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Appl. Environ. Microbiol. doi:10.1128/AEM.00833-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Microbial Community Analysis of Field-Grown Soybeans with Different Nodulation Phenotypes

Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan

^* To whom correspondence should be addressed. Email: kiwamu{at}ige.tohoku.ac.jp.

	Abstract

Microorganisms associated with the stems and roots of non-nodulated (Nod^-), wild-type nodulated (Nod⁺), and hypernodulated (Nod⁺⁺) soybeans (Glycine max [L.] Merril) were analyzed by ribosomal intergenic transcribed spacer analysis (RISA) and automated RISA (ARISA). RISA of stem samples detected no bands specific to the nodulation phenotype, whereas RISA of root samples revealed differential bands among the nodulation phenotypes. Pseudomonas fluorescens was exclusively associated with Nod⁺ soybean roots. Fusarium solani was stably associated with nodulated (Nod⁺ and Nod⁺⁺) roots and less abundant in Nod^- soybeans, whereas the abundance of basidiomycetes was just the opposite. The phylogenetic analyses suggested that these basidiomycetous fungi might represent a root-associated group in the Auriculariales.

Principal component analysis of ARISA showed that there was no clear relationship between nodulation phenotypes and bacterial community structures in the stem. In contrast, both bacterial and fungal community structures in the roots were related to nodulation phenotype. The principal component analysis further suggested that bacterial community structures in roots could be classified into three groups according to nodulation phenotype (Nod^-, Nod⁺, or Nod⁺⁺). The analysis for root samples indicated that the microbial community in Nod^- soybean was more similar to that of Nod⁺⁺ than to Nod⁺.