Seed metabolomic profiling of contrasting mung bean (Vigna radiata) genotypes under heat stress

Mung bean (Vigna radiata), a high-value leguminous crop essential for global nutritional security, suffers substantial yield losses due to increasing heat stress. While numerous studies have explored the physiological and biochemical mechanisms underlying heat stress tolerance in mung bean, the effects of heat stress on grain quality at the metabolomic level remain largely unexplored. This study presents the first comprehensive analysis of heat stress-responsive seed metabolite changes in two contrasting mung bean genotypes-the heat-tolerant (HT) PI425243 and the heat-sensitive (HS) PI223002-using an untargeted metabolomics approach. Volcano plot analysis identified 68 significant metabolites (39 upregulated and 29 downregulated) under heat stress, based on a VIP value > 1.5; log₂fold-change ≥ 1 (upregulated) or ≤ - 1 (downregulated), and p < 0.05. Notably, several metabolites, including hydrocinnamic acid, 5-hydroxyferulic acid, quercetin, myricetin, kaempferol 3-(2G-apiosylrobinobioside), and hesperetin 7-neohesperidoside, showed higher accumulation in PI425243 than in PI223002, potentially contributing to the maintenance of grain quality under heat stress. Metabolic pathway enrichment analysis further revealed the active involvement of starch and sucrose metabolism, tyrosine metabolism, steroid hormone biosynthesis, and caffeine metabolism in mediating heat stress response and tolerance. These metabolites could serve as potential biomarkers for identifying heat-tolerant mung bean genotypes and sustaining yield under high-temperature environments.