1. Department of Forest Mycology and Plant Pathology Swedish University of Agricultural Sciences Box 7026 75007 Uppsala Sweden
2. Southern Swedish Forest Research Centre Swedish University of Agricultural Sciences Box 49 230 53 Alnarp Sweden
3. Department of Microbial Ecology NIOO‐KNAW Box 50 6700 AB Wageningen the Netherlands
4. INRA Interactions Arbres – Microorganismes UMR 1136 F‐54280 Champenoux France