Potentiality of Plant Growth-Promoting Rhizobacteria in Easing of Soil Salinity and Environmental Sustainability

Salinity is one of the most prominent environmental stress found in the cultivated crops worldwide because many of the crops are susceptible to soil salinization resulting from the accumulation of salts in the soil. Salinity alters the physiology and metabolism of plants by a decrease in the rate of photosynthesis, respiration, protein synthesis, and lipid metabolism that lead to a reduction in yield of many crops. To overcome this problem, plants grown in saline conditions are engineered with plant growth-promoting rhizobacteria (PGPR agriculturally important bacteria) that inhabited in the rhizosphere of the plant. Globally, about 20% of cultivable land, as well as 50% of cropland, is under salinity stress according to the United Nations Environment Programme (UNEP). The beneficial effects of PGPR in alleviating salt stress involve boosting key physiological and biochemical pathways, viz., water and nutrient uptake, photosynthetic machinery, ion homeostasis, regulation of osmotic balance, regulation of redox status, capacity, regulation of endogenous phytohormone level, and availability of volatile organic compounds for plants. Therefore, it is recommended that the application of PGPR is an effective means to combat salinity stress in agricultural fields, thereby enhancing world crop productivity. The main emphasis of the chapter is to evaluate the salinity tolerance mechanisms exhibited by PGPR.