Study on the beneficial effects and mechanisms of native and non-native inoculum plant growth-promoting rhizobacteria on coastal saline soil

Soil salinization threatens global food security and sustainable agriculture, and microbial inoculation is increasingly viewed as an effective bioremediation strategy. However, the comparative performance and mechanisms of native target-habitat-derived strains and non-native stress-habitat-derived strains remain unclear. In this study, nine plant growth-promoting rhizobacterial strains were isolated from saline–alkali soil, sandy soil, and mine tailings. Strains from saline–alkali soil were defined as native, whereas those from sandy soil and mine tailings were defined as non-native. Pot experiments, amplicon sequencing, and soil–plant trait measurements were used to evaluate their ecological effects on coastal saline–alkali soil and alfalfa growth. Both inoculant types promoted alfalfa growth, increasing biomass by 12.6%–23.8%, and improved soil quality by reducing pH, electrical conductivity, and soluble salt content while enhancing carbon and nitrogen pools, cation exchange capacity, and nutrient-cycling enzyme activities. Inoculation also reshaped rhizosphere microbiomes and enriched beneficial taxa, including Peribacillus and Sphingomonas . Nevertheless, native and non-native strains followed distinct functional pathways. Native strains improved microbial network efficiency and stability and showed closer links with soil enzyme activity and plant biomass. Non-native strains also enhanced network performance but more strongly altered predicted microbial functions. Tailings-derived strains notably increased network complexity and centrality, indicating their role in introducing stress-related functions and restructuring microbial communities. These findings suggest that native and stress-adapted non-native strains are complementary strategies for saline–alkali soil bioremediation, rather than alternatives ranked only by geographical origin alone.