Molecular Characterization and Plant Growth Promoting Efficacy of Rhizobium sp. from Sesbania Root Nodule Adopted from Madurai Region, Tamil Nadu, India

The present study aims to evaluate the efficacy of an endosymbiotic bacterial strain associated with Sesbania species and its plant growth efficacy on peanut plants. Plant samples were collected around 10 different sites in Madurai, Tamil Nadu, India. We used the conventional isolation technique to isolate the endosymbiant. The qualitative plant growth promoting characters and a quantitative growth hormone analysis were performed. The active strains were phylogenetically studied, followed by seed germination and growth promotion characters by the grow bag method. Totally 80% of the samples (n = 8) are nodulated and 8 Rhizobium sp. are isolated. Out of eight, six isolates failed to absorb congo red on YEMA medium. About 37.5% of isolates showed positive results on ammonia, phosphate, siderophore, organic acid, and HCN production. About 25% were zinc solubilizers and ACC deaminase producers. Isolates SR1 and SR5 were found to have all plant growth characters reveal the maximum production of IAA, GA and cytokine. Both strains showed more efficient seed germination on Sesbania and peanut plants (>70%) than control. Peanuts showed seed treated with SR1 and SR5 strains had a higher maximum vitality index, than control. Both Rhizobium sp. treated data on plant growth, nodulation, and LHB content were found to be statistically significant at 0.05. Phylogenetic analysis using the 16S rRNA gene and evolutionary relatedness by the neighbor-joining method reveals that the similarity of active strains was found to be Sinorhizobium meliloti SR1 and Rhizobium leguminosarum SR5. The research concludes that the Sesbania endosymbiotic Rhizobium sp. has many physiological traits, including phytohormones and enzyme production, which can help overcome soil fertility as well as other legume plant growth promotion.