Dawson I K, Simons A J, Waugh R, Powell W
Department of Cell and Molecular Genetics, Scottish Crop Research Institute, Invergowrie, Dundee.
Mol Ecol. 1996 Feb;5(1):89-98. doi: 10.1111/j.1365-294x.1996.tb00294.x.
Gliricidia sepium provides a variety of products important for rural communities in tropical countries. Native populations in Meso-America currently form an important source of seed for distribution to farmers, but concerns centre on mechanisms which may lead to their genetic erosion, including anthropogenic dispersal and subsequent introgression from the related species, G. maculata. Populations of Gliricidia were examined genetically using approaches based on the polymerase chain reaction to test for interspecific hybridization and introgression between G. sepium and G. maculata. Analysis involved 13 RAPD and two RFLP-PCR markers which were identified to have species-diagnostic distributions. Data from both approaches corresponded and indicated three locations where multilocus genotypes were consistent with an hybrid origin. Data at one of these sites was consistent with introgression following hybridization. The hybrid origin of populations was supported by the intermediate geographical location of these sites to 'pure' populations of each species. Analysis of maternally inherited organellar DNA, which involved the detection of SSCPs in mitochondrial DNA amplification products, allowed further delineation of genetic structure among Gliricidia populations. Mitochondrial data indicated a high degree of organelle differentiation between sampled locations and identified G. sepium- and G. maculata-diagnostic haplotypes. This data supported the interpretation of genetic structure based on RAPDs and RFLP-PCR. In addition, cytonuclear analysis allowed the directionality of gene transfer during the formation of hybrid populations to be described. Despite evidence for the occurrence of interspecific hybridization and introgression in Gliricidia, important resource populations of G. sepium on the Pacific coast appear to have retained their genetic integrity. Implications in terms of the conservation and utilization of genetic resources within the genus are discussed.
柔毛甘豆为热带国家的农村社区提供了多种重要产品。中美洲的本地种群目前是向农民分发种子的重要来源，但人们担心可能导致其基因侵蚀的机制，包括人为传播以及随后与相关物种斑点甘豆的基因渗入。利用基于聚合酶链反应的方法对柔毛甘豆种群进行了基因检测，以测试柔毛甘豆和斑点甘豆之间的种间杂交和基因渗入情况。分析涉及13个随机扩增多态性DNA（RAPD）标记和2个限制性片段长度多态性聚合酶链反应（RFLP-PCR）标记，这些标记被确定具有物种诊断分布。两种方法的数据相互对应，表明有三个位点的多位点基因型与杂交起源一致。其中一个位点的数据与杂交后的基因渗入一致。这些位点在地理上处于每个物种“纯”种群之间的中间位置，这支持了种群杂交起源的观点。对母系遗传的细胞器DNA的分析，包括检测线粒体DNA扩增产物中的单链构象多态性（SSCP），有助于进一步描绘柔毛甘豆种群之间的遗传结构。线粒体数据表明，采样地点之间细胞器分化程度很高，并确定了柔毛甘豆和斑点甘豆诊断单倍型。该数据支持了基于RAPD和RFLP-PCR对遗传结构的解释。此外，细胞核-细胞质分析可以描述杂交种群形成过程中基因转移的方向。尽管有证据表明柔毛甘豆中发生了种间杂交和基因渗入，但太平洋沿岸重要的柔毛甘豆资源种群似乎保持了其遗传完整性。文中还讨论了该属内遗传资源保护和利用方面的意义。
