Isolation, selection and characterization of salt and temperature tolerant plant growth promoting rhizobacteria.

Abstract

The present study was focused on isolation, selection and characterization salt and temperature tolerant plant growth promoting rhizobacteria from rhizosphere soil of tomato. Out of one hundred thirty eight samples total forty eight isolates grown on Ashby’s Mannitol agar media. For assessment of salt and temperature tolerancy the medium was supplemented with different NaCl concentrations, MgCl2 concentration and different pH level. All the forty eight isolates showed promising salt tolerance. Out of forty eight isolates nine isolates were extremely (6% NaCl) salt tolerant (more than 5.4% salt tolerance limit). Two isolate were tolerant to NaCl concentration (2.10–3.6% salt). Nine isolates were moderately tolerant to NaCl concentration (0.09–1.50% salt). Twenty six isolates were moderately sensitive to NaCl concentration (0.15–0.60% salt). Classification of salt and temperature tolerant plant growth promoting rhizobacteria was done on the basis of salt tolerance limit. Out of forty eight isolates, eight isolates showed growth at MgCl2 concentration of 4.0%, two isolates showed growth at 3.0% MgCl2 concentration, thirteen isolates showed growth at 2.0% MgCl2, fifteen isolates showed growth at 1.0% MgCl2 and eight isolates showed growth on 0.5% MgCl2 concentration. Among forty eight isolates, eight isolates showed growth at 9.0 and remaining thirty eight isolates showed growth at pH 7.0. Out of forty eight isolates, four isolates (STTA8- Pseudomonas furukawaii, STTA12- Achromobacter sp, STTA24- Agrobacterium pusense and STTA39- Agrobacterium pusense) were showed plant growth promoting activity test positive. STTA8- Pseudomonas furukawaii, STTA12- Achromobacter sp. Shown temperature tolerance limit 600c and STTA24- Agrobacterium pusense and STTA39- Agrobacterium pusense shown temperature tolerance limit 500c.The work was carried out for the isolation, selection and characterization of salt and temperature tolerant plant growth promoting rhizobacteria which would be highly important inoculum to improve the growth and development of the tomato plant under saline environment. There is currently need to develope highly salt and temperature tolerant plant growth promoting rhizobacterial consortium.