Formulation and Evaluation of a Salt and Temperature Tolerant Rhizobacterial Consortium for Tomato Cultivation under Abiotic Stress Conditions

The present study focused on preparation of consortia of salt and temperature tolerant rhizobacteria isolated from the rhizosphere soil of tomato. A total of 138 isolates were obtained from the rhizosphere of tomato plants grown in the laboratory of the Department of Agricultural Microbiology, MPKV, Rahuri, Maharashtra, between 2020 and 2023. Out of that twelve salt and temperature tolerant were identified, six most efficient strains were selected for consortia formulation. The liquid consortium containing Six (Pseudomonas furukawaii STT-A8, Achromobacter sp. STT-A12, Agrobacterium pusense STT-A39, Priestia flexa STT-K13, Bacillus sp. STT-K24 and Brevibacterium epidermidis STT-N28) extremely salt and temperature tolerant rhizobacteria isolates were formulated for their mass production as liquid consortium by comparing the respective selective media with different concentration for these isolates. Among the selective strains, P. furukawaii STT-A8, Achromobacter sp. STT-A12, A. pusense STT-A39 and B. epidermidis STT-N28 these are nitrogen fixers, able to convert atmospheric nitrogen into usable forms it helps in improving soil fertility and crop productivity. All isolates solubilize insoluble phosphate into bioavailable forms except Bacillus sp. STT-K24 to promote root development and making plants resilient to environmental stress. Bacillus sp. STT-K24, P. flexa STT-K13, P. furukawaii STT-A8 and Achromobacter sp. STT-A12, these isolates that converts insoluble form of potash (K) into soluble form that plant can absorb and utilize. Out of five test media (M1, M2, M3, M4 and M5), M3 medium contained Mannitol (5.0 g), Peptone (5.0 g), Glucose (15.0 g), Tricalcium phosphate (3.5 g), K2HPO4 (1.50 g), Potassium aluminium silicate (1.50 g), Calcium phosphate (1.50 g), Calcium carbonate (1.50 g), Yeast extract (1.50 g), Ammonium sulphate (0.2 g), MgSO4.7H2O (0.2 g), NaCl (0.2 g), K2SO4 (0.1 g) was found best. The M3 medium was further formulated by using different concentrations of cell protectants at pH 9.00 was devised as liquid medium L5M3. After preparation of consortium, the optimum population of all six salt temperature tolerant rhizobacteria were observed upto 12 months. The composition of L5M3 media was best that consists of Standard medium (M3), Fe. EDTA (0.30 g), Arabinose (0.60 g), Glycerol (3.0ml), PVP (16.00 g), Trehalose (1.0 g) and Distilled water (1lit). This consortia applied in tomato field under extreme saline and high temperature stress condition and showed very good results.