RESUMO
AIMS: Aim of this study is to determine the genetic variation of rhizobia associated with horse gram [Macrotyloma uniflorum (Lam.) Verdc.] plants grown in different regions of Andhra Pradesh, India. METHODS AND RESULTS: Four representative isolates having most representative characters from the previous characterization were selected for 16S rRNA sequence. The sequences were submitted to the NCBI GenBank and Ribosomal Database Project (RDP). The isolates HGR-4, 6 and 13 showed more than 99% homology between them and they were grouped with Rhizobium reference strains where as the isolate HGR-25 showed 87.1, 87.4 and 87.2% homology with the isolates HGR-4, 6 and 13, respectively, and were grouped with reference strains for Caulobacter. The nodulation ability of these isolates on horse gram was confirmed by inoculation tests. CONCLUSIONS: The isolate HGR-25 was identified as Caulobacter isolated from the plants growing in soil samples collected from Khareemnagar district, Andhra Pradesh, India. Inoculation tests revealed that Caulobacter formed nodules on horse gram. It was also confirmed by RDP. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report that a legume was nodulated by a member of the genus Caulobacter, which belongs to the family Caulobacteriaceae in the order Caulobacterales of Alphaproteobacteria.