臺灣低需冷性櫻花品種選拔及低溫對其萌芽及開花之影響

Abstract

櫻花為薔薇科(Rosaceae)梅李屬(Prunus L.)櫻亞屬(Cerasus)落葉花木，主要分布在北半球溫帶地區，而臺灣位處亞熱帶地區，有原生種–臺灣山櫻花(Prunus campanulata Maxim)的分佈。本論文旨在利用原生種開發適應亞熱帶氣候景觀櫻花新品種，探討暖冬氣候下景觀櫻花開花萌芽之影響性，以及低需冷性櫻花解除休眠之感溫範圍，以作為景觀櫻花在臺灣調適管理及應用研究時之基礎。 臺灣原生山櫻花族群因雜交及自交演化而有花色、花型及耐熱、耐寒性之單株。為能選育出適合亞熱帶地區景觀利用之櫻花品種，本研究蒐集臺灣中部以北低海拔地區、開花表現佳之地方種共596份種原單株，以枝條嫁接與單株定植於桃園區農業改良場樹林分場之試驗圃，進行開花生育觀察及開花優良單株選拔。經品系繁殖及比較試驗，選育出開花期早、花量多、樹型半直立和開花低需冷特性之櫻花新品種桃園1號–報春、桃園2號–紅梅、桃園3號–春緋及桃園4號–紅華，適合亞熱帶氣候區低海拔地區景觀利用之品種，亦可提供亞熱帶地區櫻花開花低需冷性遺傳資源之學術研究利用。 為探討積冷程度對臺灣景觀櫻花休眠解除萌芽之影響，在2012–2013年冬季自然條件下之不同積冷階段，切取枝條瓶插於保鮮液，並置於觀測環境下觀測後續枝條萌芽情形。結果顯示，‘桃園1號–報春’和‘大島’在自然條件下積冷量較低時，其花芽和葉芽萌時間有延遲情形，且休眠芽萌芽率較低；‘桃園1號–報春’在本試驗不同積冷期處理，葉芽萌芽開始時間均在花芽萌發後期開始，而‘大島’在低溫累積不足時，花芽開始萌芽後數日，葉芽即接續發生萌芽，花芽葉芽有交錯萌芽直至枝條全數萌芽結束。2013–2014年冬季期間，以8℃連續積冷處理探討‘桃園1號–報春’解除休眠之需冷量，結果顯示需6度天，以低需冷性桃完成休眠期需冷量評估模式計算該品種積冷量為144.0度小時，在自然條件下田間植株到5%始花期前一週估算其積冷量為248.5度小時；‘八重’以8℃處理需10天，積冷量為240.0度小時，而自然條件植株之積冷量為325.0度小時；‘富士’以8℃處理需18天，積冷量為432.0需冷單位，惟自然條件植株積冷量僅為443.0需冷單位。‘桃園1號–報春’及‘八重’以低需冷桃完成休眠期需冷性評估模式積算之冷量有高估的情形。 為探討亞熱帶氣候冬季氣溫對低需冷性櫻花‘桃園1號–報春’解除休眠萌芽與開之影響，以8–18℃處理盆栽植株8天，結果得知8–18℃均可使植株達到50%萌芽解除休眠條件，其中14℃處理植株萌芽時間較快而花芽率最高，顯示其對‘桃園1號–報春’促進花芽開花、解除休眠期強度最強。18℃處理植株萌芽速度最慢，且花芽率最低僅有2.3%，顯示其僅能促進葉芽之萌發，促進休眠花芽的強度極低。而8℃、10℃、12℃與16℃處理花芽率22.7%–26.9%結果相近，解除休眠有效強度間雖略有差異，但處理間差異小。針對國內低海拔地區，景觀櫻花品種解除休眠開花冷量需求，2013–2014年冬季期間，相較Subtropical model 15模式之高估積冷量，RCD模式(低需冷桃完成休眠期需冷量評估模式)較適用於臺灣，惟Subtropical model 15模式將8.1–14.0℃的積冷權值提高則與本試驗結果符合，顯示櫻花需冷量評估模式仍有待精進探討。 全球氣候暖化影響物種生態的調適，具低需冷性櫻花或其他經濟作物品種的開發，需朝精準育種加速發展，而未來有機會為溫帶地區引種利用。針對亞熱帶的臺灣氣候探討不同溫度對櫻花開花影響及花期預測之評估的模式，仍需進一步研究並驗證植物感應溫度範圍。

