1. USDA‐ARS, Crop Germplasm Research Unit, 430 Heep CenterTexas A&M Univ.College StationTX77843‐2474
2. School of Plant, Environmental and Soil Sciences, Louisiana State Univ.Baton RougeLA
3. Dep. of Soil & Crop SciencesTexas A&M Univ.College StationTX77843‐2474