1. Citrus Research International, Nelspruit, 1200, South Africa
2. Department of Genetics, Stellenbosch University, Matieland, 7602, South Africa
3. Agricultural Research Council, Infruitec-Nietvoorbij: Institute for Deciduous Fruit, Vines and Wine, Stellenbosch, 7599, South Africa, and Department of Genetics, Stellenbosch University, Stellenbosch, South Africa