1. Department of Agricultural Science and Technology, School of Agriculture and Enterprise Development, Kenyatta University, P. O. Box 43844-00100, Nairobi, Kenya; CGIAR Research Program on Roots, Tubers and Bananas (RTB), International Potato Center, Sub-Saharan Africa Regional Office, ILRI Campus, Old Naivasha Road. P.O. Box 25171, 00603, Nairobi-Kenya
2. Department of Land Resource Management and Agricultural Technology, College of Agriculture and Veterinary Sciences, University of Nairobi, P.O. Box 29053-00625, Nairobi
3. CGIAR Research Program on Roots, Tubers and Bananas (RTB), International Potato Center, Sub-Saharan Africa Regional Office, ILRI Campus, Old Naivasha Road. P.O. Box 25171, 00603, Nairobi-Kenya
4. University of Applied Science Bingen (TH Bingen) Berlinstrasse 109, 55411Bingen, Germany