BACKGROUND:Triticeae, the tribe of wheat grasses, harbours the cereals barley, rye and wheat and their wild relatives. Although economically important, relationships within the tribe are still not understood. We analysed the phylogeny of chloroplast lineages among nearly all monogenomic Triticeae taxa and polyploid wheat species aiming at a deeper understanding of the tribe's evolution. We used on- and off-target reads of a target-enrichment experiment followed by Illumina sequencing. RESULTS:The read data was used to assemble the plastid locus ndhF for 194 individuals and the whole chloroplast genome for 183 individuals, representing 53 Triticeae species and 15 genera. We conducted Bayesian and multispecies coalescent analyses to infer relationships and estimate divergence times of the taxa. We present the most comprehensive dated Triticeae chloroplast phylogeny and review previous hypotheses in the framework of our results. Monophyly of Triticeae chloroplasts could not be confirmed, as either Bromus or Psathyrostachys captured a chloroplast from a lineage closely related to a Bromus-Triticeae ancestor. The most recent common ancestor of Triticeae occurred approximately between ten and 19 million years ago. CONCLUSIONS:The comparison of the chloroplast phylogeny with available nuclear data in several cases revealed incongruences indicating past hybridizations. Recent events of chloroplast capture were detected as individuals grouped apart from con-specific accessions in otherwise monopyhletic groups.

译文

背景:小麦草部落的木耳科,藏有谷类大麦,黑麦和小麦及其野生近缘种。尽管在经济上很重要,但部落之间的关系仍然不明。我们分析了几乎所有单基因组的小麦类群和多倍体小麦种中的叶绿体谱系的系统发育,目的是更深入地了解部落的进化。我们使用了靶标富集实验的靶上和靶外读数,然后进行了Illumina测序。
结果:所读取的数据用于组装194个个体的质体基因座ndhF和183个个体的全叶绿体基因组,分别代表53个小麦属和15个属。我们进行了贝叶斯和多物种合并分析,以推断关系并估计分类单元的发散时间。我们提出了最全面的过时小麦小麦叶绿体系统发育史,并在我们的研究结果框架中回顾了先前的假设。不能确认小麦属叶绿体的单亲性,因为无论是布鲁姆氏菌还是沙棘草都从与布鲁姆氏菌祖先密切相关的血统中捕获了叶绿体。 Triticeae的最新共同祖先大约发生在10到1900万年前。
结论:在一些情况下,叶绿体系统发育和可用核数据的比较表明不一致,表明过去的杂交。叶绿体捕获的最新事件被检测为是个体,除了同种分型以外,还以其他单药形式分组。

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