Rhizosphere Microbiome Variations and Soil Amelioration Potential of Medicago Species Planted in Saline-alkali Soils

Background: Soil salinization has become a critical threat to global food security and ecosystem sustainability. Conventional physicochemical remediation methods face limitations such as high costs and secondary pollution risks, whereas plant-microbe-synergistic ecological restoration techniques have gained attention due to their sustainability. Alfalfa, a perennial leguminous forage, combines economic, ecological and ornamental values. Investigating rhizosphere microorganisms associated with different alfalfa varieties and their functional roles in saline-alkali soils could provide a theoretical foundation for ecological restoration in salt-affected regions. Methods: We compared the physicochemical properties of rhizosphere soil from Medicago sativa L., Medicago falcata L. and Medicago varia Martin. planted in saline-alkali land for three years and analyzed differences in their rhizosphere microbial communities using high-throughput 16S rRNA sequencing. Result: The results showed that planting alfalfa, especially Medicago varia Martyn., can significantly reduce soil pH and conductivity and increase the content of available nitrogen, phosphorus, potassium and total nitrogen in the soil, thereby improving the soil. Alfalfa recruited specific microorganisms from the soil to the rhizosphere, with bacteria from Proteobacteria and Bacteroidetes showing higher relative abundance in the rhizosphere of Medicago varia Martyn.. These bacteria may serve as key factors in plant growth promotion, stress resistance and soil remediation. Our findings establish a theoretical basis for using alfalfa planting to improve saline-alkali lands.