1. Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK,
2. Present address: CAB International Publishing, Wallingford OX10 8DE, UK,
3. These authors contributed equally to this manuscript
4. Present address: Department of Botany, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada M5S 3B2;
5. Present address: Institute of Infectious Disease and Molecular Medicine, Faculty Of Health Sciences, University of Cape Town, Observatory 7925, Cape Town, South Africa;
6. Department of Wood Science, University of British Columbia, 4030–2424 Main Mall, Vancouver, BC, Canada V6T 1Z4;