Bacillus pumilus - A Potent IAA Producing Plant Growth Promoting Rhizobacteria with  In Vitro PGP Traits and Antagonism Against  Fusarium equiseti

Background Plant growth promotion through microbial mediation has garnered increasing focus in sustainable agriculture because of its capacity to enhance agricultural yield mustard [Brassica juncea (L.) Czern] as well as resilience. Bacillus pumilus, a PGPR, is known for synthesizing key phytohormones, such as IAA, which play a crucial role in modulating plant development. Tryptophan, a precursor for IAA biosynthesis, is another essential compound linked to the plant-bacteria interaction. HPLC serves as a powerful tool for the precise quantification of these metabolites, offering insights into the microbial mechanisms promoting plant growth. Additionally, antagonism against plant pathogens, such as Fusarium equiseti, further highlights the potential of Bacillus pumilus in crop protection. Results In this study, a bacterial isolate identified as Bacillus pumilus was evaluated for its PGP traits. The isolate demonstrated the production of significant amounts of IAA, as confirmed through HPLC analysis, revealing its metabolic capacity for enhancing plant growth. Alongside IAA production, the isolate exhibited other in vitro PGP activities, such as phosphate solubilization, and siderophore production, which are critical for improving nutrient availability to plants. Furthermore, Bacillus pumilus showed strong antagonistic activity against Fusarium equiseti, a notorious soil-borne pathogen, suggesting its role in biocontrol. Conclusion The study underscores Bacillus pumilus as a potent IAA-producing PGPR with multiple in vitro plant growth-promoting traits and effective antagonism against Fusarium equiseti. The use of HPLC for accurate quantification of IAA and tryptophan provides valuable insights into the microbial mechanisms driving plant growth promotion. These findings emphasize the potential of Bacillus pumilus as a bioinoculant in sustainable agriculture, offering a dual benefit of enhancing crop productivity and providing natural protection against plant pathogens. This research highlights the role of microbial-mediated strategies in advancing environmentally sustainable farming practices.