Graduate School of Agricultural Science, Kobe University, Kobe, Hyogo, Japan.
Western Region Agricultural Research Center, National Agriculture and Food Research Organization, Fukuyama, Hiroshima, Japan.
PLoS One. 2023 Apr 27;18(4):e0284408. doi: 10.1371/journal.pone.0284408. eCollection 2023.
Allopolyploid speciation is a major evolutionary process in wheat (Triticum spp.) and the related Aegilops species. The generation of synthetic polyploids by interspecific crosses artificially reproduces the allopolyploidization of wheat and its relatives. These synthetic polyploids allow breeders to introduce agriculturally important traits into durum and common wheat cultivars. This study aimed to evaluate the genetic and phenotypic diversity in wild einkorn Triticum monococcum ssp. aegilopoides (Link) Thell., to generate a set of synthetic hexaploid lines containing the various Am genomes from wild einkorn, and to reveal their trait characteristics. We examined the genetic diversity of 43 wild einkorn accessions using simple sequence repeat markers covering all the chromosomes and revealed two genetically divergent lineages, L1 and L2. The genetic divergence between these lineages was linked to their phenotypic divergence and their habitats. L1 accessions were characterized by early flowering, fewer spikelets, and large spikelets compared to L2 accessions. These trait differences could have resulted from adaptation to their different habitats. We then developed 42 synthetic hexaploids containing the AABBAmAm genome through interspecific crosses between T. turgidum cv. Langdon (AABB genome) as the female parent and the wild einkorn accessions (AmAm genome) as the male parents. Two of the 42 AABBAmAm synthetic hexaploids exhibited hybrid dwarfness. The phenotypic divergence between L1 and L2 accessions of wild einkorn, especially for days to flowering and spikelet-related traits, significantly reflected phenotypic differences in the synthetic hexaploids. The differences in plant height and internodes between the lineages were more distinct in the hexaploid backgrounds. Furthermore, the AABBAmAm synthetic hexaploids had longer spikelets and grains, long awns, high plant heights, soft grains, and late flowering, which are distinct from other synthetic hexaploid wheat lines such as AABBDD. Utilization of various Am genomes of wild einkorn resulted in wide phenotypic diversity in the AABBAmAm synthetic hexaploids and provides promising new breeding materials for wheat.
异源多倍体形成是小麦（Triticum spp.）和相关的冰草属（Aegilops）物种的主要进化过程。通过种间杂交产生的合成多倍体人工再现了小麦及其亲缘物种的异源多倍化。这些合成多倍体使育种家能够将农业上重要的性状引入硬质小麦和普通小麦品种中。本研究旨在评估野生一粒小麦 Triticum monococcum ssp. aegilopoides (Link) Thell. 的遗传和表型多样性，生成一套含有野生一粒小麦各种 Am 基因组的合成六倍体系，并揭示其性状特征。我们使用覆盖所有染色体的简单序列重复标记，对 43 个野生一粒小麦进行了遗传多样性分析，揭示了两个遗传上不同的谱系，L1 和 L2。这些谱系之间的遗传分化与它们的表型分化及其生境有关。与 L2 相比，L1 品系具有早开花、小穗和大穗的特点。这些性状差异可能是由于它们对不同生境的适应。然后，我们通过将硬质小麦品种 Langdon（AABB 基因组）作为母本，与野生一粒小麦品系（AmAm 基因组）作为父本进行种间杂交，开发了 42 个含有 AABBAmAm 基因组的合成六倍体。其中 2 个 AABBAmAm 合成六倍体表现出杂种矮化现象。野生一粒小麦 L1 和 L2 品系之间的表型分化，特别是开花天数和小穗相关性状，在合成六倍体中显著反映了表型差异。在六倍体背景下，谱系间的株高和节间差异更加明显。此外，AABBAmAm 合成六倍体具有较长的小穗和籽粒、长芒、较高的株高、柔软的籽粒和晚开花的特点，与其他合成六倍体小麦品系（如 AABBDD）不同。利用野生一粒小麦的各种 Am 基因组，在 AABBAmAm 合成六倍体中产生了广泛的表型多样性，为小麦提供了有前途的新育种材料。
