Abstract:

【Aim】 The transgenic Bt cotton and poplar have been widely used in China. The aim of this study is to investigate and analyze the composition and diversity of the above-ground arthropod community in the transgenic poplar-cotton composite system, so as to provide basic data for the application of transgenic poplar. 【Methods】  Two popla-cotton composite systems, transgenic poplar-transgenic cotton (composite system 1) and non-transgenic poplar-transgenic cotton (composite system 2), were constructed at a farmland in Renqiu City of Hebei Province, North China. The transgenic cotton (Gossypium hirsutu) plants were planted under the newly planted poplar (Populus nigra). The composition (the species and number of individuals) and diversity indexes (Shannon-Wiener index, dominance concentration index and Pielou index) of arthropod community on polar and cotton plants in the two poplarcotton composite systems were investigated from April to October in 2019. The dynamics of Bt insecticidal protein content in leaves of transgenic poplar and cotton was also detected.【Results】 The numbers of individuals of lepidopteran pests both on transgenic poplar and cotton plants in composite system 1 were significantly lower than those on the corresponding plants in composite system 2. The number of individuals of leaf beetles on transgenic poplars was significantly higher than that on non-transgenic poplars, while the number of individuals of parasitic wasps on transgenic poplars was significantly lower than that on nontransgenic poplars. The Shannon-Wiener index of the arthropod community on transgenic poplars was significantly higher than that on non-transgenic poplars on June 5, June 21, and September 7. The numbers of various functional groups of arthropod communities except Lepidoptera on cotton plants in the two composite systems had no significant difference. The Shannon-Wiener index, dominance concentration index and evenness index of arthropod community on cotton plants in the two composite systems had the similar dynamic trend, and showed no significant differences at the same investigation time. The only exception was the Shannon-Wiener index on August 17, which was significantly higher on cotton plants of composite system 1 than on cotton plants of composite system 2. The cumulative numbers of various functional groups from cotton and polar plants were summed and analyzed as the whole composite system, and the result showed that there was no significant difference in Shannon-Wiener index, dominance concentration index and evenness index of arthropod community between composite system 1 and compositesystem 2. Arthropod  populations were aggregated to poplar leaves during the late investigation period. The Bt insecticidal protein contents on transgenic cotton plants were extremely higher than those on transgenic poplars through the whole growth season. 【Conclusion】 The transgenic poplar can control target insects, and have a synergistic effect against lepidopteran pests on cotton. The community structure of above-ground arthropods in the transgenic poplar-cotton composite system is stable, without significant effect on the diversity of the above-ground arthropod community on cotton plants. It is necessary to persistently detect and monitor the development of insect resistance to transgenic Bt poplar.

Key words: Poplar, cotton, underwood planting, transgenic plant, poplar-cotton composite system, arthropod community, biodiversity, Bt insecticidal protein