Effects Of Transgenic Bt+CpTI Cotton On The Soil Microorganisms And Enzyme Activities

In recent years, with the generalizing and ceaselessly expanding planting area of transgenic cotton, it is important to evaluate the ecosafety of the potential ecological risks of transgenes and it has the very important ecology significance. In this study, three-room rhizobox method was used to collect soil samples from different zones of cotton root. The microbiology technique and molecular biology technique were used. And this experiment compared transgenic Bt+CpTI cotton SGK321 with conventional cotton SHIYUAN321 to investigate the effects of the different zones soil enzyme activities, soil available nutrients and soil microbial parameters in three growing stages. To reveal the mechanism of planting transgenic Bt+CpTI cotton impacts on soil microorganisms and enzyme activity. The main results in the present study are as follows:1. Compared to the conventional cotton, the planting of transgenic Bt+CpTI cotton showed no significant negative influences in soil activities of urease, alkaline phosphatase, catalase in three root zones. The results showed that soil activities of urease, alkaline phosphatase, catalase were mainly affected by the growth stages.2. Compared to the conventional cotton, the NO3--N decreased in the S1zone, S2 zone and S3 zone. It showed no significant differences in NH4+-N (p>0.05), but it significantly increased the soil P to the available form in the S2 zone (p<0.05).3. The results of traditional culture-depending method showed that the amount of soil bacteria and actinomycetes significantly decreased in S1 zone of transgenic Bt+ CpTI cotton, but the amount of three microorganisms in S2 zone and the amount of bacteria and fungi in S3 zone of transgenic Bt+CpTI cotton significantly increased (p<0.05), compared to the conventional cotton. The planting of transgenic Bt+CpTI cotton change the amount of microorganisms.4. DGGE fingerprinting indicated that the Shannon-Wiener index, evenness and the number of bands had no significant difference between transgenic Bt+CpTI cotton and conventional cotton in three growing stages (P >0.05). There was high similarity between the two cotton treatments and it was not affected by the planting of transgenic Bt+CpTI cotton.5. The planting of transgenic Bt+CpTI cotton was enhanced the different zones soil microbial biomass C during the three growing stages. But the influence of the soil microbial biomass N was different from the root spatial dynamic distribution and growth stages.In this study, soil microorganisms and enzyme activity changes in the short-term were studied, after planting transgenic Bt+CpTI cotton. The results showed that the planting of transgenic Bt+CpTI cotton change NO3--N content, available P content and amount of microorganisms in soil. But it had no significant affect on the enzyme activities, NH4+-N content and bacterial diversity in soil. It is needed to make a deep study.