Oberholster PJ1, Botha A-M2* and Grobbelaar JU1
1Department of Plant Sciences, Faculty of Natural and Agricultural Sciences, University of the Free State, PO Box 339, Bloemfontein, ZA9300
2Department of Genetics, Forestry and Agriculture Biotechnology Institute, University of Pretoria, Hillcrest, Pretoria, ZA0002, South Africa
