Abstract: The resistance level of Echinochloa crusgalli population to 4 amide herbicides and the physiological response of 3 representative Echinochloa crusgalli populations to acetochlor stress in Chengdu Plain were measured by pot method. The results showed that in 2018 and 2019, the resistance index （RI） of Echinochloa crusgalli in Chengdu Plain rice area was 12.37~16.46 and 16.15~21.86, respectively. The levels of resistance to metolachlor were low or medium, and RI were 9.41~10.44 and 9.69~10.98, respectively. The resistance levels to butachlor were low, RI were 3.74~4.59 and 4.55~5.16, respectively. The Echinochloa crusgalli population was sensitive or low resistant to P-benthiaclachlor, with RI of 2.45~3.79 and 2.73~3.98, respectively. The physiological parameters of the actual light quantum yield, intercellular carbon dioxide concentration, transpiration rate and stomatal conductance of resistant and sensitive populations showed a downward trend under acetochlor stress. The activities of glutathione S-transferase （GSTs） and superoxide dismutase （SOD） decreased gradually, and the content of malondialdehyde （MDA） showed an upward trend, but the damage of resistant Echinochloa crusgalli population was significantly lower than that of sensitive population. Therefore, Echinochloa crusgalli population tested in Chengdu Plain rice area was still sensitive to medium level of resistance to common amide herbicides, and the increase of GSTs activity was the main reason for the metabolic resistance of Echinochloa crusgalli to acetochlor.

Key words: Echinochloa crusgalli, amide herbicides, pesticide resistance, physiological and biochemical mechanism