Screening of multi-faceted phosphate-solubilising bacterium from seagrass meadow and their plant growth promotion under saline stress condition

Soil salinity is one of the major limiting factors of the crop production, it has been constantly increasing in agricultural land due to the impact of climate change and urbanisation. High salinity in the agrolands can lead ionic, oxidative, osmotic and water stress to crops. A potential phosphate solubilising bacterium, Curtobacterium luteum was isolated from marine environment (seagrass meadow) and was evaluated for the enhancement of plant growth promotion of three different agro plants (rice, tomato and chilli) using agro saline soil. The strain C. luteum exhibited efficient phosphate solubilisation in both qualitative (SI-2.88) and quantitative (208.41 µg/ml) analysis at optimised conditions. In addition to phosphate solubilisation, it showed numerous valuable traits to promote plant growth such as - production of organic acids (Tartaric and malic acids), phosphatase, phytase (SI-2.9), IAA (4.1 µg/ml), urease and nitrogen fixation. The bacterium potentially enhances the plant growth under saline stress conditions and exhibited prominent plant growth promotion in all the three plants (rice, tomato and chilli) compared to the control. Also, it enhances the concentration of phosphorous in the soil and balances the soil pH. The present results indicate that the C. luteum can serve as a multifaceted biofertilizer under saline stress condition and be an effective alternative to the toxic chemical phosphate fertilizers that cater to the single purpose of providing phosphorous to plants.