Molecular and Functional Characterization of Wheat Rhizosphere Associated Phosphate Solubilizing Bacteria. Phosphate Solubilizing Bacteria

Phosphorus (P) is a limiting crop nutrient in most of the Pakistani soils and farmers have to add huge amounts of DAP fertilizer to overcome this problem. These chemical phosphorus fertilizers not only increase the cost of crop production, but also pollute the environment. Keeping in view the importance of low cost production of wheat with high yield using environmentally safe management approach, the present study was designed to isolate P solubilizing bacteria from wheat rhizosphere of different un-explored soils and find their optimal efficacy under different growth and environmental conditions. Additionally, the mechanisms and genes involved in P solubilization were explored.Wheat rhizosphere associated phosphate solubilizing bacteria (PSB) were found to utilize and solubilize Ca-phosphate (60-280 µg/ mL), solubilized zinc (SI: 1.1-3.3), produced indole-3-acetic acid (0.6-28.1 µg/ mL), showed ACC deaminase and nitrogenase activity (281-528 nmol ethylene/h/mg protein) in in vitro studies. 16S rRNA gene sequencing identified PSB as Acinetobacter calcoaceticus, Acenitobacter heamolatycus, Enterobacter cloacae, Lactococcus lactis, Pantoea agglomerans, Pseudomonas flourescens, Pseudomonas plecoglocicida, Pseudomonas putida and Sinorhizobium meliloti. Among the organic acids detected by HPLC, gluconic acid was produced in higher quantity (102 µg/ mL) by the efficient P solubilizing Pseudomonas flourescens MS16