Seed bio-priming with ACC deaminase-producing bacterial strains alleviates impact of drought stress in soybean (Glycine max (L.) Merr.)

This study investigated the efficacy of 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase-producing rhizobacterial strains isolated from soybean rhizosphere to alleviate the negative impact of drought stress in soybean. Twenty rhizobacterial strains were isolated from disease-resistant soybeans, and only four isolates displayed ACC deaminase activity (more than 500 nmol of ketobutyrate mg protein−1 h−1). These strains also exhibited a variety of plant growth-promoting (PGP) traits, such as ammonia production, indole acetic acid concentration (>35 g mL−1), hydrogen cyanide (HCN) production, and solubilization of inorganic calcium orthophosphate (>70 μg mL−1). Bio-priming soybean seeds with these four bacterial isolates (AKAD 1-2, AKAD 1-3, AKAD 3-1, and AKAD 3-7) improved in vivo drought tolerance in soybean and identified them as Pantoea agglomerans (MH304295), Bacillus subtilis (MH304311), Bacillus cereus (MH333217), and Bacillus licheniformis (MH304284) based on 16S rDNA gene sequencing. Seed bio-priming with rhizobacteria mitigates the adverse effects of drought stress and increases shoot length (16–68.6%), root length (40–108%), proline content (14.87–42.69%), sugar content (11.36–67.3%), and protein content (11.77–45%). The potential enzymatic activities of catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) also increased by 35.87%, 26.63%, and 15.15%, respectively, in drought-stressed plants. The results support the efficacy of these isolates as effective bio-stimulants for improving crop performance in drought-affected agricultural fields. Thus, the present work opens new avenues for harnessing the potential of rhizobacterial bio-stimulants to address the challenges posed by drought stress in soybean cultivation, thereby advancing sustainable agricultural strategies for future food security.