The Breeding and Evaluation of Citrus Nucellar Lines

本省柑株因多年來在無病毒管制下輾轉嫁接繁殖，戶外的植株大部份感染一至數種病毒，造成產量低、品質良莠不齊及短命的現象。利用柑橘能產生珠心胚的特性及絕大部份病毒不經由種子傳染的原理，由田間優良植株予人工授粉、採果、播種於隔離網室，在與媒介昆蟲隔絕的狀態下，培育成無病毒之珠心胚系候選母樹。經由單幹整技法盡早逾越柑苗之幼年期，達到具開花能力的轉型期即採穗高接田間成年柑株。由五年來高接後所得部份果實資料，初步選出10個椪柑珠心胚株系，現正繁殖中，預定明年起進行區域試種。珠心胚系若未完全逾越幼年期，枝幹因其無病毒化及回春作用(Rejuvenility)常著生甚多大而銳利的刺，使栽培者不便於作業。本研究室利用單幹整枝及多次的頂梢回接方式初步發現得以解決此項缺點。 Most of the field grown citrus trees in Taiwan were more or less infected by several citrus viruses that caused the low productivity, less vigour, inferior qualities and relatively short lived. By using the natural characters of citrus which can produce nucellar embryos and most citrus viruses would not passed through the seeds to the seedlings. TART began the citrus nucellar breeding prograon under screen in 1976. The selected superior fruit qualities’ trees in the field were artificially pollinated with trifoliate orange, pummelo or lemon pollen to identify the nucellar seedlings from the zygotic ones by leaf appearances after seeds germinated. All the seedlings were potted and grown in the screenhouse as virus-free nucellar candidate stock-mother trees. They are mono-trunk-trained to accelerate maturity. Some budwoods took from already flowered twigs were topworked to the field grown trees. According to 5 harvesting years and fruits analysis records, there are 21 best fruit clones of ponkan were selected and are propagated in the screenhouse. They will be validated in the citrus groves around the island. Because the healthiness of virus-free and rejuvenility, the nucellar citrus trees are very thornny and were rejected by the farmers. By using mono-trunk--training and repeatedly shoot top grafting to their own roots, TART had successfully overcome this practical problem