Differences in microbial composition and salt tolerance between rhizosphere and bulk soil of Kalidium foliatum

Salt is an important abiotic stress that affects plant growth. Research has shown that plants can recruit beneficial microorganisms from the surrounding soil. However, the ecological functions of the rhizosphere microbiome in salt tolerant plants have not been explored to a large extent. Based on this, this study took the halophyte K. foliatum as the research object, and used metagenomics technology to analyze the differences in microbial composition and salt tolerance functional genes between the rhizosphere and bulk soil of K. foliatum in different salt habitats, providing new theoretical basis for salt alkali management. The results showed that the dominant groups in the rhizosphere soil microbial community of K. foliatum under two salt habitats were Actinobacteria, Proteobacteria, Bacteroidetes, and Chloroflexi. The abundance of 49 genera in Actinobacteria in high salt rhizosphere were significantly higher than that in low salt rhizosphere. These microorganisms belong to soil salt tolerant and halophilic microorganisms, and have the ability to improve plant salt tolerance. In high salt habitat, the expression of genes related to ion transport (nqrA, nhaC, rnfC, chaA, and yrbG) and the synthesis of osmoregulatory substances (proP, ectA) was significantly increased. These genes are associated with Na⁺, K⁺, Mg²⁺, proline and ectoine involved in transport or synthesis. The correlation indicates that halophilic archaea have a greater impact on functional genes than other microorganisms, suggesting that halophilic bacteria have a more prominent ability to regulate salt tolerance of K. foliatum.