Genetic Biodiversity of Nitrogen-Fixing Bacteria from Agricultural Soil of Madhya Pradesh State, India

Abstract

Nitrogen fixing bacteria, especially Bradyrhizobium and Rhizobium are of great importance in sustainable agriculture. Rhizobium is unique because of its ability to live symbiotically with legumes and it accounts for most of the biolologically fixed nitrogen. In the present investigation, fifty strains of Rhizobium spp. (R1, R2, R3, R4, R5, R6.........R50) from agricultural land of Madhya Pradesh were subjected to biochemical and genetic characterization. Fifty strains confirmed as Rhizobium spp. were used for further microbial diversity study. Percent G+C content of all the isolated strains was calculated by determining melting temperature of DNA (Tm). Tm of all the strains ranged between 94.3 to 95.7⁰C. However % G+C content of isolated strains ranges between 61.0 to 64.4 %. Furthermore, the pattern of genetic diversity was studied using known and established molecular biotyping methods. In the present observation isolated Rhizobium species were examined by RAPD-PCR genomic fingerprinting using 2% agarose. This technique helps to compare actual DNA fragments from the genome of bacteria. Genetic polymorphism is a technique most widely acceptable in presentation of genetic hierarchy. The Dendrogram show divergence at 25% similarity into two broader groups. R25 strain shows 75% dissimilarity with all the strains isolated from agricultural soil of Madhya Pradesh. RAPD analysis establishes similarity even upto 85% with R1, R39, R10 and R35 strains. The results indicated that RAPD is a very discriminative and efficient method for differentiating and studying genetic diversity of Rhizobium strains.

Keywords: Genetic diversity, Rhizobium, RAPD-PCR, Tm-value, %G+C content.