1. The Horticulture and Food Research Institute of New Zealand Ltd, Hawkes Bay Research Centre, Havelock North, Private Bag 1401, New Zealand;
2. Institut National de la Recherche Agronomique, Centre de Recherches d’Angers, BP57, 49071 Beaucouzé Cédex, France;
3. Plant Research International, PO Box 16, 6700 AA Wageningen, the Netherlands;
4. The Horticulture and Food Research Institute of New Zealand Ltd, Palmerston North Research Centre, Private Bag 11030, Palmerston North, New Zealand;
5. Present address: University of East Anglia, School of Biological Sciences, Norwich, NR4 7TJ, UK
6. The Horticulture and Food Research Institute of New Zealand Ltd, Mt Albert Research Centre, Private Bag· 92169, Auckland, New Zealand;
7. University of Auckland, School of Biological Sciences, Private Bag 92019, Auckland, New Zealand;