1. Natural Resources Institute (NRI), University of Greenwich, Central Avenue, Chatham Maritime, Kent ME4 4TB, United Kingdom
2. Dept. Persyst UMR Qualisud, Centre International de Recherche Agronomique pour le Développement (CIRAD), TA B-95/16, 73 av. J.F. Breton, 34398 Montpellier Cedex 5, France
3. National Agricultural Research Laboratories (NARL), NARO, P.O. Box 7065, Kawanda, Kampala, Uganda