Compositional Comparison Of Rhizosphere Microbes And Root Endophytes Between Transgenic And Non-transgenic Rice

The potential environmental risk associated with transgenic rice has caused widespread concern. Field studies of transgenic Bt rice have been carried out to assess its risk to the environment. Based on traditional culture and PLFA analysis methods, the seasonal effects of transgenic rice on soil enzyme activities, microbial communities and endophytic bacteria were compared under field conditions. The obtained results contribute to the risk assessment for transgenic Bt rice.(1) Comparison of the effects of transgenic and non-transgenic rice on rhizosphere soil enzyme activity. The results showed that at the tillering and heading stage, invertase activity in B4b68 paddy fields and polyphenol oxidase activity in Ⅱyou-Kefeng 8 paddy fields were significantly lower than in the control paddies. At the tillering stage, urease activity was significantly higher in both transgenic rice fields than in the control paddies. At the heading stage, protease activity was significantly lower in both transgenic rice paddies than in the control paddies. Considering the dynamics of the entire period, only the trend of protease activity in the IIyou-Kefeng8 paddy fields was different from that observed in the control paddy fields.(2) Comparison of the effects of transgenic and non-transgenic rice on culturable rhizosphere soil microbes. The results showed that transgenic rice did not affect the trend of the variation in the numbers of bacteria and fungi.The IIyou-Kefeng8 cultivar had a significant effect on the changes in the number of actinomycetes. The decreasing order of the three groups of microbes was bacteria, actinomycetes and fungi. At the booting stage, the total number of soil bacteria associated with IIyou-Kefeng8 transgenic rice was significantly lower compared to the non-transgenic controls.(3) Comparison of the effects transgenic and non-transgenic rice on uncultured soil rhizosphere microbes. Using the PLFA method, the influences of the transgenic rice cultivars B4b68 and Ilyou Kefeng8 on the soil microbial community structure were examined under field growing conditions. The results showed that the contents and variety of phospholipid fatty acids were great in the soil associated with transgenic rice plant roots. The relative content of phospholipid fatty acids in the four examined rice cultivars showed the following order:B4b68> B4b68 control> Ilyou-Kefeng control> IIyou-Kefeng8.(4) Comparison of the effects of transgenic and non-transgenic rice on endophytes obtained from boots. The results showed that 16 species of bacteria belonging to 9 genera could be identified using the Sherlock MIS automatic microorganism identification system. These genera were Bacillus, Microbacterium, Acinetobacter, Enterobacter, Pseudomonas, Stenotrophomonas, Photobacterium, Lactococcus and Burkholderia. Alkalophilic Bacillus were associated with both transgenic and non-transgenic rice. The distribution of the other bacteria differed between different rice varieties.