Differential Activity of Enantiopure R- and S-Flusulfinam in Rice ( Oryza sativa L.) and Barnyard Grass ( Echinochloa crus-galli ): Evidence from Metabolite Fingerprinting and Metabolomics

The enantioselective biological behavior of flusulfinam, a novel chiral herbicide for rice cultivation in China, remains largely unexplored. This study demonstrated that R-flusulfinam exhibited 2.21-17.39 times higher efficacy against monocotyledonous weeds and 3.03-7.75 times greater activity against dicotyledonous weeds than S-flusulfinam. Degradation studies indicated chiral isomerization in both plant species. Flusulfinam degraded rapidly in Oryza sativa L., with no significant difference in half-life observed between treatments with enantiopure R- and S-flusulfinam. The highly active R-flusulfinam enantiomer in O. sativa L. was mainly metabolized through hydrolysis, yielding the primary metabolites M298 and M99. In contrast, R-flusulfinam showed almost no degradation following application to Echinochloa crus-galli. Metabolomic analysis revealed that E. crus-galli treated with flusulfinam underwent substantial oxidative damage and photosynthetic inhibition. In contrast, O. sativa L. maintained a stable antioxidant metabolic system, indicating a pronounced tolerance to the herbicide.