Functional evaluation of Phosphate Solubilizing Bacteria under impacts of Salt stress
Availability of soluble phosphate is a key challenge for crop plants, specially under the impacts of various abiotic environmental stressors present simultaneously in agricultural lands. There is a need to isolate and characterize novel bacteria which can survive under harsh environmental conditions and concurrently perform activities of plant growth promotion like phosphate solubilization and production of plant growth regulators. This work was done to test rhizobacterial isolates for phosphate solubilization under impacts of salinity stress. Out of 18 rhizobacterial isolates tested only 5 showed phosphate solubilization on PKV agar plates and were labelled as PSB1, PSB2, PSB3, PSB4 and PSB5. These isolates were tested for phosphate solubilization in NBRIP broth media where they showed generation of different amounts of soluble phosphate. The performance of PSB1 being the best, it solubilised highest amount of phosphate (25.73 µg/ml) and also produced maximum decline in pH of the broth media. When tested in presence of 0.25M salt stress the phosphate solubilization by PSB1, PSB3 and PSB5 were enhanced while a reduction was observed for PSB2 and PSB4. In presence of 0.5M salt the phosphate solubilization by PSB3 was even more than that in control. The consortium of three isolates PSB1, PSB3 and PSB5 with significant phosphate solubilization index showed synergistic effect on phosphate solubilization and it was (27.91 µg/ml) better than any individual isolate tested alone. The bacterial isolates also produced indole acetic acid, a plant growth regulator and PSB1 was most efficient IAA producer.