Isolation and characterization of plant growth-promoting rhizobacteria from soil

To isolate and select useful microbial resources for agricultural environments, 26 microbial species with diverse colors and morphologies were isolated from soil.Antifungal tests against three plant pathogens revealed that seven strains, including CH22-3 (identified as Burkholderia ambifaria) and AB22-1 (Bacillus amyloliquefaciens), exhibited antifungal activity, with CH22-3 and AB22-1 showing the strongest effects.Evaluation of plant growth-promoting traits such as nitrogen fixation, phosphate solubilization, IAA, and siderophore production showed that all seven strains demonstrated nitrogen fixation, with CH22-3 achieving the highest phosphate solubilization (135.6%), and AB22-1 exhibiting the highest levels of IAA production (8.0 g ml -1 ) and siderophore production (5.7 mm halo zone).Lettuce treated with AB22-1 at concentrations of 110 5 to 110 7 cfu/ml showed increases in shoot and root biomass by 26 -31% and 18 -20%, respectively, compared to the control group, indicating AB22-1 strain potential as a biofertilizer.These results underscore the need for further comparative studies with chemical fertilizers.