1. Laboratory of Phytopathology; Wageningen University; Droevendaalsesteeg 1 6708 PB Wageningen the Netherlands
2. Department of Crops and Agronomy; National Institute of Agricultural Botany; Huntingdon Road Cambridge CB3 0LE UK
3. Laboratory of Phytopathology, Faculty of Bioscience Engineering, Coupure links 653; Ghent University; B-9000 Ghent Belgium
4. Department of Plant Pathology; University of California Davis; One Shields Avenue Davis CA 95616 USA
5. Department of Crop Sciences, Plant Pathology and Crop Protection Division; Georg-August University Göttingen; Grisebachstrasse 6 37077 Göttingen Germany