1. Department for Systematic Botany and Biodiversity, Institute for Biology, Humboldt-Universität zu Berlin, Philippstr. 13, D-10115 Berlin, Germany
2. Department of Plant Physiology and Biochemistry, University of Hohenheim, D-70599 Stuttgart, Germany
3. Laboratory of Plant Biology and Pathology, University of Nantes, F-44322 Nantes Cedex 3, France