Fruit Trait Variation Among Five Ilex Taxa: Insights from Morphology, Color, and Electronic Nose-Based Volatile Profiles

Accurate discrimination of closely related Ilex taxa is essential for effective germplasm management and taxon‑specific applications. In this study, five Ilex taxa ( Ilex rotunda Thunb., I. chinensis , I. cornuta Lindl. et Paxt., I. cornuta ‘Fortunei’, and I. latifolia Thunb.) were evaluated using an integrated framework that combines fruit morphometrics and CIELAB color parameters with electronic‑nose (E‑nose) odor fingerprints and chemometric analyses. Fruit transverse diameter, longitudinal diameter, single‑fruit weight, fruit shape index, and color parameters (L*, a*, b*, and chroma (C*)) differed significantly among taxa (one‑way ANOVA, all p < 0.001). Notably, I. cornuta exhibited the largest fruits and the highest fruit weight, whereas I. rotunda had the smallest fruit diameters but the highest redness (a*) and chroma (C*). E‑nose data from 10 metal‑oxide semiconductor (MOS) sensors were analyzed using principal component analysis (PCA), hierarchical clustering, and supervised OPLS‑DA. PCA explained 90.21% of the variance using the first two components (PC1, 71.8%; PC2, 10.5%) and revealed taxon‑specific clustering. A targeted OPLS‑DA model separating I. rotunda from the other four taxa showed strong goodness‑of‑fit and predictive ability (R²X = 0.785, R²Y = 0.944, Q² = 0.935). Permutation testing (n = 200) supported model validity (p < 0.005; 0 of 200 permutations exceeded the original model). Together, fruit phenotypes and E‑nose chemometrics provided robust discrimination among the studied taxa, with I. rotunda consistently exhibiting the most divergent profile, consistent with the phylogenetic framework used in this study.