Physiological Characterization of <scp> <i>Echinochloa crus‐galli</i> </scp> Populations Resistant to Dichloroquinolinic Acid in Paddy Fields

ABSTRACT Dichloroquinolinic acid, the most commonly used herbicide in rice fields, was originally used specifically against Echinochloa crus‐galli . Owing to the continuous use of it, E. crus‐galli is becoming increasingly more resistant to it. The results show that, under dichloroquinolinic acid stress, there were significant differences in the contents of several hormones between the highly resistant and sensitive E. crus‐galli populations. The relative changes in the levels of several hormones in highly resistant E. crus‐galli were significantly smaller than in sensitive E. crus‐galli , which indicates that dichloroquinolinic acid can kill E. crus‐galli by disturbing the changes in hormone levels. Higher activity of catalase (CAT) was associated with stronger dichloroquinolinic acid resistance. After dichloroquinolinic acid stress, glutathione transferase (GST) activity decreased, but the GST activity was lower in highly resistant plants than in susceptible plants. Moreover, CAT gene expression initially increased and then decreased, and the increase in CAT expression in highly resistant grass was significantly greater than that in sensitive grass, indicating that the higher the CAT gene expression levels, the stronger the resistance. GST expression initially decreased and then increased, and the change in GST expression of highly resistant plants was significantly smaller than that in sensitive E. crus‐galli , indicating that the higher the GST expression, the stronger the resistance. Treatment of E. crus‐galli with the compound herbicide isopropyl dichloroquinolinic acid and cyhalofop‐butyl achieved a good control effect. These findings provide a theoretical and practical basis for the comprehensive control of E. crus‐galli and ensure national food production security.