Introduction
Hibiscus belongs to family Malvaceae and have polymorphic genus of 250 species of trees, shrubs and herbs. Geographically Hibiscus is mainly situated in tropical and subtropical areas, with some species extending into the temperate regions of the world i.e. Hibiscus syriacus L. (althea or rose of Sharon) and Hibiscus sinosyriacus Bailey (Bates 1965). The similarity in their natural distribution pattern is an indication of a similar tolerance to environmental factors (Bates 1965). Among them H. syriacus, a deciduous shrub with more or less distinctly trilobate leaves, is the most popular one. Breeding work is mainly done in this species. The color of the solitary flowers in the axils on the young wood varies from white, light pink or red to purple and blue, generally with a large crimson splash at the base of the petals. Single, semi-double and double blooms are known (Kim and Lee 1991; Yu and Yeam 1972). Flowering time is from the end of July till the first part of October (Bailey 1950; Bean 1973; Kim and Lee 1991; Krussmann 1962). About 40 different cultivars, with various flower colors and shapes, are common in European landscape (Van De Laar 1997). Furthermore, large collections exist in Korea, where Hibiscus is the national flower (Van de Laar 1997; Yu and Yeam 1987). Basic chromosome number of H. syriacus is x = 20 and most cultivars are tetraploid, 2n = 4x = 80 (Skovsted 1941). H. sinosyriacus, 2n = 4x = 80 (Skovsted 1941), has broader leaves compared to H. syriacus. The leaves have short triangular lobes and the involucratal bracts outside the calyx are as long as the calyx or even longer (Bates 1965).
In the breeding of ornamentals, the role of interspecific hybridization in development of variable genotype is very important. When using interspecific hybrids in backcrosses and in new cross combinations hybrid vigor can be captured and traits that do not occur within a single species can be combined (Van Tuyl and De Jeu 1997). A lot of breeding work is done in Hibiscus syriacus and interspecific hybridization between H. syriacus and H. sinosyriacus was reported (Kyung et al. 2001a, b). But the best hybridization strategy and the inheritance of morphological traits remain unclear. Also some interspecific breeding work involving more tropical species of Hibiscus is published. Tachibana (1958) and Kuwada (1964) made successful crosses between H. mutabilis and H. moscheutos, but the obtained F1 seedlings were sterile. Attempts to create interspecific hybrids between H. syriacus and H. rosa-sinensis, especially to introduce new flower colors and forms, were not successful so far (Paek et al. 1989; Yu et al. 1976).
In this study, at temps were made to develop new Hibiscus cultivars with unique flower shape and color, uniform plant habit and hardiness through interspecific hybridization between H. sinosyriacus and H. syriacus. More specific, the aim was to introgress increased growth vigor into H. syriacus by interspecific hybridization with H. sinosyriacus.
Description and Performance
Origin
The breeding program which produced Hibiscus hybrid ‘Tohagol Red’ extended over a period of some 8 years. Hibiscus sinosyriacus ‘Seobong’ introduced from Belgium as the female, or seed parent with a proprietary selection of H. syriacus ‘Samchully’ identified as plant patent number 1481, as the male, or pollen parent. The new Hibiscus hybrid ‘R 202’ was discovered and selected in August, 2004 as a flowering plant within the progeny of the stated crosspollination in an outdoor nursery environment in the Research Institute of Rose of Sharon and Tiger Lily, Cheonan, Korea. Asexual reproduction of the new Hibiscus hybrid ‘R 202’ by hardwood grafting and softwood cuttings under controlled greenhouse environment since the spring of 2007 had shown that the unique features of this new Hibiscus plant are stable and reproduced true to type in successive generations of asexual reproduction (Fig. 1). After the plant characteristics evaluation such as growth characteristics, leaf shape, leaf size, flower characteristics, and flowering for 6 years (2004 ~ 2009), it was named as ‘Tohagol Red’ in 2011. The characteristics were evaluated based on the manual for agricultural investigation and guidelines for the conduct of tests for distinctness, uniformity and stability for Hibiscus (UPOV 2005).
