Multi-year characterization of almond ( <i>Prunus amygdalus</i> ) landraces and hybrids under recurrent drought: Identification of key traits for pre-breeding and crop improvement

Abstract Recurrent drought increasingly threatens almond production in Mediterranean and semi-arid regions, highlighting the need to exploit plant genetic resources with stable adaptive traits. This study reports a 3-year multi-genotypic evaluation of 41 almond genetic resources grown under rainfed conditions in a semi-arid environment characterized by interannual rainfall variability. Significant genotypic and interannual variability was observed across morphological, physiological and biochemical traits. Chlorophyll content ( r = 0.7 with PC1; CV &lt; 12%) emerged as a stable primary discriminant trait. Leaf nitrogen content, wood density, yield and leaf area also contributed significantly to genotype differentiation in multivariate analyses, together explaining 60% of total variance in the first principal component. A two-level hierarchical classification consistently separated tolerant, intermediate and sensitive genotypes. Among the evaluated genetic resources, ‘Princesse n° 3’, ‘Ferragnes*princesse 23’, ‘F1 melange 68/2’, ‘L 158’, ‘II A 7’, ‘(486*217)16’ and ‘GN9’ were identified as high-performing and drought-tolerant genotypes, highlighting their potential value for almond breeding and conservation programmes. This integrative, multi-year phenotypic approach provides a robust framework for identifying and utilizing drought-resilient almond genetic resources.