Bacterial Mitigation of Drought Stress in Plants: Current Perspectives and Future Challenges

Climate change is emerging as a crucial issue with global attention and leading to abiotic stress conditions. There are different abiotic stress which affects the crop production among which drought is known to be most destructive stress affecting crop productivity and world's food security. Different approaches are under consideration to increase adaptability of the plants under drought stress with plant-microbe interactions being a greater area of focus. Stress-adaptive microbes either from the rhizosphere, internal tissue, or aerial parts of plants have been reported which through different mechanisms help the plants to cope up with drought and also promote their growth. These mechanisms include the accumulation of osmolytes, decrease in the inhibitory levels of ethylene by aminocyclopropane-1-carboxylate (ACC) deaminase enzyme, and furnishing the unavailable nutrients to plants. Microbial genera including Azotobacter, Bacillus, Ochrobactrum, Pseudomonas, and Serratia are known to be self-adaptive and growth promoters under drought stressed conditions. Stress-adaptive plant growth promoting (PGP) microbes thus are excellent candidates for stress alleviation in drought environment to provide maximum benefits to the plants. The present review deals with the effect of the drought stress on plants, biodiversity of the drought-adaptive microbes, mechanisms of the drought stress alleviation through enhancement of stress alleviators, reduction of the stress aggravators, and modification of the molecular pathways as well as the multiple PGP attributes of the drought-adaptive microbes.