Phenotypic Selection of Superior Quercus glauca Thunb. Individuals as Breeding Candidates for High FruitSeed Productivity

초록

To select superior Quercus glauca Thunb. individuals as candidates for breeding programs aimed at improving fruit productivity, we identified morphological and reproductive traits associated with high seed yield. Field surveys were conducted across five regions in Korea, and eight high-yielding and eight non-high-yielding individuals were selected for comparative evaluation. Seed production was monitored over three consecutive fruiting seasons (2023–2025), and growth, leaf morphological, flowering, fruiting, and seed traits were compared between the two groups to derive candidate selection criteria. Relationships among major traits were further examined using Pearson correlation analysis and principal component analysis (PCA). Selected high-yielding individuals produced approximately seven-fold more seed than non-high-yielding individuals across regions and years, and this superiority was consistently maintained despite significant year-to-year variation in overall seed production. High-yielding individuals were characterized by significantly greater numbers of flower branches, flower stems, female flowers, and seeds per branch, whereas seed length, seed width, and individual seed weight showed no significant differences between groups, indicating that yield superiority was not attributable to larger seed size. High-yielding individuals also tended to have shorter and narrower leaves, narrower petioles, and more leaves per branch. Seed number per branch was positively correlated with flower stem number, flower branch number, and female flower number, and PCA clearly separated most high-yielding individuals from non-high-yielding individuals, with reproductive traits showing strong positive associations with high fruit productivity. These findings indicate that high seed productivity in Q. glauca is closely associated with reproductive abundance, while the observed differences in leaf morphology and leaf number also represent phenotypic variation associated with seed productivity. Thus, the significance of these traits is not limited to practical selection, but also provides basic information for understanding morphological and reproductive variation in high-yielding individuals. The high-yielding individuals identified in this study represent promising breeding candidates, and the associated phenotypic traits provide a basis for plus-tree selection, propagation, stable seed production, and further physiological and genetic studies on high-yielding traits in Q. glauca.

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