| Population dynamics of beet armyworm (Spodoptera exigua Hubner) and its dominant natural enemies were investigated in the field and the resistance of transgenic cottons such as "Guokang12(GK12)","NuCOTN33B" and transgenic Bt plus CpTI cotton "SGK321" to S. exigua Hiibner was determined with their corresponding parental non-Bt-transgenic cotton "Simian3" and "33" and "Shiyuan321" as the control. The effect of transgenic cotton on the development of main parasitical natural enemy-Microplits pallidipes Szepligeti and predatory natural enemy-Chrysoperla carnea was evaluated; transmission of Bt toxin between pests and natural enemies was detected by ELISA. The results were as follows:1. Influence of transgenic cotton on population dynamics of beet armyworm and its main predatory and parasitoid natural enemiesPopulation dynamics of beet armyworm and its main natural enemies (C. carnea and M. pallidipes Szepligeti) were systematically investigated in3transgenic cottons and their parental non-Bt-transgenic cottons fields. The results showed that:compared with parental non-Bt-transgenic cotton fields:the average number of beet armyworm was28.1%17.6%and40.4%lower in3transgenic cottons fields; the average number of M. pallidipes Szepligeti was23.3%10.5%and21.6%lower in GK12, SGK321and33B, respectively; the average number of C. carnea in SGK321and33B were21.8%and10.9%lower, respectively; the average number of C. carnea in GK12field was57per100plants and8.5%lower than that in SM3. The results of variance analysis showed that all the differences were not significant. The correlation analysis and correlation coefficient significant test results showed that only M. pallidipes population and beet armyworm population in33cotton field and C. carnea population and beet armyworm population in33B cotton field were significantly correlated between them (P<0.05), The rest were not significant. Further analysis by respectively lagging5days or10days of C. carnea population and M. pallidipes Szepligeti population in different varieties of cottons to relevant analysis with beet armyworm population, the results showed that, only M. pallidipes Szepligeti population in GK12 and33B cotton fields by lag five days or ten days were significantly correlated between them (P<0.05), and the rest were all not significant.2. Influence of leaves in the different positions of transgenic cotton plant to population growth of S. exiguaThe effect of leaves in the different positions of three varieties of transgenic cottons and their parental non-Bt-transgenic cottons on beet armyworm survival, pupae weight, the duration of each stage, fertility and index of population growth trend (I) was compared,. Results indicated that:compared with contrast:The pupae weight of beet armyworm was25.02%,22.19%and6.01%;14.59%,3.96%and-3.40%;31.61%,17.70%and6.94%lower after fed on the top third, the sixth and ninth leaves of GK12,33B and SGK321cottons respectively; the differences of survival and fertility of beet armyworm were not significant, compared with contrast. The index of population growth trend of beet armyworm was16.34%,15.49%and39.34%lower by the top third leaves of three kinds of transgenic cottons. But with the position of leaves downward, this kind of influence gradually diminished. The population growth trend index of S. exigua fed on the top ninth leaves of33B cotton was10.57%higher than its parental contrast. This indicated that the influence of transgenic cotton to beet armyworm with feeding position down gradually narrowed.3. Biotransfer and bioaccumulation of Bt toxin in cotton plant-S. exigua-natural enemyIn laboratory, the Bt protein amounts in the body and the feces of beet armyworm, in the body of its main natural enemies-C. carnea and M. pallidipes Szepligeti were detected by ELISA. The results showed that:Bt protein was found in the vivo of beet armyworm, C. carnea and M. pallidipes Szepligeti and the feces of beet armyworm. The content of Bt protein in the2nd instar of beet armyworm vivo was higher than that in the3rd instar,4th instar and5th instar; the content of Bt in the feces of the2nd instar of beet armyworm was lower than that in the3rd instar,4th instar and5th instar. Bt toxin in C. carnea which hunted the beet annyworms that were fed on three transgenic cottons was143.09±12.14ng/g,136.44±55.82ng/g and83.88±15.36ng/g respectively. And Bt toxin in M. pallidipes Szepligeti was13.54±1.75ng/g,16.04±2.64ng/g and2.35±0.49ng/g respectively.4. The effect of transgenic cotton on C. carneaUsing the transgenic cotton SGK321GK12,33B, and a conventional contrast cotton Simian-3as combination, the indirect effects of transgenic cotton on C. carnea and the predating functional response of C. carnea to beet armyworm were studied. The results showed that:compared with contrast, C. carnea preyed the beet armyworm which were fed with the transgenic cotton leaves, has no significant differences of larva duration, cocoon weight, adult life, sex ratio, and single female spawning number. Compared with control:the cocoon duration of C. carnea was prolonged after feeding on the beet armyworm that were treated with GK12, SGK321and33B by8.08%,8.68%and1.34%; the former two differences were significant and the latter difference was not significant. The predating functional response of C. carnea to beet armyworm fed on Simian3(CK), GK12,33B and SGK321cottons all accorded with the Holling Ⅱ. And the daily maximum amount of beet armyworm preyed by C. carnea in these four cottons was84.0,89.3,93.5t and87.2, respectively.5. The effect of transgenic cotton and Cry1Ac on M. pallidipesBased on three transgenic cottons and a conventional cotton Simian-3and standard Cry1Ac protein, we systematically studied the effect of transgenic cotton and CrylAc on M. pallidipes Szepligeti. The results showed that there is no significant effect of Cry1Ac protein on M. pallidipes Szepligeti adult life. Compared with contrast, when M. pallidipes Szepligeti hosted the beet armyworm which were fed with these three transgenic cotton leaves, the cocoon duration extended by0.16d,0.17d and0.14d, respectively, and the differences were significant (P<0.05); adult life was significantly shortened by0.31d,0.32d and0.41d, the difference was very significant (P<0.01); cocoon weight and adult weight had a trend of decrease, feather rate has a rising trend, but all of the difference were not significant. |
PDF Full Text Request