<i>EcUGT79-like</i> Mediated Metabolic Resistance to Auxin Herbicide Quinclorac in <i>Echinochloa crus-galli</i>

<i>Echinochloa crus-galli</i> poses a significant challenge to rice production, with herbicide resistance threatening agricultural output in South China. We investigated quinclorac resistance in <i>E. crus-galli</i> populations in rice fields in the Hainan Province, identifying a metabolically resistant (<i>R</i>) population that exhibited faster metabolism compared with the susceptible (<i>S</i>) 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 <i>R</i> biotype. Metabolomic analysis identified 28 differentially accumulated metabolites (DAMs) that were specifically enriched in the <i>R</i> biotype. Correlation analysis showed that the DEGs of <i>EcUGT79-like</i> and <i>EcUGT13248-like</i> were strongly positively correlated with most of the DAMs. Transgenic <i>Arabidopsis</i> and yeast expressing <i>EcUGT79-like</i> exhibited resistance to quinclorac and clopyralid, whereas the transgenic <i>EcUGT13248-like</i> biotype did not display resistance. Overall, <i>EcUGT79-like</i> is the primary functional gene conferring resistance to quinclorac in <i>E. crus-galli</i>.