1. UMR INRA/UHP 1136 ‘Interactions Arbres/Micro‐Organismes’, Centre INRA de Nancy, F‐54280 Champenoux, France;
2. Dipartimento di Biologia Vegetale dell′Università di Torino, Viale Mattioli I‐10125 Torino, Italy;
3. These authors contributed equally to this work;
4. Departamento de Biología Vegetal, Universidad de Alcalá, E‐28871 Alcalá de Henares, Spain;
5. Present address: Institut für Botanik – Terrestrische Ökologie, Universität Leipzig – Johannisallee 21–23 D‐04103 Leipzig, Germany
6. UMR 1095 INRA‐UBP ‘Amélioration et Santé des Plantes’, Site de Crouelle, 234 avenue du Brézet, F‐63039 Clermont‐Ferrand Cedex 2, France;