Riera-Lizarazu O, Leonard J M, Tiwari V K, Kianian S F
Department of Crop and Soil Science, Oregon State University, Corvallis, OR 97331-3002, USA.
Cytogenet Genome Res. 2010 Jul;129(1-3):234-40. doi: 10.1159/000312723. Epub 2010 May 22.
Radiation hybrid (RH) mapping is based on radiation-induced chromosome breakage rather than meiotic recombination, as a means to induce marker segregation for mapping. To date, the implementation of this mapping approach in hexaploid (Triticum aestivum L.; 2n = 6x = 42; AABBDD) and tetraploid (T. turgidum L.; 2n = 4x = 28; AABB) wheat has concentrated on the production of mapping panels for individual chromosomes. In order to extend the usefulness of this approach, we have devised a method to produce panels for the simultaneous mapping of all chromosomes of the D subgenome of hexaploid wheat. In this approach, seeds of hexaploid wheat (AABBDD) are irradiated and the surviving plants are crossed to tetraploid wheat (AABB) to produce a mapping panel based on quasi-pentaploids (AABBD). Chromosome lesions in the A and B genomes are largely masked in the quasi-pentaploids due to the presence of A- and B-genome chromosomes from the tetraploid parent. On the other hand, the chromosomes from the D-genome are present in one copy (hemizygous) and allow radiation hybrid mapping of all D-genome chromosomes simultaneously. Our analyses showed that transmission of D-genome chromosomes was apparently normal and that radiation-induced chromosome breakage along D-genome chromosomes was homogeneous. Chromosome breakage levels between D-genome chromosomes were comparable except for chromosome 6D which suffered greater chromosome breakage. These results demonstrate the feasibility of constructing D-genome radiation hybrids (DGRHs) in wheat.
辐射杂种（RH）图谱绘制基于辐射诱导的染色体断裂而非减数分裂重组，以此作为诱导标记分离进行图谱绘制的一种手段。迄今为止，这种图谱绘制方法在六倍体（普通小麦；2n = 6x = 42；AABBDD）和四倍体（硬粒小麦；2n = 4x = 28；AABB）小麦中的应用主要集中在单个染色体图谱绘制群体的构建上。为了拓展这种方法的用途，我们设计了一种方法来构建用于同时绘制六倍体小麦D亚基因组所有染色体的群体。在这种方法中，对六倍体小麦（AABBDD）的种子进行辐照，然后将存活的植株与四倍体小麦（AABB）杂交，以产生基于准五倍体（AABBD）的图谱绘制群体。由于四倍体亲本中A和B基因组染色体的存在，A和B基因组中的染色体损伤在准五倍体中大多被掩盖。另一方面，D基因组的染色体以单拷贝形式存在（半合子），从而能够同时对所有D基因组染色体进行辐射杂种图谱绘制。我们的分析表明，D基因组染色体的传递显然正常，并且沿D基因组染色体辐射诱导的染色体断裂是均匀的。除了6D染色体遭受的染色体断裂更多外，D基因组染色体之间的染色体断裂水平相当。这些结果证明了在小麦中构建D基因组辐射杂种（DGRH）的可行性。
