Long-lived plants, such as perennial woody species, are subjected to harsh environmental circumstances as a result of global warming. Drought stress is one of the most harmful abiotic stresses to plant growth and productivity of all the abiotic stresses. A group of microbes and microbe-derived substances that have been shown to improve plant development under biotic and abiotic stress conditions. Plants are home to a wide variety of microorganisms. Members of these microbial communities interact with one another and with the plant, and there is mounting evidence that the microbial community can help plants develop, enhance drought tolerance, aid disease defence, and even help with environmental remediation. These bacteria supply the plant with a variety of services and benefits in exchange for the plant providing decreased carbon and other metabolites to the microbial community. Soils are typically moist environments with low carbon content that support diverse soil microbial populations. The rhizo-microbiome's microbes are involved in nutrient acquisition and assimilation, improved soil texture, and extracellular substances such as hormones, secondary metabolites, antibiotics, and different signal chemicals are secreted and modulated, all of which leads to improved plant development. The microbes and compounds they produce are bio stimulants that help plants respond to stress. Studies have demonstrated that inoculating plants with plant-growth-promoting rhizobacteria (PGPR) or treating plants with microbe-to-plant signal molecules is an effective way to stimulate crop development. The goal of this review is to highlight the various ways in which plant growth promoting microorganisms (PGPM) can be used to improve crop production under drought stressed condition. The most up-to-date information on microbial inoculant technology is discussed. As a result, a deeper understanding of the mechanisms that determine the composition and structure of microbial communities, as well as the involvement of the host in the recruitment and management of its microbiome, is critical. Plant defence mechanisms, in particular, appear to provide a layer of protection against pathogens while also actively managing the makeup of the general microbiome, according to a growing body of studies. Plants detect water deficits at their roots and send a signal to their shoots, which cause them to synthesize abscisic acid (ABA) in their leaves. ABA is a crucial phytohormone that controls physiological and molecular responses to drought stress, including stomatal closure, gene expression, and osmo-protectants and stress proteins accumulation. The initial stage in the propagation of synthesized ABA is through ABA transporters. ABA inflow in guard cells is sensed by numerous protein kinases that regulate stomatal closure, such as SnRK2s and MAPKs, to limit water loss. To develop drought stress resistance in entire tissues, ABA mediates a wide array of gene expression machines using stress-responsive transcription factors like DREBs and AREBs. We present an overview of current research into the mechanisms used by the plant host to select and control its microbiome in this review. Recent research on the role of keystone microbial species, phytohormones, and abiotic stress in plant-driven dynamic microbial structure is reviewed in detail.
Research Review | Published online : 12-Oct-2021