Estimation of Genetic Parameters in Open Pollinated Progeny Trials from Plus Trees of Pedunculate Oak (Quercus robur L.) Selected in Posavina and Podravina and Podunavlje Seed Zones

Pedunculate oak (Quercus robur L.) is one of themost important species in Croatia, both ecologically and economically. In the 1950’s natural oak stands in Croatia were evaluated in terms of wood productivity and quality. The results and additional ecological studies delineated three seed zones and seven seed regions (NN107/08).Over the past decades, the periodicity of seed crops has not been regular, which has limited natural regeneration and artificial planting in partial naturally regenerated stands. In order to increase genetic quality and reduce seed periodicity, it was decided to establish clonal seed orchards (Vidakovi 1996). Plus trees have been selected in three seed regions, based on ten evaluated traits, and three clonal seed orchards have been established in the areas of Forest Municipality Vinkovci, Na ice and azma. Potential for genetic gain by selected plus trees can be evaluated by progeny trials in common environmental conditions and because of long lifespan of forest trees, it is crucial to evaluate it as early as possible. Considering biological and ecological characteristics of pedunculate oak, evolutionary factors shaping the genetic structure of its populations and existing research on its genetic variability in Croatia (Peri et al. 2000, Bogdan et al. 2004, 2008, Kajba et al. 2006, Kati i et al. 2010), it can be assumed that most of its genetic variability lies on the intrapopulation, namely individual level. Such a pattern of variability points to considerable possibilities of genetic improvement by individual selection. The aim of this research is to estimate the trends of genetic parameters, heritability and genetic gains for height and diameter growth of pedunculate oak in some Croatian provenance regions. Research area, material and measurements Three open pollinated progeny trials of pedunculate oak plus trees have been established, representing three seed regions: _ Progeny trial Vukojeva ki ikar (TP1), age 2+18 years, established with 21 OP families of selected plus trees from the seed region srednja Podravina , control plants from three local populations and one minus tree family. _ Progeny trial azma (TP2), age 2+7 years, established with 25 OP families of plus trees from the seed region Donja Posavina and control plants from local populations. _ Progeny trial Kunjevci (TP3), age 2+7 years, established with 24 OP families of plus trees from the seed region Gornja Posavina i Pokuplje and control plants from local populations. The experimental design in TP1 is completely randomized, with five repetitions and in