橫山梨(Pyrus pyrifolia Nakai)花粉採集技術之研究

Abstract

寄接梨生產時，多以人工授粉來提高著果率，但所需之花粉多仰賴國外進口，但進口花粉存在來源不明、品質不一致以及檢疫等疑慮。本研究探討寄接梨園疏、修剪下的‘橫山’梨徒長枝條上的花芽發育情形、萌芽表現、枝條內容物與休眠之間的關係；並檢測所得花粉之活力表現；期望建立一套梨花粉採集技術。在2013年採穗時期之花芽發育試驗結果顯示，‘橫山’梨徒長枝花芽比例在9月過後大致呈穩定狀態，約有6成以上的芽為花芽。2012年及2013年徒長枝冷藏的試驗結果顯示，隨冷藏週數增加，徒長枝總萌芽率、花芽萌芽率皆顯著提高，其中以冷藏4週以上的處理，花芽萌芽表現較好；枝條打破休眠所需的冷藏時間，會因採穗時期之不同而有差異，於9月底至10月中左右採收之枝條，冷藏3-4週即可達到40-50%的總萌芽率，而在10月底至11月初，需冷藏5週至7週方能達到。枝條開花數的表現受採穗時期的影響而不受冷藏週數的影響，不過隨冷藏週數的增加，花芽萌到一半即死亡的機會提高，降低開花的品質；內容物分析的結果顯示，枝條的氮含量與採穗時期的相關性較大，其隨採穗時期的延後而具有下降的趨勢；但與冷藏週數無關。而枝條的碳水化合物則與冷藏時間的相關性較大，碳水化合物總量與澱粉含量隨冷藏週數的增加而降低，而80%乙醇可溶性醣含量則是隨枝條冷藏週數增加而提高，且此與萌芽的表現具有相關性。花粉活力檢測的結果顯示，不同採穗時期的枝條，其花粉活力有差異，而枝條冷藏的週數並不影響花粉的活力。花粉隨貯藏的時間增加，活力由86.1%下降至83.8%，具顯著負相關之趨勢，-20℃貯藏的花粉活力較以5℃貯藏佳，但2種溫度貯藏5個月後，花粉活力分別仍有83.7%及86.0%，皆仍比市售花粉的43.6%及53.7%活力為高。

In top-grafted pear production, artificial pollination relying on imported pollen is usually used to enhance fruit set. It is concerned that the source, quality, and quarantine of the imported pollen remain in doubt. In this research, we investigated the relationship of flower bud development, budburst, and shoot content with dormancy in water sprouts of ‘Heng-Shan’ pear (Pyrus pyrifolia Nakai) pruned from orchard, and checked the pollen viability from pollens achieved. We hope to establish a pear pollen collection technique. The results from the flower bud development trial in 2013 indicated that the ratio of flower buds on water sprouts became stable after September for P. pyrifolia ‘Heng-Shan’ with more than 60% flower buds. In the cold storage experiments of sprouts in 2012 and 2013, the result showed that the increment in storage period caused a significant rise in both total budbreak and flower budbreak on sprouts. Cold storage treatment more than 4 weeks provided good results in flower budbreak. The appropriate cold storage period to break the dormancy of water sprout is different according to harvest dates. Sprouts harvested in late-September to mid-October can reach 40%-50% budbreak when given 3-4 weeks cold storage treatment, while sprouts harvested in late-October to early-November acquired same result when given 5-7 weeks cold storage treatment. The number of flower anthesis was affected by the harvest date of the sprouts but not the length of cold storage treatment. However, cold storage period lengthens, as the chance of flower death right after the flower budbreak increased, which caused a reduction in the quality of anthesis. The results from component analysis of sprouts showed nitrogen content in shoots relates with harvest date, not the cold storage period. The later the date of harvest was, the lower nitrogen content was detected. Furthermore, a relationship existed between the carbohydrate content in shoots and the cold storage period. The total carbohydrate content and starch content reduce, while the cold storage period increased. However, the total soluble solids in sprouts increased while the cold storage period prolonged, and it also correlated with the performance of budbreak. The results of in vitro pollen germination indicated that pollen viability differs in different harvest date of sprouts, while the cold have no effects on pollen viability. With lengthened storage period, pollen viability decreased from 86.1% to 83.8%, demonstrating a significantly negative correlation. Pollen viability is better when stored under -20℃ than 5℃. Pollen viabilities after five months storage in -20℃ and 5℃ were 83.7% and 86.0% for harvested pollen, which were both higher than 43.6% and 53.7% for commercial pollen.