柑橘雜交育種 雜交後代鑑定、培育與初選

Abstract

為開發本省柑橘新品種，以兼具單偽結果，耐潰瘍病等特性之桶柑及麻豆文旦為主要母木，與甜橙及寬皮柑類等雜交。主要有15雜交組合。選拔目標為耐潰瘍病、不同成熟期、少籽及品質優良。本計畫自1983年春開始授粉，初期並進行多胚性品種之胚數調查，以選擇適宜的母本。結果顯示多胚性柑橘品種中，有胚數較少者，其種子發育過程中，平均胚數均在5個以下，做為母本可得到一定比率之雜交後代，如桶柑、檸檬、四季橘。歷年來計培育實生苗二萬四千餘株，母本為多胚性品種者，其雜交苗以葉片形態、新梢顏色及胚色等特徵與珠心胚苗鑑別之。1988年春起陸續定植5,960株，果園採用寬行密植、單幹整枝的管理，幼樹於主幹150公分高處修剪，使其分枝。主要雜交組合間五年生之開花率以文旦與Hamlin、Marrsearly等甜橙之雜交苗最低，為17.5%，Fortune x Chandler最高，為60.7％。幼年期之長短主要應受母本的影響。由田間觀察，潰瘍病發生之程度隨株齡之增加而明顯的減少。親本之一為柚類者發育較旺盛。雜交後代結果者經品評及品質分析，已初選得10株分別具有早生、少籽、風味佳及耐潰瘍病等特性之品種，並分別培育苗木或高接供進一步試驗。 To develop citrus cultivars, ‘Tankan’ (Citrus tankan), ‘Wentan’ (C. grandis) and ‘Fortune’ were used as major seed parents and pollinated with sweet oranges and mandarins. The polyembryony of some cultivars were investigated for choosing suitable seed parents. ‘Liu-cheng’ had higher number of embryos, but ‘Tankan’, Calamondin and lemon contained low degree of polyembryony and produced certain ratio of zygotic seedlings. In the past years, 24,000 seedlings were raised and zygotic seedlings of polyembryonic seed parents were identifid from the nucellar by leaf morphology, embryo color and color of young shoot. A total of 5,960 zygotic seedlings were planted in field in high-density planting and single-trunk trained. Flowering rate of seedlings of the major combinations in 5 years varied from 60.7 % (‘Fortune’ x ‘Chandler’) to 17.5 % (‘Wentan’ x sweet oranges). The period of juvenile phase seems to be inherented essentially by seed parent. Seedlings were more resistant to citrus canker as they were aging. Ten promising hybrids with the characters of few seeds, early maturity, high quality or resistant to citrus canker were selected and propagated for further test.