This study employed high-throughput transcriptome sequencing to analyze gene expression changes in Medicago truncatula under salt stress （150 mmol·L^-1 NaCl） and alkali stress （135 mmol·L^-1 NaHCO₃+15 mmol·L^-1 Na₂CO₃） at five time points： 0 h， 6 h， 12 h，24 h and 48 h. The results showed that alkali stress induced more drastic gene expression changes， with downregulated genes generally outnumbering upregulated ones. Differentially expressed genes were significantly enriched in pathways related to ABA signaling transduction， osmotic regulation， antioxidant defense， and ion homeostasis. A total of 60 genes were commonly upregulated and 16 genes were commonly downregulated under both salt and alkali stresses. The commonly upregulated genes were mainly involved in stress-resistance mechanisms such as hormone regulation and signal transduction， whereas the commonly downregulated genes covered multiple functional categories including hormone signaling and cell wall remodeling. This study elucidates key genes involved in the responses of M. truncatula to salt and alkali stresses and identifies candidate genes for salt and alkali tolerance， providing a theoretical basis for molecular breeding of alfalfa.

Medicago truncatula  /  Salt and alkali stress  /  Transcriptome analysis  /  Mechanisms of stress tolerance  /  Differentially expressed genes