Micropropagation of Cubio (Tropaeolum tuberosum R & P)
Tropaeolum belongs to the family Tropaeolaceae, that includes about 100 species. It takes its name from the Greek word τρωπαLov = trophy, in allusion to the armor of ancient knights-errant. Leaves from some species look like shields and the longstalked, s
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1 Introduction Tropaeolurn belongs to the family Tropaeolaceae, that includes about I 00 species. It takes its name from the Greek word rpumcxLov = trophy, in allusion to the armor of ancient knights-errant. Leaves from some species look like shields and the longstalked, solitary and occasionally double flowers are orange to scarlated in color. Smaller than those of the garden nasturtium (Tropaeolurn rnajus). They are distributed throughout the neotropical region from Mexico to Brazil and Argentina. Cubio ( Tropaeolurn tuberosurn Ruiz and Pavon 1802) is the most important species because it produces edible tubers (Fig. I), which are consumed by inhabitants of the Andean regions.
Fig. I. Tubers of Tropaeolum tuherosum
1 Labora torio Cultivo Tejidos Vegetales, Departamento de Biologia, Facultad de Ciencias, Universidad Nacional de Colombia, A.A. 23227, Bogota, Colombia
Biotechnology in Agriculture and Forestry, Vol. 19 High-Tech and Micropropagation Ill (cd. by Y.P.S. Bajaj) (t) Springer-Verlag Berlin Heidelberg 1992
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Micropropagation of Cubio
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a Fig. 2a-e. Tropaeolum tuberosum: a Habit. b Tuber. c Detail of leaf axil. d and e Flower. (d and e from Ruiz and Pavon 1802)
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0. Torres et a!.
T. tuberosum (Fig. 2) is a prostrate or climbing herb growing to over 1-1.5 m in diameter and 0.5-0.8 m high. Aerial stems are cylindrical and slender. Leaves are alternate, their petioles are long (1 0--15 em), flexible, and serve as tendrils, the blade is peltate three-to-five-lobed. Flowers are single, zygomorphic; the peduncles as long as the petioles; the calyx is reddish, five-lobed, ending in an elongate calcar; petals are five in number, usually dark yellow or orange; there are eight stamens. The fruit is a schizocarp with three indehiscent carpels (Sparre 1973). The tubers, for which the plant is cultivated, are axillary shoots that have become thickened and filled with storage products. They are subterranean. Tubers bear axillary buds which have the potential to generate aerial stems. Adventitious roots arise from the nodes on underground stems, including tubers (White 1975). T. tuberosum is an annual plant; however, for its potential for continual tubers production this species can be classified as perennial. Sparre ( 1973) distinguishes two subspecies: T. tuberosum tuberosum, the cultivated form, and T. tuberosum silvestre, a naturally occurring form which produces no tubers. The chromosome number of T. tuberosum is 2n = 52 (Gibbs et al. 1978). Multivalent formation and the occurrence of other meiotic abnormalities suggest a possible autopolyploid origin. T. tuberosum tuberosum is a probable tetraploid in an x = 13 series. The polyploid nature of this subspecies in such a series suggests some interesting possibilities for the origin of the tuber-bearing cultivar: either autopolyploidy from subsp. silvestre, or allopolyploidy following hybridization with another closely related species such as T. cochabambae (2n = 26). To solve the problem, cytological studies of T. tuberosum sil
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