Optimisation of Growth Factors for Effective Use of Phosphate Solubilizing Bacterial Strains and Its Use as Bioinoculants for the Growth of Groundnut (Arachis hypogaea) Plant

Phosphorus (P) is one of the essential macronutrients for plant growth. Phosphate solubilizing bacteria (PSB) are organisms which are used as bioinoculants to enhance the plant growth. Plants take phosphate in the form of soluble orthophosphate ions but due to the presence of calcium, magnesium, potassium, sodium, aluminium and ferrous ions in soil, the soluble orthophosphate is converted in to insoluble form. Because of this process plants utilize very little amount of phosphate, even though phosphorus containing fertilizers are added to the plants. Phosphate-solubilizing bacteria (PSB) has been added as fertilizer to increase phosphorus uptake and plant growth. It is usually observed that the solubilization of phosphate by the phosphate solubilizing bacteria would drop the pH of the medium. Acidification of the medium may be due to production of organic acids by the bacterial strains. Such plant growth-promoting bacteria has the ability to produce enzymes such as Phosphatase and 1-aminocyclopropane-1-carboxylate (ACC) deaminase to lower plant ethylene levels, that often results in various stresses, which shows the efficacious functioning of these bacteria. This study aims in the optimization of growth factors of the isolated PSB strains for use as a Biofertilizers, specifically to study the effects of temperature, pH and different carbon, nitrogen sources and NaCl concentrations on phosphate solubilization ability. The results showed phosphate solubilization was expressed maximum at pH 6, temperature 25 °C, dextrose as carbon source, ammonium sulphate as Nitrogen source and (1.2%) NaCl concentration by the PSB strains. Further the PSB was applied as bioinoculants to enhance the root, shoot length and phosphorus accumulation content of ground nut (Arachis hypogaea) seedlings. Present study highlights the importance of these plants growth promoting bacterial strains and their uses for agriculture purposes as a Biofertilizer.