Essential Nutrients Solubilization Ability of Fluorescent Pseudomonads and their Multinutrient Management

Soil microorganisms play a significant role in maintaining the ecological balance by active contribution in Carbon, Nitrogen, Sulphur and Phosphorus cycles in nature. Phosphate (P), Potassium (K) and Zinc (Zn) essential for optimum plant growth. Fluorescent pseudomonas are a group of Plant Growth Promoting Rhizobacteria (PGPR) naturally occurring soil microorganisms that aggressively colonize plant root and enhance the growth of plant and yield by direct and indirect mechanisms. In search for efficient nutrient solubilizing strains associated to Arachis hypogeae, a total of 55 isolates (JS-1JS-55) were obtained from the rhizospheric soil of Rayalaseema region of Andhra Pradesh, India. Among 55, eleven isolates exhibited multiple plant growth promoting traits viz. , direct mechanisms Solubilization of Phosphate, Zinc and Potassium.42 isolates exhibited positively for Tri-calcium phosphate solubilization on pikovskaya agar.25 isolates were able to solubilizing zinc. JS-17 produced 22.0 mm clear haloes on solid medium amended with ZnCO3. Similarly, JS-17 and JS-7 showed 31.0 mm zone in ZnO incorporated medium, 24 isolates were able to solubilizing Potassium. Maximum K solubilization occurred when KCl was used as a potassium source followed by K2SO4 and mica. These results recommended that the environmental conditions could be optimized for growth of indispensable mineral solubilizing bacteria and these bacterial cultures could be exploited for plant growth improvement under field conditions. Such multiple positive PGP traits and their isolates can be further explored as competent bioinoculants to improving plant growth and yield.