1. Department of Plant Pathology, Physiology, and Weed Science, Virginia Tech, Latham Hall, Ag Quad Lane, Blacksburg, Virginia 24061
2. INRA, Unité de Pathologie Végétale, BP 94, 84140 Montfavet, France
3. Department of Molecular Genetics and Cell Biology, University of Chicago, 1103 East 57th Street, Chicago, Illinois 60637