1. Latvian State Forest Research Institute Silava , Rigas Street 111, Salaspils LV-2169 , Latvia
2. Institute of Forestry and Engineering, Estonian University of Life Sciences , Kreutzwaldi 5, Tartu 51014 , Estonia
3. Lithuanian Research Centre for Agriculture and Forestry, Institute of Forestry , Forest Genetics and Tree Breeding Department, Liepų Str. 1, LT-53101 Girionys, Kaunas District , Lithuania