1. Dep. of Crop and Soil Sciences; Washington State Univ.; Pullman WA 99164-6420
2. Dep. of Agronomy and Horticulture; Univ. of Nebraska; Lincoln NE 68583-0915
3. USDA-ARS, Dep. of Agronomy and Horticulture; Univ. of Nebraska; Lincoln NE 68583-0915
4. USDA-ARS, and Dep. of Plant Pathology; Univ. of Nebraska; Lincoln NE 68583-0737