Optimization of IAA production and P-solubilization potential in Bacillus subtilis KA (1) 5r isolated from the medicinal herb Aconitum heterophyllum-growing in western Himalaya, India

Abstract

Bacillus species from rhizosphere are well known to promote plant growth via acquisition of macronutrients and production of phytohormones. The present work deals with characterization of Bacillus subtilis strain KA(1)5r isolated from the rhizosphere of medicinal plant Aconitum heterophyllum for plant growth promoting traits and optimization of IAA production and P-solubilization. Optimized cultural conditions resulted in maximum P-solubilization (197 µg/ml) after 96 h of incubation at 35 °C in PVK broth (having concentration of TCP 1%) of pH 6.0 with 1% inoculum size of culture. In case of optimized cultural conditions for IAA production, the maximum IAA production (42 µg/ml) was observed after 96h of incubation at 35 °C in LB broth (with 1.0% of tryptophan concentration) of pH 8.0 amended with an inoculum size of 2%. The selected strain Bacillus subtilis strain KA (1)5r could significantly enhance the growth of tomato seedlings compared with that of non- inoculated plants. From the current study, Bacillus subtilis strain KA(1)5r emerged as noble alternatives for IAA production and P-solubilizer, further which also resulted in root and shoot biomass generation in tomato, hence can be further used as bio-inoculants for plant growth promotion.