Effect of Phosphate Solubilizing Bacteria with Multifarious Plant Growth Promoting Traits on Growth of Mung Bean

Phosphorus stands as a pivotal macronutrient crucial for the development of plants. Overuse of phosphate fertilizers can lead to groundwater contamination and soil deterioration. The utilization of phosphate solubilizing bacteria (PSB) biofertilizer provides a sustainable and eco-friendly alternative for agricultural practices. This study focused on isolating PSB strains from the rhizosphere of native plants in the Northern Western Ghats (NWG) exhibiting multifunctional plant growth-promoting traits. Five PSB isolates were chosen from the rhizospheres of Meiogyne pannosa (Dalzell) J. Sinclair (MG2, MG5), Myristica dactyloides Gaertn. (MR1, MR2), and Knema attenuata (Hook. fil. & Thoms.) Warb. (KN2). Isolates were evaluated for nitrogen fixation, indole-3-acetic acid (IAA) production, 1-aminocyclopropane-1-carboxylate (ACC) deaminase production, and ammonia production. MG2 and MG5 displayed positive traits for mentioned plant growth-promoting (PGP) characteristics, while MR1, MR2, and KN1 exhibited positive traits for four PGP attributes. MG5 showed the highest phosphorus release from tri-calcium phosphate, substantial IAA production and ACC deaminase activity. KN2 and MG2 also demonstrated significant phosphorus release and IAA production alongside ACC deaminase activity. The high R2 and negative correlation coefficient in the linear regression model between soluble phosphorus concentration and pH of NBRIP broth confirm organic acid’s role in phosphate solubilization. All five isolates significantly enhanced shoot and root length as well as plant biomass of mung beans, with KN2 having the most pronounced influence on mung bean growth, followed by MG5. This study emphasizes the importance of PGPR isolates harbouring multiple PGP activities for enhancing plant growth. KN2 and MG5 emerge as promising biofertilizer candidates with significant potential for sustainable crop production.