Effects Of Plant Insect-resistant Compounds On The Nutritional Utilization And Enzyme Activities Of Beet Armyworm, Spodoptera Exigua (Hubner)

1. Response of successive three generations of beet army worm, Spodoptera exigua (Hiibner) fed on three cotton cultivarsThe growth, development and food utilization of three successive generations of beet armyworm, Spodoptera exigua (Hubner), fed on three cotton gossypol cultivars were examined. Significantly longer larval life-span was observed in three successive generations of S. exigua fed on high gossypol cultivar 'M9101' compared with other two low gossypol cultivars 'ZMS13' and 'HZ401'. The pupal weight of the first generation was significantly lower than that of the latter two generations fed on 'ZMS13'. Significantly lower female fecundity was observed in the second and third generations of S. exigua fed on'M9101'compared with 'ZMS13' and 'HZ401'. The ECI of S. exigua was occurred significant increase in the first and third generations of S. exigua fed on'HZ401'compared with 'ZMS13' and 'M9101'. Significantly lower relative growth rate (RGR) was observed in the three successive generations of S. exigua fed on 'M9101' compared with 'ZMS13'and 'HZ401'. Cotton cultivar significantly affected the growth, development and food utilization indices of S. exigua, except for frass and approximate digestibility (AD). Beet armyworm generation only significantly affected relative consumption rat (RCR) and efficiency of conversion of ingested food (ECI) of S. exigua, except for RGR and AD, which indicated food quality on the diet-utilization efficiency of S. exigua was different along with beet armyworm generation. Measuring the development and food utilization of S. exigua at individual and population level over more than one generation provide more meaningful prediction of long-term population dynamics.2. Temporal allocation of metabolic tolerance in the body of beet armyworm in response to three gossypol-cotton cultivarsThe nutrient composition and enzyme activities in larvae of the beet armyworm, S. exigua (Hubner), fed on high, medium or low gossypol cotton cultivars were examined at different time intervals. Significantly lower free fatty acid was observed in larvae fed for6h on high gossypol 'M9101' compared to larvae fed on the low ('ZMS13') and intermediate ('HZ401') gossypol cultivars. Significantly higher trypsin activity was observed in larvae fed on high gossypol 'M9101' for24h compared to those fed for1h,4h and6h. Significantly higher catalase and total superoxide dismutase enzyme activities were observed in larvae of S. exigua fed on high gossypol'M9101'compared with low gossypol cultivars 'ZMS13' and 'HZ401' for1h,4h,6h and24h. However, significantly lower carboxylesterase and acetylcholinesterase enzyme activities were found in larvae fed on high gossypol 'M9101'compared with the other cultivars for1h,4h,6h and24h. The interaction between cotton variety and beet armyworm infestation time significantly affected the carboxylesterase enzyme activity in S. exigua. The characterization of the effects of plant allelochemicals on herbivorous larvae is important for aiding understanding of plant-insect interaction as well as in devising solutions to pest problems by breeding plant resistance, identifying metabolic targets for insecticide development, etc.3. Response of multiple generations of beet armyworm, S. exigua (Hubner), feeding on transgenic Bt cottonDevelopment, reproduction and food utilization of three successive generations of beet armyworm, S. exigua (Hubner), fed on transgenic and non-transgenic Bt cotton were examined. Significantly longer larval life-span and lower pupal weight were observed in three successive generations of S. exigua fed on transgenic Bt cotton compared with non-transgenic Bt cotton. Significantly higher survival rate and adult fecundity of S. exigua were found in three successive generations of S. exigua fed on transgenic Bt cotton compared with non-transgenic Bt cotton. The survival rate and adult fecundity of S. exigua were occurred significant increase in the third generation compared with the first generation after feeding on transgenic Bt cotton. Significantly lower consumption, frass and relative growth rate (RGR) were observed in three successive generations of S. exigua fed on transgenic Bt cotton compared with non-transgenic Bt cotton. Cotton variety significantly affected all indices of larval consumption and utilization in three successive generations of S. exigua, except for efficiency of conversion of ingested food (ECI). However, beet armyworm generation only significantly affected RGR of S. exigua. The results of this study indicated food quality on the diet-utilization efficiency of S. exigua was different along with beet armyworm generation. Measuring multigenerational development and food utilization of S. exigua at individual and population level in response to Bacillus thuringiensis (Bt) can provide a more meaningful evaluation of long-term population dynamics than experiments on a single generation. It is imperative to develop an appropriate multigenerational pest management tactic to monitor the field population dynamics of non-target pests (e.g. beet armyworm) in agricultural Bt cotton ecosystem.4. Effects of Bt-transgenic cotton on expression of enzyme activity in multiple generations of beet armyworm, S. exigua (Hiibner)The assimilation and detoxification enzymes of beet armyworm, S. exigua (Hubner), fed on transgenic and non-transgenic Bt cotton for three successive generations were examined in this experiment. Compared with non-transgenic Bt cotton, significantly lower lipase, arboxylesterase (CarE) and acetylcholinesterase (AChE), and significantly higher trypsin and total superoxide dismutase (T-SOD) were observed in S. exigua fed on transgenic Bt cotton for three successive generations. Cotton variety significantly affected the assimilation enzymes (i.e., lipase and trypsin) and the detoxification enzymes (i.e., AChE, CarE and T-SOD) in the body of S. exigua. However, significant difference was only observed in trypsin enzyme of S. exigua among three successive generations. The interaction between cotton variety and armyworm generation significantly affected lipase, trypsin and AChE enzymes activities. The results indicated that Transgenic Bt cotton could induce enzymes activities change in the body of S. exigua under the continuous selection pressure of the toxin protein through three successive generations. Measuring multi-generational enzymes activities of S. exigua in response to Bt cotton can provide a more meaningful evaluation on its resistance under continuous selection pressure of Bt toxin protein through the successive generations.