Introduction: Chickpea (Cicer arietinum L.) is a critical source of dietary protein in semi-arid regions, which are increasingly vulnerable to climate change. Rising temperatures and erratic rainfall patterns, particularly during the sensitive reproductive stage, pose a severe threat to global chickpea yield. While drought tolerance is a known trait in chickpeas, the synergistic impact of combined drought and heat stress remains poorly characterized, limiting the development of resilient cultivars. This study aimed to physiologically and biochemically dissect the responses of diverse chickpea genotypes to individual and combined stress scenarios.
Methods: A controlled-environment experiment was conducted using ten chickpea genotypes with varying genetic backgrounds. Plants were subjected to four treatments at the flowering stage: well-watered control, drought stress, heat stress, and combined drought-heat stress. Physiological parameters (photosynthetic rate, stomatal conductance, canopy temperature) and biochemical markers (proline content, antioxidant enzyme activity) were measured. Yield components, including pod set percentage and seed weight, were quantified at maturity.
Results: The results demonstrated that combined stress inflicted significantly greater damage than individual stresses. While all stresses reduced photosynthetic efficiency by over 50%, the combined stress led to a near-complete shutdown (85% reduction). Genotype ICC 4958 maintained superior relative water content and photosystem integrity under drought, but its advantage diminished under heat and combined stress. In contrast, genotype ICC 15614 exhibited a robust antioxidant response, with a 3-fold increase in catalase activity under combined stress, correlating with a 30% higher pod retention compared to the most sensitive genotype.
Conclusions: This study demonstrates that combined heat-drought stress is the critical limiter of chickpea productivity, requiring distinct tolerance mechanisms beyond drought resilience alone. Genotypes with robust antioxidant responses offer a key target for breeding programs aimed at safeguarding yields under future climates.
