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Pollination behavior and reproductive barrier of Neoregelia
breeding,hydrogen peroxide,pollen-pistil interaction,self-incompatibility,stigma receptivity,
|Publication Year :||2020|
彩葉鳳梨之花序自葉杯中抽出，總梗粗短，白色、紫色或薰衣草色小花著生於花序末端上形成短總狀花序。雌蕊為三枚心皮合生，螺旋狀柱頭。彩葉鳳梨花朵壽命不長，晴日約於0700 HR開花，1250 HR過後花瓣開始萎凋，1600 HR花瓣已向內捲曲萎縮。取彩葉鳳梨‘Gold Fever’為母本與‘Pink Sensation’為父本，於0700-0950 HR、1000-1250 HR、1300-1550 HR、1600-1800 HR四個時段雜交授粉，結果顯示僅於中午前授粉才能獲得雜交種子。另取‘Gold Fever’及‘Little Rose’為母本，與多個品種進行雜交授粉，應證上午與下午授粉之差異，仍顯示以中午前授粉為宜。彩葉鳳梨授粉時間短之特性與柱頭可授性相關，於花開前一天、開花當日不同時段及開花後一天取彩葉鳳梨‘Gold Fever’雌蕊，於柱頭滴加一滴0.88 M (約3%)過氧化氫，觀察3分鐘內反應，結果顯示開花前一天至開花當天0400-0650 HR皆無反應或極微弱，開花當天0700-1250 HR期間則有明顯氣泡反應，開花當天1300-1550 HR亦有氣泡反應，但已減弱，花後一天者仍有微弱氣泡反應。另於花開前一天、花開當天及花後一天取數個彩葉鳳梨品種之花粉培養於25℃、黑暗下，以含10%蔗糖之MBK培養基培養12小時，結果顯示彩葉鳳梨品種花粉萌芽率是否隨開花日程而變化有品種差異，部分品種在開花後一天仍有一定花粉萌芽率。
取12個彩葉鳳梨品種行自花授粉、同株異花或營養繁殖系異花自交授粉，皆無法產生種子。觀察參試7個彩葉鳳梨品種之雌蕊，依其長度可大致分為兩群，長花柱品種之花柱長度介於2.6-3.0 cm，而短花柱品種之花柱長度介於1.9-2.0 cm。取參試7個彩葉鳳梨品種於3年自然花期間，陸續進行長花柱品種間、短花柱品種間、短花柱為母本與長花柱為父本、長花柱為母本與短花柱為父本等共19個雜交組合(含6個正反交)，以短花柱品種為母本，較易獲得雜交種子，而長花柱品種為母本則無法產生種子。
將自交、短花柱品種間雜交、短花柱品種為母本與長花柱品種為父本、長花柱品種為母本與短花柱品種為父本、長花柱品種間雜交等組合之雌蕊於授粉後1至5天取下，以螢光染色法觀察花粉萌發與花粉管生長。結果顯示自交授粉後，花粉雖於柱頭表面萌發，但花粉管無法進入柱頭組織。親和的雜交組合中(短花柱×短花柱、短花柱×長花柱)，花粉管約於授粉後3至5天進入胚珠、完成受精。不親和的雜交組合中(長花柱×短花柱)，花粉管僅能生長至花柱中段或2/3處，即發生先端膨大或生長停止等異常，導致無法受精。長花柱品種間雜交，雖可見花粉管進入胚珠，但並未獲得種子，可能有受精後障礙。取長花柱‘Meyendorffii’、‘Perfecta Tricolor’、‘Skotak’s Orange Crush’為母本，以‘Gold Fever’為父本，進行去除一半長度花柱再授粉，並以未切除花柱為對照組。去除花柱再授粉可以克服長花柱品種為母本之雜交障礙並取得種子。螢光染色觀察顯示授粉後4天可見花粉管進入胚珠、已完成受精。
取葉片有斑塊及無斑塊之彩葉鳳梨品種進行雜交，後代於栽培4-6年後成熟，表現出穩定葉色性狀。彩葉鳳梨葉片斑塊性狀由單一基因座控制，參試之有斑塊品種為異質結合顯性(Bb)，無斑塊品種為同質結合隱性(bb) (χ2 = 0.18-3.00)。因無刺‘Deroose’s Medusa’為長花柱品種，故取葉緣有刺品種為母本與之雜交。結果顯示葉緣無刺性狀相對於葉緣有刺性狀為顯性遺傳。葉緣無刺後代生長緩慢且易早夭。
Neoregelia has been widely used for outdoor landscaping and indoor decoration for their leaf color variegation and low maintenance. Developing new cultivar are required for market demands. However, there has been limited information regarding pollination habits and hybridization barriers is presently limited. This study aimed to 1) observe floral organ, 2) test pollination habits, 3) understand reporductive barriers, 4) overcome hybridization barrier through cut-style pollination, 5) obtain hybrid progenies, and 6) study inheritance of leaf blotching and spinulose. The knowledge would assist breeding of new Neoregelia cultivars.
