1. Department of Plant Sciences, P.O. Box 339, University of the Free State, Bloemfontein, 9310 South Africa
2. Department of Zoology and Entomology, P.O. Box 339, University of the Free State, Bloemfontein, 9310 South Africa
3. Department of Rural, Environmental and Agricultural Development, Private Bag X804, Potchefstroom, 2520 South Africa
4. Department of Genetics, P.O. Box 339, University of the Free State, Bloemfontein, 9310 South Africa