【作者】 游光霞；

【导师】 张学勇；

【作者基本信息】 中国农业科学院 ， 作物遗传育种， 2003， 硕士

【摘要】 遗传多样性是生物多样性的基本组成部分，是种内不同群体之间或同一群体内部不同个体之间遗传差异的总和。研究物种的遗传多样性，不仅可以为遗传资源的收集与保存工作提供理论指导，还可以为物种的起源、进化和分类的研究以及核心种质的构建提供重要的理论依据。同时，对资源的有效利用也具有十分重要的意义。 本文围绕着“五十年来黄淮冬麦区选育品种的遗传多样性变化及核心种质的构建”等问题，利用SSR的分子标记技术，主要研究了以下两个基本问题：首先，以96份随机样品为材料，探讨了客观反映品种间遗传关系所需的最少SSR位点数(等位变异数)；其次，以该区选育品种的448份初选核心种质样品为材料，研究了黄淮冬麦区选育品种的遗传多样性结构及其五十年来的多样性变化，并探讨了其核心种质的构建问题。得到以下主要结论： 1．客观反映小麦品种间的遗传关系至少需要73个多态性较好的SSR位点，位点的选取必须覆盖小麦A、B、D基因组的所有21条染色体。样本的大小对所需位点数的影响甚微。 2．我国小麦地方品种与选育品种是两个相对独立的遗传群体，地方品种的遗传多样性明显地高于选育品种。 3．在我国普通小麦的遗传资源中，虽然B基因组拥有最高的遗传多样性，但地方品种与选育品种之间的遗传差异可能主要存在于D基因组，地方品种在D基因组中拥有较多的特异性等位变异。 4．黄淮冬麦区选育品种间存在着较大的遗传差异，其遗传相似系数的平均值仅为0.329．五十年来，黄淮冬麦区完成了5-6次品种更换，小麦品种的遗传结构发生了很大变化。从整体上看，80年代以前育成的品种，其遗传多样性和品种间的遗传差异都有一个不断上升的趋势；80年代育成的品种其平均等位变异丰富度还呈上升趋势，但其遗传离散系数和品种间的遗传差异却呈下降趋势；到了90年代，其育成品种的遗传多样性和品种间的遗传差异均存在一个较为明显的下降趋势，其品种间的平均遗传距离已急剧下降到0.650，应引起我们的注意。 5．从各种取样方法保留等位变异的效果看，建立在聚类图基础上的随机取样法和定向取样法都可以建立较好的核心种质，而定向地选取拥有年代特异等位变异品种的取样方法效果则更好，但是这种取样方法可能会丢失部分重要育种材料或生产品种，如果能在其基础上补充进这部分材料或品种，则可取得更令人满意效果。 6.建立了195个品种的黄淮冬麦区选育品种的核心种质。此核心种质具有很好的代表性，它保留了该区选育品种93.3%的遗传多样性:其基本包含了该区选育品种的全部重要育种材料和生产品种，以及许多特异的遗传材料，包括许多矮秆材料、早熟材料、大穗资源、多穗资源、抗逆抗病品种。更多还原

【Abstract】 Genetic diversity is the fundamental element of biodiversity, including the genetic differentiation between populations in a species and the genetic variation among individuals within a population. Genetic diversity research is helpful for collection, conservation and efficient utilization of the genetic resources. It is also useful for studying the origin, evolution and classification of species.Two main problems were focused on in this paper. Firstly, the minimum number of SSR loci (alleles) needed to reveal the genetic relationships in wheat varieties was investigated with 96 random samples. Secondly, genetic diversity of 448 candidate core collections of modern varieties was assayed, which were released in Yellow and Huai River Valley Winter Wheat Region in the past half century. The major conclusions are following.1. More than 73 highly informative SSR loci are needed to reveal the genetic relationships realistically in wheat varieties. The SSR loci must cover all of the 21 chromosomes of wheat. Sample size has no evident effect on the loci needed.2. Chinese modern varieties and the landraces are two relatively independent populations. Genetic diversity of the landraces is much higher than that of the modern varieties.3. B genome showed the highest genetic diversity among the three genomes in Chinese common wheat. However, the main genetic differentiation between the landraces and the modern varieties existed in the D genome. The D genome of the landraces conveys more specific alleles.4. High genetic differentiation exists in the modern varieties released in Yellow and Huai River Valley Winter Wheat Region since 1949. Their average genetic similarity index is only 0.329. In the past five decades, the genetic diversity of the modern varieties in this region changed strongly due to the 5-6 times of variety replacements. Genetic diversity increased before 1980s, which was supported by changes of average genetic richness, Simposon index and average genetic distance among varieties released in each decade. Average allelic richness of the varieties reached the highest in varieties released in1980s. However, since this time, the average genetic dispersion indices among varieties have decreased. In varieties released in 1990s, both average allelic variation and Simposon index significantly decreased. We should pay attention to this phenomenon.5. Evaluation by the ability to keep allelic variation shows that a good core collection can be developed by random sampling or directed sampling based on the dendrogram of SSR data. Directed sampling based on decade-specific alleles can keep more variation, but the core collection developed by this sampling strategy may discard some important varieties having taken essential role in production and breeding. Therefore, a perfect core can be built if these varieties can be added to.6. A core collection of 195 entries was developed for the modern varieties in Yellow and Huai River Valley Winter Wheat Region. This core collection, which covers 93.3 percent of the genetic diversity of the modern varieties in this region, is a high-quality core. It holds all of the important varieties in production and breeding and many specific germplasms such as dwarf materials, early ripening varieties, and many varieties with large spikes or muti-spikelets, and varieties with stress resistance or resistance to diseases.更多还原