Rhizosphere microbiota diversity and salt stress-alleviating functional genes in coastal wild salt-tolerant plants

Saline-alkali land significantly threatens global food security and ecological safety, and root-associated microorganisms help plants survive salt-alkali stress. However, the ecological functions and factors that influence the rhizosphere microbiomes of salt-tolerant plants remain poorly understood. In this study, we used high-throughput sequencing and metagenomics to reveal the microbial communities and functional traits of bulk and rhizosphere soil from salt-tolerant species (Suaeda glauca, Phragmites australis, and Spartina alterniflora) growing in saline soil. Bacterial and fungal taxa were significantly enriched in the rhizosphere soil compared to the non-rhizosphere soil. Metagenomic analyses revealed that metabolic pathways, including glycolysis and ABC transporters, were highly enriched in the rhizosphere. Functional profiling indicated that salt stress-related pathways were more abundant in the core genera Pseudomonas and Woeseia. The abundance of functional genes related to plant growth-promoting traits, including phosphate solubilization and salt adaptation pathways, was higher in the rhizosphere soil than in the non-rhizosphere soil, which was mainly driven by soil salinity, total nitrogen content, and total carbon content. Additionally, P. aeruginosa obtained from the rhizosphere of S. alterniflora exhibited high phosphorus solubilization efficiency (908.38 μg/mL), nitrogen fixation activity (2.84 μg/mL) and salt tolerance (≦ 5 % NaCl). These findings demonstrate that salt-tolerant plants shape microbial activities by controlling the rhizosphere microenvironment, mitigating salt stress, providing a scientific and practical foundation for the development of targeted microbial inoculants for saline-alkali land reclamation.