日日春之雄不稔性、花色遺傳與盆花選育

Abstract

日日春[Catharanthus roseus (L.) G. Don]盆花品種透過雜交育種育成，利用雄不稔植株進行雜交可省略去雄步驟，而了解花色遺傳模式有助於育種。本研究探討日日春雄不稔之成因與穩定性、研究花冠與眼圈顏色之遺傳，並選育大花、深紫色或大型白色眼圈、植株低矮及分枝性良好之新品種。 觀察日日春‘Cora Cascade’系列自交一代雄可稔及雄不稔植株縱徑1.0-3.0 mm花苞之花藥塑膠切片，結果顯示雄不稔之花藥囊腔中小孢子母細胞能夠正常減數分裂形成四分體。於穿透式電子顯微鏡觀察雄不稔日日春縱徑2.0-2.9 mm花苞之花藥，其絨氈層細胞之分泌腺體流出。以掃描式電子顯微鏡觀察雄不稔植株開花當天之花粉，其形態皺縮，推測花粉敗育的原因可能是絨氈層發育不正常。觀察雄可稔及雄不稔植株縱徑3.0 mm花苞及發育前一、二、三天之花藥石蠟切片，並螢光染色觀察，結果顯示雄不稔花藥囊腔中胼胝質分解不完全。 日日春‘Cora Cascade’系列自交一代中有部分雄不稔植株，其花粉可於低溫20/17℃萌發。將雄不稔株扦插繁殖，放置人工氣候室日夜溫20/15℃、25/20℃及30/25℃之自然光照室，並分別進行花粉未敗育及萌發檢測、人工自交及雜交授粉，以花粉正常之品種為花粉親進行雜交。結果顯示雄不稔株於30/25℃及25/20℃處理之花粉未敗育率及花粉萌發率皆低於1%，於20/15℃處理之花粉未敗育率及花粉萌發率提升至13.7%及4.0%，自交後雖會著果但未產生種子，於25/20℃處理雜交著果率最高及種子數最多。 萃取日日春深紫色、櫻桃紅色、粉紅色、橘紅色、杏色花冠，以及紅色和橘紅色眼圈之花青素，以液相層析串聯質譜儀分析，結果顯示杏色花冠有矢車菊素衍生物，其餘具有飛燕草素衍生物。將深紫色花冠、櫻桃紅色花冠及粉紅色花冠品種進行自交及雜交授粉，結果顯示杏色花冠對深紫、櫻桃紅、粉紅、及橘紅色花冠為隱性，由一基因座hf控制，hf基因座使花冠不具有飛燕草素衍生物。將紅色及深紫色眼圈品種進行自交及雜交授粉，結果顯示深紫色眼圈對紅色眼圈為隱性，對橘紅色眼圈為顯性，由兩個基因座Re及Pe控制。 將11種不同眼圈大小之日日春品種置於日夜溫30/25℃，結果小型、中型及大型眼圈日日春眼圈直徑分別小於1 cm、1-2 cm及大於2 cm。大型及中型白色眼圈視為白色擴大眼圈，小型眼圈為白色狹窄眼圈，將白色擴大或白色狹窄眼圈品種進行自交及雜交授粉，結果顯示白色擴大眼圈對於白色狹窄眼圈為顯性，由一基因座W控制。 從日日春‘Cora Cascade Strawberry’ × ‘Jams `N Jellies Blackberry’、‘Cora Cascade Cherry’ × ‘Jams `N Jellies Blackberry’、‘Ray’ × ‘Nirvana Cascade Pink Splash’及‘Cora Cascade Strawberry’ × ‘Summer Mikan’雜交二代中，挑選植株低矮、早花、大花、具深紫色眼圈之單株，自交至第四或五代並雜交，得到3個純系與3個雜交種，品系比較試驗結果選出1個純系與1個雜交種，具有盆花商業生產之潛力。

