朱蕉之開花調節及雜交授粉技術之研究

朱蕉[Cordyline fruticose (L.) A. Chev.]為天門冬科(Asparagaceae)朱蕉屬(Cordyline)之常綠灌木，被譽為是熱帶觀葉植物之王。葉色及葉型多變，廣泛應用於綠美化工程。本研究探討朱蕉雜交育種方式與葉斑形成機制，以利新品種選育。朱蕉之花期短，且品種間花期不一致，需進行花期調節以利雜交授粉。於4月及10月噴施5000 mg·L-1之激勃酸於心部葉片，結果顯示艷紅朱蕉(‘Thelma’)、密葉朱蕉(‘Hawaiian Compacta’)、娃娃朱蕉(‘Dolly’)、彩葉娃娃朱蕉(‘Cointreau’)及彩虹朱蕉(‘Amanda’s Blush’)於任何時期處理激勃酸2個月後皆可開花；亮葉朱蕉(‘Red Sister’)、白馬朱蕉(‘White Edge’)、錦葉朱蕉(‘Fire Fountain’)、錦翠朱蕉(‘Youmeninshiki’)、紅白馬朱蕉(‘John Klass’)、彩葉朱蕉(‘Tricolor’)、暗紅朱蕉(‘Cooperi’)、細葉朱蕉(‘Bella’)、’Willi’s Gold’、大葉紅邊朱蕉(‘Plumdinger’)、紅朱蕉(‘Rubra’)、喀麥隆朱蕉(‘Cameroon’)與巧克力朱蕉(‘Miss Andrea’)僅可於10月處理激勃酸誘導開花；咖啡公主朱蕉(‘Tartan’)、火焰朱蕉(‘Chocolate’)、月光朱蕉(‘Moonlight’)與夏威夷小朱蕉(‘Baby Ti’)僅於4月處理激勃酸可誘導開花；而斜紋朱蕉(‘Pink Diamond’)與翡翠朱蕉(‘Kiwi’)無論4月或10月處理激勃酸皆無法誘導開花。矮性品種娃娃朱蕉、彩葉娃娃朱蕉、彩虹朱蕉、喀麥隆朱蕉、月光朱蕉與夏威夷小朱蕉開花時皆無花粉產生。朱蕉之不稔性與倍數性無關，以綠葉朱蕉(‘Ti’)為二倍體參考樣本，將不同植株大小之18個朱蕉品種進行流式細胞儀檢定皆為二倍體。於冬季將朱蕉17個品種及5個品系在開花當天進行雜交授粉，共獲得649顆果實，平均著果率為63.6%，平均每個果實含有6.3顆種子。在正反交的組合中，除了‘Willi's Gold’ × 品系UN-20外皆可以授粉成功，於品種間雜交、品系及品種雜交、品系及品系雜交亦可成功獲得果實。於夏季將10個朱蕉品種進行雜交授粉皆無法成功得到果實。為確認高溫對朱蕉不稔性之影響，將亮葉朱蕉栽培於日/夜溫為30/25℃ 及35/30℃並處理激勃酸誘導開花，35/30℃處理之花藥呈灰白色無法開裂，且無花粉產生。30/25℃處理有花粉產生，以含15%蔗糖之B K進行體外培養，結果皆無花粉管萌發，且花粉外觀異常、較不飽滿。經H2O2及α-naphthyl acetate檢測，柱頭於30/25℃及35/30℃處理下皆具有可授性，因此夏季授粉無法成功得到果實為花粉於高溫下無法萌發花粉管所致。朱蕉為異交作物，屬於配子體型自交不親和，切除50%、75%及100%之花柱後自交授粉無法得到種子，顯示切花柱授粉無法克服朱蕉之自交不親和。朱蕉種子具有發芽率低、發芽速度慢及發芽不整齊的問題。艷紅朱蕉 × 品系UN-22之種子於刻傷後浸泡於0-150 mg·L-1 GA3發芽率及平均發芽天數皆無顯著差異。艷紅朱蕉 × 品系UN-22之種子於調製成-0.65 ~ -1.15 MPa之聚乙二醇(polyethylene glycol, PEG)溶液進行滲調處理14天，其第一粒種子開始發芽所需之天數(T0)及平均發芽時間皆較未處理者顯著縮短，發芽率則無顯著差異。朱蕉品系UN-20 × UN-19之種子於調製成-0.65 ~ -1.15 MPa之PEG溶液處理7天14天，其T0及平均發芽時間皆顯著縮短較未處理者顯著縮短，且處理14天種子T0顯著較處理七天短。白馬朱蕉之葉斑形成機制為葉綠素型，於黃白色葉斑葉肉組織之葉綠素含量較少，亮葉朱蕉之葉斑形成機制為葉綠素型加色素型，於紫紅色葉斑處之葉肉組織沒有葉綠素，且於接近上下表皮之葉肉組織有紅色色素累積。

