1. R. A. Jorgensen is in the Department of Plant Sciences, University of Arizona, Tucson, AZ 85721-0036, USA..
2. R. G. Atkinson and R. L. S. Forster are at HortResearch, Private Bag 92169, Auckland, New Zealand.
3. W. J. Lucas is with the Section of Plant Biology, University of California, Davis, CA 95616, USA..