Photosynthetic drivers of heat resilience in peanut

Abstract

Rising temperatures threaten peanut (Arachis hypogaea L.) production worldwide, emphasizing the need for cultivars with enhanced heat tolerance. Wild-derived genotypes represent valuable genetic sources for improving thermotolerance. This study aimed to (1) distinguish heat-sensitive and heat-resilient peanut genotypes using net photosynthesis (A_N) as a physiological marker, and (2) identify photosynthetic traits contributing to heat stress responses. We evaluated 28 peanut genotypes, 10 cultivars and 18 wild-derived advanced lines, under field-imposed heat stress at the University of Georgia in Tifton, Georgia. Heat stress was induced using heat-trapping shelters that increased canopy temperature by 5–10 °C for 14 days, and gas exchange and chlorophyll fluorescence were measured before, during, and after heat exposure. Net photosynthesis varied significantly over time; enabling the identification of both heat-tolerant and heat-sensitive genotypes. Wild-derived lines RBS-BC3–225_B, RBS-BC3–59_A, TVS-20–624–13-MR-MR-Tan, and TVS-19–82–38-MR-MR, along with cultivar TifNV-High O/L, showed greater heat tolerance than other genotypes evaluated. Principal component analysis revealed six photosynthetic traits driving genotypic differentiation under heat: stomatal conductance (g_s), electron transport rate for CO₂ assimilation (ETR_a), electron transport supporting photorespiration (ETR_p), quantum yield of photosystem II (Φ_PSII), chloroplast CO₂ concentration (C_c), and non-photochemical quenching (NPQ). These findings demonstrate that photosynthetic performance is a robust indicator of peanut heat tolerance and provides trait-based targets for breeding climate-resilient cultivars.