Soil Salinity and Climate Change: Microbiome-Based Strategies for Mitigation of Salt Stress to Sustainable Agriculture

Abstract

Global climate change, environmental stresses, intensification of cropping practices, changed precipitation cycles, depleted water resources and reduction in soil fertility are the major constraints limiting crop productivity. Among various environmental (abiotic) stresses, soil salinity is one of the serious climate change impact, which affects about 20 and 33% of the total cultivated and irrigated agricultural lands, respectively. In recent years, soil salinization of agricultural land, along with water and environmental pollution; have emerged as significant threats to worldwide food security and agricultural sustainability. Salt stress results from excessive accumulation of salts in the soil that significantly affects soil fertility, stability, biodiversity, and consequently affects crop productivity. These problems necessitated the search of sustainable and eco-friendly agri-technologies to ameliorate the adverse effects of salt stress on plant growth and crop yield. In this context, some microorganisms inhabiting either the plant rhizosphere in extreme environments, or within halophytic plant roots, also possessing other plant growth-promoting traits, showed enormous potential in enhancing the adaptation ability of stressed plants to salinity stress conditions. These plant-associated beneficial microbes play key role in salt stress mitigation by producing osmoprotectants, antioxidants, ACC deaminase enzyme, hormones, exopolysaccharides, organic acids, nitric oxide and siderophores along with increased nutrient availability. Subsequent inoculations of crop plants with such salt–tolerant plant growth–promoting bacteria (PGPB) were found to increase the plant growth and crop yield of different plants grown in saline soils. This review briefly summarizes the different biochemical and molecular mechanisms employed by rhizospheric microbial communities for alleviation of salinity stress. Further, in-depth knowledge related to beneficial interactions of salt-tolerant microbes with the native crop plants is needed to facilitate plant growth and crop productivity under saline agro-ecosystems.