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Abstract
The increasing frequency and intensity of global heatwaves pose a growing threat to crop productivity, with peanut (Arachis hypogaea L.) being particularly vulnerable to heat-induced physiological stress. This challenge is projected to intensify under future climate scenarios, underscoring the urgent need for research and breeding efforts focused on enhancing heat tolerance in peanut. This research integrated controlled-environment and field experiments to elucidate the physiological and biochemical mechanisms underlying heat tolerance in peanut. Growth chamber studies compared commercial cultivars with synthetic allotetraploids derived from wild diploid species. Wild-derived genotypes exhibited enhanced antioxidant enzyme activities, particularly catalase (CAT), superoxide dismutase (SOD), and ascorbate peroxidase (APX), reflecting superior reactive oxygen species (ROS) scavenging capacity. Field trials were also conducted using Snow Arch shelters to impose two weeks of heat stress during the reproductive stage. Gas-exchange and chlorophyll fluorescence analyses revealed strong genotypic variation in photosynthetic and photochemical responses. While susceptible cultivars exhibited marked photoinhibition, several wild-derived advanced backcross lines maintained photosynthetic activity through structural adjustments, and sustained PSII efficiency. However, tolerance during stress did not always correspond to full recovery, underscoring the importance of integrating both traits when evaluating resilience. Collectively, this research provides a comprehensive understanding of heat stress adaptation in peanut by linking antioxidant defense, photosynthetic performance, and PSII stability. Building on these findings, an automated ranking framework, Peanut-ThermoTool, was developed to quantify and classify genotypic thermotolerance and recovery potential under controlled conditions. The model will be calibrated and validated using field data to enhance predictive accuracy and facilitate its application in breeding programs. The integration of these physiological insights into the Peanut-ThermoTool offers a scalable, data-driven approach for identifying and breeding heat-resilient cultivars, contributing to climate-smart peanut improvement and sustained productivity under rising global temperatures.