Bread wheat (Triticum aestivum) became a globally dominant crop after incorporating the D genome from the donor species Aegilops tauschii, but the evolutionary history that shaped the D genome during this process remains to be clarified. Here, we propose a renewed evolutionary model linking Ae. tauschii and the hexaploid wheat D genome by constructing an ancestral haplotype map covering 762 Ae. tauschii and hexaploid wheat accessions. We dissected the evolutionary trajectories of Ae. tauschii lineages and reported a few independent intermediate accessions, demonstrating that low-frequency inter-sublineage gene flow had enriched the diversity of Ae. tauschii. We discovered that the D genome of hexaploid wheat was inherited from a unified ancestral template, but with a mosaic composition that was highly mixed and derived mainly from three Ae. tauschii L2 sublineages located in the Caspian coastal region. This result suggests that early agricultural activities facilitated innovations in D-genome composition and finalized the success of hexaploidization. We found that the majority (51.4%) of genetic diversity was attributed to novel mutations absent in Ae. tauschii, and we identified large Ae. tauschii introgressions from various lineages, which expanded the diversity of the wheat D genome and introduced beneficial alleles. This work sheds light on the process of wheat hexaploidization and highlights the evolutionary significance of the multi-layered genetic diversity of the bread wheat D genome.

中文翻译：

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面包小麦 D 基因组的进化和遗传多样性


面包小麦 （Triticum aestivum） 在整合了来自供体物种 Aegilops tauschii 的 D 基因组后成为全球主导作物，但在此过程中塑造 D 基因组的进化历史仍有待阐明。在这里，我们提出了一个将 Ae 联系起来的更新进化模型。tauschii 和六倍体小麦 D 基因组通过构建覆盖 762 Ae 的祖先单倍型图谱。Tauschii 和六倍体小麦种质。我们剖析了 Ae 的进化轨迹。tauschii 谱系并报告了一些独立的中间种质，表明低频亚谱系间基因流丰富了 Ae 的多样性。陶斯奇。我们发现六倍体小麦的 D 基因组继承自统一的祖先模板，但具有高度混合的镶嵌组成，主要来源于三个 Ae。tauschii L2 亚系位于里海沿岸地区。这一结果表明，早期的农业活动促进了 D 基因组组成的创新，并最终确定了六倍体化的成功。我们发现大多数 （51.4%） 遗传多样性归因于 Ae 中不存在的新突变。tauschii，我们鉴定了大 Ae。tauschii 从各种谱系中渗入，这扩大了小麦 D 基因组的多样性并引入了有益等位基因。这项工作阐明了小麦六倍体化的过程，并强调了面包小麦 D 基因组多层遗传多样性的进化意义。