EcUGT79-like Mediated Metabolic Resistance to Auxin Herbicide Quinclorac in Echinochloa crus-galli

Echinochloa crus-galli poses a significant challenge to rice production, with herbicide resistance threatening agricultural output in South China. We investigated quinclorac resistance in E. crus-galli populations in rice fields in the Hainan Province, identifying a metabolically resistant (R) population that exhibited faster metabolism compared with the susceptible (S) population. RNA-Seq revealed 18 differentially expressed genes (DEGs), including two of the P450 family, four glutathione S-transferases (GSTs), six glycosyltransferases (GTs), one ABC transporter, and one hydrolase, that were upregulated in the R biotype. Metabolomic analysis identified 28 differentially accumulated metabolites (DAMs) that were specifically enriched in the R biotype. Correlation analysis showed that the DEGs of EcUGT79-like and EcUGT13248-like were strongly positively correlated with most of the DAMs. Transgenic Arabidopsis and yeast expressing EcUGT79-like exhibited resistance to quinclorac and clopyralid, whereas the transgenic EcUGT13248-like biotype did not display resistance. Overall, EcUGT79-like is the primary functional gene conferring resistance to quinclorac in E. crus-galli.