| Cotton is one of the most important industrial crops in China and the world. The Helicoverpa armigera is one of the calamity pests in cotton field. These years along with the planting and extension of the transgenic cotton, the injury of Helicoverpa armigera to the cotton was controlled effectively. But it is necessary to further study the dynamic evolve relationship of resistance between transgenic cotton and Helicoverpa armigera. In this paper, we focused the research on the changing process of the resistance of cotton bollworm which fed by the transgenic cotton many generations continuously in the laboratory and the sensitivity of Helicoverpa armigera to Bt biologic pesticide or transgenic cotton. The cottonseed and cotyledon of transgenic cotton varieties were used to detect the variety resistance to cotton bollworm in order to explore a new biologic rapid detection method. The results were as follows:1. Using the half-artificial diet contenting cottonseed powder of transgenic cotton ZHONGMIAN 29 to feed the Helicoverpa armigera eleven generations continuously, the mortality of the larvae was obviously lower from 50% initially to 10%, the pupation rate and the emergence rate was increased from 47% and 65% in the first generation to 85%. The larvae weight increased obviously, the percent of the length to 15 mm of larvae fed thirteen days increased from 2.6% in the first generation to 65%. All index above showed that the Helicoverpa armigera had produced early resistance to transgenic cotton. When the resistant female to mate with the resistant male, the mortality of late larva and pupa, pupation rate, the emergence and the length of the larvae were all lower than the ones of using the resistance female to mate with the sensitive male. This showed that the adapt speed of the hybrid propagating to the artificial diet including cottonseed powder of was lower than the inbred propagating, and its resistance producing speed lower than the inbred propagating.2. After resistance screening ten generations continuously, the toxic sensitivity of the Helicoverpa armigera to the Bt biologic pesticide was obviously lower. The difference among the hybrid propagating, inbred propagating and sensitive population was significantly difference. For example, using Bt biologic pesticide QINGCHONGLING (16000IU/mg ) 200 times dilution to treat six days, the correctly larvae mortality of the sensitive population was 97.87%, the ones of the hybrid population and the inbred population was only 53.33%, 19.17%,spectively. This result showed that the effect of the Bt biologic pesticide to the hybrid population and the inbred population was obviously descend.3. After the resistance of Helicoverpa armigera screened ten generations continuously, The resistance level of transgenic cotton to the resistance cotton bollworm line was significantly descend. The results showed the comprehensive resistance level of ZHONGMIAN 29,LUMIAN15,KEMIAN1,NANKANG3 to the sensitive larvae was high-resistance, nearly-high-resistance, medium-high-resistance and high -resistance, synthetically. But the one of those varieties to resistance larva was medium-high-resistance, medium-high-resistance, lower-resistance and medium-high-resistance, synthetically.4. Applying un-transgenic cotton varieties as the check in the experiment, we found that different un-transgenic cotton varieties as the check had no influence to the identification result of the varieties resistance level to cotton bollworm.5. Using cottonseeds and cotyledon of transgenic cotton to detect the transgenic cotton varieties resistance, we found it was feasible, rapidly. This new detect method could be exploited through further technique improving.The studying results above could optimize the strategy of detecting and controlling the resistant population of Helicoverpa armigera in transgenic cotton field and be helpful to establish the rapid technology of detecting the pest resistance of the new transgenic cotton varieties. |
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