Abstract

The ability of a few soil microorganisms to convert insoluble forms of phosphorus (P) to an accessible form is an important trait in plant growth-promoting bacteria for increasing plant yields. The use of phosphate solubilizing bacteria as inoculants increases the P uptake by plants. In this study, isolation and characterization of 3 strains of phosphate solubilizing bacteria (PSB) from Central province of Iran were carried out. Identification of three isolates was carried out by 16S rDNA sequencing. Three strains namely Bacillus lentus strain PS5, Bacillus Licheniformis strain PS7 and Pseoudomonas putida strain PS13 were isolated from the rhizospere of Beta vulgaris and solanum tuberosom. All of the three strains were selected in vitro for their phosphate solubilizing abilities from alkaline soils. Among the three strains, PS5 and PS7 were the most efficient strains in terms of their capabilities to grow and solubilize phosphorus in the presence of 5% NaCl and 42°C. Root colonization analyses were performed to determine the distribution and metabolic activity of the strains in the potato rhizosper. The soil containing potato seedling was treated with all strains marked with lux genes for bioluminescence, as well as resistance to kanamycin and rifampin prior to planting in non-sterile natural soil. The introduced bacteria were quantified on roots by dilution plating on antibiotic media along with observation of bioluminescence. Results demonstrated the strains could survive in the potato root system under stress conditions. The significance of this study lies in the fact that the bacterial strains isolated from alkaline soils have ability to solubilize phosphate in high salt, pH and temperature conditions.

Key words: Phosphate solubilization, potato, Bacillus, Pseudomonas, Iran.