Comparison of partial 23S rDNA sequences from Rhizobium species.

A hypervariable region of Rhizobium 23S rDNA was amplified by polymerase chain reaction and phylogenetic relationships of several strains were determined by comparing nucleotide sequences of the amplified product. Variation in the 23S rDNA nucleotide sequences was consistent with phylogenetic relationships determined by host nodulation specificity and (or) 16S rDNA sequence analysis. Six strains representing three Rhizobium species (R. leguminosarum bv. trifolii, R. meliloti, and R. etli), and two strains each of Bradyrhizobium and Agrobacterium were clustered into five rDNA groups. Unique features identified by secondary structure analysis of the 23S rRNA sequenced region were consistent with the hypothesis that 23S rDNA could be used to design species- or strain-specific Rhizobium probes.