1. INRA, Agrocampus Ouest, Univ. Rennes1, UMR1099 BiO3P (Biology of Organisms and Populations applied to Plant Protection), F–35653 Le Rheu, France
2. INRA, Agrocampus Ouest, Univ. Rennes1, UMR118 APBV (Amélioration des Plantes et Biotechnologies Végétales), F–35653 Le Rheu, France
3. Rothamsted Research, Harpenden, Herts AL5 2JQ, UK