Target‐gene overexpression and metabolic enhancement confer bentazone resistance in <scp> <i>Amaranthus retroflexus</i> </scp>

BACKGROUND: Resistance to photosystem II (PSII)-inhibiting herbicides is increasingly widespread in Amaranthus retroflexus, a major weed in soybean production, yet the underlying mechanisms remain unclear. This study aimed to characterize the molecular basis of bentazone (BTZ) resistance in this species. RESULTS: BTZ-resistant genotype (B24) showed a resistance index of 11.30 relative to susceptible B06. No target-site mutations were found, but psbA expression was 1.14-to 2.42-fold higher in B24. Transcriptomics and RT-qPCR identified 11 significantly upregulated genes, including four glycosyltransferases, three ABC transporters, and four cytochrome P450s. Molecular docking revealed strong binding of BTZ with ArUGT86A2, ArABCG5, and ArCYP71A1, and heterologous expression in yeast confirmed that ArCYP71A1 confers BTZ resistance. CONCLUSION: This research provides the first evidence that both target-site overexpression and metabolic enhancement drive BTZ resistance in A. retroflexus. These findings establish a foundation for mechanistic studies and improved management of resistant populations. © 2026 Society of Chemical Industry.