Neoregelia cultivars have terminal inflorescences with a thick and short peduncle emerge from the leaf tank. Inflorescence, a short raceme with many small white, violet or lavender flowers appear in the socket centre of the rosetted leaves that are placed at the same level and almost hidden at the bottom of the cavity that usually bloom in the water stored there. Pistil is composed of three carpels and has conduplicate-spiral dry stigma.
Neoregelias have rather short anthesis time frame. Anthesis starts at around 0700 HR, corolla lobes begin to wilt at around 1250 HR, and completely wilted at around 1600 HR under sunny conditions. Neoregelia ‘Gold Fever’ was used as female parent and crossed with ‘Pink Sensation’ as male parentand pollinations were made at 0700-0950 HR, 1000-1250 HR, 1300-1550 HR, and 1600-1800 HR. Results showed that pollination should be made before noon to obtain hybrid seeds. Further confirmation was made using ‘Gold Fever’ and ‘Little Rose’ as female parents, and crossed with other cultivars. Subsequent results support that cross-pollination should be made before noon. The short pollination time of Neoregelia is related to the stigma receptivity. Stigma receptivity was tested using hydrogen peroxide (H2O2) method in order to elucidate cause of short pollination time frame. A single drop of 0.88 M (3%) H2O2 was applied to the stigma of pistil collected at one day before anthesis, various time at the day of anthesis, and one day after anthesis, and then observed for three mins. Little on no response to H2O2 was observed one day before anthesis to 0400-0650 HR at antehsis, While significant response was observed at anthehsis (0700-1250 HR), then gradually decreased at 1300-1550 HR. and weak response at one day after anthesis. Pollen of several cultivars were collected at one day before anthesis, the day of anthesis, and one day after anthesis. The collected pollen was incubated at 25oC, in the dark, using modify BK medium containing 10% sugar for 12 h. Pollen germination percentage differs among cultivars and time of harvest, however, some cultivars did germinate even at one day after anthesis.
Twelve Neoregelia cultivars were received autogamous, geitonogamous, and vegetative-geitonogamous self-pollination, and results showed none produced seeds. Pistil lengths were observed in seven tested Neoregelia cultivars, and could be divided into two groups based on style length, one with relative long style lengths (2.6-3.0 cm), and another with relative short style lengths (1.9-2.0 cm). These seven cultivars were cross-pollinated when naturally-flowered to form 1) crosses between long-style cultivars, 2) crosses between short-style cultivars, 3) short-style (♀) × long-style (♂), and 4) long-style (♀) × short style (♂) across three years and a total of 19 cross combinations. Hybrid seeds were obtained only when short-style cultivars were used as female parent.
Pistils of self-pollination and cross combinations between cultivars with different style lengths were collected after pollination and observed for in vivo pollen tube growth using fluorescence staining. Results showed that pollen germinated but could not grow into stigma tissue after self-pollination. In contrast, pollen tube grew into ovule and fertilization took place in compatible crosses (short-style × short-style, short-style × long-style) at 3 to 5 days after pollination. Nevertheless, pollen tube could grow into style until half to two-thirds length of the style where abnormal pollen tube tip occurred in the incompatible cross (long-style × short-style). Cross between long-styled cultivars showed that pollen tube did grow into ovule but no seed could be harvested, indicating a post-ferilization barrier.
Half the length of the long-style ‘Meyendorffii’, ‘Perfecta Tricolor’, ‘Skotak’s Orange Crush’ were removed using sharp scissors and subsequently pollinated with short-style ‘Gold Fever’, while style of control remain intact. Cut-style pollination could overcome hybridization barrier of long-style cultivars and obtain hybrid seeds. Corresponding in vivo observation also showed that pollen tube grew into ovules and fertilization took place at four days after pollination.
Crosses between Neoregelia cultivars with and without blotching were made. These progenies took 4-6 years to reach maturity with stable leaf variegation. Results show that leaf blotching in Neoregelia was governed by single locus, cultivars with blotching were heterozygous dominant (Bb), and non-blotching cultivars were homozygous recessive (bb) (χ2 = 0.18-3.00). Since non-spinulose ‘Deroose’s Medusa’ has long style, unilateral crosses between spinulose and non-spinulose cultivars were made. Results show that entire margin was dominant to spinulose margin. Progenies with entire margins grew slowly and tended to die when young.
|Appears in Collections:||園藝暨景觀學系|
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