1. Debre Zeit Agricultural Research Center; P.O. Box 32 Debre Zeit Ethiopia
2. Institute of Crop Science and Resource Management, Phytomedicine; Univ. of Bonn; Nussallee 9 D-53115 Bonn Germany
3. Max-Planck-Institute for Plant Breeding Research; Carl-von-Linné-Weg 10 D-50829 Cologne Germany