1. Department of Agronomy, University of Wisconsin, 1575 Linden Drive, Madison, Wisconsin 53706 (N.M.S., H.F.K., S.M.K.); Department of Plant Sciences, University of Arizona, Tucson, Arizona 85721 (C.A.N., V.L.C.); and Division of Biological Sciences, University of Missouri, Columbia, Missouri 65211 (K.C.C.); Pioneer Hi-Bred International, Inc., Johnston, Iowa 50131 (D.A.S.); and Arizona Cancer Cent