Biochemical Mechanism Of Resistance To Imidacloprid In Wheat Aphids

The susceptibility of wheat aphids to imidacroprid and the enzyme activities related to resistance were tested in this study. The physiological and biochemical differences of the aphids feeding on different host plants and in different areas were analysised, to further explore the susceptibility changes and the biochemical mechanisms of wheat aphids resistance to imidacloprid. In addition, the time effect of sublethal dose of imidacroprid on esterase in Rhopalosiphum padi were studied, in order to provide a theoretical basis for the effective governance and integrated control of wheat aphid.1.Study of susceptibility of wheat aphids to imidacroprid of different host plants and the activities of enzymes related to resistanceThe susceptibility of Rhopalosiphum padi and Sitobion avenae to imidacroprid of three different host plants and the activities of two enzymes related to resistance were measured. The results indicated that there were significant differences on the susceptibility to imidacroprid among Rhopalosiphum padi and Sitobion avenae feeding on different host plants, and the susceptibility decreased gradually in the Rhopalosiphum padi and Sitobion avenae feeding on wheat, oat and roegneria. There were significant differences on the esterase activities of Rhopalosiphum padi feeding on different plants, and the roegneria strain was1.96fold than the strain of wheat. Significant differences also exist on the esterase activities of Sitobion avenae feeding on different plants, and the roegneria strain was the highest. It is2.71fold than the strain of wheat.There were no significant difference of AChE among Rhopalosiphum padi feeding on different host plants(P>0.05). But the AChE of Sitobion avenae feeding on roegneria was2.62fold than the stain on wheat, they were significantly different(P<0.05). Therefore, activity variations of esterase may be in consistent with susceptibility to imidacroprid.2. Study of susceptibility of wheat aphids to imidacroprid of different areas and the activities of esteraseThe susceptibility of Rhopalosiphum padi and Sitobion avenae to imidacroprid of three different areas were detected. Significant difference exsits in susceptibilities of populations of Rhopalosiphum padi in different areas to imidacroprid. The population from Xiaogan was2.79times less sensitive than Sichuan to imidacloprid. The susceptibilities of populations of Sitobion avenae in different areas to imidacroprid were also significantly different. The population from G was3.13times less sensitive than Xinjiang to imidaeloprid. The activities of esterase of different areas in Rhopalosiphum padi and Sitobion avenae were measured. The results showed that there were significant different on the esterase activity of Rhopalosiphum padi and Sitobion avenae of different areas(P<0.05) and the esterase activities were positively correlated with the LC50values. Indicated that elevated activity of esterase is one of the mechanisms of wheat aphid resistance to imidacloprid.3. The time effect of sublethal dose of imidacroprid on esterase in Rhopalosiphum padiThe time effect of sublethal dose of imidacroprid on esterase in Rhopalosiphum padi were studied by biochemical analysis. The results showed that the activity of esterase changed with time after being processed with sublethal concentration of imidacroprid. The activity of esterase reduced at the beginning and reached to the minimum at the sixth hour. Then the enzyme activity recovered slowly, but the rebounded enzyme activity didn’t reach normal activity level after48hours. The enzyme activity in aphids treated with imidacloprid is significantly lower than that of control. The results indicated that the esterase activity of Rhopalosiphum padi was inhibited by the sublethal concentration of imidacloprid and had a time effect.