濒危资源植物甜菜树的种质保护及其系统位置研究

Yunnanopilia longistaminea is an important resource plant which is endemic to south-western China. The species had been put in different genera hinting its significance in the phylogeny of Opiliaceae. More urgently it was in the danger of severe population decreasing due to excess untilization and habitat disturbance. However,less researches were reported about its breeding biology and conservation except general classification.Based on former field investigaton and collection of data, we focused on studying the breeding system and germplasm conservation of this species,as well as its phylogeny through field and labratary experiments in this program. Specifically, the population stucture,habitat disturbance and pollination biology will be studied by using field and laboratory experiments to ascetain its survival condition and reproduction charactersitics.The genetic structure and genetic variations will be studied by using sequencing and analysis of cpDNA and nrDNA,to probe its ESU(Evolutionary significant unit). Furthermore, the seed physiology and seedling cultivation will be studied for setting its viable artificial propagation technology. Based on the convenience of sampling in Yunnan,the relationship of this species with allid taxa will also be studied and verified by using synthetic morphology and molecullar systematics. Through the implementation of this research program, the protection strategies and population preservation measurements,as well as viable artificial propagation technology of Yunnanopilia longistaminea will be put forward opportunely, providing meaningful and referential ideas and case studies for the preservation of other endangered plants.

甜菜树为我国西南特有的珍贵优质野生资源植物，其系统地位仍存在争议，同时因过度利用和生境恶化，其种群已大量减少处于极度濒危状况，但该物种除了分类等报道外很少被研究。本项目拟在前期资源分布调查与相关研究的基础上，通过野外与室内实验，对甜菜树的种质保护及其系统学进行研究。项目主要采用野外观察和实验方法，研究甜菜树的种群结构、生境干扰、传粉生物学特征，揭示甜菜树的繁殖生态特性及生存状况；同时基于cpDNA 和nrDNA基因片段测序研究甜菜树自然居群的遗传多样性及遗传分化，确定其进化显著单元（ESU）及优先保护居群；同时通过种子生理与幼苗繁殖试验获得该物种的可行人工繁育技术；此外，利用采样便利条件，通过综合比较形态学和分子系统学方法，深入探讨该植物与近缘类群的系统分类关系，以期澄清其分类地位。最终提出甜菜树种质资源保护方案及人工繁殖抚育技术，为该珍贵种质资源的保护提供科学依据和可行技术。

本项目以濒危资源植物甜菜树为研究对象，通过野外调查和室内试验研究对其种质保护和系统学位置开展了研究，取得了以下主要成果：（1）甜菜树野生居群均被过度采摘、破坏现象严重，罕见开花结实野生个体。同时由于其居群数量少，且分布片段化，导致其生存受到威胁，野生种群处于濒危状态；（2）甜菜树种子存在生理上胚轴休眠，对脱水敏感。甜菜树种子萌发过程分为两个阶段：第一阶段为胚根伸长突破种皮，第二阶段为胚芽突出。低温层积将有效缓解上胚轴休眠，促进胚芽的突出。（3）基于cpDNA和nrDNA序列分析的保护遗传学研究表明，甜菜树物种水平上的遗传多样性较高，而总核苷酸多样性低；根据单倍型多态性和核苷酸多态性推测甜菜树在冰期可能存在两个冰期避难所。根据甜菜树16个居群的单倍型地理分布以及单倍型间的AMOVA分析，可划分出5个进化显著单元（ESU A-E）；（4）综合比较形态学和分子系统学研究表明，甜菜树应为山柚子科的单型属的一种，相对于台湾山柚，泰国山柚与它有更近的亲缘关系。上述研究为甜菜树的种质保护和种群恢复提供了科学依据。