16S microbial phylogeny of multifunctional plant-growth-promoting rhizobacteria from the rhizosphere of maize (Zea mays L.) for agricultural soil fortification

Soil microbial diversity plays an important role among the factors that affect plant growth. The present study was conducted with a focus on the isolation and characterization of native microbial strains from maize rhizosphere and the determination of their abilities for promoting plant growth and biocontrol in the for the fortification of agricultural soil. We isolated 156 microbial strains and qualitatively assayed their ability to synthesize ammonia, phosphate, indole acetic acid (IAA), and siderophores. Moreover, we tested their biocontrol traits, such as the synthesis of hydrolytic enzymes and antagonistic potential toward the fungal pathogen Fusarium moniliforme. Of the strains tested, 106 produced ammonia, 55 solubilized phosphate, 71 synthesized indole-3-acetic acid (IAA), 33 were positive for siderophores, 83 were able to hydrolyze cellulose, 84 were pectinase producers, and 44 strains were antagonistic to Fusarium moniliforme, a pathogen of maize. The potential strains were selected and phylogenetically characterized using 16S rRNA sequencing to study their evolutionary relatedness. Phylogenetic studies have revealed organisms of the genera Bacillus, Pseudomonas, Klebsiella, and Acinetobacter, which were previously found to be associated with the rhizosphere of maize and have varied diversity at the species level. The retrieved sequences were then submitted to the GenBank database. We found that a majority of the tested strains possessed at least one or more plant-growth-promoting features, indicating their role as potential plant-growthpromoting rhizobacteria (PGPRs). An application of these microorganisms in the field as PGPRs or biocontrol agents should be beneficial for sustainable agriculture.