435 Generation of New Ornamental Varieties Through Genetic Modification of Pigment Biosynthesis K.M. Davies, G.B. Marshall, D.H. Lewis, C.S. Winefield, S.C. Deroles, M.R. Boase, H. Zhang, K.M. Nielsen and K.E. Schwinn Crop & Food Research Private Bag 11-600, Palmerston North, New Zealand S.J. Bloor and E. Swinny Industrial Research Limited P.O. Box 31-310, Lower Hutt New Zealand C.R. Martin John Innes Centre Colney Lane, NR4 7UH, Norwich United Kingdom Keywords: flavonoid, carotenoid, betalain, flower colour, gene regulation Abstract The introduction of new colours and forms through genetic modification is likely to become an integral part of the breeding of new ornamental varieties. Although application of these techniques to floriculture has been slow to progress in comparison with the major crop species, there are now transgenic carnations for sale in several countries, and many more floriculture products are in development. We have a programme aimed at understanding the basis of the colour variation observed in nature, so that strategies for modifying flower and plant colour can be developed. Recent progress in the field is reviewed, including prospects for controlling the production of flavonoids, carotenoids, betalains and non-plant pigments. Emphasis is given to the flavonoids, as these are the most common, the most commercially important, and from a biotechnology point of view the most amenable of the pigment groups. The review highlights, in particular, some of the progress in our laboratories on the genes regulating the flavonoid biosynthetic pathway and the biosynthetic mechanism for aurones and 3-deoxyanthocyanins. INTRODUCTION Flower colour is a key element in consumer selection between ornamental varieties. For some ornamental species, however, only a narrow colour spectrum is available, whilst in others, specific colours such as blue or yellow are lacking. Genetic modification of pigment biosynthesis can introduce colours outside the existing range. The extensive information available on the genetics and biochemistry of pigment bio- synthesis provides a strong foundation to such research, increasing the probability of success. The major pigments responsible for plant colour are the flavonoids, carotenoids, chlorophylls and the taxonomically restricted betalains. Chlorophylls have an obvious role in providing the green colour of photosynthetic tissues but they also influence colour as background pigments and are responsible for the rare cases of green flowers (eg. Anthurium and Cymbidium). Outside of the plant pigments, there is also the prospect of introducing the biosynthesis of pigments normally found in bacteria and fungi. This review concentrates on flavonoids, as these are the main focus of our research and from a metabolic engineering point of view they are the most studied and most amenable of the plant pigment groups to modification. Where possible, in the interests of conserving space, the reader is referred to recent reviews for more extensive citing of the original research reports. FLAVONOIDS The flavonoids are a group of water-soluble, typically vacuolar-located pigments responsible for many of the colours seen in nature, in particular pink, red, orange, scarlet, purple, blue, blue-black and some yellow colours. In addition, they provide ‘depth’ to Proc. XXVI IHC – Elegant Science in Floriculture Eds. Th. Blom and R. Criley Acta Hort. 624, ISHS 2003 Publication supported by Can. Int. Dev. Agency (CIDA)