Harnessing Salt-Tolerant Plant Microbiomes and SynComs for Resilient Agriculture under Salinity Stress

Abstract

Soil salinization is one of the most pressing global challenges to agriculture, currently affecting more than one billion hectares of land and threatening food security. Salinity imposes osmotic, ionic, and oxidative stress, reducing plant growth and yield. Traditional strategies such as breeding, genetic engineering, and agronomic management have provided limited success due to the complex, multigenic, and environment-dependent nature of salt tolerance. In recent years, plant-associated microbiomes particularly salt-tolerant plant growth-promoting rhizobacteria (PGPR) and rationally designed synthetic microbial communities (SynComs) have emerged as sustainable and ecologically sound solutions. These microbiomes enhance salinity resilience by improving osmotic adjustment, regulating Na⁺/K⁺ homeostasis, enhancing antioxidant defenses, modulating phytohormone signaling, and conditioning the rhizosphere through exopolysaccharide secretion. Advances in metagenomics, multi-omics integration, and microbial engineering have enabled the design of SynComs tailored to diverse crops and environments. This review synthesizes current knowledge on microbiome-mediated salinity tolerance, explores strategies for SynCom development, highlights the role of host genetics and microbiome-assisted breeding, and addresses field translation challenges. Future perspectives include leveraging artificial intelligence, nanotechnology-based delivery systems, halophyte-informed microbiomes, and a holobiont-centered framework to realize resilient and sustainable saline agriculture.