1. Dep. of Plant Sciences; North Dakota State Univ.; 166 Loftsgard Hall, PO Box 6050 Fargo ND 58108-6050
2. USDA-ARS, Sunflower and Plant Biology Research Unit, Edward T. Schafer Agricultural Research Center; 1616 Albrecht Blvd. N. Fargo ND 58102-2765