Enhancement of plant growth by Bacillus is well documented and several mechanisms have been suggested for the phytostimulatory activity of this group of plant growth-promoting rhizobacteria (PGPR). In the present work, the PGP potential of plant associated Bacillus spp. and their growth-promoting effect on wheat were studied. Six out of 35 strains were chosen based on seed germination assay, plant growth-promoting abilities, enzymatic function, and auxin production. All tested strains were subjected to pot experiments and their phenotypic and molecular assays were also done. Two Bacillus strains including WhIr-15 and WhIr-12 produce maximum amount of auxin (16.2 and 14 μg ml−1, respectively). Strain WhIr-15 had just the ability to produce indo-3-acetic acid (IAA), lipase, and protease enzymes. Strain WhIr-12 was also recorded positive for siderophore, auxin production, and phosphorus (P) solubilization. Bacterial IAA production positively correlated with root length (r = 0.875; p ≤ 0.05). Significant enhancement in root weight (71% and 53%) and in panicle weight (91% and 77%) was recorded in WhIr-15 and WhIr-12, respectively, over untreated controls. Based on phenotypic and 16S rDNA sequencing, these two strains belong to Bacillus sp. Based on our results, phytohormone-producing Bacillus sp. can be applied at field level to improve wheat productivity.

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