Liao Pei-Chun, Tsai Chi-Chu, Chou Chang-Hung, Chiang Yu-Chung
Department of Biological Science and Technology, National Pingtung University of Science and Technology, Pingtung 912, Taiwan.
Kaohsiung District Agricultural Research and Extension Station, Council of Agriculture, Pingtung 908, Taiwan.
Int J Mol Sci. 2012;13(5):6469-6491. doi: 10.3390/ijms13056469. Epub 2012 May 24.
The landrace strains of Momordica charantia are widely cultivated vegetables throughout the tropics and subtropics, but not in Taiwan, a continental island in Southeast Asia, until a few hundred years ago. In contrast, the related wild populations with smaller fruit sizes are native to Taiwan. Because of the introduction of cultivars for agricultural purposes, these two accessions currently exhibit a sympatric or parapatric distribution in Taiwan. In this study, the cultivars and wild samples from Taiwan, India, and Korea were collected for testing of their hybridization and evolutionary patterns. The cpDNA marker showed a clear distinction between accessions of cultivars and wild populations of Taiwan and a long divergence time. In contrast, an analysis of eight selectively neutral nuclear microsatellite loci did not reveal a difference between the genetic structures of these two accessions. A relatively short divergence time and frequent but asymmetric gene flows were estimated based on the isolation-with-migration model. Historical and current introgression from cultivars to wild populations of Taiwan was also inferred using MIGRATE-n and BayesAss analyses. Our results showed that these two accessions shared abundant common ancestral polymorphisms, and the timing of the divergence and colonization of the Taiwanese wild populations is consistent with the geohistory of the Taiwan Strait land bridge of the Last Glacial Maximum (LGM). Long-term and recurrent introgression between accessions indicated the asymmetric capacity to receive foreign genes from other accessions. The modern introduction of cultivars of M. charantia during the colonization of Taiwan by the Han Chinese ethnic group enhanced the rate of gene replacement in the native populations and resulted in the loss of native genes.
苦瓜地方品种在热带和亚热带地区广泛种植，但直到几百年前才传入东南亚的大陆岛屿台湾。相比之下，果实较小的相关野生种群原产于台湾。由于农业用途品种的引入，这两个类群目前在台湾呈现同域或邻域分布。在本研究中，收集了来自台湾、印度和韩国的品种及野生样本，以测试它们的杂交和进化模式。叶绿体DNA标记显示台湾品种和野生种群之间有明显区别，且分化时间较长。相比之下，对8个选择性中性核微卫星位点的分析未发现这两个类群的遗传结构有差异。基于隔离迁移模型估计了相对较短的分化时间以及频繁但不对称的基因流。还使用MIGRATE - n和BayesAss分析推断了历史上和当前从品种到台湾野生种群的基因渐渗情况。我们的结果表明，这两个类群共享丰富的共同祖先多态性，台湾野生种群的分化和定殖时间与末次盛冰期（LGM）台湾海峡陆桥的地质历史一致。类群间长期且反复的基因渐渗表明从其他类群接收外源基因的不对称能力。汉族在台湾殖民期间现代引入苦瓜品种提高了本地种群的基因替代率，并导致本地基因的丧失。
