Plant growth promoting rhizobacteria (PGPR) are beneficial bacteria that colonize plant roots and enhance plant growth by a wide variety of mechanisms. Thus the present study focuses on the screening of effective PGPR isolate with multiple traits related to biocontrol of phytopathogenic fungi. In our study, a total of 51 bacterial isolates from the rhizosphere soil samples were isolated and screened for their antagonistic activity against wide range of phytopathogens. Bacterial antagonist showing highest percent and broad spectrum antagonism against fungal phytopathogens was selected and further identified as Pseudomonas aeruginosa FP6 on the basis of 16S rDNA gene sequence analysis. P. aeruginosa FP6 was screened for other plant growth promoting factors like phosphate solubilization, production of IAA, ammonia, siderophore and cell wall degrading enzyme activities- cellulase, chitinase and protease. The isolate was able to solubilize phosphate, produce IAA, siderophore, HCN, ammonia and biosurfactant. Study on effects of volatile and non-volatile antibiotic compounds on fungal phytopathogens inhibition showed volatile and diffusible metabolites as the major mechanism. The intrinsic antibiotic test showed that FP6 isolate was resistant to tetracycline, erythromycin, cotrimoxazole, rifampicin, ampicillin, cefepime and cefoxitin. Part of this study focused on the effect of NaCl, temperature, and pH on Pseudomonas aeruginosa FP6. Strain Pseudomonas aeruginosa FP6 was able to grow on up to 4.5 M NaCl, between 20 and 60°C and at pH 5–10. Inoculation of cowpea seeds with the P. aeruginosa FP6 significantly (P < 0.05) enhanced seed germination, seedling vigor index, plant height, and also fresh and dry weight in comparison with the control. Results from this study show the multifarious plant growth promoting activities of P. aeruginosa and suggests its potential use in developing a cost-effective eco-friendly multifunctional biofertilizer.
