Soil persistence of Bacillus thuringiensis (Bt) toxin from transgenic Bt cotton tissues and its effect on soil enzyme activities
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A silty loam soil was incubated with the leaves and stems of two transgenic Bacillus thuringiensis (Bt) cotton varieties and nontransgenic Bt cotton to study the soil persistence of the Bt toxin from the decomposing transgenic Bt cotton tissues and its effect on soil enzyme activities. The results showed that after Bt cotton tissue amendment, Bt toxin was introduced into soil upon decomposition; about 50% of the introduced Bt toxin persisted in soil for at least 56 days. No Bt toxin was detected in the nontransgenic Bt cotton-amended soil; the amount of Bt toxin was the highest in the soil treated with the residue with the higher Bt toxin content. Activities of soil urease, acid phosphomonoesterase, invertase, and cellulase were stimulated by the addition of Bt cotton tissues, whereas activity of soil arylsulfatase was inhibited. Probably cotton tissue stimulated microbial activity in soil, and as a consequence, enzyme activities of soil were generally increased. This effect can mask any negative effect of the Bt toxin on microbial activity and thus on enzyme activities.
KeywordsTransgenic Bt cotton Bacillus thuringiensis (Bt) toxin Soil enzyme activity
This research was funded by the Knowledge Innovation Project, CAS (KZCX3-SW-445) and National Natural Sciences Foundation of China (no. 40101016); this work was also financially supported in part by the Global Environment Research Fund of Ministry of the Environment, Japan. The authors thank Prof. G. Stotzky in the Laboratory of Microbial Ecology, Department of Biology, New York University, for providing information about Bt toxin measurement, and the Editor-in-Chief of Biology and Fertility of Soils, Prof. Nannipieri, for his very important suggestions and detailed revision in the improvement of this manuscript.
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