BACKGROUND: Rhizosphere soil microbes associated with plants influence the health and growth of plants through a variety of mechanisms. This study investigated the effects of rice genetically modified to be resistant against rice blast and rice bacterial blight on the soil microbial community. A comparative analysis of the effects of rice genetically modified for disease resistance (GM rice) and the Nakdong parental cultivar (non-GM rice) on the soil microbial community at each stage was conducted using soil samples from the rhizospheres of the GM rice and Nakdong rice.
METHODS AND RESULTS: The soil chemistry at each growth stage and the bacterial and fungal population densities were analyzed. Soil DNA was extracted from the samples, and the microbial community structures of the two soils were analyzed by pyrosequencing. No significant differences were observed in the soil chemistry and microbial population density between the two soils. A total of 98,839 pyrosequencing reads were obtained from the pyrosequencing analysis. The taxonomic analysis showed that Chloroflexi, Proteobacteria, Firmicutes, Actinobacteria, and Acidobacteria were present in all soils as the major phyla and dominant classes in all soils were Anaerolineae and Deltaproteobacteria. Although the source tracking and XOR analysis per phylogenetic rank revealed that there were differences in the bacteria between the GM soil and non-GM soil as well as among the cultivation stages, the GM soil and non-GM soil were grouped according to the growth stages in the UPGMA dendrogram analysis.
CONCLUSION: The difference in bacterial distribution rate between Nakdong and OsCK1 rice soils at each phylogenetic level detected in metagenome analysis by pyrosequencing may be due to the difference between GM and non-GM, or due to heterogeneity of the soil environment. In order to clarify this, it is necessary to analyze the changes of primary and secondary metabolite pathways in the plant body occurred by introducing transgene. A more detailed study involving additional multilateral soil analyses is required.