Submitted to: Acta Horticulture Proceedings
Publication Type: Proceedings
Publication Acceptance Date: May 16, 2005
Publication Date: October 31, 2006
Citation: Hammond, J. 2006. Current status of genetically modified ornamentals. Acta Horticulture. 722:117-128. Interpretive Summary: The potential advantages of genetic engineering to introduce specific new traits into horticulturally adapted varieties of ornamental plants are briefly reviewed. It is possible to introduce such traits as disease resistance, or to modify such characteristics as flower color or fragrance, or the way that a plant branches, by transferring one or a few genes from another organism. The lack of genes for resistance to diseases affecting ornamental crops is one area where genetic engineering has significant potential for increases in crop productivity and quality. The status of experimental work on disease resistance is compared to the current commercial availability of only a few varieties of genetically modified carnations, in which flower color was modified by introduction of an enzyme that affects the biosynthetic pathway. This results in production of floral pigments that are not normally produced in carnation, and a range of blue/purple flowers. Achievements in obtaining resistance to virus diseases of significance to ornamental plants are reviewed, with special emphasis on genetic engineering of ornamental crops to obtain virus resistance.
Technical Abstract: Biotechnology offers new means of improving ornamental crops by the addition of desirable traits to existing horticulturally-adapted cultivars. Traditional plant breeding involves the exchange of many hundreds or thousands of genes between related species to create novel combinations; improved genotypes must be selected from thousands of segregating progeny over multiple cycles of selection. Introgression of a single desirable new character, such as disease resistance, from an unadapted relative of a crop species may require multiple backcross generations to regain the horticultural or ornamental qualities of the original cultivar, often resulting in reduced intensity of expression of the back-crossed character. In the case of many ornamental species, related germplasm with the desired disease resistance has not been identified. This is particularly true in the case of viruses, where few sources of resistance are known among ornamentals and related species. However, it has been demonstrated that effective resistance against many plant viruses can be obtained, in model systems and in some field crops, by introduction of virus-derived sequences or various anti-viral genes. Viral infection is a significant problem in many ornamentals, and especially floral crops, because so many ornamentals are vegetatively propagated; virus infection frequently reduces floral quality and value as well as yield. Transformation of crop species with one or more gene constructs can lead to addition of desirable traits, typically with minimal effects on other desirable characteristics. Transformation systems have currently been developed for over 30 species of herbaceous ornamentals and several woody species, and efforts continue in many laboratories around the world. Several groups are working to introduce virus resistance into various ornamentals, including lilies, gladiolus, chrysanthemums, and various orchids. Other traits of interest include plant architecture, floral longevity, flower color, and resistance to other environmental stresses including drought, pests, and fungal and bacterial diseases. A few genetically modified ornamental crops have been commercialized, notably carnations with altered flower color, and there is future expectation of the introduction of effective virus resistance into commercial floral crops.