Halophyte-associated bacterial endophytes in salt phytoremediation: Evidence, mechanisms, and knowledge gaps

Soil salinization is a serious global challenge that threatens agricultural productivity, ecosystem functioning, and freshwater resources. While conventional remediation approaches can reduce soil salinity, they are often costly, disruptive, and difficult to implement at scale. Halophyte-based phytoremediation offers a low-impact alternative, capitalizing on the unique capacity of salt-tolerant plants to sequester or excrete excess salts from contaminated soils. However, slow remediation rates, variable field performance, and constraints on plant establishment under extreme salinity have limited widespread adoption. Increasing evidence suggests that plant-associated bacterial endophytes may help overcome these limitations by enhancing halophyte growth, stress tolerance, and physiological performance under saline conditions. Halophyte-associated endophytes frequently possess plant growth–promoting traits and intrinsic salt tolerance, positioning them as promising yet underexplored tools for improving salt phytoremediation outcomes. This review synthesizes current knowledge on halophyte mechanisms of salt tolerance and remediation, the diversity and functional roles of halophyte-associated bacterial endophytes, and emerging evidence for endophyte-assisted salt phytoremediation. We critically assess the extent to which endophytes enhance phytoremediation through increased plant biomass versus direct effects on ion transport and accumulation, highlighting substantial context dependence and persistent knowledge gaps. In particular, evidence linking endophyte activity to soil-scale salt removal remains limited, and field-based validation is largely absent. By integrating insights from plant physiology, microbial ecology, and biotechnological applications, this review identifies key research priorities and conceptual pathways needed to advance endophyte-assisted salt phytoremediation from controlled experiments toward effective and scalable deployment in salt-affected landscapes.