溫度及尿素催芽對‘Merton Thornless’黑莓腋芽生長之影響

Abstract

黑莓(Rubus spp.)之消費量在近十年大幅增加，為一具經濟潛力的莓果類作物。黑莓的花芽分化時程與條件受品種與栽培地區影響，在臺灣等亞熱帶地區常因低溫不足導致花芽分化不良，產量有限。本研究以‘Merton Thornless’黑莓為試驗材料，期能釐清花芽誘導與創始之條件，改善黑莓於亞熱帶地區萌芽時間不一及花芽形成率低的問題。試驗假說以尿素作為催芽劑，可提早一年生枝條之腋芽萌發，而當年生枝條經適當涼溫誘導會由營養生長態轉換為生殖生長態，進行花芽創始與分化。本試驗比較葉面施用10%尿素水溶液與施用自來水，並將植株置於日夜溫35/30℃、25/20℃、20/15℃及15/13℃，自然光照條件之人工氣候室中，調查不同處理組合對萌芽率、當年生新梢後續生長、花芽形成及關鍵開花基因FLOWERING LOCUS T (FT)和TERMINAL FLOWER 1 (TFL1)表現量之影響。試驗結果顯示，尿素處理與15/13℃顯著提升黑莓之萌芽率，而尿素處理與35/30℃、25/20℃和20/15℃促進新梢生長平均長度。25/20℃尿素處理組之FT相對表現量高於對照組，且TFL1表現被抑制，具誘導花芽創始的潛力。15/13℃尿素處理之FT與 TFL1相對表現量整體低於對照組，不利於花芽分化。本研究指出當年生枝條經適當的涼溫誘導，配合妥善田間管理，可能使黑莓進入花芽創始及分化。未來可進一步延長觀察時間與增加調查頻率，結合分子與形態學調查，深入闡明黑莓花芽形成之分子機制與環境調控因素。

Consumption of blackberry (Rubus spp.) has markedly increased over the past decade, making it a berry crop with considerable economic potential. The timing and conditions required for floral bud initiation of blackberry vary with cultivar and cultivation region. In subtropical areas such as Taiwan, insufficient chilling often leads to poor floral bud differentiation and low yield. This study used ‘Merton Thornless’ blackberry as the experimental material and aimed to clarify the conditions for floral bud induction and initiation, in order to improve the inconsistent budbreak timing and low floral bud formation commonly observed in subtropical regions. We hypothesized that urea acts as a forcing agent capable of advancing the budbreak of lateral buds on one-year-old canes, and that current-season shoots subjected to appropriate cool-temperature induction would transition from vegetative to reproductive growth, thereby initiating and differentiating floral buds. Plants were subjected to a foliar application of 10% urea solution or tap water before placing to a phytotron under natural light at day/night temperatures of 35/30°C, 25/20°C, 20/15°C, or 15/13°C. Budbreak rate, subsequent shoot growth, floral bud formation, and the expression of key flowering genes FLOWERING LOCUS T (FT) and TERMINAL FLOWER 1 (TFL1) were recorded to evaluate the effects of different treatment combinations. Results showed that urea treatment and 15/13°C significantly enhanced budbreak rate, while urea combined with 35/30°C, 25/20°C, or 20/15°C promoted shoot elongation. In the 25/20°C urea treatment, FT exhibited higher relative expression than the control, whereas TFL1 was suppressed, suggesting a potential role in inducing floral bud initiation. In contrast, both FT and TFL1 relative expression levels were generally lower under urea treatment at 15/13°C, which was unfavorable for floral bud differentiation. This study indicates that current-season shoots exposed to appropriate cool-temperature induction, combined with proper field management, may enter floral bud initiation and differentiation. Future research may extend the observation period and increase sampling frequency, and integrate molecular and morphological approaches to further elucidate the molecular mechanisms and environmental regulatory factors involved in blackberry floral bud formation.