1. Department of Environmental Sciences, Botany, Zurich-Basel Plant Science Center, University of Basel, Hebelstrasse 1, Basel 4056, Switzerland
2. INRA, UMR1136 Interactions Arbres-Microorganismes, Champenoux 54280, France
3. Universit� de Lorraine, UMR1136 Interactions Arbres-Microorganismes, Vandoeuvre-l�s-Nancy 54500, France
4. Agro�cologie, AgroSupDijon, CNRS, INRA, Universit� de Bourgogne Franche-Comt�, Dijon 21000, France