Effects Of RRS On The Diversity Of AOB And AOA In Rhizospheric Soils

Roundup Ready Soybean (RRS) [Glycine max (L.) Merr.] was one of genetically modified crops and produced by the Monsanto company in the United States. The release of GM plants to agricultural ecosystems has raised a number of questions, including the ecological impact of these plants on soil ecosystems. Recently, the impact of GM crops on communities of microorganisms, microbe-mediated processes and functions in soil ecosystem was becoming more and more concerned in the world.As materials of the experiment, four genotypes'soybean including RRS, the parent of RRS (RRS-S), the cultivated soybean variety Dongnong 46 (D-46) and the wild soybean (W-S) were compared in the study. The experiment were conducted in this study in order to investigate effects of Roundup Ready Soybean (RRS) on the diversity of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) in rhizospheric soils using molecular techniques polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and DNA sequencing targeting ammonia monooxygenase (amoA) gene.The conclusion about effects of RRS on AOB communities in the study: the diversity analysis indicated that Shannon-Wiener diversity indexes (Dsh) and evenness indexes (Jsh) related to ammonia-oxidizing bacteria (AOB) in RRS rhizospheric soils were all lower than those of near-isogenic counterparts (RRS-S), W-S and D-46; the principal component analysis demonstrated that the compositions of ammonia oxidizing bacterial communities in RRS rhizospheric soils were different from those of its parent RRS-S and other soybeans (D-46 and W-S); sequencing of DGGE bands and phylogenetic analysis revealed that Nitrosospira-like AOB were the most dominant AOB inhabiting in the rhizospheric soils of different genotypes'soybeans, the amoA sequences associated with the soil samples mostly grouped within the amoA cluster 3a, cluster 9 and cluster 1, RRS promoted some groups of ammonia oxidizing bacterial communities, such as groups represented by bands 10 and 19, however, inhibited the other groups, such as groups represented by band 1, 8, 12 and 20. Our results indicated that RRS reduced the diversity of AOB, changed ammonia-oxidizing bacterial community structure and affected the growth and distribution of some groups of AOB in rhizospheric soil to some extent.The conclusion about effects of RRS on AOA communities in the study: the diversity analysis indicated that Shannon-Wiener diversity indexes (Dsh) and evenness indexes (Jsh) related to ammonia-oxidizing archaea (AOA) in RRS rhizospheric soils were similar to those of near-isogenic counterparts (RRS-S), W-S and D-46, and the difference was not significant among them; the principal component analysis demonstrated that the compositions of ammonia oxidizing archaeal communities in RRS rhizospheric soils were different from those of the other soybeans (D-46 and W-S), but not significantly different from its parent RRS-S; AOA amoA gene sequencing of DGGE bands and phylogenetic analysis revealed that parts of AOA in the rhizospheric soils of different genotypes'soybeans belonged to clusters which had presented in the present references in the soils, others belonged to unknown clusters or groups in the present references,but none of AOA identified belonged to water-like AOA or sediment-like AOA. In addition, the AOA amoA sequences associated with the soil samples mostly grouped within the amoA cluster 6, cluster 7 and cluster 8, and cluster 6 AOA were the most dominant AOA inhabiting in the rhizospheric soils of different genotypes'soybeans. RRS promoted some groups of ammonia oxidizing archaeal communities, such as groups represented by bands 3, however, inhibited the other groups, such as groups represented by band 1, 20 and 25. Our results indicated that RRS didn't affect the diversity of AOA or there were only a smaller impact on the diversity and the community structure of AOA ,but RRS affected the growth and distribution of some groups of AOA in rhizospheric soils to some extent.