Phylogenetic relationships and natural hybridization in Triadica inferred from nuclear and chloroplast DNA analyses |
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Affiliation: | 1. Non-timber Forestry Research and Development Center of Chinese Academy of Forestry, Zhengzhou 450003, Henan, China;2. The Eucommia Engineering Research Center of State Forestry Administration, Zhengzhou 450003, Henan, China;3. Total Genomics Solution Limited, Shenzhen 518081, China;1. School of Biological & Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK;2. School of Science and Health, University of Western Sydney, Locked bag 1797, Penrith, 2751 Sydney, Australia |
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Abstract: | Triadica (Euphorbiaceae) is a small genus endemic to East Asia and Southeast Asia, consisting of three species differentially adapted to heterogeneous habitats. To date, the phylogenetic relationships of this genus have not been resolved, and there has been no evidence for interspecific hybridization in Triadica. In this study, we sequenced the nrITS regions, two nuclear genes and a chloroplast gene to reconstruct the molecular phylogeny of Triadica and to test the hypothesis of natural hybridization between Triadica sebifera and Triadica cochinchinensis, and between T. sebifera and Tridica rotundifolia. Phylogenetic analysis showed that T. sebifera diverged first within this genus, and T. cochinchinensis and T. rotundifolia were sister species. Both of the two putative hybrids show chromatogram additivity at each of the two nuclear genes, providing convincing evidence for natural hybridization between T. sebifera and T. cochinchinensis, and between T. sebifera and T. rotundifolia. The chloroplast gene sequences of both hybrids were identical with that of T. sebifera, suggesting that T. sebifera was the maternal parent of the two hybrids. This is the first report of natural hybridization in Triadica, and the hybrids identified in this study should be a good starting point for further hybridization-based breeding in T. sebifera. |
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Keywords: | Natural hybridization Phylogeny Nuclear genes Chloroplast DNA |
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