Abstract
Alfalfa (Medicago sativa L.) is a crucial plant for saline and alkaline soil development, which is crucial for managing the salinization of global land resources. It can withstand saline and alkaline stress and can fix nitrogen. By secreting phytohormones, fixing nitrogen, and boosting antioxidant capacity, nitrogen-fixing bacteria, rhizobacteria, and other inter-root biotrophic bacteria encourage alfalfa development and reduce salinity stress. Alfalfa's symbiotic association also encourages other plants to tolerate salinity and greatly boosts the amount of nitrogen in the soil. The mechanism by which inter-root growth-promoting bacteria mitigate saline and alkaline stress in alfalfa remains a prominent research focus. This paper reviews the current state of research on inter-root probiotic bacteria associated with alfalfa, utilizing literature mining to summarize the resource information of inter-root nitrogen-fixing bacteria found in saline-alkaline soils. We elucidate their nitrogen-fixing mechanisms and adaptive characteristics, explore their roles and potential applications in the improvement of saline-alkaline lands, and provide a theoretical foundation for the development of novel nitrogen-fixing bacterial fertilizers and restoration technologies for saline-alkaline environments.