Cherry blossoms, the deciduous woody plants belong to the subgenus Cerasus of the genus Prunus L. in the Rosaceae family, mainly distributed in temperate regions of the Northern Hemisphere. Taiwan, located in a subtropical region, has native species such as the Prunus campanulata Maxim. This paper was conducted to develop the subtropical new cherry blossom cultivars from native species for landscape utilization, exploring the effects of warm winter climates on the sprout and flowering, and identifying the chilling requirements for breaking dormancy in low-chill cultivars. The results could serve as a foundation for the management and application of landscape cherry blossoms in Taiwan. The native species of Prunus campanulata Maxim population, due to hybridization and self-breeding, exhibits variations in flower color, flower shape, heat tolerance, and cold tolerance. To select cherry blossom cultivars adaptive to subtropical landscapes, the study collected 596 single plants from low-altitude areas in central and northern Taiwan that performed excellent flowering characteristics. The grafted plants or seedlings were planted at the Shulin Branch station of Taoyuan District Agricultural Research and Extension for flowering observation and selection of superior plants. Through line propagation and comparative trials, new cherry blossom cultivars were selected, including ‘Taoyuan No. 1-Spring’, ‘Taoyuan No. 2-Red Plum’, ‘Taoyuan No. 3-Spring Red’, and ‘Taoyuan No. 4-Red Glory’, which have early flowering, abundant blossoms, semi-upright tree shape, and low chilling requirements, making them applicable to low-altitude areas in subtropical climates. These cultivars also provide genetic resources for academic research on low-chill cherry blossoms in subtropical regions. To study the effect of chilling accumulation on the dormancy release and sprout of landscape cherry blossoms in 2012-2013 winter, the shoots were collected at different chilling stages under natural conditions, standing in preservative solution, and observed for sprout in the controlled environment. The results showed that ‘Taoyuan No. 1-Spring’ and ‘Oshima’ experienced delayed flower and leaf budburst and lower sprout rates under low chilling accumulation. In different chilling stages, ‘Taoyuan No. 1-Spring’ started leaf budburst at the end of flower, while ‘Oshima’ began leaf budburst a few days after flower under insufficient chilling, with flower and leaf buds alternating until all buds had burst. Under different forcing chilling treatments in 2013-2014 winter, ‘Taoyuan No. 1-Spring’ required six days at 8°C, with a chilling requirement of 144.0 chill units, by the chilling evaluation model of domestic low chilling peach completing rest, the value under the natural field observation by the same evaluation model was 248.5 chilling unit. ‘Double’ required ten days at 8°C, with 240.0 chill units, and 325.0 chill units in natural conditions. ‘Taiwan Fuji’ required eighteen days at 8°C, with 432.0 chill units, and 433.0 chill units in natural conditions. The chilling requirement of ‘Taoyuan No. 1-Spring’ and ‘Double’ estimated by the domestically developed low-chill peach model of complete rest, the value of dormancy release under natural field conditions was higher than the forcing low temperature treatment at 8°C. To investigate the impact of winter temperatures in subtropical climates on the dormancy release and sprout of the low-chill ‘Taoyuan No. 1-Spring’, potted plants were treated at 8–18°C for eight days. Results showed that all temperatures induced 50% budburst, with 14°C resulting in the fastest budburst and highest flower bud rate, indicating the strongest effect on promoting flower budburst and dormancy release. Plants treated at 18°C had the slowest budburst and lowest flower bud rate (2.3%), indicating it primarily promoted leaf budburst with minimal effect on dormancy flower buds. Treatments at 8°C, 10°C, 12°C, and 16°C resulted in similar flower bud rates (22.7%–26.9%), with minor differences in dormancy release effectiveness. For landscape utilization of landscape cherry blossom, determining the chilling requirements evaluation of sprouting and flowering of the cultivars was necessary. Compare with Subtropical model 15, which tended to overestimate the chilling requirements in 2013-2014 winter. The evaluation model of low-chill peach complete rest was more applicable for low-altitude areas in Taiwan. However, the chilling value range to 8.1-14.0℃when the Subtropical Model 15 increases, the result was aligned with the experiment, and indicated that the chilling requirement evaluation model for cherry blossoms still requires further investigation. The impact of global warming on species adaptation necessitates precise breeding and rapid development of low-chill cherry blossoms and other economic crops, potentially introducing them to temperate regions. Further research and validation of temperature response models for predicting flowering and assessing the effects of different temperatures on cherry blossoms in Taiwan's subtropical climate are required.