Molecular Analysis of Soil Bacterial Community Structures for Environmental Risk Assessment with Varieties of Genetically Modified Soybean and Hot Pepper

Abstract

With the advance of gene technology, genetically modified (GM) crops have increased in recent years. GM crops offer us various benefits. But there are potential risks of GM crops on the environment. In this study, the impacts of transgenic plants on soil microbial community structures were assessed by using both cultivation and molecular methods during two consecutive years, 2015 and 2016. Two varieties of soybean (Glycine max L.) and hot pepper (Capsicum annuum L.) were used in this study. The herbicide resistance gene, bar, was introduced in soybean and hot pepper. The field plot consisted of four subplots planted with GM soybean, non-GM soybean, GM hot pepper, and non-GM hot pepper. To investigate whether or not GM crops have effects on the densities of soil microorganisms, specific selective media were used. To assess the effects of transgenic crops on microbial community structures, PCR-amplified 16S rRNA genes and nitrogenase genes (nifH) of soil microbial population were analyzed with denaturing gradient gel electrophoresis (DGGE) procedure. 16S rRNA gene sequencing on Illumina MiSeq platform was also performed to analyze soil microbial community distribution. Additionally, persistence of transgenes was monitored using quantitative real-time PCR procedure. The cultural methods and DGGE analysis indicated that soil microbial communities were not significantly different between GM and non-GM lines during the experimental period. The Amplicon-based community profile on Illumina MiSeq platform showed that soil microbial community structures were similar between GM and non-GM lines. The level of the introduced gene (bar) into soybean was greatly increased in soil when the crops were actively growing in the experimental field, but thereafter its level was gradually decreased to the initial level. Meanwhile, the level of the introduced gene (bar) into hot pepper was repeatedly increased and decreased about 4 times in soil depending on its flowering stages. These results indicated that soil microbial community structures were not significantly affected by cultivation of GM soybean and hot pepper varieties.