Impact of microbial consortium of Rhizobium tropici and Rhizobium mayense on the growth of Phaseolus vulgaris L.

The main objectives of the present investigation was to characterize and recognize potential indigenous Rhizobium spp. associated with red clover nodules, as well as to evaluate the influence of prospective rhizobia inoculation (individual and consortia) on common bean plant growth. Total of 8 rhizobia like bacteria were isolated and were investigated for their specific PGP traits, production of hydrolytic enzymes. Results revealed, four isolates synthesize IAA (22.3 ± 1.45 to 88.6 ± 1.45 μg mL−1), three isolates solubilized phosphate (40.69 ± 1.25 to 216.3 ± 1.31 μg mL−1), three isolates solubilized potassium, produced siderophore, and showed chitinase production, two isolates possess ACC deaminase activity, one isolate was able to solubilize zinc, 5 isolates produced β- 1, 3-glucanase (0.38 ± 0.005 to 2.82 ± 0.011 % units) and four isolates produced cellulase. Two bacterial isolates found to exhibit most of the PGP activities, were selected and identified on the basis of phenotypic, biochemical tests and 16S rRNA sequencing, as Rhizobium tropici IHTF-1 and Rhizobium mayense IHTF-2. Interaction of these potential rhizobium strains individually and consortia with common bean plants under greenhouse conditions boosted root and shoot length, fresh and dry biomass compared to un-inoculated control plants. SEM study revealed that both the strains, IHTF-1 and IHTF-2 colonized common bean roots. These results imply that Rhizobium spp., identified in this work, can be used as bio-inoculants to increase common bean plant production in a sustainable way.