Characterization of root-associated bacteria from paddy and its growth-promotion efficacy

Bacteria from rhizosphere (Bacillus pumilus) and endorhizophere (Pseudomonas pseudoalcaligenes) of rice plant were isolated and evaluated for their effect on the growth-promotion efficiency on rice in greenhouse. Ability to solubilize phosphate, siderophore, indoleacetic acid (IAA), gibberellin production and utilization of ACC (1-aminocyclopropane-1-carboxylate) as sole nitrogen source were evaluated, which were produced in high concentration by P. pseudoalcaligenes in this present study. Inoculation of isolated microorganism resulted in the reduction of pH (from neutral to acidic) of the medium used for phosphate solubilization, and has direct relation with titratable acidity, but gluconate production showed an opposite trend. P. pseudoalcaligenes better helped the plant to overcome or suppress fungal pathogen infection by producing beta-1,3-glucanase and chitinase as well as also have enhanced dry weight, plant height, and root length. Based on these results, P. pseudoalcaligenes in this study proved a better candidature as PGPR than B. pumilus.