The Effect Of Genetically-Modified Cotton On The Diversity Of Soil Bacteria

As the improvment of genetic engineering Genetically-modified (GM) crop brings a good revolution to the prevention of insect pests. The technique plays an important role of breeding pest prevention. Moreover, it can bring harmony of economic returns. But the potential risk due to its complexity and unpredictability of the transgenic crops has aroused great concerns of the scientists allover the world. Many countries made some strict assessments on the ecological safety before the GM cottons had been used.Soil is the base camp of microorganism, the effect of the GM cotton on the soil microorganisms is an important part of GM evaluation system. Returnning straw into farmland is widely used in many countries, so the effect of GM plant residue to soil microorganisms is also impretant. Entomogenous fungi are a kind of soil function microorganisms, and reviewing the changes of Entomogenous fungi by RT-PCR has great significance. It is urgent to construct a system of ecological safety assessment for the GM cotton.In this study, the diversity of soil bacteria in different cotton growth phases was analyzed by enumeration of plate count method combined with statistical methods. The results indicated that the diversity of soil bacteria changed along with the temperature and growth phase of cotton. The numbers of bacteria increased firstly, and then decreased. The value arrived peak at squaring stage. The numbers of fungus decreased firstly, and then increased. The value arrived peak at boll stage. The value of actinomyces showed a downtrend. Through statistical analysis, we could n’t find the effect of GM cotton to soil microorganisms.We also detected the dehydrogenase, the urease and the phosphatase of soil sample in different cotton growth phases. The results indicated that the urease and the phosphatase is unchanged,in the intact period of duration, but the dehydrogenase has a little changed. The results showed that the GM cotton did’t has effect to soil enzyme activity. Moreover, the soil enzyme activity of the sample which added the different concentration of GM cotton plant residue was detected. The results indicated that high concentration of plant residue can increase the soil enzyme activity, but lower concentration of plant residue only can change the dehydrogenase activity. At the condition of high concentration of plant residue, GM cotton could reduce the soil enzyme activity.