Genetically-modified, colour-altered varieties of the important cut-flower crop carnation have now been commercially available for nearly ten years. In this review we describe the manipulation of the anthocyanin biosynthesis pathway that has lead to the development of these varieties and how similar manipulations have been successfully applied to both pot plants and another cut-flower species, the rose. From this experience it is clear that down- and up-regulation of the flavonoid and anthocyanin pathway is both possible and predictable. The major commercial benefit of the application of this technology has so far been the development of novel flower colours through the development of transgenic varieties that produce, uniquely for the target species, anthocyanins derived from delphinidin. These anthocyanins are ubiquitous in nature, and occur in both ornamental plants and common food plants. Through the extensive regulatory approval processes that must occur for the commercialization of genetically modified organisms, we have accumulated considerable experimental and trial data to show the accumulation of delphinidin based anthocyanins in the transgenic plants poses no environmental or health risk.

The status quo of flavonoid biosynthesis as it relates to flower color is reviewed together with a success in modifying flower color by genetic engineering. Flavonoids and their colored class compounds, anthocyanins, are major contributors to flower color. Many plant species synthesize limited kinds of flavonoids, and thus exhibit a limited range of flower color. Since genes regulating flavonoid biosynthesis are available, it is possible to alter flower color by overexpressing heterologous genes and/or down regulating endogenous genes. Transgenic carnations and a transgenic rose that accumulate delphinidin as a result of expressing a flavonoid 3 0 ,5 0 -hydroxylase gene and have novel blue hued flowers have been commercialized. Transgenic Nierembergia accumulating pelargonidin, with novel pink flowers, has also been developed. Although it is possible to generate white, yellow, and pink-flowered torenia plants from blue cultivars by genetic engineering, field trial observations indicate difficulty in obtaining stable phenotypes.

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An important part of the assessment of the potential environmental impact from the introduction of a genetically modified (GM) plant is an evaluation of the potential for gene flow from the GM plant to related wild species. This information is needed as part of the risk-assessment process, in the context of whether gene flow to wild species is possible. One method for evaluating gene flow is to use molecular techniques to identify genes in wild species populations that may have originated from a cultivated species. An advantage of this method is that a phenotypic marker or trait is not required to measure gene flow. In the present study we analyzed the seedlings of seeds from three wild native Rosa species (R. multiflora Thunb., R. luciae Rochebr. et Franch. ex Crép. and R. rugosa Thunb.) selected from several locations across Japan where the wild rose was growing in close proximity to cultivated rose plants (Rosaϫhybrida). To determine whether gene flow from cultivated rose had occurred, young leaves of 1,296 seedlings from the wild Rosa plants were analyzed by PCR for the presence of the KSN locus. This locus originated from a sport of R. chinensis Jacq. var. spontanea (Rehd. et Wils.) Yu et Ku and is involved in the recurrent flowering phenotype observed for cultivated rose hybrids, but is absent in Japanese species roses. The KSN locus was absent in all seedlings sampled, indicating no gene flow to wild Rosa species from the cultivated rose had occurred, and providing evidence that the probability of gene flow from cultivated to wild Rosa species in Japan is low or non-existent.

No abstract reveived.