Genetic variation of the genus Dioscorea in Taiwan
Date Issued
2015
Date
2015
Author(s)
Kung, Tsai-Li
Abstract
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.
Subjects
genetic diversity
yam
germplasm collection
ISSR marker
morphological characteristic
Dioscorea japonica Thunb.
D. doryphora Hance
Type
thesis
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