Title: Study of the Susceptibilities to Malathion and Deltamethrin and Their Toxicological Mechanisms in the Field Populations of Oxya chinensis (Thunberg)
Abstract: The differences of malathion and deltamethrin susceptibilities and the corresponding enzyme activity among the three populations of Oxya chinensis (Thunberg) under different levels of insecticide selection pressure were studied using bioassays and biochemical analysis. These 3 Oxya chinensis populations were collected from 3 sites (paddy land in Hanzhong county where insecticides have been applied for many years, corn field in Fanshi county where farmer used to apply insecticides, grasslands in Linyi county where insecticides have seldom been applied). The results of bioassay showed that the LD50 values of Hanzhong population were the highest, followed by Linyi population, and those of Fanshi population were the lowest to malathion and deltamethrin, which indicated that the selection pressure of insecticides played an important role in the differences of susceptibilities to insecticides among the three populations. The level of insecticide resistance of Fanshi population decreased gradually after the insecticides application stopped. The results of biochemical analysis showed that the esterase activities of Hanzhong population were 2.54 and 1.57 fold with α-NA, 1.61 and 1.53 fold with α-NB and 1.84 and 1.59 fold with ?茁-NA higher than those of Linyi and Fanshi populations, respectively. GST activity of Fanshi population was the highest, and those of Linyi and Hanzhong populations were similar. Furthermore, AChE activities of Fanshi population were the highest, followed by Linyi population, and AChE activities of Hanzhong population were the lowest. The results of AChE inhibition in vitro using three oxidative organophosphorus inhibitors showed that the ki values in Hanzhong population were lower than those in Fanshi and Linyi populations. AChE from Hanzhong populations was 7.20 and 8.50 fold, 1.21 and 1.77 fold, 7.91 and 13.43 fold less sensitive to inhibition by paraoxon, demeton-s-methyl, and chlopyrifos-oxon than those from the Linyi and Fanshi populations, respectively. This findings may suggest that the elevated esterase activities and insensitivity of AChE appear to be the dominant factors and the changes of GST and AChE activities play minor roles in the differences of susceptibilities to insecticides among the three populations.
Publication Year: 2006
Publication Date: 2006-01-01
Language: en
Type: article
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Cited By Count: 1
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