Effect Of Transgenic Bt Maize On Soil Microbial Diversity

Transgenic Bt maize was one of the most quickly commercialized genetically modified crops all over the world, it has been genetically modified to express the cry1Ab gene from Bacillus thuringiensis(Bt) and produce an insecticidal toxin to kill lepidopteran pests, especially the corn borer. With the generalizing and ceaselessly expanding planting area of transgenic Bt crops around the world, it has been paid more attention by researchers in many disciplines for their effects on environment and soil ecosystem. In this study, three-room rhizobox method was used to collect the growth room(S1),rhizosphere(S2)and non-rhizosphere(S3)soil samples from three different zones of maize, traditional microbiological methods and molecular methods were combined to analysis the effects on soil microbial(bacteria, actinomycetes, fungi) amount, soil bacterial diversity, soil available nutrients, soil enzyme activities, soil microbial biomass C and N of transgenic Bt maize and its parental maize at 40,50 and 60 days after sowing. The results of the researches showed as follows:1. Effects of transgenic Bt maize on populations of soil bacteria.The results of traditional culture-depending method showed that planting transgenic Bt maize significantly reduced the amount of soil cultivable bacteria and actinomycetes in S1 zone at 50 and 60 days and reduced the amount of soil cultivable fungi in S1 zone at 40 and 60 days, but increased the amount of cultivable bacteria in S2 zone and actinomycetes in S3 zone at 40 and 50 days, and showed no significant impact in the other zone. Planting transgenic Bt maize influenced the populations of microorganisms, but changed with the different zones and growing stages.2. Effects of transgenic Bt maize on soil bacterial diversity.The soil bacterial diversity was analyzed by applicated PCR-DGGE technology. In three growing stages, the soil bacterial diversity in root zones of transgenic Bt maize and parental maize was abundant. DGGE fingerprints indicated that DGGE bands, diversity index and homogeneous degree index of bacteria were not significantly different in three sampling stages(P<0.05). Planting transgenic Bt maize was not affected the soil bacterial diversity significantly.3. Effects of transgenic Bt maize on soil available nutrients and enzyme activitys.The results showed that, compared with the parental maize, planting Bt maize had no significant influence on soil nitrate content, but soil ammonium nitrogen and available phosphorus content of the root zone at different days were changed, and no significant variation, Soil catalase activity had no significant changed, soil urease activity significantly increased 6.91 % at 50 day in S1 root zone, alkaline phosphatase activity significantly reduced 8.12 % at 60 day in S1 root zone. Principal component analysis showed that soil available nutrients and enzyme activitys of transgenic Bt maize was similar with non-transgenic parental maize, only a little difference from three sampling days. The influence on soil available nutrients and enzyme activities for planting transgenic Bt maize was rather small.4. Effects of transgenic Bt maize on soil microbial biomass C and N.Researched the changes in content of soil microbial biomass C and N, the results showed that, planting Bt maize had no significant influence on soil microbial biomass C, but reduced the content of soil microbial biomass N at 40 d compared with the parental maize, soil microbial biomass C and microbial biomass N significantly increased at 50 d, soil microbial biomass C and N content was different from the root spatial dynamic distribution at 60 d. The soil microbial biomass C/N was different between transgenic Bt maize and the parental maize, changed with the different zones and growing stages.