1. Forest Research Institute , Department of Sylviculture and Forest Tree Genetics , Braci Leśnej 3, Sękocin Stary, 05-090 Raszyn , Poland
2. University of Life Sciences in Lublin , Faculty of Agrobioengineering , Institute of Plant Genetics, Breeding and Biotechnology , Akademicka 13, 20-950 Lublin , Poland