Molecular mechanisms and agronomic strategies for thermotolerance in chili pepper (Capsicum annuum L.).

Heat stress is a primary environmental constraint on chili pepper (Capsicum annuum L.) productivity and fruit quality across global agricultural systems. Elevated temperatures adversely affect plant growth, flowering, fruit set, pod morphology, physiology, and metabolism. The severity of these impacts varies with the duration and intensity of heat exposure and with the stage of plant development. Reproductive development is especially vulnerable, resulting in compromised fruit formation and a decline in productivity. Heat stress disturbs photosynthesis, cellular structure integrity, and membrane stability through oxidative stress. Chili plants counter heat stress through complex molecular networks that encompass activation of antioxidant systems, heat shock protein (HSP) synthesis, osmolyte biosynthesis, and stress-responsive transcription factor expression. Recent advancements in genomics, transcriptomics, and metabolomics have elucidated fundamental regulatory pathways governing thermotolerance, highlighting the importance of heat-responsive genes, including CaHSPs, CaWRKYs, and CaNACs. This comprehensive review integrates contemporary understanding of physiological, biochemical, and molecular heat stress responses in chili pepper. Additionally, it evaluates potential agronomic and breeding strategies to strengthen crop adaptation to escalating global temperatures.