[1] Univ Pretoria, Postgrad Sch Agr & Rural Econ, Fac Nat & Agr Sci, Private Bag X20, ZA-0028 Hatfield, South Africa
[2] ICIPE, Dept Plant Hlth, Duduville Campus,POB 30772-00100, Nairobi, Kenya
[3] Int Crops Res Inst Semi Arid Trop, BP 320, Bamako, Mali
[4] Fujian Agr & Forestry Univ, Inst Appl Ecol, Fuzhou 350002, Peoples R China