Triticum aestivum cultivar:Chinese Spring Genome sequencing and assembly. Triticum aestivum cultivar:Chinese Spring

Sequencing the bread wheat (Triticum aestivum L.) genome is a challenging task because of its size (17Gb) and hexaploid status (2n=6x=42 AABBDD). However, flow sorting of individual chromosomes has allowed us to purify and shotgun sequence telocentric chromosomes 4DS and 4DL. A survey sequence was obtained by pyrosequencing of flow-sorted 4DS (7.2x) and 4DL (4.1x) arms. Single ends (SE) and long mate pairs (LMP) reads were assembled into contigs (223Mb) and scaffolds (65Mb) that were aligned to the bread wheat D-genome ancestor Aegilops tauschii draft genome assembly and physical map, anchoring 34 Mb to chromosome 4. Structural annotation of scaffolds larger than 6Kb rendered 822 gene models. A virtual gene order comprising 1,973 wheat orthologous gene loci and 381 wheat gene models was build. This order was largely consistent with the scaffold order determined based on a published high density map from the Ae. tauschii chromosome 4, using bin-mapped 4D ESTs as a common reference. Comparisons with the other chromosomes of the homoeologous group 4, showed a higher collinearity with 4B compared to 4A. Additionally, a combination of different approaches allowed the construction of a virtual map and the prediction of ~5,700 genes on bread wheat chromosome 4D (~2,200 on 4DS and 3,500 on 4DL). The information provided here is a valuable tool for understanding the structure of this chromosome and for its use in breeding programs.