1. Centro Nacional de Investigaciones Agropecuarias; APDO Postal 102 Acarigua 3301-A Venezuela
2. Dep. of Agronomy; Univ. of Wisconsin; Madison 53706
3. Dep. of Plant Pathology; Univ. of Wisconsin; Madison 53706
4. USDA-ARS, Dep. of Agronomy and Plant Genetics, 411 Borlaug Hall, 1991 Upper Buford Cir.; Univ. of Minnesota; St. Paul MN 55108