Mechanisms Underlying Differential Flusulfinam Sensitivity between Oryza sativa and Echinochloa crus-galli

Abstract Flusulfinam is a novel postemergence HPPD-inhibiting herbicide with excellent safety on direct-seeded indica rice, but the mechanism underlying its selectivity between rice and Echinochloa crus-galli remains unclear. Rice exhibited 41–141-fold higher GR50 values than E. crus-galli, with cultivar-dependent tolerance. Residue analysis showed higher flusulfinam absorption in E. crus-galli, whereas metabolism was significantly enhanced in rice and inhibited by P450 and GST inhibitors. Transcriptomic and qRT-PCR analyses identified OsGSTU16 as highly expressed in rice compared with E. crus-galli. Functional validation using Escherichia coli expression, rice callus overexpression, knockout experiments, and molecular docking demonstrated that OsGSTU16 contributes to flusulfinam tolerance. These findings suggest that GST-mediated metabolic detoxification is an important contributor to flusulfinam selectivity and provide insights into potential genetic resources for improving herbicide tolerance in crops.