尾叶桉生长和材性基因作用方式及其育种群体的遗传分化特点

In order to understand the degree of genetic variation at different levels in detail among provenances / families deeply, and find out the correlation of phenotypic and genotypic among interesting traits of growth, wood density and fiber shape, we plan to assess the genetic differences of these traits on three generation breeding population established of E. urophylla. Parent GCA / SCA, additive effect and non-additive effect of the growth and wood properties will be estimated on the current hybrid testing trials, so as to reveal the parents genetic characters and the genetic control pattern in gene recombination. Phenotypic differentiation coefficient (QST) will be calculated based on all the interesting traits, to detect the degree of phenotypic differentiation on E. urophylla breeding population. Meanwhile, a Q-type clustering analysis will be performed also based on the interesting traits towards learning the regularities of the traits variations among clusters. Another work is to explore genetic diversity and genetic structure of natural provenances using microsatellite loci on 1st generation breeding population. Compare the clustering analysis based on Nei’s unbiased genetic distance in UPGMA method and Q-type clustering, to check whether the clusters based on two method will coincide with each other, and to study the relationship between every cluster and the geographical data of their provenances. What we mainly dedicate is to detect the characteristic of inheritance of gene information among three generation, genetic lineage and diversity among three generation breeding population of E. urophylla. All the finding in this study will provide a scientific basis not only for the selection of genetic materials in advanced population improvement on E. urophylla systematically, and also for the selection of plus families and trees when controlling pollination, so that great genetic gains will be got in a short-term breeding program.

评估尾叶桉三代育种群体生长、木材密度和纤维形态等指标的遗传变异，了解尾叶桉育种群体种源家系的遗传变异水平，分析尾叶桉生长和材性性状间的表型及遗传相关。分析尾叶桉杂交子代生长和材性的亲本配合力、加性和非加性效应，揭示尾叶桉目标性状基因重组时的亲本遗传特点及其基因作用方式。结合生长和材性等性状估算尾叶桉育种群体的表型分化系数(QST)揭示其表型分化程度，并进行Q型聚类，分析各类群间性状差异的规律。借助微卫星标记分析尾叶桉第一代育种群体天然种源的遗传多样性和遗传结构，并对比其基于遗传距离的UPGMA聚类与Q型聚类的结果，总结表型变异与遗传基础的吻合程度，揭示各类群与其种源分布的关系。重点评估三代尾叶桉育种群体间的遗传信息传递特点、遗传亲缘关系及多样性的变化。综合上述研究，以期为尾叶桉的高世代改良提供遗传材料选择的依据，也为尾叶桉优良家系和单株的选配提供理论指导，以大幅提升其短期改良的遗传增益。

尾叶桉是我国最重要的桉树改良树种之一。长期以来国内积累了丰富的尾叶桉种质资源。目前，国内的尾叶桉改良已处于第二或第三代。尾叶桉高世代群体是在其第一、第二代育种群体内，经高强度人工选择得到的优良家系的自由授粉子代，遗传基础较之前的世代群体发生了很大的变化。因此，在推进尾叶桉进入下一世代的改良，选择构成下一代群体的遗传材料之前，了解各世代群体目标性状的遗传变异规律，及其遗传基础的变化则尤为重要。本研究全面分析了尾叶桉各世代群体生长和木材密度的遗传变异规律，并利用微卫星位点系统分析了尾叶桉第一代引种群体的遗传多样性、遗传结构和遗传分化等，及其高世代群体的遗传多样性，重点对比了各世代群体遗传多样性、世代间基因流及遗传分化的变化规律。主要研究结果包括：(1) 尾叶桉三代群体木材密度和生长性状的表型变异在种源和亚群体间都存在显著的遗传差异。胸径的多重聚类分析显示，第一代群体种源Apui、Arnau、Old Uhak和Ilwaki间存在显著的表型分化。树高的聚类分析则显示更多的天然种源间存在显著的表型分化。木材密度的多重聚类显示，种源Mandiri、Lewotobi、Wukoh、Egon1和Bangat间存在显著的表型分化。因群体构成材料为上一世代的自由授粉子代，尾叶桉第二代和第三代生长和木材密度的表型分化不明显。(2) SSR基因分型显示，尾叶桉每个世代的等位基因数(Na)、有效等位基因数(Ne)和Shannon信息指数(I)都在逐代增加。群体基因丰富度(AR)和私有等位基因(Npa)以第二代育种群体最大。相较第一代，尾叶桉第二代和第三代育种群体的期望杂合度(He)和观测杂合度(Ho)均呈增长趋势，说明第二代和第三代育种群体的遗传多样性在逐代增加。Wright指数(F)显示，三个世代内群体的遗传分化程度均不高，但第三代群体的遗传分化相对最高，反映其内部的遗传差异较大。本项目的研究结果有望为尾叶桉育种群体的世代改良和目标性状改良提供理论基础，也为更好的利用尾叶桉的杂种优势，制定优良亲本的选配方案开发新品种提供理论依据。

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