Soil salinization is an abiotic stress factor that can harm plant growth. Root endophytic bacteria may be associated with the resilience of plants to saline–alkaline stress. This study investigated the diversity, composition, and function of endophytic bacterial communities in alfalfa roots under saline–alkali stress, and screened a key bacterial strain associated with saline–alkali resistance. 16 S rRNA amplicon sequencing showed that high levels of saline alkalinity significantly reduced the diversity of endophytic bacterial communities and the relative abundance of beneficial bacterial taxa, such as Rhizobiales and Pseudomonas. Long durations of saline–alkali significantly decreased the abundance of predicted functional genes related to nitrogen metabolism in the alfalfa root endophytic bacterial community. Additionally, we isolated a key strain Pseudomonas with saline-alkali tolerance which could colonise roots and considerably improve physiological characteristics and plant growth. We found that colonization with Pseudomonas can considerably enhance plant resistance to saline-alkali stress and that the composition and function of the endophytic bacterial communities in roots likely contribute to plant tolerance to saline-alkali stress.

土壤盐碱化是一种非生物胁迫因素，会损害植物生长。根内生细菌可能与植物对盐碱胁迫的恢复能力有关。本研究探讨了盐碱胁迫下苜蓿根部内生细菌群落的多样性、组成和功能，筛选了一株与耐盐碱相关的关键菌株。 16S rRNA 扩增子测序表明，高水平的盐碱度显着降低了内生细菌群落的多样性以及有益细菌类群（例如根瘤菌和假单胞菌）的相对丰度。长时间的盐碱环境显着降低了苜蓿根内生细菌群落中与氮代谢相关的预测功能基因的丰度。此外，我们还分离出了一种具有耐盐碱能力的关键菌株假单胞菌，它可以在根部定殖并显着改善生理特性和植物生长。我们发现假单胞菌的定殖可以显着增强植物对盐碱胁迫的抵抗力，并且根部内生细菌群落的组成和功能可能有助于植物对盐碱胁迫的耐受性。