浑善达克沙地榆遗传多样性的研究

The Study of Genetic Diversity of Ulmus pumila var. sabulosa

浑善达克沙地榆 ( Ulmuspumila var. sabulosa)是白榆的一个变种 ,天然分布于浑善达克沙地 ,在维护草原生态系统的稳定方面起着重要作用。本文应用 RAPD技术对浑善达克沙地榆的遗传多样性和系统地位进行了研究。在浑善达克沙地榆六个居群和对照白榆两个居群中 ,1 6个有效引物共获得了 1 1 5个位点 ,其中居群水平多态性位点为 49个 ,占 42 .6 ,高于 H amrick等的统计得出的平均多态位点比率 ( 3 4 ) ,表明在长期的进化过程中 ,居群内发生了较高的遗传变异 ,个体水平多态性位点为 89个 ,占 77.4。根据遗传距离进行聚类得出 :居群水平上以 0 .1为阈值 ,浑善达克沙地榆和对照白榆聚为明显的两支 ,本实验结果支持浑善达克沙地榆作为白榆一个变种的结论 ;遗传多样性指数分析表明 ,个体水平上浑善达克沙地榆各居群之间遗传距离有一定的差异 ,并与地理分布范围相关。浑善达克沙地榆由于各居群都存在相对较大的遗传变异 ,反映了在居群内具有较大的变异潜力。本实验结果也表明 ,RAPD可应用于浑善达克沙地榆遗传多样性及系统学的研究。文中还对浑善达克沙地榆的遗传变异与繁育系统的关系进行了讨论。

Ulmus pumila var. sabulosa, which classified position was disputed, is one of native trees in Hunshandake sandland, and plays important role in recovering and regenerating of grasslands ecological system. In this thesis, RAPD technique was used to study U. pumila var. sabulosa, trying to determine its systematic position and level of genetic diversity. The results are as follows:(1) 16 effective primers were used to amplify genomic DNA samples of six U. pumila var. sabulosa populations and two contrasted populations of U. pumila. Altogether 115 fragments were produced, among which 49 fragments (at a proportion of 42.6%) were polymorphic at the level of population, above the statistical average value(34%), and 89 fragments(at a proportion of 77.4%) showed polymorphism at individual level. (2)Cluster analysis (UPGMA) was performed on genetic distance. At the level of population, when threshold value was 0.1, populations of U. pumila var. sabulosa and contrasted populations can be sorted into 2 different groups. The results demonstrated that U. pumila var. sabulosa can be regarded as a variety of U. pumila. Cluster analysis of individual level indicated that there were certain differentiae among populations of U. pumila var. sabulosa, which was related to geographical distributions. (3)By means of genetic diversity index analyzing, it was indicated that there were clear genetic differentiae in populations of U. pumila var. sabulosa, and coefficient of gene differentiation was 0.20, which indicated U. pumila var. sabulosa has relatively high level of differential potentialities within populations. The results of this thesis demonstrates applicability of RAPD in the study of genetic diversity and systematics of U. pumila var. sabulosa was practicable.