以限制酵素片段長度多型性研究菸草屬之親緣關係

Abstract

本研究以3個皺葉菸草（Nicotiana plumbaginifolia）的cDNA選殖體及26個單或低拷貝基因組選殖體為探針，偵測菸草屬Alatae節及Tomentosae節植物的細胞核DNA限制酵素片段長度多型性，並以此遺傳標誌為特徵，利用PHYLIP軟體的最儉約法則及距離方法程式，推演Alatae節及Tomentosae節，節內及節間的親緣關係。結果符合Goodspeed（1954）的結果，即屬於Tomentosae節的N. otophora、N. tomentosiformis、N. glutinosa群聚為一分支群；而屬於Alatae節的N. sylvestris、N. alata、N. langsdorffii、N. longiflora、N. plumbaginifolia亦群聚為一分支群，且相同染色體基數的植物會群聚在一起。本研究結果支持將分類地位較具爭議性的N. sylvestris置於Alatae節中，且由所得的親緣關係樹亦可證實Goodspeed（1954）所提Alatae節染色體基數由n＝12演化為n＝9及n＝10的假設。另外，研究結果發現，N. longiflora與N. plumbaginifolia形成並系群，顯示N. plumbaginifolia可能尚未分化為一獨立的種，其種階級的合法性需要再深入研究。

Using three cDNA clones and twenty-six genomic clones of Nicotiana plumbaginifolia, restriction fragment length polymorphisms (RFLPs) of nuclear DNA were studied to infer the inter- and intrasectional phylogenetic relationship of section Alatae and section Tomentosae of genus Nicotiana L.. By using these RFLPs markers as discrimination characters, phylogenetic trees were obtained based on parsimony and distance matrix methods of PHYLIP package. The taxonomic hierarchy revealing in the tree topologies indicated that all three species in the section Tomentosae (N. otophora, N. tomentosiformis, and N. glutinosa) were grouped in one clade, while all species in the section Alatae (N. alata, N. langsdorffii, N. longiflora, N. plumbaginifolia and N. sylvestris) were grouped in a different clade. In the clade of section Alatae, subclades were grouped according to the basic chromosome numbers of these species. Our results therefore support the proposals of Goodspeed (1954) that N. sylvestris is in section Alatae, and that the evolutionary scheme of the chromosome number in section Alatae is from n = 12 to n = 9 and n = 10. N. longiflora and N. plumbaginifolia were grouped paraphyletically, indicating that the two taxa have not differentiated completely. The validity of N. plumbaginifolia for being a species should be study further.