紫薇栽培品种的起源与遗传关系研究

Crape myrtles (Lagerstroemia indica L.), belonging to the genus Lagerstroemia of the family Lythraceae, are famous and important woody plants for ornament and environmental protection. However, the decreased resistances caused by inbreeding depression have occurred during the breeding practice of crape myrtle cultivars. How to reasonably utilize the extant germplasm resources of cultivars and closely related species of Lagerstoemia and how to conduct germplasm innovation are key problems to be resolved. Elucidating the genetic relationship and origins of crape myrtle cultivars of Lagerstroemia is a fundamental scientific issue. Thus, in this study, in order to improve efficiency of directed breeding, high-throughput sequencing technique is to be employed to collect genetic information from the chloroplast genome, nuclear genes and SSR (simple sequence repeats) loci for reconstruction of the phylogeny of Lagerstroemia, clarification of the origins and genetic relationship of crape myrtle cultivars, and realization of their accurate identification at molecular level. This study is of important value for breeding, and for conservation and reasonable utilization of Lagerstroemia germplasm resources.

紫薇是千屈菜科紫薇属的灌木或乔木，是著名的观赏花木和重要的环保树种。然而，在紫薇栽培品种的育种中，出现了近交衰退、抗性较低等问题。如何利用现有的紫薇品种种质资源和野生近缘物种进行种质的创新是必须要解决的关键问题。阐明紫薇栽培品种的遗传关系及品种的起源是一个基础的科学问题。因此，为了提高定向育种的效率，本项目拟利用叶绿体基因组、核基因序列以及微卫星分子标记等遗传信息，重建紫薇属植物的系统发育关系，揭示紫薇栽培品种的起源及品种间的遗传关系，实现紫薇栽培品种的分子鉴定。本研究对于紫薇栽培品种的选育及紫薇种质资源的保护与合理利用具有重要价值。

系统发育分析结果显示，该属为单系群，内部含有4个进化分支。我们的年代分析显示，紫薇属起源于古新世晚期（the late Paleocene, 6000万年前），在中新世中期(the middle Miocene)开始多样化。大多数物种的多样化主要发生在更新世（the Pleistocene）。植物鉴定是植物科学研究的基础。为了准确鉴定、正确命名和数字化管理全球植物，本文报道，在一个核苷酸分子水平上选择和利用分子性状的新方法。经过筛选的单核苷酸多态位点来自叶绿体基因组的大单拷贝区，作为关键的分子性状用于编制分子分类检索表，可以精确鉴定紫薇属物种。我们的方法对于全球紫薇属植物资源的分类修订、数字化管理、保护和利用具有重要价值。