Bacterial exopolysaccharide amendment improves the shelf life and functional efficacy of bioinoculant under salinity stress.

AIM:Bacterial exopolysaccharide (EPS) possesses numerous properties beneficial for the growth of microbes and plants under hostile conditions. The study aimed to develop a bioformulation with bacterial EPS to enhance the bioinoculant's shelf-life and functional efficacy under salinity stress. METHODS AND RESULTS:High EPS-producing and salt-tolerant bacterial strain (SD2) exhibiting auxin-production, phosphate-solubilization, and biofilm-forming ability was selected. EPS-based bioformulation of SD2 improved the growth of three legumes under salt stress, from which pigeonpea was selected for further experiments. SD2 improved the growth and lowered the accumulation of stress markers in plants under salt stress. Bioformulations with varying EPS concentrations (1% and 2%) were stored for 6 months at 4°C, 30°C, and 37°C to assess their shelf-life and functional efficacy. The shelf life and efficacy of EPS-based bioformulation was sustained at higher temperature, enhancing pigeonpea growth under stress after six months of storage in both control and natural conditions. However, the efficacy of non-EPS-based bioformulation declined following four months of storage. The bioformulation modulated bacterial abundance in the plant's rhizosphere under stress conditions. CONCLUSIONS AND IMPACT STATEMENT:The study brings forth a new strategy for developing next-generation bioformulations with higher shelf-life and efficacy for salinity stress management in pigeonpea under saline conditions.