Flowering Induction, Hybridization and Mutation Breeding of Cordyline
Date Issued
2014
Date
2014
Author(s)
Wu, Tsung-Hsien
Abstract
Cordyline [Cordyline fruticosa (L.) A. Chev.] (= C. terminalis Kunth) is an Agavaceae evergreen shrub. With variations in leaf shape and color, drought tolerant, and a wide range of light intensity tolerance, Cordyline is know as the king of tropical foliage plants, and is widely used as landscape and indoor plants in the tropical and subtropical areas. Climate in Taiwan is suitable for growing and breeding cordyline. However, limited cordyline cultivars have been developed in Taiwan and the hybridization technique is little known. The objects of this thesis were to establish the hybridization protocols for cordyline.
Flowering regulation is crucial for hybridization since cordylines are self-sterile and had short flowering durations and various flowering time, depending on cultivars. Results showed that the flowering rate of 7 cordyline cultivars increased with increasing gibberellic acid concentration from 0 to 5000 mg‧L-1. The effect of GA3 treatment on flowering varied across different seasons and cultivars. A spray of 5000 mg‧L-1 GA3 on top leaves until run-off in April induced plants to flower in June in ‘Chocolate’, ‘Fire Fountain’, ‘Lemon Lime’, ‘Plumdinger’, ‘Red Sister’, ‘White Edge’, ‘Cooperi’, ‘John Klass’, ‘Kiwi’, ‘Tartan’, ‘Thelma’, ‘Cameroon’, ‘Cointreau’, ‘Dolly’, ‘Miss Andrea’, ‘Moonlight’, ‘Amanda’s Blush’, ‘Baby Ti’, ‘Bella’, ‘Hawaiian Compacta’, and ‘Youmeninshiki’. However, only the first six cultivars produced flowers with yellow anthers containing yellow pollen after treatment, whereas the other cultivars produced flowers but had grey, shrivelled anthers without pollen. A spray of 5000 mg‧L-1 GA3 on top leaves until run-off in September induced plants to flower in November in ‘Chocolate’, ‘Fire Fountain’, ‘Lemon Lime’, ‘Plumdinger’, ‘Red Sister’, ‘White Edge’, ‘Cooperi’, ‘John Klass’, ‘Kiwi’, ‘Tartan’, ‘Thelma’, ‘Tricolor’, ‘Peter Buck’, ‘Cameroon’, ‘Cointreau’, ‘Dolly’, ‘Miss Andrea’, and ‘Moonlight’. However, no pollen was produced in ‘Cameroon’, ‘Cointreau’, ‘Dolly’, ‘Miss Andrea’, and ‘Moonlight’.
Pollen of ’White Edge’ and ‘Red Sister’ obtained from natural flowering in winter was cultured on B&K medium containing 0%-20% sucrose. Highest pollen germination rate was obtained in medium with 15% sucrose. Nearly all pollen of ‘Tricolor’ collected at anthesis germinated, while pollen collected 1 day before or after anthesis almost failed to germinate. ‘White Edge’ and ‘Fire Fountain’ pollen collected at anthesis and stored at 4oC for 6 days remained with 30% or higher germination rates, indicating that cordyline pollen could be stored up to one week. Tissue section was performed on self-pollinated flowers of ‘Red Sister’ to observe pollination behavior. Results showed that the pollen germinated and pollen tubes reached the base of the style but not the ovary, indicating gametophytic incompatibility in cordyline.
Seeds of cordyline had tough seed coats. Natural seeds had low germination rates, and incongruent and long germination time, although the seeds were viable as shown with TTC method. Scarificated cordyline seeds increased germination rate and reduced germination time. Germination rate and time to germination did not differ between mechanical scarification and seed coat removal treatments. Chemical scarification with concentrated sulfuric acid did not reduce time to germination, but reduced germination rate after soaking for 20 minutes or longer. Soaking scarified seeds in 0 - 200 mg‧L-1 GA3 for 12 h did not affect germination rates, while 100 mg‧L-1 GA3 treatment resulted in shorter time to germination, as compared with control. Soaking seeds in 25 oC water for 10 and 20 days did not affect the germination of cordyline seeds. Germination was inhibited by hot water immersion treatment at 70oC for 5 min or longer. Seeds treated with dry heat at 35oC for 16 days failed to germinate. Light and dark treatments did not affect germination of cordyline seeds. Seeds sown with the fruit intacted had reduced germination rate. As mean daily temperature increased from 14.0 oC to 32.5 oC, time to germination decreased linearly.
Cordyline ‘White Edge’ were cultured under day/night temperature 35/30, 30/25, 25/20, and 20/15. Best leaf growth and leaf variegation was obtained in 30/25℃.
As γ radiation dose increased from 0 to 150 Gy, survival rate of ‘Baby Ti’ stem segment cuttings decreased linearly, with LD50 of 21 Gy. As γ radiation dose increased from 0 to 250 Gy, survival rate of stem segment cuttings and lateral shoot cuttings of ‘Dolly’ decreased linearly, with LD50 of 165 Gy.
Thirty-five Cordyline cross combination, more than 9000 seeds, were obtained in this thesis. Different hybrids will be evaluated for their suitability as pot plant or landscaping material in terms of plant size, leaf shape, and colors.
Subjects
龍舌蘭科
開花調節
觀葉植物
花粉培養
種子發芽
γ射線
SDGs
Type
thesis
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