Description
Plants of ‘Tohagol Red’ were semi-compact, uprightspreading with abundant production of violet purple (N80C) (Royal Horticultural Society Flower Council of Holland 2001) flowers of moderate size (11 ~ 13 cm) with a violet-purple, red eye spot at the base of each petal, which was visible from a distance (Fig. 2). This cultivar was very fertile with abundant seed pods produced from insect pollination. The lower stem leaves were generally cordate in shape and might be entire or with short side lobes. Proceeding up the stem they becameoval to lobed-elliptical in shape. Those just below the flowers might be entire. The leaf apex was acute, the base shallowly acute. Leaf margins were irregularly dentate. The leaves were 7.2 cm long and 5.4 cm wide. They were medium to darkgreen in color. The intensity of the green coloring depended upon the nitrogen nutrition of the plant. The new Hibiscus × ‘Tohagol Red’ in well grown plants attained a diameter of leaf shoulder of 2.1 cm and a petiole of 2.1 cm (Table 2).
The corolla was composed of five slightly fan type of petals, 7.1 cm long by 4.7 cm at the widest point. The petals were violet purple (N80C). The base of each petal was slightly darker red (60B) in color for 1.2 cm, the five petal bases thus forming a glabrous eye spot (Table 3 and Fig. 2). Upon anthesis in the early morning the flower petals reflex, then gradually returned to nearly right angles to the central axis and remained thus for the life of the flower. When fully expanded the corolla may measure 12.7 cm in diameter (Table 4). A stout staminal column protruded from the central petal attachment that measured 3.6 cm long (Table 5). It beared numerous short-stalked yellow stamens along the basal two-thirds then became bare for about 1.2 cm before terminating into five stigmatic branches, each terminating in a capitate stigmatic lobe. In color the column shaded from light yellow (NN155C), at the base to cream (154D), at the stigmatic lobes. The pistil protruded from the tip of the anther column before separating into five styles, each 0.5 cm long (Table 5). Hibiscusx ‘Tohagol Red’ started to flower each year in early July and continued for about four months, depending upon environmental conditions. The plants then produced sporadic flowering until frost. The flowers were borne singly in the axils of leaves beginning about mid-way of the stems progressing upward (Table 6).
The flower color in Hibiscus × ‘Tohagol Red’ was intermediate between the flower colors of H. sinosyriacus ‘Seobong’ and H. syriacus ‘Samchully’. In size, the flowers of Hibiscus × ‘Tohagol Red’ were larger than in any of its parent cultivars. In pose, the flowers of Hibiscus × ‘Tohagol Red’ somewhat resembled those of the species H. sinosyriacus in that the flowers expanded their petals widely. The oval three-lobed leaves of Hibiscus × ‘Tohagol Red’ also resembled those of H. sinosyriacusin shape. The stiff, upright main stems of Hibiscus × ‘Tohagol Red’ apparently were derived from H. syriacus. H. sinosyriacus was allied to H. syriacus, but had broader leaves, with three short triangular lobes (Bates 1965; Bean 1973).
Notes for Productionq
The new Hibiscus × ‘Tohagl Red’ can be planted in welldrained soil. The soil should contain a lot of organic matter, such as peat. Don’t use packaged potting mixes because they contain too much inert organic matter, which makes the soil too moist for Hibiscus × ‘Tohagol Red’. A mix of soil, peat, perlite and coarse sand is good. Place drainage material such as stones, broken terra cotta tiles or coarse clinker ashes in the bottom of container, and then cover with wood shavings before adding the soil. Hibiscus plants need lots of water and full sun for optimum blooming. Use a fertilizer that includes trace elements or iron, copper and boron. Perform all pruning in late winter, during the plant’s dormant period.
Availability
An application was filed for variety protection of ‘Tohagol Red’ at the Korea Seed and Variety Service (Application no. 2010-152) and the plant variety protection rights have been registered as grant number 3803 on February 8, 2011. Additional information or a list of nurseries propagating ‘Tohagol Red’ is available on written request to Research Institute of Rose of Sharon and Tiger Lily (RIRS & TL), Cheonan, Korea (e-mail: Shimkk@chol.com). In addition, specimens of the releases have been deposited in the Research Institute of Rose of Sharon and Tiger Lily where it will be available for research purposes. The cultivar had been already released by RIRS & TL, Cheonan, Korea and has been selling as commercial variety for domestic market. It is requested that appropriate recognition be made if this germplasm contributes to the development of a new breeding lines or cultivars.
