1. Faculty of Forest Sciences, Section of Forest Genetics, Ludwig‐Maximilians‐University Munich, Am Hochanger 13, D‐85354 Freising, Germany (R. Schubert for correspondence);
2. GSF‐National Research Center for Environment and Health, Institute of Biochemical Plant Pathology, Ingoldstädter Landstr. 1, D‐85764 Neuherberg, Germany;
3. Faculty of Forest Sciences, Institute of Forest Botany, Phytopathology, Ludwig‐Maximilians‐University Munich, Am Hochanger 13, D‐85354 Freising, Germany;
4. Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK