多胚性與橙類雜交育種效率改進之研究

Abstract

為探討甜橙之胚性及其雜交苗率，以做為雜交育種母本選擇的參考，以柳橙、桶柑為母本，分別與柚類、根殼及甜橙類雜交，並以五個甜橙品種進行品種問雜交。於果實成熟時採取種子，分離胚播種，發芽後三個月至二年間，依葉片形態區別雜交苗。且於果實發育過程中調查桶柑、柳橙胚數的變化。 柳橙之胚數與桶柑有很顯著的差異，雖然二者均具有多胚性。柳橙之平均胚數由六月逐漸增加，至八月上旬可達20個以上，可辨別的胚數逐漸減少至10月上旬的10個左右。桶柑胚數變化小，絕大部份之胚數均在5個以下，並且有許多單胚的種子。雜交苗率，柳橙以柚類及枳殼授粉者分別為6.6%及0%。桶柑以甜橙授粉者，1985年無單胚種子出現，雜交苗率為20.6%；1986年有40.0%的單胚種子，雜交苗率為64.9%；以枳殼授粉之雜交苗率為66.7%。顯示胚數多者，雜交苗率低，少者則高，胚數甚多的種類，果實成熟時的胚數已不能代表其發育過程中所產生的胚數。柳橙及桶柑以枳殼授粉，其著果率、平均種子數均較柑橘屬授粉者少，而柳橙以枳殼授粉之雜交苗率為0%，因此與枳殼之親和力較差或雜交胚發育較弱者，其雜交苗率將甚低，所以以枳殼授粉的結果不能代表以其他柑橘授粉所產生的雜交苗。柳橙、雪柑、晚侖夏、Hamlin及Pineapple等甜橙品種間相互雜交，雜交苗率均低，各組合分別介於27%至10.7%間。 In order to improve the breeding efficiency in oranges(Citrus sinensis), the polyembryony and ratio of zygotic progenies were studied. ‘Liu-cheng’ (C. sinensis) and Tankan (C. tankan) were polyembryonic, their open-pollinated fruits were picked at different growing stages, and number of embryos were counted with dissecting microscope. Among these speices, ‘Liu-cheng’ had higher number of embryos, but Tankan contained lower degree of polyembryony. The mean number of embryos of ‘Liu-cheng’ orange changed greatly during the development of seeds, it increased from mid June to early August, the number of embryos might excess 20, then the distinguishable number of embryos decreased to about 10 in early October. Mean number of embryos produced per seed of Tankan was mostly less than 5 during the development of seeds. ‘Liu-cheng’ orange and Tankan pollinated with trifoliate, the percentage of fruit set and seeds per fruit were generally lower in comparing with those pollinated with pummelos or sweet oranges. Percentage of zygotic seedlings of ‘Liu-cheng’ crossed by pummelos and trifoliate were 6.6% and 0%, respectively. The percentage of monoembryo seeds of Tankan crossed by sweet oranges changed greatly at different years. In 1985, all the 1559 hybrid seeds were polyembryo, but 40% monoembryo seeds were found in 3326 hybrid seeds in the following year. Crosses were made within Citrus sinensis, the percentage of zygotic seedlings which can be distinguished from leaf morphology varied from 2.7% to 10.7%.