利用节节麦-小麦单片段代换系精细定位节节麦粒重基因的研究

Thousand seed weight is one of the three elements in wheat yield components. Increase grain weight is a main target of spike character improvement, and has been the research focus of high yield and super-high-yield wheat breeding. In our previous work, the BC3F3 population derived from the crossing of bread wheat Zhoumai18 and Aegilops tauschii T093 demonstrated a 10-20% increase in thousand seed weight from 4.8% individual plant compared with that of Zhoumai18, and a single segment substitute lines 137191-3 apparently related to grain weight was also obtained. In this project, the secondary separation population will be constructed based on the crossing of 137191-3 and Zhoumai18, and polymorphism SSR markers within the range of substitution segments will be designed and screened to conduct fine mapping of Aegilops tauschii controlled grain weight gene on the foundation of published physical and genomic map of Aegilops tauschii. The other individual plant with obviously increased thousand seed weight will be detected through polymorphism SSR markers between parents. Each locus of grain weight controlled by Aegilops tauschii will be primarily located through the relative analysis of SSR markers and thousand seed weight phenotype. This project will lay foundation for further map-based cloning of Aegilops tauschii grain gene, and will also provide novel genetic resource for high yield breeding of wheat.

千粒重是小麦产量构成的三要素之一，提高千粒重是穗部性状改良的主要目标，也是目前高产和超高产小麦育种的重要研究内容。作为本项目的前期工作，我们在节节麦T093-普通小麦周18的BC3F3群体中，检测到有4.8%的单株千粒重较周18增加了10-20%，并在其中发现了一个与籽粒粒重显著相关的单片段代换系137191-3。本研究拟利用该单片段代换系与周18进一步杂交，构建次级分离群体，根据已发表的节节麦物理图谱和基因组图谱，设计并筛选在该代换片段区间的多态性SSR标记，对节节麦控制籽粒粒重基因进行精细定位；同时，利用亲本间有多态性的SSR标记对其它千粒重显著增加的单株进行检测，通过与千粒重进行相关性分析，对节节麦控制粒重的各个位点进行初步定位。研究结果为节节麦粒重基因的进一步图位克隆奠定基础，也为小麦高产育种提供新的遗传资源。

节节麦是普通小麦D基因组的供体种，按照其遗传背景的相似性可以分为D1系和D2系。由于仅有特定区域的少数D2系节节麦基因型参与了普通小麦的起源，因而使得普通小麦D基因组的多样性极为贫乏。相比较D2系节节麦，D1系节节麦的分布更为广泛，含有更为丰富的遗传多样性，为改良普通小麦D组遗传背景提供了丰富的遗传资源。本项目利用在亲本节节麦和小麦间有多态性的分子标记，通过对连续2年4个环境中的千粒重表型数据分析，精细定位出1个共有的稳定的节节麦控制籽粒粒重基因紧密连锁的分子标记Xcfd53，该QTL位点的加性效应来自节节麦，表现为正效应，最高能解释的表型效应为10.69%。同时还发现有位于其它染色体上的6个QTL位点，其中一个QTL位点在两个环境中都能检测到，表现为负效应。另外，在构建的节节麦-小麦代换系群体中，筛选出7个综合农艺性状较好、并且千粒重较高的株系，可以作为小麦高产育种的中间材料。