Heat-tolerance and Flower Characteristics of Petunia Cultivars and Their Selfed or Cross Hybrid Progenies
進行耐熱育種時，若能建立耐熱指標和瞭解耐熱性狀之遺傳，可提高育種效率。本研究分別比較高溫對矮牽牛 (Petunia ×hybrida Hort. Vilm. Andr.) F1種子系品種或營養系品種之細胞膜熱穩定性、生長特性及花粉萌芽之影響，並進一步進行雜交，比較耐熱程度不同之親本雜交所得後代細胞膜熱穩定性表現，和其花朵型態之分離情形。F1種子系品種 ‘Primetime Carmine’、‘Wave Blue’ 及 ‘Tidal Wave Silver’ 分別置於25/20 ℃及30/25 ℃栽培18天後，取剛成熟之完全展開葉，利用不同水浴溫度25、42、44、46、48、50、52、54、56℃加熱其葉圓片20分鐘，相對熱傷害值 (relative injury, RI) 隨水浴溫度之上升而呈S形曲線關係。參試F1種子系矮牽牛RI值S形曲線之反曲中點溫度約為48 ℃，因此可利用48 ℃水浴溫度鑑別參試F1種子系矮牽牛品種之耐熱性。栽培於30/25 ℃之‘Wave Blue’及‘Tidal Wave Silver’者之RI值較低，且S形曲線較25/20 ℃者有向右移之趨勢，顯示兩品種可被熱馴化，表現較高之耐熱性，而 ‘Primetime Carmine’則為熱敏感品種。高溫30/25 ℃造成分枝數與枝梢乾重下降情形，與細胞膜熱穩定性有類似之表現，耐熱品種 ‘Tidal Wave Silver’ 之分枝數與枝梢乾重較不易因高溫而下降，而熱敏感之 ‘Primetime Carmine’ 下降較顯著。養系矮牽牛‘Cascadias Soft Pink’、‘Petitunia Bordeaux Dream’、‘Sunray’及‘Petitunia Blue Dream’，經高溫30/25 ℃栽培後細胞膜熱穩定性亦可被熱馴化，耐熱程度佳，且以50 ℃為S形曲線之反曲點，較參試F1種子系矮牽牛品種者之48 ℃高。顯示參試營養系矮牽牛品種之耐熱性較參試F1種子系矮牽牛品種佳。營養系矮牽牛‘Sunray’ 及‘Petitunia Blue Dream’之花粉於30 ℃培養者萌芽率較高，而‘Cascadias Soft Pink’ 及‘Petitunia Bordeaux Dream’則以25 ℃培養者萌芽率較高。高溫30/25 ℃造成Cascadias Soft Pink’及‘Petitunia Bordeaux Dream’分枝數、枝梢及根乾重之下降較 ‘Sunray’及‘Petitunia Blue Dream’顯著。結果顯示參試營養系矮牽牛品種間之耐熱程度仍有差異。30/25 ℃熱馴化18天後，參試F1種子系矮牽牛雜交後代之葉圓片利用48 ℃水浴加熱20分鐘後，以矮牽牛 ‘Primetime Carmine’ 為花粉親者之後代RI值較高，而以 ‘Wave Blue’ 及 ‘Tidal Wave Silver’ 為花粉親者之RI值較低。以 ‘Tidal Wave Silver’ 為花粉親者，後代RI值分布高峰較低，介於30% - 40%，而以 ‘Primetime Carmine’ 為花粉親者之RI分布高峰則較高，介於45% - 55%間，顯示雜交後代細胞膜熱穩定性可能受花粉親之影響較大。查參試營養系矮牽牛經自交或雜交後，後代之花冠顏色、花瓣脈紋表現程度與花藥顏色之分離情形，結果顯示白花品種 ‘Sunray’ 及藍花品種 ‘Petitunia Blue Dream’ 之自交後代花色與親本相同，而桃紫色花之‘Petitunia Bordeaux Dream’後代花色會分離為粉紅色、桃紫色及紫色。不同花色之矮牽牛雜交後，後代之花色分布介於兩親本間。花冠上具脈紋之品種，與花冠上沒有脈紋之品種 ‘Cascadias Soft Pink’雜交所得後代，大部分為具有脈紋者，而有少量後代沒有脈紋之表現。具黃色花藥之矮牽牛‘Sunray’及‘Cascadias Soft Pink’進行自交或雜交後，其後代之花藥顏色大部分為黃色或白色。而具紫色花藥之品種‘Cascadias Pink Spark Improved’、‘Petitunia Bordeaux Dream’、‘Petitunia Blue Dream’自交或雜交，或與黃色花藥品種雜交時，後代之花藥顏色較多，分別有白色、黃色與紫色。
Establishing heat-tolerant indicators and understanding the inheritance of the associated characteristics for heat-tolerance breeding of petunia are desirable. The objectives of this study were 1) to determine the high temperature effects on cell membrane thermostability (CMT) as measured with electrolyte leakage technique, growth and pollen germination of seed- or vegetatively-propagated petunias, and 2) to compare the CMT and flower characteristics of selfed or cross progenies obtained from petunia parents with differential heat-tolerance.lants of F1 seed-propagated cultivars Primetime Carmine, Wave Blue, and Tidal Wave Silver were treated at 25/20 and 30/25 ℃ for 18 days. The recently developed leaves of these cultivars were evaluated for CMT measured at water bath temperatures of 25, 42, 44, 46, 48, 50, 52, 54, and 56℃ for 20 mins. The relationship between the relative injury (RI) value occurring in leaf tissue discs of petunia cultivars and treatment temperature was sigmoidal. The RI values near the midpoint of the sigmoid response curve occurred at the 48 ℃ treatments. The cultivars Wave Blue