合成六倍体小麦的遗传育种

Genetic Improvement of Synthesized Hexaploid Wheat in Breeding

普通小麦是由四倍体小麦栽培类型与野生二倍体节节麦远缘杂交形成的异源六倍体。普通小麦保持了四倍体小麦的高产潜力,D基因组的加入丰富了食品加工产品类型、增强了环境适应能力。与二倍体作物不同,普通小麦有3个亚基因组,存在大量重复基因,基因组缓冲性、可塑性强,单个基因拷贝可能对育种改良的效果有限。小麦3个亚基因组的遗传多样性是不对称的,其中D基因组遗传多样性最低。通过模拟普通小麦起源过程人工创制的六倍体小麦为桥梁,可以将节节麦和四倍体小麦的遗传变异同时导入普通小麦。与普通小麦相比,人工合成小麦存在大量的优良等位变异、在转录组水平具有新的表达特征,为育种提供了有利遗传基础,在小麦育种中被寄予厚望,但是目前的应用效果还很有限。细胞学不稳定性、综合农艺性状差影响其育种利用效率。优化杂交方法和选择方法将推动人工合成小麦在普通小麦育种中的应用。

The common wheat(Triticum aestivum L.)is an allohexaploid crop species originating from the distant hybridization between the cultivated tetraploid wheat(T.turgidum L.)and the wild diploid grass Aegilops tauschii Coss.Common wheat inherits the high-yielding potential of tetraploid wheat,extends potential to make diverse food products and has broad adaptability to environments afforded by the incorporation of D genome.Different from diploid crops,common wheat hosts three sub-genomes harboring a large number of repetitive genes and shows a strong capacity of genomic buffering and plasticity.Thus,allelic variation at a single locus often results in an insubstantial effect during wheat improvement.The genetic diversity among three subgenomes of common wheat was not symmetric,and D sub-genome diversity was the lowest.By simulating the origination process of common wheat,synthetic hexaploid wheat can be produced as a bridge to incorporate the genetic variations of Ae.tauschii Coss.and tetraploid wheat into common wheat.In contrast to common wheat,synthetic hexaploid wheat harbors abundant favorable variations and owns new expression characteristics at transcriptome level,which provide novel genetic basis for breeding.Although synthetic hexaploid wheat is to be placed with great expectation,the utility remains very limited in wheat breeding.Cytological instability and poor comprehensive agronomic performance are disadvantaging in breeding utilization.Optimization of the crossing and selecting strategies will promote the application of synthetic hexaploid wheat in common wheat breeding.