1. Department of Plant Pathology, University of California, Davis, CA 95616
2. Department of Plant Pathology, Entomology and Microbiology, Iowa State University, Ames, IA 50011
3. Department of Plant & Microbial Biology, University of California, Berkeley, CA 94720
4. U.S. Department of Agriculture-Agricultural Research Service, Corvallis, OR 97330