Comparative Research Of The Effect Of Bt Rice And Pesticide Application On The Rhizosphere Microbial Activity And Diversity

Comparative effects of transgenic Bt rice and the application of pesticide on the rhizosphere soil microbial activities and bacterial diversity were investigated over the rice development. Results showed that, although there were some apparent differences in rhizosphere soil microbial activity among transgenic Bt rice and non-Bt rice with the application of pesticide triazophos in different experimental sites and at certain stages of rice development, there was little effect of the transformation of Bt crylAb gene into rice genome over rice development. In contrast, effects of spacial heterogeneity and the application of triazophos on the rhizosphere soil microbial activity were considerablely higher.PCR-DGGE was used to analyze the potential impacts of Bt transgenic rice and the application of pesticide on the soil bacterial community composition in rhizosphere over the rice development, as compared to non-Bt parental rice and its isoline. Result indicated that, either the transformation of Bt crylAb gene or the application of triazophos had no apparent effects on the bacterial diversity in rhizosphere soil over rice development with the exception of seedling and heading stages, at which significant differences in rhizosphere soil bacterial diversity between Bt transgenic rice and Gd and between triazophos application and Ck were found, respectively.On the basis of the index values of non-Bt parent rice (Ck) and its isoline (Gd) obtained through above-mentioned experiments, a rough risk assessment system was put forward. Comparative risks of the transformation of Bt crylAb gene into* rice genome and the application of triazophos were evaluated according to NNs BP model and the assessment system. Evaluating Results indicated that the risk of the transformation of Bt crylAb gene into rice genome on the rhizosphere soil microbial ecology was considerablely lower as compared to that of the application of triazophos over rice development at Huajiachi with the exception at the seedling stage.