Unravelling the potential of microbes isolated from rhizospheric soil of chickpea (Cicer arietinum) as plant growth promoter.

In the present study, the Cicer arietinum (chickpea) rhizosphere bacterial strains Azotobacter chroococcum (AU-1), Bacillus subtilis (AU-2), Pseudomonas aeruginosa (AU-3) and Bacillus pumilis (AU-4) were isolated and characterized for plant growth-promoting traits with an aim of developing bio-fertilizing agent to improve growth and yield of chickpea plants under normal conditions. The ACC degrading potential of strains AU-1, AU-2, AU-3, and AU-4 was in the range of 600-1700 nmol α-ketobutyrate per mg of cellular protein per hour, respectively. These four rhizobacteria exhibited Indole acetic acid production approximately between 20 and 35.34 µg/ml. The phosphate solubilization potential was in the range of 78-87.64 mg Soluble P/L with maximum solubilization displayed by strains P. aeruginosa and B. pumilis. All the growth-promoting isolates displayed Fe-chelating siderophore and ammonia production while no isolate was able to produce hydrocyanic acid. Besides evaluating the presence of multifaceted in vitro plant growth-promoting traits, these four rhizobacterial isolates were halotolerant as well as water stress (drought) tolerant of up to - 1.2 Mpa of PEG 6000. The optimum pH and temperature for their growth were found to be pH 7 and 30 °C temperature. Under normal conditions, inoculation with formulated bacterial consortia significantly improved the (P ≤ 0.05) germination index, plant height, leaf area index, stem diameter, and chlorophyll content by ~ 50%, 100%, 63%, 185%, and 63%, respectively, as compared to uninoculated chickpea plants. The consortia of halotolerant and drought tolerant bacterial strains were shown to exert a positive impact on the growth of chickpea plants under normal conditions.