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.

Abstract
Introduction
Materials and Methods
    1. Study sites and plant materials
    2. Exploration and selection of high-yielding candidatetrees
    3. Seed collection and storage
    4. Evaluation of seed production and seed traits
    5. Evaluation of growth and morphological traits
    6. Evaluation of flowering and fruiting traits
    7. Statistical analysis
Results and Discussion
    1. Seed productivity of high-yielding and non-high-yieldingindividuals
    2. Comparison of fruiting and seed traits betweenhigh-yielding and non-high-yielding individuals
    3. Comparison of growth and morphological traits betweenhigh-yielding and non-high-yielding individuals
    4. Correlation analysis among major morphologicaland fruiting traits
    5. Trait distribution of high-yielding and non-high-yieldingindividuals based on principal component analysis
    6. Implications for the selection and utilization ofhigh-yielding individuals
Acknowledgements
References

• Seong Hyeon Yong(Post-doc, Division of forest biodiversity, Korea National Arboretum, Pocheon, 11186, Korea)
• Myung Suk Choi(Graduate Student, Department of Forest Resources, Gyeongsang National University, Jinju, 52828, Korea, Professor, Division of Environmental Forest Science & Institute of Agriculture and Life Science, Gyeongsang National University, Jinju, 52828, Korea) Corresponding author
• Ji Hyeon Lee(Graduate Student, Department of Forest Resources, Gyeongsang National University, Jinju, 52828, Korea)
• Seung A Cha(Graduate Student, Department of Forest Resources, Gyeongsang National University, Jinju, 52828, Korea)
• Do Hyun Kim(Graduate Student, Department of Forest Resources, Gyeongsang National University, Jinju, 52828, Korea)
• Kwan Been Park(Graduate Student, Department of Forest Resources, Gyeongsang National University, Jinju, 52828, Korea)
• Seon A Kim(Graduate Student, Department of Forest Resources, Gyeongsang National University, Jinju, 52828, Korea)
• Jenna Jung(Graduate Student, Department of Forest Resources, Gyeongsang National University, Jinju, 52828, Korea)
• Seo Mi Jeong(Graduate Student, Department of Forest Resources, Gyeongsang National University, Jinju, 52828, Korea)