and Tidal Wave Silver exhibited heat-acclimation and had lower RI values than the ‘Primetime Carmine’. Reduced branch number and shoot dry weight were more apparent in the heat-intolerant ‘Primetime Carmine’ than the heat-tolerant ‘Tidal Wave Silver’ after grown at 30/25 ℃, as compared with those at 25/20 ℃.ll the vegetatively-propagated cultivars Cascadias Soft Pink, Petitunia Bordeaux Dream, Sunray, and Petitunia Blue Dream exhibited heat-acclimation as shown with reduced RI under the 30/25 ℃ treatment. The RI values of the vegetatively- propagated cultivars near the midpoint of the sigmoid response curve occurred at water bath temperature of 50 ℃, higher than the 48 ℃ for seed-propagated cultivars tested in this study. Most pollens germinated at 30 ℃ in ‘Sunray’ and ‘Petitunia Blue Dream’, as compared with 25 ℃ in ‘Cascadias Soft Pink’ and ‘Petitunia Bordeaux Dream’. High temperature at 30/25 ℃ decreased more branch number, shoot and root dry weights in ‘Cascadias Soft Pink’ and ‘Petitunia Bordeaux Dream’ than ‘Sunray’ and ‘Petitunia Blue Dream’. Results suggested that vegetatively-propagated cultivars had higher heat-tolerance than seed-propagated cultivars. However, differential heat-tolerance existed in these vegetatively-propagated cultivars.rogeny seedlings were raised and moved to 30/25 ℃ for 18 days, and then leaf RI of these progenies was measured at water bath temperature of 48 ℃ for 20 mins. Higher RI vales were measured in progenies obtained from ‘Primetime Carmine’as pollen parent, as compared with lower RI vales in progenies from ‘Wave Blue or ‘Tidal Wave Silver’ as pollen parents. RI ranged between 30 % and 40 % in most progenies obtained from ‘Tidal Wave Silver’ as the pollen parent, while RI values were between 45 % and 55 % in most progenies from ‘Primetime Carmine’ as the pollen parent. Results suggested that CMT of petunia progenies at 30/25 °C were largely affected by the pollen parents.orolla color, conspicuousness of vein on the upper corolla, and anther color segregation were recorded in the selfed or cross progenies from vegetatively-propagated cultivars. Selfed progenies and the parents had the same corolla color in white-flowered ‘Sunray’ and blue-flowered ‘Petitunia Blue Dream’. Corolla color exhibited pink, violet red or purple in the selfed progenies of the violet red-flowered ‘Petitunia Bordeaux Dream’. Corolla color regimes of cross progenies were between those parents with different colors. Conspicuousness of vein was observed in most progenies from the vein less ‘Cascadias Soft Pink’ crossed with those with veins on the upper corolla. Anther color almost exhibited yellowish white or yellow in the selfed or cross progenies from ‘Sunray’ and ‘Cascadias Soft Pink’ with yellow anthers. However, anther color exhibited yellowish white, yellow, or violet in the selfed or cross progenies from ‘Cascaidas Pink Spark Improved’, ‘Petitunia Bordeaux Dream’, and ‘Petitunia Blue Dream’ with violet anthers.
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