1. Department of Agronomy, Iowa State University , Ames, IA 50011, USA
2. Department of Statistics, Iowa State University , Ames, IA 50011, USA
3. USDA—Agricultural Research Service, Corn Insects and Crop Genetics Research Unit , Ames, IA 50011, USA
4. Department of Genetics, Development and Cell Biology, Iowa State University , Ames, IA 50011, USA