1. Plant Research International, PO Box 16, 6700 AA Wageningen, The Netherlands
2. De Ruiter Seeds, PO Box 1050, 2660 BB Bergschenhoek, The Netherlands
3. INRA, 28 rue de Herrlisheim, 68021 Colmar Cédex, France
4. Unité de Phytopathologie, IRD, BP 5045 Montpellier, France