Decomposition Dynamics Of Bar Transgenic Rice Straw In Soil

In order to know the impact of bar gene on the decomposition of transgenic rice and soil ecological environment, we investigated the kinetics of the degradation for rice straw, DNA release and bar gene residues in soil. Meanwhile, we also detected exctracelluar bar gene DNA in soil to detect the event of bar gene horizontal transferring to microbes.The decomposition dynamics of bar transgenic rice (B2) straw in soil were studied in Haikou and Beijing respectively compared with nontransgenic rice Xiushui11(W). The results showed that the degradation rate of straw biomass was fast and then slow over time, which fit the single phase exponential equation. In Haikou, half-degradation times of B2and W were36.7days and35.7days, and their biomass remained3.22%and3.05%on the180th day. In Beijing, the half-degradation time of B2and W were198.4days and182.4days, the biomass of B2and W remained25.78%and22.7%after360days of decomposition. There were no significant differences in decomposition rate between B2and W. The half-degradation time of B2biomass was one day longer than W in Haikou, but that was enlarged to16days in Beijing.There were no significant differences in dynamics between residual DNA content in B2and W from Haikou. They can be described by same single phase exponential equation, and the half-degradation time was calculated, which was35.36days. The half-degradation time of residual DNA content of B2and W were87.7days and80.6days, respectively.Exogenous gene bar and endogenous gene sps had been dectected in B2and W correspondingly by PCR. They had been detected from180-days-samples from Hainan, which, indicates that not only bar and sps in B2but also sps in W were still residued after180days. In order to have a more accurate analysis of the degradation decomposition dynamic of bar and sps, real-time PCR was applied to quantify bar and sps gene in Beijing samples. The results showed that the half-degradation time of bar gene was14.9days, which the sps gene in B2and W were14.3days and15.7days respectively. That the bar and sps in transgenic rice straw was slightly faster than that in wild type.In order to find the phenomenon of bar gene transferring to soil microorganisms, a method of extracting extracelluar and intracullar DNA from soil was established, based on the former researches. The DNA purity can meet the requirements for PCR. Extracellular and intracellular DNA can avoid any contamination from DNA released by each other. Extracellular and intracellular DNA which were extracted from straw litter surface soil were detected for bar and sps gene by PCR. The result indicated that there was no bar gene transfer from plant to soil microorganism. To sum up, bar transgenic rice straw would not pose a threat to the soil microorganisms.