Effect Of Resistance Selection On Biochemical Character Of Plutella Xylostella

Bacillus thuringiensis insecticidal crystal proteins, because of its highly specific and harmless to humans, animals and non-target insects, is widely used to control pests such as Lepidoptera. P. xylostella as a worldwide important lepidopteran pests of cruciferous vegetables, as early as1990report, had resistant to Bt preparation, but the current findings are not completely explaining its Bt resistance mechanism and many important factors to resistance should be further proved. Relevant reports, Bt toxin in vivo have against pests three enzymes, including digestive enzymes, protective enzyme to some extent.In this study, we use three host plants indoors to select developmental uniformity P. xylostella generations, then will be screened for highly resistant to CrylAc strains, and the highly resistant strains of P. xylostella will survay and evaluate digestive enzymes and protective enzymes so as to provide research base of P. xylostella resistance mechanism to Cry1Ac. The results are as follows.1. Different hosts plants indoor rearing against multiplication differences of P. xylostellaOviposition distributed more intensive and high pupation rate (cabbage seedlings with93.2%, radish sprouts with75.6%), spawning rate (cabbage seedlings with92.3%, radish sprouts with78.8%) and eggs hatching rate (cabbage seedlings with94.7%, radish sprouts with74.3%) with cabbage seedlings than radish sprouts. Survival rates of larvae in cabbage seedlings, cabbage leaves and radish sprouts on three host plants were91.3%,82.7%and73.7%; developmental period of larval were14.7days,12.3days and10.6days. P. xylostella generations were tidy, less prone to overlapping generations, easy to manage and carry out resistance selection with cabbage seedlings, and got a large number of developmental uniformity P. xylostella population for Cry1Ac resistance selection.2. Elimination of P. xylostella strains to Cry1Ac toxinAfter27generations of Cry1Ac toxin elimination, P. xylostella populations sensitive to Cry1Ac toxin decreased significantly, and value LC50form1.19mg·L-1 before breeding to946.40mg·L-1after breeding, relatively ratio increased to795.69times.3. Digestive enzymes activities changes of Cry1Ac resistant P. xylostella larvaeThe results that digestive enzyme activity of P. xylostella susceptible and resistant to Cry1Ac toxin was measured showed that, differences of Cry1Ac susceptible and resistant P. xylostell Protease activity and Lipase activity were both significant,but differences of CrylAc susceptible and resistant P. xylostell α-Amylase activity was not significant,the results also showed that CrylAc have a minimal impact on protease activity of P. xylostell1st instars, the greatest impact in4th instars; a minimal impact on Lipase in2nd instars, greatest impact in4th instars.4. Protective enzymes activities changes of Cry1Ac resistant P. xylostella larvaeThe results that protective enzymes activity of P. xylostella susceptible and resistant to Cry1Ac toxin was measured showed that, differences of Cry1Ac susceptible and resistant P. xylostella catalase activity.. eroxidase activity and superoxide dismutase activity were significant, the results lso showed that CrylAc have minimal impact on P. xylostella catalase activity in3rd instars, the greatest impact in4th instars; minimal impact on peroxisome in2nd instars, the greatest impact in3rd instars; minimum impact on superoxide dismutase in4th larvae, the greatest impact in1st instars.