Microbial management of crop salinity stress: Mechanisms, applications, and prospects

Abstract

Salinity stress is a major deterrent to crop growth worldwide. A high concentration of salt in soil and irrigation water reduces water uptake by plants, which triggers a range of cellular and metabolic processes ultimately resulting in lowered crop yield. Genetics of salinity tolerance in plants is well understood and has been successfully utilized to breed improved crop varieties; however, such strategies are long drawn and cost intensive. Microorganisms due to their immense metabolic diversity can be very useful to devise low-cost strategies to ameliorate salinity stress in crop plants. An intricate and highly complex interaction between plant and microbe results in alleviation of salt stress. Although the cross talk between the plant and microbe is not clearly understood, regulation of osmotic balance and ion homeostasis by microorganisms are mostly mediated through modulation of phytohormone production, alteration in gene expression, protein function, and metabolite synthesis in plants. Consequently, improved antioxidant activity, accumulation of compatible solutes, proton extrusion mechanism, salt compartmentalization, and improved nutrient status in plants can reduce the osmotic shock and ionic toxicity. Microbial management of salt stress offers an eco-friendly, cost-effective approach which however requires a rigorous selection, testing, and validation of the microbial strain(s) besides understanding the cross talk between the plant and microbe. Therefore, the aim of this chapter is to discuss the salinity response in plants and also to understand the mechanisms of microbe-mediated salinity stress alleviation on the molecular basis.