The genetic diversity of chickpea strains was studied by using 30 isolates obtained from nodules on chickpeas growing in uninoculated fields over a wide geographic range. The following taxonomic approaches were used: DNA-DNA relatedness analysis, restriction fragment length polymorphism analysis of the amplified 16S ribosomal DNA (rDNA) intergenic spacer (IGS), and total 16S rRNA sequence analysis. The division of chickpea-infective strains into two major phylogenetic groups (groups A and B) that has been described previously was confirmed by the polymorphism of the 16S IGS rDNA. We identified a total of five genomic species, including the previously described species . All of the group B strains except one were homogeneous and belonged to a single genomic species corresponding to . Group A was heterogeneous, containing three genomic species and five strains that remained unclassified, and its members had very different PCR restriction fragment length polymorphism profiles. The complete 16S rRNA sequences of strains representing the two major groups. UPM-Ca7 (T = type strain) and genomic species 2 strain UPM-Ca36, exhibited 19 mismatches. Both of these strains belonged to the branch; UPM-Ca7 was closely related to , and strain UPM-Ca36 was clearly separated from and closely related to . Thus, genomic species 2 could be distinguished from by its 16S rRNA sequence, by DNA relatedness data, by the polymorphism of the 16S IGS rDNAs, and by previously described multilocus enzyme electrophoresis results and phenotypic characteristics. Therefore, we propose that strains belonging to genomic species 2 should be classified in a new species, , and that strain UPM-Ca36 should be the type strain.


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