Isolation and identification of diazotrophic bacteria from rice, wheat and kallar grass

Three bacterial isolates were obtained from the roots of rice, wheat and kallar grass. These isolates fix nitrogen in pure culture as confirmed by acetylene reduction assay in semi-solid nitrogen-free growth media. Production of growth hormones by these isolates was confirmed by colorimetric method. The isolates from wheat (strain Wb-3) and rice (strain N-4) were identified as Azospirillum brasilense and A. lipoferum, respectively, on the basis of their morphology, carbon utilization pattern and biochemical tests. The isolate K-l from kallar grass, previously identified as Azospirillum brasilense, was confirmed to belong to a newly named genus Azoarcus (Reinhold-Hurek et al., 1993) by using 16S rRNA-targeted oligonucleotide probes and some morphological and physiological characteristics.