Plant growth-promoting rhizobacteria from Ocimum basilicum improve growth of Phaseolus vulgaris and Abelmoschus esculentus

Abstract

The aim of the current study was to isolate, characterize, and assess the plant growth-promoting traits of bacterial isolates inhabiting the rhizosphere of the Ocimum basilicum (basil plant) in the Al-Ahsa region. Five bacterial isolates were isolated from the rhizosphere of the basil, and characterized morphologically, biochemically, and genotypically. Our isolates displayed multiple plant growth-stimulating features, such as nitrogen fixation , solubilization of inorganic phosphate, and production of phytohormones, ammonia, and acetoin . All bacterial isolates were able to grow under elevated NaCl concentrations of up to 3 %. Only FPW14 grew at 10% NaCl. Comparative sequence analysis of the 16S rRNA gene revealed that FPM11 and FPI13 belonged to Pseudomonas alcaliphila and Pseudomonas hunanensis , respectively, to which they showed 98.66% and 97.36% homology, respectively. Strains FCL6, FPK12, and FPW14 showed 16S rRNA gene sequences with 97.21%, 98.08%, and 98.37% identities with those of Streptomyces laurentii , Sinorhizobium sp., and Bacillus safensis , respectively. A neighbor-joining phylogenetic tree constructed using the 16S rRNA gene sequences clustered the bacterial isolates with their corresponding recognized bacterial species, providing robustness to the taxonomic affiliation of our strains. Bacterial inoculation significantly enhanced the root growth parameters of Phaseolus vulgaris L. In conclusion, all isolates belong to plant growth-promoting bacteria and can be used as biofertilizers to increase soil fertility and plant productivity in the Eastern region of Saudi Arabia.