Note: The majority of species originally classified as Chrysanthemum were reclassified into 38 satellite genera (Heywood 1976, Humphries 1976a 1976b). The genus Chrysanthemum now contains two species, C. coronarium and C. segetum (Anderson 1987 2006, Boase et al. 1997). Cultivated greenhouse and garden chrysanthemums are classified as Dendranthema x grandiflora Tzvelv. (Kitamura) (Ramatuelle) (=Chrysanthemum x morifolium Ramat.; =C. x hortorum Ramat.), a crop species within the Asteraceae Dumort. family (=Compositae; Tribe: Anthemideae, Subtribe: Chrysantheminae) (Heywood and Humphries 1977, Anderson 1987 2006). 20 Chrysanthemum Biotechnology Harue Shinoyama 1* • Neil Anderson 2 • Hideo Furuta 3 • Atsushi Mochizuki 4 • Yukio Nomura 1 • Rudra Singh 5 • Subodh K. Datta 6 • Bochu Wang 7 • Jaime A. Teixeira da Silva 8** 1 Fukui Agricultural Experimental Station, Japan 2 University of Minnesota, Dept. of Horticultural Science, 1970 Folwell Avenue, St. Paul, MN 55108 USA 3 Fukui Prefectural Office, Japan 4 Chief, Introd. Insect Assessment Unit, Dept. of Biol. Safety, National Institute for Agro-Environmental Sciences, 3-1-1 Kai-nondai, Tsukaba 305-0864 Japan 5 Agriculture and Agri-Food Canada, Potato Research Centre, P.O. Box 20280, 850 Lincoln Road , Fredericton, New Brunswick, E3B 4Z7, Canada 6 National Botanical Research Institute, Botanic Garden & Floriculture, Lucknow 226 001, Uttar Pradesh, India 7 Bioengineering College, Chongqing University, Chonqing 400044, PR China 8 Kagawa University, Faculty of Agriculture, Department of Horticulture, Miki-cho, Ikenobe, 761-0795, Japan Corresponding authors: * harue_shinoyama@fklab.fukui.fukui.jp; ** jaimetexdasilva@yahoo.com Keywords: chimera, Dendranthema, mutation breeding, somatic embryogenesis, transformation ABSTRACT Chrysanthemum will remain an important global floricultural crop leader due to its extensive range of plant and flower colours, shape and form. Recent studies have demonstrated genotype-independent phenotypic plasticity of this ornamental crop, making it a suitable candidate as a floricultural model plant for in vitro studies on development and transformation. Significant findings in in vitro regeneration from thin cell layers and biotechnological breeding protocols involving somatic embryogenesis, intergeneric somatic hybridization, mutation/classical breeding, and genetic transformation demonstrate to the reader significant research in understanding the dynamic processes underlying growth, development, and flower induction of this plant. Although there is now a trend to use ion beams and genetic transformation to primarily induce novel flower characters, classical mutation breeding (using physical and chemical mutagens) remains an important source of variation. Protoplast electrofusion has been used to generate intergeneric, rust-resistant hybrids with wormwood which, together with the successful introduction of several insect, virus/viroid, and fungal resistance genes in a wide range of cultivars, will serve as a model plant to overcome many pest-related problems plaguing ornamentals in the global floricultural industry. Preliminary studies also indicate that, due to the capacity of the plant to withstand great stresses in and ex vitro, chrysanthemums might very well be suitable candidates for ornamental phytoremediation. Well-studied, established regeneration and transformation protocols will undoubtedly allow for rapid advances in the biotechnology of this jewel plant. 1. INTRODUCTION The breeding of new chrysanthemum [Dendranthema x grandiflora (Ramat.) Kitamura; =Chrysanthemum x morifolium Ramat.] cultivars, one of the most important global cut flower, herbaceous perennial (garden), and flowering pot plant crop, has limitations when using classical breeding methods: a restricted gene pool, self incompatibility, interspecific incompatibility due to parental ploidy differences, aneuploidy, euploidy, inbreeding depression, genetic load, sterility, and the polygenic nature of growth and flowering. Cultivated chrysanthemums are allohexaploid (2n=6x=54) with somatic chromosome numbers of 2n=47-63 (Dowrick 1953). In order to overcome these limitations and allow for more extensive and diverse crop improvement by allowing the introduction of traits coded by genes across taxonomic barriers, traditional breeding and genetic and molecular techniques have focused on the enhancement of the plant's ornamental value through the improvement of flower colour, size and form, vegetative height, growth form and sensitivity to light quality and quantity. Globally, chrysanthemums are the second most important economic floricultural crop following rose, and one of the most important ornamental species. Various aspects of chrysanthemum biotechnology, cryopreservation and post-harvest technology have recently been covered (Teixeira da Silva 2003d 2004b, Anderson 2006), and thus this chapter will focus on the latest developments and biotechnological advances affecting the improvement and maintenance of chrysanthemum germplasm in vitro, and presents exclusive, practical protocols for successful intergeneric breeding, somatic embryogenesis and transformation.