Dihaploids result when tetraploids produce reduced eggs that develop without fertilization into diploid progeny. This process is useful for reducing genome complexity and studying trait expression at different ploidal levels. In this study we evaluated genetic inheritance and expression of diplospory (D) and parthenogenesis (P) in a population of dihaploids produced by tetraploid apomictic Erigeron. From 400 mostly maternal (tetraploid) progeny, we identified 64 (16%) dihaploids with 2n = 18 (53 plants) or 2n = 19 (11 plants). Differential interference contrast (DIC) imaging of ovules was used to evaluate megasporogenesis (meiosis vs. diplospory) and capacity for parthenogenetic embryo development. Seed production was estimated as the proportion of filled seeds. For 60 analyzed dihaploids, diplospory vs. meiosis segregated approximately 1: 1 (P = 0.44) while all exhibited parthenogenetic embryo development. Parthenogenesis for meiotic progeny (n = 27) was observed in approximately 50% of ovules. Apomictic dihaploids (combining D and P; n = 33) produced seeds with mean 24.8% (range 1.3-74.4%) of total flowers. The dihaploid population consisted of half apomicts (D + P) and half parthenogens (P only). We infer that formation of dihaploid seeds requires the parthenogenesis locus. The highest seed values obtained for diploid apomicts are comparable to those recorded for wild type polyploid apomicts. This is one of the first reports of diploid apomixis in the Asteraceae and it demonstrates that both diplospory and parthenogenesis can be transmitted and expressed at a high level in the diploid condition.
摘要：在作物野生近缘了解遗传结构是作物改良和保护重要的。最近，有两个基因库（ MI和MII）报告了野生利马豆（四季豆lunatus ）来自墨西哥，中美洲地方品种的驯化中心。然而，证据是基于有限的基因组取样。在这里，我们试图通过增加基因组和人口抽样，以确认这两个基因库的存在。我们的特点P. lunatus 67野生种群从墨西哥与10个微卫星座位和AMOVA分析，聚类分析，分配测试和地理参考地图手段研究了遗传结构。 AMOVA表明，大多数的变异是种群中（77％ ），而不是发现人群（ 23％）之内。分配测试是关键，以确认这两个基因库（ MI和MII）不仅在墨西哥的存在，但也提出在密西根州（ MIA和MIB ）中可能存在的两个亚组。而MI和MII主要分歧地域，米娅和MIB中的分布重叠。混合个人，这可能代表的基因库中的基因流动的情况下，进行检测。我们的研究结果表明，野生利马豆在墨西哥的遗传结构比较复杂比以前想象和提出三个基因库（MIA ， MIB ，和MII ） ，每一个具有较高水平的遗传多样性的存在。我们还需要更多的证据，然而，以确认无疑的基因库心肌梗死的分裂成亚米娅和MIB 。 |
