Effects Of Transgenic Rice On The Structure And Function Of Soil Microbial Community

With the commercialization of transgenic plants, their ecological risk assessment is forthcoming. Currently, ecological risk assessments of transgenic crops are focused on maize, cotton and potatoes. In this study, Bt-transgenic rice and its parent, non-transgenic rice were used to study the effects of transgenic rice on the structural and functional diversity of soil microorganisms in the Biological Ecosystem in Shoushan and the Wufeng experimental field site using the denatured gradient gel electrophoresis (DGGE) culture method. The primary results are as follows.(1) The results of the culture method showed that the amount of culturable microorganisms in the soil of various transgenic rice gradually increased from the seedling stage. The amount of soil microorganisms began to decrease after climbing to its peak in the booting and heading stages. The ratio between bacteria, fungi and actinomycetes was broadly maintained in the transgenic rice soils. When ranked by their amounts, the decreasing order of the various groups microorganisms was actinomycete, bacteria and fungi. The amounts of microorganisms in transgenic rice and non-transgenic rice soils were not significantly different. However, the amounts of microorganisms of different species in the transgenic rice soils at the Wufeng experimental field site were clearly higher than those of Soushan.(2) The measurements of urease, protease, invertase and polyphenol oxidase activities showed that the enzymatic activity of transgenic rice soil gradually declined from the seedling stage, then began to rise until the booting stage and reached a maximum at the heading stage. Transgenic rice increased the soil urease activity, invertase, and polyphenol oxidase activities, although these differences were not significant. As above, the enzymatic activities of the different species of microorganisms in transgenic rice soil from the Wufeng experimental field site were clearly higher than those of Soushan.(3) The molecular weight of amplified16S rDNA fragments was200bp in the transgenic rice and parental non-transgenic rice soils, which correspond to the specific fragments of the V3region of16S rDNA in bacteria. Genes. The DGGE fingerprints showed no significant differences in the numbers or placement of the microbial16S rDNA fragments between the transgenic rice and parental non-transgenic rice. Therefore, the influence of transgenic rice on the microbial diversity was not significant. A cluster analysis based on the DGGE patterns indicated that the transgenic rice were genetically closer to the parental non-transgenic rice than to the transgenic rice from other experimental field sites.(4) The spatial and temporal variations in the physiological function of the soil microbial community during various periods were analyzed using the method of Biolog. Based on the results of the diversity index and principal component analysis regarding the metabolic profiles of the microbial communities and a comparison of means analysis regarding the average well ccolor ddevelopment (AWCD) value of the metabolic reaction of the transgenic rice and parental non-transgenic rice, the metabolic activity of the transgenic rice soil microbial community was significantly lower than that of the non-transgenic rice microbial community in the maturity period. There was no significant difference at the booting or heading stage. However, the Mclntosh index can reflect the metabolic ability between the transgenic rice and parental non-transgenic rice soil microbial communities.