In the context of variable climate conditions, selecting high-quality Sessile oak (Quercus petraea (Matt.) Liebl.) reproductive material is crucial for sustainable forestry. This research aimed to assess the genetic potential of 86 selected plus trees by analyzing seedling morphological characteristics and quality indices. The ultimate goal was to identify the most promising genotypes for establishing seed orchards. Root collar diameter (D), seedling height (H), stem dry mass (SDM), and root dry mass (RDM) were measured under uniform nursery conditions. The following derived indices were calculated: seedling height to root collar diameter ratio (H/D), stem dry mass to root dry mass ratio (SDM/RDM), and Dickson’s quality index (DQI). Descriptive statistics, one-factorial analysis of variance (ANOVA) and Pearson correlation analysis were performed as well. The results showed significant variability in all observed morphological characteristics and quality indices among half-sib families, confirming a strong genetic influence. Correlation analysis indicated strong positive relationships between DQI and all primary morphological characteristics (r≤0.94), confirming DQI as the most effective integrative indicator of seedling quality. The combined ranking of the half-sib families, based on DQI, H/D, and SDM/RDM, identified those with optimal morphological characteristics, including an optimal H/D ratio, balanced SDM/RDM, and a high DQI value. The identified superior half-sib families represent valuable genetic material for the establishment of future seed orchards, thereby contributing to the production of better-quality seedling material and to improved forest ecosystem resilience under climate change.

Oak forests are among the most ecologically and economically significant in Europe. Due to the consequences of climate change on the environment, successful restoration of these ecosystems has been reduced in recent times. In order to increase the regeneration of oak forests, the analysis of quality parameters of one hundred and twenty pedunculate oak (Quercus robur L.) seedlings of ten different half-sib families have been carried out in the nursery of the Institute of Forestry in Belgrade (Serbia). This study showed the influence of origin (mother trees) on the morphological characteristics of pedunculate oak seedlings. A high degree of variability has been determined for root collar diameter, height, weight of aboveground part, root weight, Roller’s sturdiness coefficient and seedlings quality index. The largest variability has been determined for the height of seedlings where a large number of transitional half-sib families is noticed between the largest and the smallest values. A small number of half-sib families (33.33%) showed high quality of seedlings, based on the cluster analysis of quality parameters. There was a high degree of correlation between root weight and aboveground part weight, giving the potential for the selection of quality reproductive material with a properly formed habitus. There was a high degree of correlation between root weight and aboveground part weight, which suggests the potential for selecting quality reproductive material with a properly formed habitus. This study facilitates the selection of suitable reproductive material sources for regenerating pedunculate oak forests within this particular region of distribution.