Genetic variability of leaf temperature and underlying morpho-physiological traits in a grapevine diversity panel

Selecting varieties with limited canopy warming can help adapt crops to climate change, but underlying traits and their genetic bases remain poorly understood. Using a diversity panel of 279 Vitis vinifera L. cultivars, we investigated genetic variation in leaf temperature (Tleaf) and questioned which morpho-physiological traits involved in leaf energy balance are genetically controlled and drive these variations. Specifically, we measured Tleaf, stomatal conductance, leaf inclination, area, unfolding, reflectance, and transmittance under irrigated field conditions. Substantial genetic variability was found for Tleaf and all morpho-physiological traits, which have been little explored together from a genetic perspective. Empirically, stomatal conductance had the strongest influence on genetic variations in Tleaf, followed by transmittance, although theoretically, based on energy balance, leaf traits with their observed ranges of variation could all impact Tleaf with similar amplitude. Genome-wide association studies revealed independent genetic control for Tleaf, stomatal conductance, leaf inclination, and transmittance, suggesting multiple independent genetic levers. Screening these genomic regions highlighted relevant candidate genes respectively involved in thermal dissipation (PetC), stomatal development (YODA, LOB), phototropism (YY1), and trichome initiation (GTL1). We disclosed allelic combinations jointly favouring leaf cooling, water saving, and light interception. Our results provide novel insights for breeding climate-resilient grapevines.