Isolation of salt tolerant endophytic and rhizospheric bacteria by natural selection and screening for promising plant growth-promoting rhizobacteria (PGPR) and growth vigour in tomato under sodic environment

The importance of plant growth promoting rhizobacteria in growth promotion and their ability to elicit ‘induced systemic tolerance’ against abiotic stresses has been documented. However, the performance of these microbes under various abiotic stresses especially saline-sodic conditions will be of great importance in the current agricultural scenario. In this study, we isolated 16 rhizobacteria through natural selection from saline sodic soils, and characterized them using morphological and biochemical parameters. These bacteria were assessed for their plant growth-promoting rhizobacteria (PGPR) traits like indole-3-acetic acid (IAA) production, ammonia and hydrogen cyanide (HCN) production, phosphate solubilization, etc. Furthermore, they were screened for in-vitro salt (NaCl) tolerance and Na+ uptake pattern, where two stress tolerant rhizobacteria B-1 and B-3 identified as Bacillus pumilus and Bacillus subtilis showed all PGPR traits with tolerance to salinity. These isolates also elicited significantly higher vigor index in tomato seedlings grown in pot culture experiments under saline sodic soils of pH 9.35 and EC 4.2.   Key words:  Rhizobacteria, salt tolerant, natural selection, PGPR.

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