Seventy bacterial strains were isolated from root nodules of the legume Hedysarum flexuosum grown wild in soils from Northwest Morocco. Repetitive extragenic palindromic (REP)-polymerase chain reaction (PCR) clustered the strains into 30 REP-PCR groups. The nearly complete sequence of the 16S rRNA gene from a representative strain of each REP-PCR pattern showed that 17 strains were closely related to members of the genus Rhizobium of the family Rhizobiaceae of the Alphaproteobacteria. Pairwise alignments between globally aligned sequences of the 16S rRNA gene indicated that the strains from H. flexuosum had 99.75-100% identity with Rhizobium sullae type strain IS123(T). The phenotypic characteristics analyzed allowed description of a wide physiological diversity among the isolates, where the carbohydrate assimilation test was the most discriminating. Analysis of the 16S rRNA gene of a representative strains from the remaining 13 REP-PCR groups showed they belong to a wide variety of phylogenetic groups being closely related to species of genera Stenotrophomonas, Serratia, Massilia, Acinetobacter, Achromobacter, and Pseudomonas from the Beta- and Gammaproteobacteria. The R. sullae strains identified in this study produced effective symbiosis with their original host plant. None of the other bacterial strains could form nodules on H. flexuosum.
Keywords: 16S rRNA gene; Hedysarum flexuosum; Phylogenetic tree; Rhizobium sullae.
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