臺灣低海拔地區梨(Pyrus pyrifolia Nakai.)生產改進I. 海拔高度對新興梨花芽形成與休眠性之影響II. 果實內無機成分與台中二號梨儲藏過程中梨蜜症發生機率之關係

Abstract

Three experiments were conducted to improved high quality pear production at lowland areas in Taiwan. I. Effect of altitude on flower bud formation and necrosis in ‘Shinko’ pears in subtropical Region. Time-specific responses of flower bud formation were investigated in ‘Shinko’ (Pyrus pyrifolia Nakai) pear grown at two altitudes from July through December 2013 in order to determine the suitability of using them as scions in the top-grafting system. Flower bud formation and bud necrosis were determined on each of three sections of one-year-old shoots: terminal, middle, and basal. Flower bud visible started in September in the highland of Li-Shan area, whereas in July in the lowland of Zhou-Lan area. In Li-Shan area, flower bud formation was higher in the middle and basal segments during growing season. However, flower bud formation occurred rapidly in the terminal segment after leaf fall. Flower buds began to development from the terminal segment of the shoot and severe flower bud necrosis was noted in Zhou-lan area. Flower buds developed normally in July however, some of the buds at the basal segment showed browning in early August. During leaf fall, some flower buds showed the symptoms of necrosis with rapid and complete browning. Flower bud necrosis began at the basal segment and progressed rapidly towards middle and terminal sections. Before leaf fall, flower buds fell off when scales swelled. The terminal and middle parts of the current-year shoots Collected on October or later from Li-Shan area, with some flower buds, could be used as scions for top-grafting of 'Shinko' pear. Each grafting scion is a 3-5cm shoot with one flower bud. Those shoot collected from Zhou-Lan area show necrosis and might not be suitable as scions. II. Effect of cold storage duration on bud-burst and flowering of ‘Shinko’ pear scion. Current year shoot of ‘Shinko’ pear were collected in January, November and December, 2013, respectively, from Li-Shan and Zhou-Lan. Materials were sterilized by 8-HQS for 10 minutes, then stored in 5°C for 0, 2, 4, 6, 8 weeks for those collected in January 2013, and 0, 2, 4, 6 weeks for those collected in November and December Bud burst and flowering ratio were investigated after storage. Ten one-bud-cutting with similar length were incubated in growth chamber at 20/15°C condition for each treatment. The results showed that the bud from Li-Shan sprouted after one week in all treatments and had 90% bud burst rate for those stored for 4 and 6 weeks in the material collected in January, Those collected in November and December after 4-weeks cold storage was the best treatment, which had almost 90% bud bursting. The highest flowering rate of the materials from Li-Shan area was 60%, 40% and 40% for January, November, and December samples, respectively. Both bud burst and flowering rate of shoots collected from Zhou-Lan were low. The shoots from Zhou-Lan area are not suggested to be used due to the low flowering rate and high chilling requirement. III. The potassium to magnesium ratio enables the prediction of water core during cold storage of asian pears Taichung No. 2’ is a new Asian pear cultivar developed in Taiwan with low chilling requirement; however, is likely to develop water core under low temperature storage conditions. The impact of storage time on flesh water core in pears were investigated fruits were harvested from 22 orchards in 2010 and 2011, and analyzed the levels of nutrients in different fruit parts such as the peel, flesh, and core. Calcium and potassium contents were higher in the flesh and peel, respectively, of more severely browned fruits, whereas a lower magnesium content was recorded in the peel and core of these fruits. Nitrogen and potassium contents in the peel, and calcium content in the flesh were positively correlated with the water core severity level. In contrast, the magnesium content in the core was negatively correlated with the water core severity level. However, the nutrient contents in fruits varied between the two sampling years considered. Only the K/Mg ratio was an effective predictor of the water core severity and showed a positive linear correlation in the two years. We recommend that the K/Mg ratio should be lower than 10 to avoid severe water core in pears.