Synergistic rhizobacteria enhance physio-biochemical resilience and sustain tomato yield under drought stress

Beneficial rhizobacteria can enhance plant growth and stress resilience through multiple, complementary mechanisms. In this study, we investigated the combined effects of Azotobacter chroococcum, Pseudomonas putida, and Bacillus subtilis on tomato plants subjected to drought stress. The primary objective was to assess whether a combined bacterial inoculation could mitigate the negative impacts of drought on tomato growth and productivity. We hypothesized that the consortium would act synergistically to improve drought tolerance by enhancing physiological performance and biochemical defense systems, including photosynthetic activity and antioxidant enzyme responses. The combined application of beneficial rhizobacteria significantly increased total chlorophyll content from 0.85 to 1.70 mg g⁻¹ FW and relative water content from 55.41 to 72.06%, while maintaining higher photosynthetic pigment levels than drought-stressed controls. Biochemical analyses revealed markedly higher activities of antioxidant enzymes, with superoxide dismutase increasing to 35.4 µmol min⁻¹ mg⁻¹ FW, catalase to 74.6 µmol min⁻¹ mg⁻¹ FW, and peroxidase to 0.89 µmol g⁻¹ FW, indicating more effective mitigation of drought-induced oxidative stress. All individual rhizobacterial treatments significantly increased tomato yield relative to drought stress, reaching 0.81, 0.86, and 0.88 kg plant⁻¹ under inoculation with (A) chroococcum, P. putida, and (B) subtilis, respectively. The bacterial consortium produced the highest yield of 0.94 kg plant⁻¹. Overall, these findings demonstrate that synergistic plant-microbe interactions can substantially enhance drought tolerance and productivity in tomato. Future studies should examine the long-term stability and field performance of microbial consortia, their interactions with native soil microbiomes, and their scalability for sustainable crop production in water-limited agroecosystems.