Bacterial Endophytes from Halophytes: How Do They Help Plants to Alleviate Salt Stress?

Abstract

Soil salinization is one of the main factors influencing the reduction of crop yield all over the world. Solutions for saline agriculture based on biological systems involving plants or cultivars well-adapted to grow in soils affected by salinity and associated microorganisms are gaining interest. Halophytes can survive and reproduce in environments with high salt concentration and are excellent models to study plant adaptation to saline environments. Plant growth and adaptation, particularly in stress conditions, is highly influenced by microorganisms that colonize rhizo-sphere and endosphere. Halophyte microbiome has to be adapted to soil salinity and contribute to plant growth in the presence of high concentrations of NaCl. Endophytic bacteria isolated from halophytes growing in saline soils may help to alleviate plant by altering plant hormone status and uptake of nutrient elements and/or modulating the production of reactive oxygen species (ROS) through different mechanism, including 1-aminocyclopropane-1-carboxylic acid (ACC)-deaminase activity, phosphate solubilization, nitrogen fixation, and the production of indole-3-acetic acid (IAA), abscisic acid (ABA), siderophores, and volatiles, among others. In this chapter, the main genera of endophytes isolated from halophytes, the presence of plant growth-promoting properties in these endophytes, and how they could help to alleviate salt stress in plants are reviewed and discussed.