橫山梨(Pyrus pyrifolia Nakai)花粉採集技術之研究

Abstract

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.