關鍵字

育種；種子滲調；花粉培養；觀葉植物；葉斑形成

並列摘要

Cordyline [Cordyline fruticose (L.) A. Chev.] is an Asparagoideae evergreen shrub. Cordyline is widely used for landscaping and known as the king of tropical foliage plants with various leaf shapes and variegations. A better understanding of hybridization technique and mechanism and inheritance of leaf variegation facilitate breeding and selection of cordyline. Flowering regulation is crucial for hybridization since cordyline cultivars had short flowering durations and various flowering time, depending on cultivars. Cultivars of Thelma, Hawaiian Compacta, Dolly, Cointreau and Amanda’s Blush could be induced flower after a spray of 5000 mg·L-1 GA3 in April and October. In contrast, ‘Red Sister’, ‘White Edge’, ‘Fire Fountain’, ‘Youmeninshiki’, ‘John Klass’, ‘Tricolor’, ‘Cooperi’, ‘Bella’, ‘Willi’s Gold’, ‘Plumdinger’, ‘Rubra’, ‘Cameroon’ and ‘Miss Andrea’ could be induced to flower after a spray of 5000 mg·L-1 GA3 in October. ‘Tartan’, ‘Chocolate’, ‘Moonlight’, ‘Baby Ti’, ‘Pink Diamond’ and ‘Kiwi’ flowered after a spray of 5000 mg·L-1 GA3 in April. However, plants of ‘Pink Diamond’ and ‘Kiwi’ did not flower after GA3 treatment. No pollen was found in dwarf cultivars of ‘Dolly’, ‘Cointreau’, ‘Amanda’s Blush’, ‘Moonlight’ and ‘Baby Ti’. All the 18 cultivars are diploid as measured with a flow cytometry, suggesting absence of pollen was not related to ploidy in cordyline. Seventeen cordyline cultivars and 5 lines were cross-pollinated during winter, and a total of 649 fruits were obtained. The average fruit set rate is 63.6%, and the average amount of seeds per fruit is 6.3. Most crosses between cultivars and/or lines produced fruits successfully in winter whereas no fruit was obtained from cross-pollination during summer. After a spray of GA3, cordyline ‘Red Sister’ grown at 35/30℃ produced pale-white anther without pollen. Pollen from plants grown at 30/25℃ failed to germinate when cultured on B K medium containing 15% of sucrose. Stigma remained receptive in plants grown at 30/25℃ and 35/30℃, as releaved by H2O2 and α-naphthyl acetate. Removal of 50%, 75%, or 100% of the style failed to overcome the self-incompatibility of cordyline. Cordyline seeds had low germination percentage, with incongruent germination time. Soaking scarified seeds in 0-150 mg·L-1 did not affect germination rate and mean time to germination. Priming scarified seeds of ‘Thelma’ × UN-22 with -0.65 ~ -1.15 MPa polyethylene glycol (PEG) for 14 d reduced the time for germination. Priming scarified seeds of UN-20 × UN-19 in the osmotic solution of PEG at -0.65 MPa for 7 and 14 d reduced the time for germination. The formation mechanism of foliar variegation in ‘White Edge’ is chloroplast type, with light-green area containing low content of chloroplasts. The formation mechanism of foliar variegation cordyline ‘White Edge’ is chloroplasts type and pigment type, where the light purple area contained pigments but without chloroplasts.