Effects Of Insect And Herbicide Resistant Transgenic Rice On Soil Rhizosphere Microbial Communities

Nowadays,transgenic technology is developing rapidly.However there are also some problems regarding its safety. The safety problem associated with GM crops have attracted the attention of many people in society. One of the important factors regarding environmental safety is the influence of GM crops on soil microorganisms. This study used cultivation-dependent(Biolog,and plate culture methods)and independent methodologies(PCR-DGGE)to study the effects of the two main types of transgenic rice and glyphosate herbicides on soil microbial community structure and functional diversity.Soil samples were collected at different rice rhizospheres and at different developmental stages to study the effects of the two main types of transgenic rice on soil microbial communities..Through plate count records the biomass of microorganisms in all the rice rhizosphere soil samples at the different stages (seedling, tillering and maturity)was found. In every developmental stage, there were no changes between transgenic rice and non-transgenic rice. Indicated transgenic rice had no effect on cultivable bacterial colony numbers.The 16s rDNA sequences in the total DNA from soil samples were amplified and analyzed using PCR-DGGE.. The results showed that transgenic rice influenced soil microbial biomass and microbial community structure less than non-transgenic rice.Generally, we will use herbicides when we plant transgenic rice. Therefore, a short-term plot study was carried out using two concentrations of glyphosate (27 and 270mg active ingredient kg-1 soil, as a commercial formulation, Roundup Plus) arranged in a completely randomized design with three replicates. Results showed that after herbicide (27mg/kg) treatment, a glyphosate-induced stimulation of the biomass of the soil microbial community's cultivable portion was observed. A maximum was reached 7 days after glyphosate treatment. However, after another herbicide (270mg/kg) treatment, the biomass of the soil microbial community's cultivable portion gradually decreased (p<0.05).After 15 days, this trend was reverted. Analysis of carbon metabolism characteristics (Biolog ECO) showed that two concentrations of glyphosate affected bacterial abundance and carbon metabolism characteristics. Two concentrations of glyphosate influenced bacterial and actinomycete soil community structure. A high concentration of glyphosate had a more significant effect.A greenhouse plot study was carried out using an indicator (azotobacter) to observe changes in microbial biomass and microbial community structure in the rhizosphere soil of GM rice (glyphosate-tolerant rice). Results showed that 2 days after glyphosate treatment, there was a significant increase in the number of indicator bacteria and cultivable soil microbial biomass. However, utilization of carbon substrates resulted in no effect on bacterial abundance and carbon metabolism characteristics. The result from DGGE showed that soil bacterial, actinomycete, and azotobacter community structure and functional diversity were unchanged.