Isolation and selection of highly effective phosphate solubilizing bacterial strains to promote wheat growth in Egyptian calcareous soils

Abstract

Forty phosphate solubilizing bacterial (PSB) isolates were isolated from the root zone of wheat plants cultivated in the Delta and the Northwestern coast regions of Egypt. All isolates proofed their ability to dissolve tricalcium phosphate on the National Botanical Research Institute's phosphate growth medium (NBRIP) by producing clear zone and increasing the available phosphorus that ranged between 40 and 707 mg l−1. They were designated as Egyptian native phosphate solubilizing bacteria (ENPSB). All strains proofed their ability to dissolve tricalcium phosphate on (NBRIP) medium by producing clear zone and increasing the available phosphorus that ranged between 40 and 707 mg l−1. The ENPSB 1, 2, and 3 strains were highly efficient as they gave 707, 653, and 693 mg l−1 soluble phosphorus respectively. Intriguingly, the two highly efficient strains for phosphate solubilization were isolated from the Northwestern coast alkaline soils. Moreover, 75% of strains were also produced profitable amounts of indole acetic acid (IAA) ranged from 0.79 to 50.5 mg l−1. Amazingly, the most efficient strain ENPSB 1 in solubilizing phosphorus (707 mg l−1soluble P) was the best one for producing IAA (50.5 mg l−1). The three efficient strains were identified using the sequencing of 16S rRNA. Sequence analysis of 16S rRNA for selected strains confirmed that the strains ENPSB 1, 2, and 3 were genetically closed to Enterobacter aerogenes; Pantoea sp. and Enteriobacter sp. respectively. The inoculation by mix cultures of strains (ENPSB 1, 2, and 3) contributed to raising the dry weight and P content of wheat plants by 76% and 12% over the full fertilized plants. Inoculation of soil PSB can be used to solve the deficiency of phosphorus and promote plant growth effectively in calcareous soils.