鳳仙花屬植物之種間雜交障礙

Abstract

非洲鳳仙花(Impatiens walleriana Hook.f.)為鳳仙花屬植物，是臺灣最重要之花壇植物，然臺灣有棣慕華鳳仙花(I. devolii Huang)、黃花鳳仙花(I. tayemonii Hayata)及紫花鳳仙花(I. uniflora Hayata)三原生種鳳仙花，或許可供為育種之親本。本研究以非洲鳳仙花‘Accent Rose’及三種原生鳳仙花為育種材料，調查原生鳳仙花自然生長狀況、四種鳳仙花於開花過程中，花藥開放、花粉活力及雌雄蕊相對位置之變化，並進行自交與雜交授粉，觀察花粉管於雌蕊中生長狀況、果莢、胚珠與胚之發育，以瞭解鳳仙花屬種間雜交障礙之型式；另以胚拯救技術培養雜交之胚，以期得到雜交後代。 在梅峰地區，棣慕華鳳仙花種子於三、四月間萌芽，六月中旬後植株快速生長、開花，花期主要集中於七、八月；黃花鳳仙花種子主要於十一月至隔年三月間萌芽，小苗可耐冬季低溫並緩慢生長，三月後植株快速生長，花期由五月至十月；紫花鳳仙花具種子繁殖及地下莖繁殖二種方式，二者皆於三月開始發芽，花期主要集中於七、八及九月。三種鳳仙花之花瓣凋謝後，膨大的子房約20天後成熟、開裂，並於冬季遇低溫後植株枯萎。 鳳仙花屬植物之花絲包圍雌雄，其中棣慕華鳳仙花之花藥位於雌蕊前端，花柱於開花當天伸入花藥內；而黃花鳳仙花、紫花鳳仙花及非洲鳳仙花‘Accent Rose’之花絲包住柱頭前端，花藥位於雌蕊側邊，柱頭於開花過程不會伸入花藥內，待花藥脫落後才露出雌蕊。 棣慕華鳳仙花之花粉適合培養於含10%-15%蔗糖之Brewbaker and Kwack (BK)培養基，於10-30 ℃發芽率佳，並於開花當日有最佳之發芽率；黃花鳳仙花之花粉亦適合培養於含10%-15%蔗糖之BK培養基，10-35 ℃皆可順利發芽，其中以20 ℃最佳，開花第二天之花粉發芽率最好；紫花鳳仙花之花粉以含0%-10%蔗糖之BK培養基、10-25 ℃培養發芽最佳，但於30-35 ℃亦可發芽，以開花第二天及第三天之花粉發芽率較佳；非洲鳳仙花‘Accent Rose’之花粉培養於僅含0%-5%蔗糖之BK培養基便可發芽，於25 ℃發芽率優於其他溫度，開花第三天之花粉發芽率最佳。 以四種鳳仙花為親本自交或雜交，於授粉24小時後，皆可於花柱中與胚珠處觀察到花粉管螢光；然以石蠟切片觀察胚發育，僅黃花鳳仙花與紫花鳳仙花之正反交、黃花鳳仙花與非洲鳳仙花‘Accent Rose’雜交，可發育至球胚期，其他雜交胚停滯於原胚階段，所有雜交組合胚之發育皆無法超過授粉後12天，顯示以此四種鳳仙花為親本進行雜交，有雜交障礙。以黃花鳳仙花為種子親與非洲鳳仙花‘Accent Rose’為花粉親雜交，取授粉後7、9及11天之胚珠，以含30或60 g∙L-1蔗糖之Nitsch and Nitsch培養基於20 ℃培養，於培養20天內胚珠全數褐化。

Impatiens walleriana Hook.f is one of the most important bedding plants in Taiwan or worldwide. In Taiwan, there are three native Impatiens species, I. devolii Huang, I. tayemonii Hayata, and I. uniflora Hayata, could be used as breeding materials. Self- and inter-specific pollination between three native Impatiens and Impatiens walleriana Hook.f ‘Accent Rose’ were investigated in this study. The objectives were to investigate 1) the native Impatiens species growth behavior under natural conditions at Mei-Feng area, 2) anther dehiscence, pollen germination rate, and changes in stamen-pistil relative position during flowering, 3) in vivo pollen tube growth, developments of ovary, ovule and embryo, and thus to clarify hybridization barriers in Impatiens. Hybrid embryos were cultured to rescue possible inter-specific progenies. Under natural conditions in Mei-Feng area, seeds of Impatiens devolii Huang germinated in March and April. In late June, young plants grew rapidly and flowered in July and August. For Impatiens tayemonii Hayata, the seeds of germinated between November and March, the seedlings could tolerate the cold winter and continued to grow. Young plants grew rapidly from March and mature plants flowered from May to October. For Impatiens uniflora Hayata, there were seed- and rhizome- propagations. Both seed germination and rhizome sprouting occurred in March. Mature plants flowered in July and August. Capsules of the three species matured about 20 days after self-pollination and. Old plants senescenced when winter was came. The pistil of Impatiens species was surrounded by the filaments. For I. devolii Huang the anther just located in frount the pistil, and the stigma elongated and entered to the anther at anthesis. The stigma of I. tayemonii Hayata, I. uniflora Hayata and I. walleriana Hook.f ‘Accent Rose’ was surrounded by the filaments, and the anther was beside the pistil. a And the stigma did not reach the anther in I. tayemonii Hayata, I. uniflora Hayata and I. walleriana Hook.f ‘Accent Rose’ during the flowering process. The Brewbaker and Kwack (BK) medium containing 10%-15% sucrose was suitable for pollen germination of I. devolii Huang. Water bath temperature of 10 to 30 ℃ did not affect pollen germination rate. Pollens obtained at anthesis had the highest germination rate. Pollens of I. tayemonii Hayata germinated well on BK medium containing 10%-15% sucrose at 10 to 35 ℃, with highest rate at 20 ℃. Pollens obtained one day after anthesis had the highest germination rate. Pollens of I. uniflora Hayata germinated well on BK medium containing 0%-10% sucrose. Pollens could germinate at 30-35 ℃ but germinate better at 10 to 25 ℃. Pollens obtained one or two days after anthesis had the highest germination rate. Pollen of I. walleriana Hook.f ‘Accent Rose’ could germinate well on BK medium containing 0%-5% sucrose, the optimum germinate temperature was 25 ℃, and the highest pollen germination rate was two days after anthesis. Pollen tubes could all be observed at the pistils and ovules 24 h after self- and inter-specific pollinating between I. devolii Huang, I. tayemonii Hayata, I. uniflora Hayata and I. walleriana Hook.f ‘Accent Rose’. There were no pre-fertilization barriers among these four parents. Paraffin section revealed that all self-pollinations resulted in well-developed embryos. The embryos could only reach the globular stage in cross-pollination between I. tayemonii Hayata and I. uniflora Hayata, and between I. tayemonii Hayata with I. walleriana Hook.f ‘Accent Rose’, and did not reach beyond pro-embryo stage for other cross-pollinated combinations. All cross-pollinated embryos failed to develop further and aborted 12 days after pollination. The ovules were taken 7, 9, and 11 days after pollination from crossing I. tayemonii Hayata with I. walleriana Hook.f ‘Accent Rose’ and cultured on Nitsch and Nitsch medium containing 30 or 60 g∙L-1 sucrose. All ovules became browning within 20 days when cultured in vitro.