Studies on molecular characterization of Azospirillum spp. isolated from Thanjavur district.

Altogether 30 Azospirillum strains isolated from paddy rhizosphere soil were identified as nitrogen fixers. A preliminary screening of all the species isolated from soils were made for nitrogen fixing activity.Among 30 strains three species of Azospirillum showed promising activity. These strains were classified as a unique grass by RAPD fingerprinting restriction enzyme analysis and 16S rRNA gene sequencing. Phylogenetic analysis of the 16S rRNA gene indicated that these diazotrophic strains belonged to the genus Azospirillum and were closely related to A. brasilense (with 84% similarity), A.amazonense (78% similarity) and A. halopraferens (93% similarity).