1. Department of Forest Mycology and Plant Pathology Swedish University of Agricultural Sciences Uppsala Box 7026, 750 07 Sweden
2. Department of Crop and Forest Sciences University of Lleida, Alcalde Rovira Roure 191 Lleida 25198 Spain
3. Joint Research Unit CTFC‐AGROTECNIO Alcalde Rovira Roure 191, Lleida 25198 Spain
4. Skogforsk Svalöv Ekebo 2250, 268 90 Sweden