Isolating, characterizing and identifying plant growth- promoting rhizobacteria from wheat rhizosphere

This study focused on isolating, characterizing and identifying plant growth promoting rhizobacteria (PGPR) related to wheat (Triticum aestivum L.) rhizosphere from multiple locations in Egypt. One hundred thirty rhizobacteria were successfully isolated from the rhizosphere of five different geographical regions where wheat is growing. The primary screening evaluated the main characteristics of the PGPR, which included indole-3-acetic acid (IAA), gibberellins (GA3), dissolution of phosphate and potassium, and the production of siderophores. Sixty- six of the isolates displayed functional traits that promote plant growth, with IAA concentrations that range from 5.15 to 528.70 µg/mL, gibberellin production levels ranging from 0.73 to 132.06 µg/mL, and phosphate solubilization capacity with halo areas ranging from 187.5% to 900%. Of the isolates, about 83.07% showed the ability to solubilize potassium. Further evaluations, including hydrogen cyanide (HCN) and ammonia production, were conducted. Then the most potent eighteen isolates were screened for phosphatase and nitrogenase activities as well as root colonization capacity. Finally, the three isolates (SA30, EK86 and SD102) that exhibited the highest PGPR performance in the previous screening were identified using 16S rRNA as Bacillus velezensis (PQ661188MTaher) for isolate SA30, Pseudomonas aeruginosa (PQ661189MTaher) for isolate EK86, and Bacillus tequilensis (PQ661190MTaher) for isolate SD102. These strains could be used as strong PGPR inocula due to their multifunctional plant growth-promoting properties. These results support the potential use of local Egyptian PGPR isolates in sustainable agriculture as environmentally friendly alternatives to synthetic agrochemicals.