Heat stress-induced metabolomic shifts in chickpea (Cicer arietinum L.) flowers insights from contrasting genotypes

Chickpea (Cicer arietinum L.), a vital cool-season pulse crop, experiences significant yield losses when exposed to heat stress during its reproductive stages, a vulnerability exacerbated by weather extremes. Chickpea plants synthesize numerous metabolites when subjected to heat stress; however, the underlying metabolomic mechanisms of heat tolerance remain poorly understood. In this study, we employed widely targeted metabolomics to identify key metabolites and potential biomarkers in the flower buds of two contrasting chickpea genotypes: the heat-tolerant PI518255 and the heat-sensitive PI598080. The tolerant genotype showed improved chlorophyll index, photochemical efficiency, antioxidant activity, along with low electrolyte leakage and malondialdehyde content. In contrast, the sensitive genotype exhibited low chlorophyll index, photochemical efficiency and low antioxidant activity, and high electrolyte leakage and malondialdehyde content, under heat stress conditions (35/20 °C day/night). Volcano plot analysis identified 86 up-regulated and 230 down-regulated metabolites in response to heat stress. Heatmap analysis revealed that elevated levels of specific flavonoids, phenolic acids, lignans, coumarins, alkaloids, quinones, and terpenoids characterized the heat-tolerant genotype, suggesting their potential as biomarkers for screening heat stress tolerance. KEGG enrichment and pathway analysis highlighted isoflavonoid biosynthesis, flavonoid metabolism, lysine degradation, and butanoate metabolism as key pathways affected by heat stress. Future targeted metabolomics studies may provide deeper insights into the biochemical mechanisms underlying chickpea acclimation to heat stress.