Salt-Tolerant Bacteria (Brachybacterium sp. and Bacillus spizizenii ) Enhance Growth, Photo-synthetic Pigments, and Antioxidant Defense of Vicia faba under Drought Stress

This study evaluates the mitigating effects of five salt-tolerant bacterial strains on drought-induced growth suppression in bean plants. An experiment was conducted with V. faba subjected to drought and treated with five salt-tolerant bacterial strains. Growth traits were measured at 7 days, 15 days, and during a recovery stage. All bacterial treatments enhanced growth traits relative to the control across time points. At 7 days, Bact2 (Brachybacterium sp.) and Bact4 (Bacillus spizizenii ) showed the strongest responses, with increases of 275%,339% in shoot fresh weight, 209%, 373% in shoot dry weight, 153%, 170% in shoot length, and 205%, 222% in leaf number, respectively. By 15 days, Bact2 and Bact4 again yielded the highest values across traits, with substantial but slightly reduced relative gains. During recovery, Bact2 and Bact4 markedly continued to boost growth metrics over the control. Fresh and dry weights rose steadily from day 7 to recovery, Bact4 leading, followed by Bact 2; plant length and leaf number also increased over time, with Bact2 and Bact4 driving the largest gains. Pigment content rose significantly in all bacterial treatments, with Bact2 and Bact4 achieving the greatest enhancements. Salt-tolerant bacteria enhanced pigment content and antioxidant enzymes in Vicia faba under drought. By day 15, Bact2 and Bact4 most strongly boosted chlorophylls, carotenoids, APX, and PPO versus control, with recovery further elevating these markers. These strains show promise for sustainable strategies to bolster crop productivity in arid environments. These findings highlight potential microbial inoculants for sustainable faba bean cultivation under water scarcity.