1. Department of Agronomy, Iowa State University, Ames, Iowa, USA
2. Department of Agronomy, Horticulture and Plant Science, South Dakota State University, Brookings, South Dakota, USA
3. Bayer CropScience Research Station, Beaver Crossing, Nebraska, USA
4. USDA-ARS Cereal Crops Research Unit, Fargo, North Dakota, USA
5. Department of Agronomy and Plant Genetics, University of Minnesota, St Paul, Minnesota, USA