Drought Adaptive Strategies in Mediterranean Grapevine Cultivars: Functional Trait Variability

Climatic changes in the Mediterranean area affect grapevine growth and productivity due to an increase in the magnitude and frequency of extreme climatic events. Functional traits of the vegetative stages of grapevines are drivers of stress tolerance, and their characterization may aid in the selection of cultivars showing greater resistance. Our aim was to evaluate and compare the adaptability to hot and arid climatic conditions of two varieties typical of small satellite islands of Sicily (Zibibbo and Corinto) with the two most common grape varieties grown on the main island (Catarratto and Nero d’Avola). The four selected varieties grew in a common rain-fed experimental germplasm repository. We followed seasonal changes in stomatal conductance, leaf water potential and leaf temperature, relating them to leaf water relation traits and xylem structural characteristics of the leaf vein network. We observed significant differences in functional traits and physiological behaviour of the four cultivars. Leaf water potential at turgor loss point was one of the most informative traits, together with midday leaf water potential and midday stomatal conductance. Nero d’Avola, Catarratto, and Zibibbo showed the highest adaptability to Mediterranean summer–autumn drought and heat stress through different physiological strategies; whereas, Corinto appeared more vulnerable. These findings highlight the importance of functional trait analysis for supporting cultivar selection, vineyard management, and future breeding strategies under climate change scenarios.