Study On Resistance Selection And Mechanisms Of Myzus Persicae (Sulzer) To Two Insecticides

The resistance of alphamethrin and imidacloprid in Myzus persicae (green peach aphid) was selected in laboratory. In order to learn about the resistance developing dynamic and gene frequency, the resistance development was monitored through the bioassay and the 96-well microplate reader for measuring change of esterase (Est). The resistance mechanisms of Myzus persicae to alphamethrin were studied after 10 times selection to enrich the research contents of Myzus persicae resistance and provide protocol design of resistance management. After two years study, the main research results are summarized as follows.1. The selection of resistance to alphamethrin in Myzus persicae and esterase activity, content dynamicThe results showed that the resistance level gradually rose with the increase of selection time. After three generations, the resistant level of green peach aphids to alphamethrin was 13-fold. While ten generations later, the resistant level amounted to 49.86-fold and the slope (b) value of LD-p lines have decrease tendency. It suggested that the green peach aphids have developed obvious resistance to alphamethrin and resistance would further develop. As resistance developed, enzyme protein content and Est activity increased significantly than susceptible batch and there was a significant correlation between resistance leveal and enzyme protein content, Est activity, respectively. The results showed that the Est might play an important role in the resistance development of green peach aphids to alphamethrin. Comparing the frequency distribution of enzyme protein content and activity, more and more individuals possessed higher content and activity.2. Resistance mechanisms of Myzus persicae to alphamethrin2.1 Est and the resistance of Myzus persicae to alphamethrinThe Est activity of susceptible and resistant green peach aphids were studied using the method of microplate reader, the results showed that the Est activity, Km and Vmax of resistant batch were 2.555-fold, 1.520-fold and 2.587-fold compared with those in susceptible batch, respectively. The esterase isozyme electrophoretic indicated that the resistant batch of Myzus persicae had no E3 esterase band and had higher esterase activity.2.2 GSTs and the resistance of Myzus persicae to alphamethrinThe GSTs activity of resistant batch were 1.734-fold than the susceptible batch. The comparison of Km of GSTs between resistant and susceptible batch showed that the affinity of GSTs of resistant batch to substrate was stronger than susceptible batch. Comparing the frequency distribution of GSTs activity, it was found that more and more individuals possessed higher activity.23 Phosphatase and the resistance of Myzus persicae to alphamethrinBy biochemical assay, the activities of ACP and ALP in resistant batch were significantly higher than those in susceptible batch, respectively. Both Km and V_max of ACP between resistant and susceptible batch have no obvious change. Compared to susceptible batch, K_m of ALP in resistant batch has no obvious change. On the contrary, Vmax was obviously increased. These declared that the increase of phosphatase activity might be an important role in the resistance of green peach aphid against alphamethrin.2.4 MFO and the resistance at Myzus persicae to alphamethrinThe biochemical assay showed that the development of MFO activity in resistant batch was an important reason for the resistance to alphamethrin of Myzus persicae.2.5 AChE and the resistance of Myzus persicae to alphamethrin2.5.1 AChE activity of susceptible and resistant Myzus persicaeThe AChE activity of susceptible and resistant batches were detected by microplate reader in the experiment. The activity and Vm of resistant batch were significant higher than those of the susceptible batch. These results showed that AChE content of resistant green peach aphids increased. Comparing the frequency distribution of aphid AchE activity, we found that more and more individuals possessed higher AChE activity.2.5.2 AChE inhibition of suscepitible and resistant Myzus persicae...