1. a Department of Forest Genetics and Plant Physiology , Swedish University of Agricultural Sciences , Umeå, S‐901 83, Sweden
2. b N.AG.RE.F. , Forest Research Institute , Vassilika, Thessaloniki, GR‐7006, Greece
3. c Genesis Forest Science Canada Inc. , C.P. 64 Succursale Haute‐Ville, Québec, QC, G1R 4M8, Canada