Halotolerant actinobacteria as nature-based solutions for salinity-affected agricultural systems

Soil salinization, an increasingly serious global problem affecting more than 1 billion hectares and about 20–30% of the total area of irrigated agricultural land worldwide, may lead to yield losses greater than 50% in sensitive crops. The traditional remediation efforts are frequently expensive, inefficient and unsustainable to the environment. Halotolerant Actinobacteria- including Streptomyces, Micromonospora, Nocardiopsis , and Frankia , exhibit increases in plant biomass of between 20 and 40%, when salinity is controlled4, making them a promising but under-validated biological strategy. Due to their natural resistance to osmotic, ionic and oxidative stress. These microbes promote plant growth by synthesizing phytohormones (e.g., indole-3-acetic acid, gibberellins), hydrolyzing ethylene precursors through the action of ACC deaminase, acquiring nutrients using siderophores, and ionic (Na + /K + ) homeostasis. The osmoprotectins and antioxidant enzymes released by them also reduce abiotic stress. More importantly, the production of exopolysaccharide (EPS) mediates soil structural enhancement processes such as aggregates stabilization, enhanced hydraulic conductivity, and prevention of toxic immobilization of ions. Introduction of Actinobacteria into compatible microbial consortia, enhanced delivery systems and soil amendments (gypsum, biochar) increases the microbial survival and activity under field conditions. The review summarizes the existing data on the ecological diversity, metabolic characteristics, and interactions of the halotolerant Actinobacteria with the soil, and highlights their possible role as ecosystem engineers to manage soils sustainably. However, many questions remain about functional gene-level understanding and strain selection in multi-stress scenarios even at the field scale.