in vitro and in vivo effectiveness against soybean root rot. This study compared the sensitivity of various Fusarium species causing soybean root rot to pydiflumetofen and fluopyram. The results showed that pydiflumetofen had a good inhibitory effect on the mycelial growth stage of several Fusarium species, with EC ₅₀ values ranging from 0.05 to 5.02 μg/mL, significantly better than fluopyram with the highest EC₅₀ value exceeding 100 μg/mL. Using molecular docking, the study compared the binding ability of both agents to the target protein succinate dehydrogenase (SDH) subunit C (SdhCs) in Fusarium oxysporum and they were found to bind most tightly to the SdhC1 subunit. Furthermore, pydiflumetofen was found to be the more effective SDHI. The mean EC₅₀ values of pydiflumetofen against F. oxysporum were 0.004 μg/mL for macroconidia production, 0.049 μg/mL for microconidia production, 0.008 μg/mL for conidial germination and 0.003 μg/mL for germ tube elongation, all of which were significantly lower than those for mycelial growth. At 10 μg/mL, pydiflumetofen exhibited over 90% protective efficacy, compared to 58.8%–66.7% curative efficacy, demonstrating its superior protective activity. These results revealed the potential of pydiflumetofen as a candidate fungicide to effectively combat soybean root rot.