Study On Resistance Determination And Biochemical Mechanism Of Leptochloa Chinensis (L) Nees. To Cyhalofop-butyl In Paddy Field Of Hunan Province

Leptochloa chinensis（L）Nees.is an annual weed which has caused great damage to paddy in Hunan province.In this study,experiments were conducted to determine the influence of environmental factors on seed germination and emergence of Leptochloa chinensis（L）Nees.,monitor the resistance level of the populations collected from paddy fields in Hunan Province to cyhalofop-butyl,and the differences in GSTs,SOD,POD and CAT of the resistant（R）and susceptible（S）populations to cyhalofop-butyl were determined by using physiological and biochemical methods.The results were as follows:（1）Stripped the glume of the seeds,with 400mg/L GA₃ soak 24 h can effectively break the seed dormancy so that the germination rate can reach 82%.In the daytime temperature of 30℃,night temperature of 25℃and light/dark 12 h alternately,the seed germination rate can be maintained at more than 90%.Located on the surface of the soil is the most beneficial to seed emergence.（2）The results of whole-plant experiments showed that among the 10 Leptochloa chinensis（L）Nees.populations,the Meijiang population in Lianyuan Loudi was the most sensitive to cyhalofop-butyl,and the GR₅₀ was 6.506 g·hm^-2.Meijiang population was identified as susceptible population,the relative resistance index（RI）of other populations to cyhalofop-butyl was 1.2¹1.0,and the highest resistance index（RI）was 11.0,which was found in Chashan-ao Town of Hengyang,and the GR₅₀ was 71.731 g·hm^-2.（3）The activity of GSTs in resistant population increased significantly after 2 days of treatment with cyhalofop-butyl,reached the highest value after 3 days,then decreased and became flat after 5 days;1 day after the drug treatment,the activity of GSTs in susceptible population increased sharply and reached the maximum on the second day,and then declined.The activity of GSTs in the susceptible population was lower than that of the resistant population in 3⁷ days.The trend of SOD,POD and CAT activity in resistant and susceptible populations was similar,but the resistant population was significantly higher than the susceptible population.The resistance of the resistant population to cyhalofop-butyl may be related to the enhancement of GSTs,SOD,POD and CAT activity.