Vol. 7, Issue 2, Part A (2025)

The increasing demand for sustainable agriculture has intensified research on plant growth-promoting rhizobacteria (PGPR), with Bacillus subtilis emerging as a promising candidate due to its diverse biochemical capabilities and adaptability to soil environments. This study aimed to isolate B. subtilis from the rhizospheric soil of paddy fields and evaluate its plant growth-promoting (PGP) traits through comprehensive biochemical characterization. Soil samples were subjected to serial dilution and heat treatment to selectively isolate endospore-forming bacteria. Colonies showing typical Bacillus morphology were purified and identified via Gram staining and endospore staining. Biochemical tests confirmed the identity of the isolate as B. subtilis. The strain was further evaluated for key PGP attributes, including phosphate solubilization, indole-3-acetic acid (IAA) production, siderophore production, ammonia production, and hydrogen cyanide (HCN) activity. The isolate showed positive results for phosphate solubilization on Pikovskaya’s agar and produced significant levels of IAA in tryptophan-amended broth. The bacterium exhibited moderate ammonia production, indicating potential nitrogen assimilation benefits. However, HCN production was absent, supporting its non-toxic interaction with host plants. The study demonstrates that B. subtilis isolated from paddy fields possesses multiple PGP traits and can be considered a viable bioinoculant for rice cultivation. Its ability to promote plant growth through direct and indirect mechanisms highlights its potential role in reducing chemical fertilizer dependency and enhancing sustainable crop productivity. Further in planta trials and genomic characterization are recommended to explore its full agronomic potential.