Genome architecture of the allotetraploid wild grass Aegilops ventricosa reveals its evolutionary history and contributions to wheat improvement

The allotetraploid wild grass Aegilops ventricosa (2n = 4x = 28, genome D^vD^vN^vN^v) has been recognized as an important germplasm resource for wheat improvement owing to its ability to tolerate biotic stresses. In particular, the 2N^vS segment from Ae. ventricosa, as a stable and effective resistance source, has contributed greatly to wheat improvement. The 2N^vS/2AS translocation is a prevalent chromosomal translocation between common wheat and wild relatives, ranking just behind the 1B/1R translocation in importance for modern wheat breeding. Here, we assembled a high-quality chromosome-level reference genome of Ae. ventricosa RM271 with a total length of 8.67 Gb. Phylogenomic analyses revealed that the progenitor of the D^v subgenome of Ae. ventricosa is Ae. tauschii ssp. tauschii (genome DD); by contrast, the progenitor of the D subgenome of bread wheat (Triticum aestivum L.) is Ae. tauschii ssp. strangulata (genome DD). The oldest polyploidization time of Ae. ventricosa occurred ∼0.7 mya. The D^v subgenome of Ae. ventricosa is less conserved than the D subgenome of bread wheat. Construction of a graph-based pangenome of 2AS/6N^vL (originally known as 2N^vS) segments from Ae. ventricosa and other genomes in the Triticeae enabled us to identify candidate resistance genes sourced from Ae. ventricosa. We identified 12 nonredundant introgressed segments from the D^v and N^v subgenomes using a large winter wheat collection representing the full diversity of the European wheat genetic pool, and 29.40% of European wheat varieties inherit at least one of these segments. The high-quality RM271 reference genome will provide a basis for cloning key genes, including the Yr17-Lr37-Sr38-Cre5 resistance gene cluster in Ae. ventricosa, and facilitate the full use of elite wild genetic resources to accelerate wheat improvement.