Morpho-phenological and pomological characteristics in differentiating and selecting superior quince (Cydonia oblonga...

Iranian plateau is the center of origin and diversity of quince (Cydonia oblonga Mill.) tree. This study aimed to evaluate morphological and phenological diversity among 52 quince genotypes and to identify the key characteristics contributing to genotype differentiation. Accordingly, morpho-phenological traits influencing genotype differentiation were evaluated across 52 quince genotypes from various Iranian provinces using 43 national descriptors. Analyses revealed complex variation, with flower- and fruit-related traits forming the main axes of differentiation. Phenological traits, such as leaf bud burst and flowering onset, were relatively stable (CV ≈ 18-19%), whereas growth habit and tree form showed high variability (CV > 40%). Leaf size traits exhibited moderate variation (CV ≈ 30-31%), while leaf morphology and fruit structural traits showed the highest fluctuations, with fruit neck thickness varying the most (CV ≈ 98.4%). Principal component analysis (PCA) revealed that the first two components explained 27.3% of the total variance among the studied genotypes. Strong correlations were observed among fruit and flower traits (e.g., FSi-FPS, r ≈ 0.99; FrWe-FrSi, r = 0.68), while negative correlations suggested trade-offs between tree architecture and fruit characteristics. NMDS and Envfit analyses identified fruit size and fruit neck as key explanatory traits (r² > 0.5). The studied genotypes exhibited considerable variation in fruit size, tree vigor, astringency, and fruit quality. Overall, fruit related traits showed the highest discriminative power, while phenological and leaf traits provided useful information on adaptability. These findings offer valuable insights for germplasm conservation, management, and breeding of superior quince cultivars.