Genetic variation of the genus Dioscorea in Taiwan

本論文以簡單序列重複區間DNA標誌(ISSR DNA marker)及植株外表性狀評估台灣薯蕷屬(日本山薯、戟葉田薯、山芋、華南薯蓣、裡白葉薯榔、大薯及假山藥薯)種原之遺傳歧異性及親緣關係，以作為未來種原蒐集及育種利用之參考。 ISSR分子標誌分析結果顯示，日本山薯、戟葉田薯、山芋、華南薯蓣、裡白葉薯榔、大薯及假山藥薯種原間最大遺傳距離分別為69.2%、56.2％、71.4%、70.9%、58.3%、64.9%及54.8%，表示7個薯蓣屬物種內均具有高遺傳歧異度。群聚分析結果，發現7個物種種原均重疊分佈在台灣之4個地理區域，並未受地理隔離影響；而依據種原間之遺傳相似度，其中日本山薯之細葉野山藥與基隆野山藥2個變種群間可明顯區分，薄葉野山藥變種則介於細葉野山藥與基隆野山藥2個變種之間，而大薯種原可區分紫(紅)皮大薯與黃(褐)皮大薯種原。AMOVA結果顯示，上述7個物種均以縣市(次族群)內具有最主要之變異成分，依次分別為95.94%、93.35%、96.23%、91.34%、93.04%、85.29%及78.13%。POPGENE遺傳變異分析結果，日本山薯、戟葉田薯、山芋、華南薯蓣、裡白葉薯榔、大薯及假山藥薯種原測得遺傳歧異度(H)分別為0.193、0.257、0.275、0.256、0.237、0.230及0.250，物種豐富度指數(I)分別為0.314、0.402、0.423、0.396、0.369、0.359及0.371，顯示7個物種種原間具有高度遺傳變異；族群分化係數(Gst)分別為0.340、0.503、0.448、0.561、0.497、0.567及0.861，均高於一般異花作物中風媒花植物之平均值(0.143)及蟲媒花植物之平均值(0.197)，其中以假山藥薯種原(0.861)最高，顯然其族群分化程度最高；而基因流轉值(Nm)分別為0.970、0.495、0.615、0.391、0.506、0.382及0.081，其中以日本山薯種原(0.970)最高，其基因流轉值接近1，顯示出整體族群之間基因交流幾近順暢，其餘6個物種之種原基因流轉值低於1，即整體族群之間均存有基因交流障礙，其中又以假山藥薯種原(0.081) 基因交流障礙最為嚴重。在4個地理區之中，台灣北部地區同時具有3種野生日本山薯變種之分布，次族群(縣市)間之基因交流流暢，且具有最大之遺傳歧異度、物種豐富指數及基因流轉值，可視為台灣野生日本山薯之遺傳變異中心。 根據植株性狀調查結果顯示，8個質量性狀中，日本山薯種原之葉基部形性狀，戟葉田薯及華南薯蕷種原之老葉顏色、幼葉顏色、莖蔓顏色及芽色性狀，山芋、裡白葉薯榔及假山藥薯種原之莖蔓顏色及芽色性狀，大薯種原之幼葉顏色、莖蔓顏色及芽色性狀，以上植株性狀之頻度分佈較均勻，適合遺傳變異評估及品種鑑定參考。數量性狀調查分析結果，日本山薯及山芋種原之葉長度、葉柄長度、葉長前寬比及葉長中寬比，戟葉田薯種原之葉中寬及葉長中寬比，華南薯蕷種原之莖部直徑及莖節間長度，裡白葉薯榔種原之葉柄直徑、葉前部寬度及葉中部寬度，大薯種原之節間長度、葉柄長度及莖部直徑與假山藥薯種原之葉柄長度、葉中部寬度及節間長度，可作為辨識重要指標。以植株外表性狀群聚分析來評估七個物種薯蓣屬種原遺傳歧異性，結果顯示地區族群相互重疊。 本論文針對台灣薯蕷屬種原進行系統性之研究，並建立台灣薯蕷屬作物之種原蒐集、評估及利用上重要資訊。In this study, inter simple sequence repeat (ISSR) DNA markers and morphological characteristic were used to assess the genetic diversity and relationship for the germplasm of Dioscorea species (D. japonica Thunb.；D. doryphora Hance；D. bulbifera L.；D. collettii Hook. f.；D. matsudae Hayata；D. alata L.；D. persimilis Prain & Burkill) in Taiwan. The results of this study could provide information for the germplasm collection and application of breeding. ISSR molecular marker analysis showed that the greatest genetic distance among seven species (D. japonica Thunb., D. doryphora Hance, D. bulbifera L., D. collettii Hook. f., D. matsudae Hayata, D. alata L., D. persimilis Prain & Burkill) were respectively 69.2%, 56.2%, 71.4%, 70.9% , 58.3%, 64.9% and 54.8%, indicating that seven species of the genus Dioscorea had a high degree of genetic diversity. Cluster analysis found that the distribution of seven species was overlapping in four geographic regions of Taiwan and not affected by the impact of geographical isolation. And based on the genetic similarity, the varieties oldhamii and pseudojaponica were separated into different clusters and var. japonica was grouped with both varieties, and could be distinguished by the purple (red) skin and yellow (brown) group of D. alata L. AMOVA results showed that variation within counties (subpopulation) for the seven species had a