Regeneration of Plants from Protoplasts of Saintpaulia ionantha H. Wendl. (African Violet)
The African violet was described scientifically for the first time in 1893, and named Saintpaulia ionantha by Wendland (1893). The genus belongs to the family Gesneriaceae, and the 20 species originate from South-East Africa. Breeding was done mainly with
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1 Introduction The African violet was described scientifically for the first time in 1893, and named Saintpaulia ionantha by Wendland (1893). The genus belongs to the family Gesneriaceae, and the 20 species originate from South-East Africa. Breeding was done mainly with Saintpaulia ionantha and S. confusa, and as a result the cultivars existing today are regarded as S. ionantha hybrids (Moore 1957). Intensive breeding efforts led to a wide spectrum of cultivars in different flower colors and shapes. The economic importance of S. ionantha as an ornamental warmhouse plant increased, so now it is one of the most-sold plants in Europe and the USA. However, important characters have to be improved, like plant quality with regard to transport ability, cold tolerance, disease and pest resistances, especially against the Californian flower thrips (Frankliniella occidentalis), and yellow, orange, or true red flower colors. Since conventional cross-breeding as well as mutation induction did not lead to these new flower colors, new techniques for increasing the genetic variability in this species, like gene transfer or somatic hybridization, may be helpful. Until now, there have been no publications reporting success in transforming S. ionantha with Agrobacterium tumefaciens. The prerequisite for applying the latter techniques is a system for plant regeneration from protoplasts. Although there are many reports on the in vitro regeneration and propagation of Saintpaulia (for a review see Jungnickel and Zaid 1992), only a few concern protoplast isolation and culture. Besides the references of the mechanical isolation procedure of Bilkey and Cocking (1982) and the enzymatic protoplast isolation described by Fernandez and Torres (1984) and U~ Cong-Linh (1987), until now only two protocols for the generation of plants from Saintpaulia protoplasts exist (Winkelmann and Grunewaldt 1992; Hoshino et al. 1995). One possible application is somatic hybridization with those species, which cannot be combined sexually. Fusion of protoplasts of Saintpaulia ionantha and Episcia species (flame violets), for example, may result in hybrids with new lInstitute for Vegetable and Ornamental Crops, Department of Plant Propagation, Mittelhiiuser Str., 99189 Kiihnhausen, Germany 2Federal Centre for Breeding Research on Cultivated Plants, Institute for Ornamental Plant Breeding, Bornkampsweg 31, 22926 Ahrensburg, Germany
Biotechnology in Agriculture and Forestry, Vol. 38 Plant Protoplasts and Genetic Engineering VII (ed. by Y.P.S. Bajaj) © Springer-Verlag Berlin Heidelberg 1996
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T. Winkelmann and 1. Grunewaldt
flower colors, since there are yellow and red flowering types of Episcia (Bilkey and McCown 1978). In addition, a direct gene transfer into Saintpaulia protoplasts could also be realized to reach other important breeding aims like resistance to pests and diseases or cold tolerance.
2 Isolation of Protoplasts Viable protoplasts could be isolated from leaves and peduncles of in vitro grown shoots, but further development was never observe
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