1. Dep. of Plant Agriculture, Crop Science Bldg.; Univ. of Guelph; Guelph ON Canada N1G 2W1
2. INTA Balcarce-Universidad Nacional de Mar del Plata; CC 276 7620 Balcarce Argentina
3. Dep. of Molecular and Cellular Biology; Univ. of Guelph; Guelph ON Canada N1G 2W1
4. This study was supported, in part, by the Natural Sciences and Research Council of Canada; Ontario Ministry of Agriculture, Food, and Rural Development; and Syngenta Biotechnology, Research Triangle Park, NC