1. Interdepartmental Genetics Program; Iowa State University; Ames IA 50011 USA
2. Plant Science Research Unit; USDA-Agricultural Research Service; Saint Paul MN 55108 USA
3. Department of Statistics; Iowa State University; Ames IA 50011 USA
4. Department of Plant Pathology & Microbiology; Iowa State University; Ames IA 50011 USA
5. Department of Agronomy; Iowa State University; Ames IA 50011 USA
6. Corn Insects and Crop Genetics Research Unit; USDA-Agricultural Research Service; Ames IA 50011 USA