| Transgenic cotton has been developed and planted widely to control cotton bollworm (Helicoverpa armigera) in Yangzi river valley in recent years.As a new genetic modified crop and a new method for pest control,its efficiency,stability and possible influence on arthropod community and ecology has been extensively studied in different area. Our work with 4 transgenic Bt cotton varieties concentrated on the evaluation of resistance, the temporal and spatial express of the resistance and the influence on the diversity of arthropod community in Jiangsu coastal region. The results were summarized as fellows:1) The resistance level of 3 transgenic cotton varieties (Zhongmian29, Lumian15, GK22 ) to the cotton bollworm was tested by the methods of refining larva to cotton seedling stage leaves in the lab and refining adults in field cages where cotton plants were squaring,respectively. Based on the 12 kinds trial data investigatde above,we caculated the comprehensive resistance value (C) to quantitive the level of resistance to cotton bollworm. The test results showed that the K value of Zhongmian 29, Lumian 15 and GK22 was 3.67,3.33 and 3.92,respectively. Compared to the classfied standard of K value for different resistance level, The Zhongmian 29 and GK 22 were high resistance and Lumian 15 was nearly high resistance to cotton bollworm. They could be used to control cotton bollworm efficiencely.2) According to the results of resistance bioassay and Bt toxin content test in lab, we found that resistance of transgenic cotton varied with the temporal and spatial express of Bt toxin content and varied with the traits of variety also.As the plants developed,the resistance went down step by step.Among the plant organs, nutrient organs i.e leave showed the higher resistance than the reproductive organs i.e squares or bolls. The Bt toxin content in the same kind of organ would be declined with the delay of developing stages. The Bt toxin content in the same time but in different organs wouldn't be the same among different varieities.3) In order to overall evaluate the ecological safety and planting risk of insect resistant transgenic Bt cotton,the composition and diversity of the arthropod community in 3 transgenic Bt cotton varieties: Zhongmian29, SukanglO3 and GK22 was studied by means of the quantitative analysis method in yancheng of Jiangsu coastal region.No marked difference in arthropod species was found between each of transgenic Bt cotton varieties and traditional variety check (Sumian-9).The dominant species and their abundance were very close among them.According to the results of research on the structure of arthropod community in different cotton fields,we found that the species richness and total individuals of arthropod community in the transgenic cotton fields was very close to the ones in common cotton fields. There were no marked difference of temporal sequence dynamic of pest, natural enemy and arthropod community between the transgenic cotton and common cotton.The abundance of all kind of pests in pest sub-community(Pi) and the abundance ofnatural enemy in it's sub-community(Pj) were tested. The result revealed that there was no obviously difference of Pi or Pj between the transgenic cotton and common cotton besides the Pi value of some kinds of Lepidoptera pest in it's sub-community in common cotton was higher obviously than the ones in transgenic cotton.Based on the test results of abundance of major nutrient classes, guilds and groups to the whole arthropod community (Pk), the Pk value of predatory classes in the major nutrient classes of different kind of cotton is close or higher than phytophagous classes.The dominant species of natural enemy were Coccinellidae and spider. The structure and composition of natural enemy community in the transgenic cotton fields was similar to the ones in the common cotton. The pest with the piercing-sucking mouthparts was the dominant guilds in the all kind of phytophagous classes. The Pk value of Lepidoptera pests in the transgenic cotton fields was lower than in the commo... |
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