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.
Keywords: ACC deaminase; Biofertilizer; Indole acetic acid; PGPR; Rhizosphere.