1. Institute of Sugar Beet Research (IfZ), 37079 Göttingen, Germany;
2. Institute of Crop Science and Resource Conservation (INRES)–Plant Diseases and Plant Protection, University of Bonn, 53115 Bonn, Germany
3. Greenhouse Horticulture, Wageningen University and Research, 6708PB Wageningen, Netherlands
4. Institute of Agricultural Sciences, ETH Zürich, 8092 Zürich, Switzerland