Microbe-Mediated Drought Tolerance in Plants: Current Developments and Future Challenges

Abstract

Drought is a conspicuous stress-causing deleterious effect on plant growth and productivity. In order to compensate the yield loss due to drought, efficient and sustainable strategies are required for its management. Drought stress tolerance is complex trait involving clusters of genes; hence, genetic engineering to generate drought-resistant varieties is a challenging task. In this context, the application of plant growth-promoting microbes (PGPM) to mitigate drought stress is gaining attention as an attractive and cost-effective alternative strategy. PGPM have envisaged a plethora of mechanisms to overcome drought stress in plants which encompasses ACC (1-aminocyclopropane-1-carboxylate) deaminase activity, production of exopolysaccharide (EPS) and volatile organic compounds (VOCs), osmolyte and antioxidant production, enhanced uptake of mineral nutrients, phytohormones production, and modulation. These mechanisms either individually or collectively bestow the PGPRs to combat drought stress in plants. The association of arbuscular mycorrhizal fungi (AMF) with the roots of crop plants can significantly promote water and nutrient uptake by host plants and induce tolerance to drought stress. The inoculation of PGPM in crop plants is also capable of modulating host transcriptome for induced drought tolerance. Further, efforts are needed to develop proficient microbial consortia for enhancing plant growth under drought stress. Thus, the application of PGPM/AMF represents a promising approach to increase nutrient availability and expedite the development of sustainable agriculture.