Soil microbiome: Applications and mechanisms for salinity stress mitigation in plant and soil ecology: A review

Abstract

Soil health is paramount for sustainable agriculture, impacting crop production, nutrient cycling, and ecosystem stability. The microbial communities inhabiting diverse environments, termed microbiomes, play crucial roles in soil health and ecosystem functions. Among various stresses affecting plant growth, salinity stress poses significant challenges, resulting from high concentrations of soluble salts in the soil. This stress disrupts physiological processes in plants, impeding growth and productivity. Globally, extensive areas of agricultural lands face salinity issues, leading to substantial economic losses. Physiological responses of plants to salinity stress include osmotic and ionic stresses, as well as oxidative stress. Halophytes, adapted to high salt concentrations, contrast with glycophytes, which are more susceptible to salinity stress. The impact of salinity stress on plants extends from osmotic stress to ionic toxicity, affecting nutrient uptake, photosynthesis, and reproductive development. This review paper focuses on microorganisms, particularly salt tolerant plant growth promoting rhizobacteria (ST-PGPRs), which employ various strategies to mitigate salinity stress in plants. These strategies encompass cellular adjustments, salt-in approaches, osmolyte accumulation, and direct and indirect mechanisms for plant growth promotion. Direct mechanisms include nitrogen fixation, phosphorous solubilization, ammonia production, and the production of plant hormones. Indirect mechanisms involve the synthesis of ACC deaminase, Trehalose, siderophores, antioxidant enzymes, Hydrogen cyanide, Exopolysaccharide, Nitric oxide, ion homeostasis and compartmentalization, and biofilm formation. Understanding these microbial strategies is crucial for developing sustainable agricultural practices in saline soils, ultimately enhancing soil health and agricultural productivity in salt-affected regions.