Physiological, Morphological and Biochemical Mechanisms Underlying Drought Tolerance in Almond Genotypes

Rising temperatures and declining precipitation driven by climate change, especially in the Mediterranean region, are subjecting crops to escalating water stress. Understanding the morpho-physiological and biochemical mechanisms underlying drought tolerance is therefore essential for developing effective adaptation strategies. The almond tree (Prunus dulcis), recognized for its adaptive plasticity in response to drought, serves as a relevant model for exploring these mechanisms due to its high genetic variability and great economic importance in the Mediterranean area. In this study, thirty-five almond genotypes cultivated under rainfed conditions were evaluated for sixteen morpho-physiological and biochemical traits considered as indicators of water stress. Descriptive, correlative, and principal component analyses revealed a wide diversity of functional responses, identifying three discriminating traits: chlorophyll content, leaf nitrogen, and wood density, which could serve as integrative markers of water stress tolerance. On this basis, genotypes ‘II A 7’ and ‘Ferragnes × Princess 23 were classified as the most resilient, while ‘Ferragnes’, ‘Ferraduel’, ‘Ferralise 124’, ‘Lauranne’, and ‘Ferralise’ were identified as the most drought sensitive. These results demonstrate that physiological and biochemical traits can be interpreted as integrative functional indicators reflecting the adaptive strategies of genotypes. They offer a foundation for establishing functional breeding programs and indicate that the almond tree represents a valuable model for elucidating water resilience mechanisms in fruit tree species.