Cytochrome P450 and glutathione S ‐transferase may confer bensulfuron‐methyl resistance in Cyperus iria

BACKGROUND: Rice flatsedge (Cyperus iria L.) is one of the most troublesome weeds infesting rice fields across China. Bensulfuron-methyl, an acetolactate synthase (ALS)-inhibiting herbicide, has been widely used for the control of Cyperaceae weeds in rice production. However, long-term and extensive use of this herbicide has resulted in the evolution of resistant C. iria populations. In this study, a suspected bensulfuron-methyl-resistant (R) population collected from a rice field that survived field-recommended applications was investigated to elucidate its resistance level and underlying mechanism. RESULTS: Compared with a susceptible (S) population, the R population exhibited a high level of resistance to bensulfuron-methyl [resistance index (RI) = 12.88] and cross-resistance to metazosulfuron (RI = 11.66), bispyribac-sodium (RI = 9.10) and penoxsulam (RI = 6.35). No mutations were detected in the ALS gene, and ALS expression levels did not differ significantly between the R and S plants. Pretreatment with the cytochrome P450 inhibitor malathion and the glutathione S-transferase inhibitor 4-chloro-7-nitrobenzoxadiazole effectively reversed bensulfuron-methyl resistance in R plants. Liquid chromatography tandem mass spectrometry analysis showed that the R plants metabolized bensulfuron-methyl significantly faster than the S plants. RNA sequenccing analysis revealed remarkable upregulation of CYP97A3 and GSTF1 in the R population, while molecular docking indicated strong binding affinities between both enzymes and bensulfuron-methyl at their active sites. CONCLUSION: These results reveal that enhanced expression of CYP97A3 and GSTF1 may contribute to bensulfuron-methyl resistance in C. iria, highlighting the role of metabolic detoxification in the evolution of non-target-site resistance in this species. © 2025 Society of Chemical Industry.