1. Agricultural Research Council – Institute for Tropical and Subtropical Crops, Nelspruit, South Africa
2. Unit for Environmental Sciences and Management, Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
3. Laboratory of Tropical Crop Improvement, Department of Biosystems, Faculty of Bioscience Engineering, University of Leuven (KU Leuven), Heverlee, Belgium