多穗蕉體營養系變異的研究

A Study of the Somaclonal Variation of Multi-bunching in Banana

從具有多穗性狀的親本採吸芽，以組織培養繁殖無性世代，檢定多穗 性狀的表現特性。在新植世代的營養系190株中出現各種果穗型：包括單果穗、部份多穗、完全多穗、多雄花苞等類型。單穗型及多穗型植株的百分率分別為78.9%及21.1%。由新植世代隨機選採90株留宿根觀察，宿根世代其單穗及多穗植株的頻率分別為38.9及61.1%。多穗蕉在宿根世代有明顯增加，同時少部份植株出現假莖二分生現象。從兩個無性世代的譜系分析，單穗或多穗在後代的表現沒有固定規律，二者之間的回變（reversion）均有可能。比較多穗與正常單穗蕉的園藝性狀，在多穗蕉的果把數（17.5把）及果指數（259指）比正常單穗蕉（分別為9.1把及145指）有明顯增加，但其單株產量（15.2kg）反而不及正常單穗蕉（17.6kg）。可見目前的多穗蕉因果指細小，不具經濟價值。本文並對多穗蕉在無性世代中出現不同類型的成因及理想中的多穗型香蕉加以討論。

A study of the somaclonal variation on multiple bunches was carried out in the asexual generation of a multi-bunching clone of banana (AAA, Cavendish subgroup). Micropropagation using meristem culture of banana sucker was used to produce the asexual plantlets for this study. Among 190 plants studied, various types of bunch morphology, varying from single bunch, partially multiple bunches, completely multiple bunches and multiple male buds were observed. The frequencies of plants with single bunch or multiple bunches were 78.9 and 21.1%, respectively. 90 plants were randomly selected to investigate the bunch morphology in the ratoon generation. Among them, 38.9% were single bunching and 61.1% were multi-bunching. Plants with multi-bunching were greatly increased in the ratooning generation. Also, a new type with dichotomy of pseudostem was found in some plants of this generation. From the pedigree analysis, no regularity was found in the occurrence of bunch types in the asexual offsprings. Change of bunch types, either from single to multiple or the reverse are possible. Comparison of five horticultural traits between plants of single and multibunching was studied. Although the no. of hands (17.5) and fingers (259) in the multibunching type were higher than those in the single bunching type (9.1 and 145, respectively), the bunch weight of the multi-bunching type (15.2kg) was less than those of the single bunching type (17.0kg). Therefore the fruit size of multi-bunching plants was low and had no commercial value. The possible causes of the occurrende of various bunch types in the asexual generation and the ideal morphology of the multibunching banana were also discussed.