Phosphate mobilizing microorganisms of agricultural plants in arid ecosystems of the Astrakhan region

Crop productivity and yield are negatively affected by the deficiency of phosphorus in agricultural soil. Phosphate fertilizers are widely used to improve crop yields globally. Therefore, there is an urgent need to increase plant-available phosphorus in soil using feasible environmentally friendly technologies. Isolation and screening of strains with increased phosphate-solubilzing activity are necessary stages of research to intensify the phosphorus nutrition of plants by presowing inoculation of seeds with effective microorganisms. 50 isolates of microorganisms (49 bacterial and 1 yeast) were isolated from the rhizosphere and rhizoplane of agricultural plants in arid ecosystems of the Astrakhan region. Bacterial isolates are morphologically represented by Gram-positive spore-forming (3 pcs.) and non-spore-forming (43 pcs.) rod-like bacteria and cocci (3 pcs.). Preliminary screening of phosphate solubilization by isolates on solid nutrient media revealed a group of 6 isolates with maximum specific phosphate mobilization (the specific phosphate mobilization coefficient – Kr –value was 2.0–6.9 units) and the ability to reduce the pH of the medium. Determination of the dynamics of mobile phosphate content allowed us to identify an isolate capable of maintaining the mobile phosphorus amount at up to 6 μmol/ml and lowering in pH up to 4.73 in the medium. The studied isolate should be recommended as the basis of a biological preparation for optimizing the mineral nutrition of plants.