1. Department of Plant and Microbial Biology University of Minnesota St. Paul MN 55108 USA
2. Department of Plant Sciences and Center for Population Biology University of California Davis CA 95616 USA
3. Department of Agronomy and Plant Genetics University of Minnesota St. Paul MN 55108 USA
4. Department of Plant Pathology University of Minnesota St. Paul MN 55108 USA
5. Genome Center University of California Davis CA 95616 USA