Comparative Effects of <i>Bacillus</i> strains applied Via Seed Biopriming and Soil Drenching Applications on the Morpho‐Physiological and Transcriptional Aspects of Cotton

Biofertilizers are considered as a sustainable solution for promoting the growth and productivity of crops while reducing the dependence on chemical fertilizers. There is a growing need for the sustainable agricultural solutions to lessen the reliance on chemical fertilizers; thus, evaluating Bacillus strains as biofertilizers for cotton growth promotion can support eco-friendly and economically viable crop production. Therefore, the growth promoting potential of endophytic Bacillus altitudinis strain TM22 and B. atrophaeus strain MCM61 applied as soil drenching or seed treatment, was evaluated on cotton cv. 'SS32'. In vitro, the qualitative assay both TM22 and MCM61 showed proteolytic, amylolytic, lipolytic, cellulolytic, and chitinolytic activity. TM22 and MCM61 strains also demonstrated the ability to produce siderophores, indole 3-acetic acid (IAA), and phosphate solubilization. In the pot experiment, seed biopriming with TM22 and MCM61 had better performance regarding plant growth and biomass, photosynthetic pigments, stomatal conductance, and relative leaf water contents than the soil drenching application. The gene expression analysis of growth hormones-related genes demonstrated that TM22 and MCM61 showed an upregulated expression of ARF1, ARF18, EXP6, IAA9, GIB1b, and CKX6 while ERF and ERF17 genes were downregulated. Overall, these findings suggest that seed biopriming with B. altitudinis TM22 and B. atrophaeus MCM61 is an effective method with the potential to enhance the biomass of cotton.