Currently, most commercial cultivars of potted periwinkle [Catharanthus roseus (L). G. Don] are released through hybridization. Emasculation can be omitted when using male sterile plants as seed parents for cross-pollination. Understanding of inheritance of flower color facilitates breeding. The aims of this study were to explore the causes and the stability of male sterile periwinkle, determine the inheritance of corolla and eye color, and breed and select new cultivars with deep purple or large white eye, dwarf, well-branched, and large flowers. The anthers in 1.0-3.0 mm floral buds were sampled and sectioned from male fertile and male sterile progenies of selfed periwinkle ‘Cora Cascade’ series. Tetrads in male sterile anther locules were observed after meiosis of microspore mother cells. Anthers in 2.0-2.9 mm floral buds of male sterile plants were observed with a transmission electron microscope. Results revealed that the secretion globules flowed out of the tapetal cells. Fresh pollen from male sterile plants all collapsed, as observed with a scanning electron microscope. Thus, defective pollen might result from abnormal tapetal development. Paraffin sections of the anthers from 3.0 mm floral buds and 1, 2, 3 days before 3.0 mm floral buds. Results showed that callose dissolution was imcomplete in male sterile anther locules, as observed by fluorescence staining. Pollen of some male sterile progenies from self-pollinated periwinkle ‘Cora Cascade’ series could germinate at 20/17℃. Male sterile plants were propagated by cutting and placed at 20/15℃, 25/20℃, and 30/25℃ under natural phytotron conditions to measure pollen nonabortion and pollen germination percentages. Fruit set percentage and seed number were recorded from selfing male sterile plants and crossing between male sterile and fertile plants at each temperature. Pollen nonabortive and pollen germination percentages in male sterile plants were lower than 1% when grown at 30/25℃ and 25/20℃, as compared with 13.7% and 4.0% in plants at 20/15℃, respectively. Selfed male sterile plants had fruit set at 20/15℃ but did not produce any seeds. Highest fruit set and most hybrid seeds were recorded when cross-pollinated at 25/20℃. Anthocyanidin extracts from corolla with deep purple, cherry, pink, or apricot, and eye zones with red or orange red were analyzed using a liquid chromatograph tandem mass spectrometer. Anthocyanidins of apricot corolla were cyanidin derivatives, whereas other corollas or eye zones were delphinidin derivatives. Deep purple, cherry, and pink corolla periwinkle cultivars were self- and cross-pollinated, and the segregation of corolla colors in the progenies showed that apricot corolla was recessive to cherry, pink, orange red, and deep purple corolla. Apricot corolla was controlled by a single nuclear locus hf, which delphinidin derivatives are not produced in corolla. Red and deep purple eye periwinkle cultivars were self- and cross-pollinated. Results showed that deep purple eye was recessive to red eye, and dominant to orange red eye. Red, deep purple, and orange red eye were controlled by two nuclear loci Re and Pe. Eleven periwinkle cultivars were placed at 30/25℃ under natural phytotron conditions. Small, medium, and large eye were defined as <1 cm, 1-2 cm, and >2 cm diameters, respectively. Large and medium white eye cultivars had white broad eye, whereas small white eye cultivars had white narrow eye. White broad eye and white narrow eye cultivars were self- and cross-pollinated. Results showed that white broad eye was dominant to white narrow eye. White broad eye was controlled by a single nuclear locus W. Dwarf, early flowering, and large flowers with deep purple eye periwinkle were selected from F2 progenies of ‘Cora Cascade Strawberry’ × ‘Jams `N Jellies Blackberry’, ‘Cora Cascade Cherry’ × ‘Jams `N Jellies Blackberry’, ‘Ray’ × ‘Nirvana Cascade Pink Splash’, and‘Cora Cascade Strawberry’ × ‘Summer Mikan’. These were self-pollinated thereafter until F4 or F5, and cross-pollinated. Three pure lines and three hybrids were obtained. After examination of plant performance, one pure line and one hybrid with commercial potential were selected in this study.