天使花的多倍體育種與花色遺傳

Abstract

天使花(Angelonia angustifolia Benth.)為世界上重要的花壇植物之一，其耐熱且耐濕特性適應臺灣夏季氣候，廣泛應用於景觀。不過天使花之花朵小且不耐旱，而多倍體植株常能展現較大的器官，以及較佳的逆境耐受性，因此期望透過秋水仙素(colchicine)誘導產生多倍體天使花，以提升其觀賞價值及耐旱性。另外測試四倍體天使花之花粉發芽力，並進行二、四倍體之間的雜交，期望獲得三倍體後代，比較其與二、四倍體天使花之性狀差異。另外，選育具市場潛力之四倍體天使花品系，並進行介質體積含水量(volumetric water content, VWC)試驗，了解不同VWC栽培對四倍體品系生長與光合作用之影響。最後透過二倍體天使花‘Serena Purple’與‘Serena White’之雜交，探討花色遺傳模式。 本研究以0%-0.2%秋水仙素處理天使花‘Serena Purple’及‘Serena White’之種子或實生苗12小時，以及滴加於天使花‘Serena Purple’之莖頂三天，四倍體誘導率皆低於10%。誘導產生之四倍體天使花，其花朵大於‘Serena Purple’及‘Serena White’，氣孔長與寬皆顯著較大、氣孔密度較低，且花粉直徑較大。其中包含兩個優良四倍體天使花品系，分別為紫花的SPU320102與白花的SWH110115，其花朵大、花瓣排列緊密。由於0%-0.2%秋水仙素處理之誘導率低，因此另以高濃度秋水仙素0%-1.0%浸泡‘Serena Lavender Pink’之種子，結果0.8%秋水仙素處理之四倍體誘導率為27.8%，為所有處理中最高。 二倍體天使花‘Serena Purple’與‘Serena White’以及誘導產生之四倍體品系之花粉經培養3小時後，所有品系之花粉發芽率皆超過80%，推測誘導形成之四倍體為異源多倍體。將天使花‘Serena Purple’、‘Serena White’與四倍體品系雜交，以四倍體為母本時，蒴果形成率較高且種子數多，但所有組合種子發芽率皆低。最後獲得1株三倍體後代，其花粉發芽率顯著低於其親本，不過其花朵小，觀賞價值低。 另將性狀優良四倍體品系SPU320102與SWH110115與對照品種進行性狀比較。結果顯示SPU320102與SWH110115之葉片較寬而濃綠、葉表帶有光澤，且其花朵大、花瓣反捲程度弱、花喉較寬且花喉內部之斑塊較濃密，另外，SPU320102之花色較深。而後以20%、40%及70% VWC栽培天使花四倍體品系SPU320102及SWH110115與對照品種‘Serena Purple’與‘Serena White’。結果顯示乾旱逆境下，四倍體品系葉片較寬而厚、葉色濃綠且較堅挺，且栽培期間之澆水次數較少，因此四倍體之耐旱性較佳。 ‘Serena Purple’自交後代以及‘Serena Purple’與‘Serena White’正反交後代，皆分離出紫色3：淡粉色1之植株分離比，而‘Serena White’自交後代花色皆為白色。推測天使花之花色由W基因及P基因控制，當W基因為顯性(W_)，則花瓣有花青素累積，當W基因為隱性(ww)，則花瓣為白色；另外當P基因為顯性(P_)，花瓣累積紫色花青素，當P基因為隱性(pp)，花瓣呈現淡粉色，且W基因相對於P基因具有隱性上位性之關係，並推測天使花‘Serena Purple’與‘Serena White’之基因型分別為WWPp與wwPp。

Angelonia angustifolia Benth. is one of the most important bedding plants in the world. Due to its excellent heat and waterlogging tolerance, angelonia has been widely used by landscapers in Taiwan. However, angelonia is susceptible to drought, and its ornamental value is limited by its relatively small flowers. The objective of this study is to improve the ornamental traits and drought tolerance by inducing polyploids from Angelonia angelonia, as polyploids usually produce larger organs, and are stress-tolerant. Pollen germinability of tetraploid angelonia was tested, and diploid angelonia was crossed with tetraploid to obtain triploid progeny. After that, the traits of triploid were compared with diploid and tetraploid angelonia parents. Tetraploid lines with market potential were also selected, where the effect of volumetric water content (VWC) on growth and photosynthetic capacity of tetraploid angelonia lines was evaluated. The flower color inheritance pattern of the crossing of diploid Angelonia angelonia ‘Serena Purple’ and ‘Serena White’ was also investigated. By soaking seeds or seedlings of Angelonia angelonia ‘Serena Purple’ and ‘Serena White’ with 0%-0.20% colchicine solution for 12 hours, and dripping on the apical meristem of Angelonia angelonia ‘Serena Purple’ with 0%-0.20% colchicine solution for three days. The tetraploid induction rate among both treatments were less than 10%. The tetraploid Angelonia has a larger flower, stomata, and pollen diameter while the stomatal density is lower than that of the diploid. Due to the low tetraploid induction rate when treated with 0%-0.20% colchicine, the seeds of Angelonia angelonia ‘Serena Lavender Pink’ were treated with 0%-1.0% colchicine instead. The tetraploid induction rate after 0.8% colchicine treatment was 27.8%, the highest among all treatments. The pollen germination rates were over 80% among diploid ‘Serena Purple’, ‘Serena White’, and tetraploid lines after 3 hours of pollen culture, indicating the induced tetraploids were allotetraploids. After crossing diploid ‘Serena Purple’ and ‘Serena White’ with tetraploid lines, the capsule formation rate and seeds per capsule were higher when using tetraploid angelonia cultivars as seed parents. Traits of tetraploid lines SPU320102 and SWH110115 were compared with the control cultivars. SPU320102 and SWH110115 had wider and darker green leaves, larger flowers, and weak corolla reflexing. The flower chamber was wider and the markings inside the chamber were denser than diploid comparative cultivars. Moreover, the flower color of SPU320102 was darker than ‘Serena Purple’. Cultivating Angelonia angelonia ‘Serena Purple’, ‘Serena White’, tetraploid lines SPU320102 and SWH110115 with 20%, 40%, or 70% VWC. The leaves of tetraploid lines were wider, thicker, darker, and do not wilt under drought stress. The water demand was also lower in tetraploid lines, thereby showing an increase in drought tolerance for the tetraploid lines. Flower colors of progeny from selfing of ‘Serena Purple’ and reciprocal crosses between ‘Serena Purple’ and ‘Serena White’ resulted in a 3:1 ratio (purple：light pink). Selfing of ‘Serena White’ resulted in all-white progeny. Flower color inheritance was proposed to be controlled by two genes (W, P). Genotype ww resulted in a white flower, and genotype W_ resulted in colored flowers. Genotype P_ resulted in purple flower, while genotype pp resulted in a light pink flower. W gene has recessive epistasis when compared to P gene. The genotypes of ‘Serena Purple’ and ‘Serena White’ were proposed to be WWPp and wwPp, respectively.