Numerous species of soil bacteria which flourish in the plant rhizosphere, but may grow in, on, or around plant tissues, stimulate plant growth by various direct and indirect mechanisms. These bacteria are collectively known as PGPR (plant growth promoting rhizobacteria). The search for PGPR and investigation of their modes of action are increasing at a rapid pace as efforts are being made to exploit them commercially as biofertilizers. In this study a total of 27 bacteria having unique colony and cell morphology were isolated from the rice rhizosphere soil. These isolates were screened for plant-growth promoting (PGP) traits, including indole acetic acid (IAA) production, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, P-solubilization, and siderophore, cyanide (HCN) and ammonia (NH3) production. Percentage of isolates having IAA, ACC deaminase, P-solubilization, siderophore, HCN and NH3 activities was 85.2%, 18.5%, 44.4%, 37%, 25.9% and 48.2% respectively. 11.1% of the total isolates did not have any PGP traits whereas the percentage of isolates having one and six PGP traits was 22.2% and 3.7% respectively. There was a positive correlation (0.630, p<0.05) between phosphate solubilizers and NH3 producers and there was no significant relationship among other PGP traits in rhizobacteria. Further evaluation of the isolates exhibiting multiple PGP traits on soil–plant system is needed to uncover their efficacy as effective PGPR.
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