Rhizosphere microbiome-dependent metabolic reprogramming enhances potato salt tolerance in saline soils

Soil salinization is increasing globally, causing yield losses, especially in irrigated agriculture. Rhizosphere microorganisms can improve plant salt tolerance, but evidence in potato remains limited. In this study, rhizosphere microbial community diversity and structure differed markedly between salt-tolerant and salt-sensitive potato under saline and non-saline conditions. Under field salinity, salt-tolerant genotypes retained more network-associated rhizosphere taxa, particularly Pseudomonadota members, and showed enrichment of Pseudomonas . From tolerant rhizospheres, Pseudomonas aeruginosa BK43, a salt-tolerant, growth-promoting strain, was isolated. In sterilized saline field soil, the salt-tolerant phenotype was abolished in the absence of microbial inoculation, while introduction of BK43 significantly restored growth (plant height ~10.8 to ~16.3 cm; leaf area ~16 to ~80 cm 2 ), demonstrating a direct microbial contribution to salt tolerance. In non-sterilized saline soil, enrichment of this bacterium accelerated early post-emergence growth of tolerant plants without affecting seedling emergence. Salt tolerance was also conferred to an otherwise sensitive genotype following pre-colonization with BK43, with root lipid peroxidation reduced by ~43% and higher chlorophyll content under salt stress. Multi-omics analyses linked BK43-mediated protection to basal activation of host defense and metabolic pathways under non-stress conditions and salt-amplified phenylpropanoid, redox-related, and stress-signaling responses after salt exposure.