刺番荔枝人工授粉技術之研究

Research on Artificial Pollination Technology of Soursop (Annona muricata L.)

刺番荔枝花朵具雌蕊先熟之特性，在臺灣地區因缺乏授粉昆蟲，自然狀況下的著果率低，且果實的聚合果特性會因授粉不良而產生畸型果。為穩定果實生產，本研究擬建立刺番荔枝人工授粉技術，觀察花朵發育情形，並探討雌蕊成熟度、授粉時間與月份及授粉方法等對著果率及果實品質等之影響。刺番荔枝花朵在發育過程外花瓣會逐漸開裂、顏色由綠色轉為黃綠色，花藥則在轉為灰黃色的當天傍晚（17:00~19:30）成熟開裂。雌蕊成熟度可依花瓣外觀及花藥顏色變化分為4級，其中第3級花朵為雌花期，第4級花朵為雌花末期或雄花期，兩種成熟度花朵於人工授粉後，著果率及果實品質無顯著差異，且明顯優於自然授粉處理。刺番荔枝授粉時間除配合傍晚花藥開裂之時間外，亦可將花粉冷藏，於隔天早晨再取出授粉。相較於自然授粉，人工授粉之著果率及果實品質不受到季節影響，著果率可穩定達80%以上，單果重超過2.8 kg，惟果實生育期仍有季節性差異，越晚授粉，停滯期日數及發育期日數越長。刺番荔枝雌蕊的成熟時間雖然較雄蕊早，但其活力可維持到花藥開裂的時候，授粉方法採人工自花授粉（同朵花授粉）、人工同株異花授粉及人工異株授粉在著果率及敗育率並無顯著差異，顯示其授粉時間及授粉方法較具彈性，可依環境狀況調整。

Soursop flowers exhibit protogynous dichogamy. In Taiwan, due to the lack of insect pollination, the fruit set rate of soursop is low under the natural condition. Additionally, inadequate pollination often leads to irregular shape of its aggregate fruit. In order to stabilized the fruit production, this study aimed at establishing artificial pollination technology of soursop by defining flower development stages, and investigating the impact of pistil maturity, pollination diurnal time and months, and pollination ways on fruit set rate and fruit quality. Throughout the development stages of soursop flowers, the outer petals would gradually split and the color change from dark green to yellow-green. Anther maturation and dispersal occurred in the evening (between 17:00 and 19:30) once their color shifted to grayish-yellow. Based on petal appearance and anther color changes, the maturity of pistils could be divided into 4 levels. The level 3 flowers represent female stage, and the level 4 flowers indicate late female stage or male stage. The fruit set rate and fruit quality by artificial pollination had no significant difference between level 3 and level 4 flowers, both surpassing those by natural pollination. In addition to follow the pollen dispersal time at evening, the artificial pollination time can be changed to the next morning by storing fresh pollen in refrigerator. As compared to natural pollination, the fruit set rates and fruit quality of artificial pollination were not affected by seasons. The fruit set rates were stably up to 80%, and the fruit weights exceeded 2.8 kg. The timing of artificial pollination affected the duration of fruit growth. Pollination in later months were associated with prolonged periods of quiescence and development days. Although the mature time of pistils is ahead of stamens, the viability of pistils persisted until pollen dispersal. There were no significant difference in fruit set and abortion rates among artificial self-pollination, geitonogamy, and xenogamy treatments. It indicates that the pollination time and pollination ways adopted by soursop are more flexible and can be adjusted according to environmental conditions.