dominant component, accounting for 95.94%, 93.35%, 96.23%, 91.34%, 93.04%, 85.29% and 78.13%, respectively. POPGENE analysis of genetic variation showed that the seven species measured degree of Nei''s gene diversity (h) respectively 0.193, 0.257, 0.275, 0.256, 0.237, 0.230 and 0.250, Shannon''s information Index (I) were 0.314, 0.402, 0.423, 0.396, 0.369, 0.359 and 0.371, respectively, showing that seven species had high degree of genetic diversity. The coefficient of gene differentiation(Gst), were 0.340, 0.503, 0.448, 0.561, 0.497, 0.567 and 0.861 respectively, which were higher than the average of wind-pollinated flower plants (0.143) and entomophilous flower plants (0.197), and D. persimilis (0.861) was the highest in which. The gene flow values (Nm) were 0.970,0.495,0.615,0.391,0.506,0.382 and 0.081, respectively, among which D. japonica (0.970) had the highest gene flow value close to 1, showing that gene flow between the overall populations was almost smooth, and the gene flow values of the other six species were less than 1, suggesting that there were barriers to gene exchange between the overall population. D. persimilis (0.081) had the greatest barriers to gene flow. Among the four geographical regions, the northern regions of Taiwan also had three kinds varieties of D. japonica, between counties that gene exchanges smooth, and had a maximum degree of Nei''s genetic diversity(H), Shannon''s information Index(I) and gene flow value (Nm). This region could be regarded as the center of Taiwan''s genetic variability of D. japonica. According to the distribution frequency, the qualitative traits in D. japonica (leaf base shape), D. doryphora and D. collettii (matured leaf color, young leaf color, stem color and bud color), D. bulbifera D. matsudae and D. persimilis (stem color and bud color), D. alata (young leaf color, stem color and bud color), were in uniform. These traits are suitable for the assessment of genetic variation and species identification. The quantitative traits of D. japonica and D. bulbifera (Leaf length, petiole length, the ratio of leaf length and terminal width leaf length), D. doryphora (medial leaf width, the ratio of leaf length and medial width), D. collettii (stem diameter and internode length), D. matsudae (petiole diameter, terminal leaf width and medial leaf width), D. alata ( internode length, petiole diameter and stem diameter), D. persimili (petiole length, medial leaf width and internode length), could be used as important indicators for species identification. Based on plant traits, the cluster analysis showed the overlapping distribution in regions for the seven species. In this thesis, systematic studies of the genus Dioscorea germplasm in Taiwan have been established, and such important information will be useful in germplasm collection, evaluation and application