Floral morphology, inheritance, and breeding of double-flowered Catharanthus roseus

• Main Authors: Chin-Mu Chen, 陳錦木
• Other Authors: Der-Ming Yeh
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/10994414790331162944

博士 === 國立臺灣大學 === 園藝暨景觀學系 === 101 === Periwinkle [Catharanthus roseus (L.) G. Don] is a heat and sun-loving plants with prolonged flowering duration. Cultivars have been developed rapidly in recent years. This study aimed to compare flower bud development of TYV1, a double-flowered periwinkle mutant, and its parent, single-flowered ‘Pacifica Polka Dot’ by dissection and wax sectioning to determine the origin of doubled petals. Plants of TYV1 and ‘Pacifica Polka Dot’ were also grown under different temperatures to establish cultural, cell membrane thermostability, and pollen germination information. With functioning pistils and stamens, TYV1 was cross-pollinated with single-flowered cultivars to create reciprocal F1 hybrid, F2, and back-crossed F1 generation to determine the inheritance of double-floweredness in periwinkle. Moreover, based on morphological and genetical information, the procedure of breeding and selection for double-flowered periwinkle was established. TYV1 has five salverform outer corolla lobes and five funnel-shaped inner corolla lobes. Sectioning results showed inner corolla lobes of TYV1 originated from adaxial meristem originally formed into orifice in ‘Pacifica Polka Dot’. Plants of TYV1 and ‘Pacifica Polka Dot’ were grown at day/night temperature of 30/25oC, flower buds at different developmental stages were taken for anatomical observations. The overlap between the top end of the pistil and bottom ends of anthers in TYV1 and ‘Pacifica Polka Dot’ flowers at 1-2 d after anthesis was 0.56±0.01 and 0.82±0.02 mm, respectively. TYV1 had fewer ovules per ovary than ‘Pacifica Polka Dot’. Based on flower bud longitudinal length, 12 stages were proposed for flower bud development of periwinkle and the first six stages were taken for further observations. At stage 1 (0.5-0.9 mm long), undifferentiated carpel was surrounded by five stamens, then five polypetals, and five thin sepals outermost. At stage 2 (1.0-1.9 mm long), polypetals had fused into sympetal and stamens and pistil were enclosed within. Dissecting stage 2 flowers showed that TYV1 had initiated inner corolla lobe at the transition of corolla tube and lobe, but not for ‘Pacifica Polka Dot’. At stage 3 when petals and sepals have same lengths, inner corolla lobes started to elongate and had marginal hairs. Sectioning results showed both outer and inner corolla lobes had the same originality. Corolla tube rapidly elongated from stage 5 (4.0-4.9 mm long) until stage 10 (21.0-25.9 mm long). Flower anthesis at stage 11 and corolla lobe fully expanded at stage 12. Young seedlings from self-pollinated TYV1 had crinkled leaf before the sixth pair of leaves emerged, as compare with smooth leaf surface in ‘Pacifica Polka Dot’. Petiole length of TYV1 and ‘Pacifica Polka Dot’ was 1.3 and 0.4 cm, respectively. Plants of TYV1 and ‘Pacifica Polka Dot’ were grown at day/night temperatures of 20/15, 25/20, and 30/25oC, for the evaluation of the responses of growth, flowering, and cell membrane thermostability. Results showed that plants at 20/15oC had poor growth, both TYV1 and ‘Pacifica Polka Dot’ exhibited reduced plant height, flower diameter, and branching, and more days to flowering, but fewer node number below the flower. Optimum temperature for growth and flowering of TYV1 and ‘Pacifica Polka Dot’ was 25/20oC. The relationship between the RI value, as measured with water bath temperature from 25 to 75℃ for 30 min, occurring in leaf tissue discs and the water bath temperature was sigmoidal in both TYV1 and ‘Pacifica Polka Dot’. ‘Pacifica Polka Dot’ showed more heat acclimatization response than TYV1, but TYV1 could tolerate higher temperatures than ‘Pacifica Polka Dot’. Pollen from plants grown at 30/25oC was tested for incubation temperatures of 10-45oC, and results showed that the optimum pollen germination temperature was 25-30℃ for TYV1 and 20-40oC for ‘Pacifica Polka Dot’. Vegetative propagated double-flowered TYV1, single-flowered ‘Little Pinkie’, and ‘Titan Burgundy’ were used for self-pollination, cross between single- flowered and double-flowered lines (F1), F2, and back-crossed F1 of seed parents. Self-pollinated TYV1 produced all double-flowered progeny compared to self-pollinated single-flowered lines which produced all single-flowered progeny. F1 plants between TYV1 and ‘Little Pinkie’ or ‘Titan Burgundy’ were all single. Three among four F2 population segregated into 3 single : 1 double ratio (χ2 = 0.78-1.53, P = 0.22-0.37). Two BCF1 population segregated into 1 single : 1 double ratio (χ2 = 0.25-0.69, P = 0.41-0.62). Results indicated a double-flowered form was controlled by a recessive allele. A single dominant gene expressed in the homozygous or heterozygous state resulted in the single-flowered phenotype. DNA length of double-flowered TYV1 and single-flowered ‘Titan Burgundy’ did not differ with diploid ‘Little Pinkie’, and estimated to have 1468.0, 1508.1, and 1457.2 Mbp, respectively. Double-flowered TYV1 was used as female parent and crossed with single-flowered TYV3 and TYV4. Fifteen single-flowered F1 seedlings were selected based on bigger flower diameter and vigorous growth habit. Five double-flowered lines with desirable traits were selected after the first selection and two line comparison tests, and were named as ‘Taoyuan No.1 Rose Girl ’, ‘Taoyuan No.2-Peach Lady’, ‘Taoyuan No.3-Red Butterfly’, ‘Taoyuan No.4-Summer Snow’, and ‘Taoyuan No.5-Red Lady’. The new double-flowered cultivars were suitable for potted flower production characterized with more branching, flower number per plant, and shorter plant height. All the selectrd cultivars had two whirls of compacted petals in funnel-shaped, and had flower diameter of 3.3 ± 0.3 cm. The selected new double-flowered cultivars had been certified of plant breeders’ right (PBR) by Council of Agriculture, Taiwan, and were the world’s first PBR protected double-flowered periwinkle cultivars.