Heritability and Expected Genetic Gain for Early Growth in Quercus Petraea Matt. Liebl. from Two Bosnian-Herzegovinian Populations: An Open-Pollinated Progeny Test Under Nursery Conditions

Sessile oak is one of the most important deciduous forest species in Bosnia and Herzegovina, where 66% of forests with sessile oak are coppice stands, reflecting past overexploitation. This study evaluates the degree to which growth traits are inherited and estimates the potential for genetic improvement using progeny from 20 mother trees. Seedlings originating from two natural populations (Konjic-Bradina, n = 533 and Goražde, n = 743), representing ten families per population in three replications, were measured for height and root collar diameter at age three. Mixed-model REML analyses were performed to estimate variance components and calculate broad-sense (H2) and narrow-sense (h2) heritability, including 95% confidence intervals. The five parent trees whose offspring showed the highest mean values were identified, and expected genetic gain and selection differential were calculated. Offspring from Konjic-Bradina showed slightly higher mean height and root collar diameter than those from Goražde, but heritability estimates were higher in Goražde, particularly at the family level (height: h2 = .27, 95% CI: 0.03–0.08; root collar diameter h2 = .40, 95% CI: 0.38–0.42), compared with Konjic-Bradina (height: h2 = .04, 95% CI: 0.00–0.30; root collar diameter: h2 = .40, 95% CI: 0.38–0.42). Corresponding potential genetic gains in Goražde using the top five trees were 0.9 cm (≈2%) for height and 0.2 mm (≈2.7%) for root collar diameter, increasing to 1.5 cm (≈3.3%) and 0.3 mm (≈5.0%) when selecting the single best tree. In Konjic-Bradina, gains were smaller (0.1–0.3 cm for height and 0.1–0.3 cm for root collar diameter). These results indicate that family-level selection, especially for root collar diameter, can achieve moderate genetic improvement, while individual seedling selection is largely ineffective. Follow-up evaluations under field conditions are recommended to confirm the stability of these traits and the practical applicability of early selection for breeding and conservation programs. Cite this article as: Memišević Hodžić, M., & Ballian, D. (2026). Heritability and expected genetic gain for early growth in Quercus petraea Matt. Liebl. from two Bosnian- Herzegovinian populations: an open-pollinated progeny test under nursery conditions. Forestist, 76, 0105, doi: 10.5152/forestis.2026.25105.