Abstract
BACKGROUND: Common vetch (Vicia sativa L.) is an important annual leguminous forage crop commonly used for green manure, fodder, and soil improvement. It is widely cultivated as a green manure and forage crop in Yunnan Province during winter and spring. However, the dry conditions and minimal rainfall during these seasons greatly limit common vetch growth. Therefore, screening for drought-tolerant, high-yielding common vetch varieties is a critical objective in breeding programs. RESULTS: Preliminary screening by our research team identified a drought-tolerant variety, Luquan common vetch (LQ), which was compared with Lanjian No. 1 (LJ) as a control to assess changes in agronomic traits, physiological indicators, transcriptome, and metabolome under drought stress. Under drought stress, LQ exhibited significant increases in Superoxide Dismutase (SOD) activity and proline (Pro) content at 6.31% and 165.79%, respectively, relative to the control. Transcriptomic analysis revealed 87.03 Gb of clean bases. In LQ, 4,436 differentially expressed genes (DEGs) were identified, comprising 2,249 upregulated and 2,187 downregulated genes. In LJ, 4,464 DEGs were identified, encompassing 2,294 upregulated and 2,170 downregulated genes. Metabolomic analysis detected 4,856 metabolites, primarily consisting of jasmonates, flavonols, and flavanones. Weighted gene co-expression network analysis identified several key genes (e.g., jg28014.t1, jg50423, jg18380, jg27018.t1, and jg27016) with high expression under drought, suggesting involvement in regulating drought tolerance. Furthermore, our integrated analysis revealed significant enrichment in α-linolenic acid metabolism and flavonoid biosynthesis pathways. Specifically, methyl jasmonate, 9,10-epoxy octadecadienoic acid (9,10-EOT), apigenin, and pinocembrin exhibited significantly increased abundance in LQ. These two pathways function synergistically to enhance the tolerance of LQ to drought stress. CONCLUSION: This study confirms the important roles of α-linolenic acid and flavonoid biosynthesis in drought resistance and identifies various key genes and metabolites. Overall, the findings reveal the coordinated roles of α-linolenic metabolism and flavonoid biosynthesis in enhancing drought tolerance of common vetch, providing both mechanistic insights into stress adaptation and valuable molecular targets for the breeding of resilient forage crops. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12870-026-08325-z.