By: Prof. Torbjörn Fagerström, Dr. Roy B. Mugiira and Prof. Lisa Sennerby Forsse a) Värtavägen 39, SE 115 29 Stockholm, Sweden, b) Directorate of Research Management and Development, State Department of Science and Technology, Ministry of Education, Science and Technology, Nairobi, Republic of Kenya, c) Swedish University of Agricultural Sciences (SLU), Box 7070, Uppsala, S-750 07 Sweden.