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

本研究分為三個試驗，主要目的為提高台灣低海拔梨生產的品質。 第一部份為探討海拔高度對梨花芽形成的影響，以及‘新興’梨花芽在亞熱帶氣候下，發生壞疽(necrosis)的情形。調查2013年7月至12月兩個不同海拔的‘新興’ (Pyrus pyrifolia Nakai)梨穗的花芽形成的情形，藉此來決定梨穗是否適合用於高接 (top-grafting)梨的系統。將梨的一年生枝條分為頂端 (terminal)、中段 (middle)以及基部 (basal)，調查其花芽發育與壞死現象。梨山地區內眼可見的花芽發育起始於九月，然而在卓蘭地區於七月開始肉眼可O 見的花芽發育。梨山地區的花芽大部分位於中段和基部；但梨樹落葉後，花芽在頂端快速發育。卓蘭地區的梨芽從7月就有花芽之形成，然而在8月初芽體由基部芽開始褐化；在葉片掉落時期，花芽快速的壞疽褐化。花芽壞疽由基部開始，進而往中段、頂端發生。在落葉前，在花芽鱗片開始膨大時並掉落。在梨山採集10月或10月以後‘新興’當年生枝條，於枝條頂端和中段具有足夠的花芽，且含有一個芽的接穗每段長度約3-5 cm，可以用於‘新興’梨的高接梨穗，因此梨山地區的‘新興’梨枝條的頂端和中段，可以用來當接穗使用；然而在卓蘭地區的花芽容易發生壞疽，因此在未改良的狀態下，不適合用來當接穗。 第二部分為低溫儲藏對‘新興’芽的生長及花芽影響，於2013年1、11、12月分別採集梨山和卓蘭地區的當年生的‘新興’梨穗枝條。將植物材料以8-HQS消毒10分鐘，並以5℃低溫儲藏不同週數，再以單芽插觀察。2013年1月份採集的枝條，分別低溫儲藏0、2、4、6和8周，2013年11、12月份採集的枝條分別低溫儲藏0、2、4和6 周。在低溫儲藏後，將每段長度近似的單芽插枝條，放置於20/15℃的生長箱裡，並以十個單芽插調查芽體發芽及花芽的比例。結果顯示梨山區的單芽插在一周後，所有處理周數之芽皆開始萌發；於1月採集儲藏4和6周的枝條發芽率達90%；而在11月和12月採集儲藏4周的枝條，發芽率幾乎都有達90%，為最佳的處理。梨山地區枝條最高的花芽比例依1、11和12月，分別為60%、 40% 和40%。卓蘭地區芽體萌發和花芽的比例低，因此，使用卓蘭地區‘新興’梨穗當高接梨穗可能不適用，因為具有高低溫需求及低花芽比例。 第三部分為梨果實 (Pyrus pyrifolia)鉀與鎂含量比例對梨蜜症的影響。‘臺中2號’梨為臺灣低溫需求低的新品種東方梨，在低溫儲藏下，此品種果實的內部易發生梨蜜症。於2010和2011年調查22個果園中採收的梨果實，並以低溫儲藏，分析果實的果皮、果肉和果心的營養元素含量，包含氮、磷、鉀、鈣和鎂。‘臺中2號’果實內部發生梨蜜症的發生率，與果實各部份的氮及磷的含量，顯示相關性並不一致。在2010年採收的果實，嚴重梨蜜症的症狀的果實，果肉和果心含有較高的鈣濃度；然而在2011年，有嚴重梨蜜症的症狀的果實，果皮的鉀含濃度較低。果實具有嚴重梨蜜症，在果皮及果心中鎂的濃度低；然而調查中只有於2010年的果肉鎂濃度低。於果心的營養元素分析，鉀與鎂含量與梨蜜症發生的嚴重程度呈正向的線性相關，因此可以用此來當作果實梨蜜症嚴重程度的指標。

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.