Halophilic Microbe Interactions with Plants to Mitigate Salt Stress

Abstract

Because salt-affected soils including saline, sodic, and saline-sodic soils, are poor in organic matter content, biomass and microbial activity are significantly affected, thereby affecting the microbiologically mediated processes required for plant growth. Halophilic microbes are those that are present in saline environments. During the recent past, the diversity and ecology of halophiles have been studied by several workers. In salt-affected soils, several species of halophiles have been isolated and reported from different parts of the world. Endophytes from halophilic plants have also been isolated and reported from hypersaline areas. Halophiles have a mechanism to tolerate salt stress by expressing aminocyclopropane-1-carboxylic acid (ACC) deaminase activity that removes stress and ethylene from the rhizosphere, and some halophiles produce auxins that promote root growth. Plant growth-promoting (PGP) bacteria that thrive in association with roots of the plants alleviate salt stress for improved plant growth and yield through their own mechanisms of osmotolerance, osmolyte accumulation, nonsymbiotic nitrogen fixation, solubilization and mineralization of essential plant nutrients, and production of useful plant hormones. Plant growth-promoting bacteria induced salt stress tolerance in plants has been studied to come up with a cost-effective solution for saline soils and improve agricultural crop yields. Salt-tolerant arbuscular mycorrhizal fungi (AMF) is also known to mitigate soil salinity stress and improve agricultural crop on inoculation in salt-affected soils. Inoculation of halophilic plant growth-promoting bacterial strains mitigates salt stress and enhances crop growth and yields. Thus, the aim of the present chapter is to focus on halophilic microbe interactions with plants to mitigate salt stresses.