Abstract
SummaryWheat is one of the most important staple crops worldwide and also an excellent model species for crop evolution and polyploidization studies. The breakthrough of sequencing the bread wheat genome and progenitor genomes lays the foundation to decipher the complexity of wheat origin and evolutionary process as well as the genetic consequences of polyploidization. In this study, we sequenced 3286 BACs from chromosome 7DL of bread wheat cv. Chinese Spring and integrated the unmapped contigs from IWGSC v1 and available PacBio sequences to close gaps present in the 7DL assembly. In total, 8043 out of 12 825 gaps, representing 3 491 264 bp, were closed. We then used the improved assembly of 7DL to perform comparative genomic analysis of bread wheat (Ta7DL) and its D donor, Aegilops tauschii (At7DL), to identify domestication signatures. Results showed a strong syntenic relationship between Ta7DL and At7DL, although some small rearrangements were detected at the distal regions. A total of 53 genes appear to be lost genes during wheat polyploidization, with 23% (12 genes) as RGA (disease resistance gene analogue). Furthermore, 86 positively selected genes (PSGs) were identified, considered to be domestication‐related candidates. Finally, overlapping of QTLs obtained from GWAS analysis and PSGs indicated that TraesCS7D02G321000 may be one of the domestication genes involved in grain morphology. This study provides comparative information on the sequence, structure and organization between bread wheat and Ae. tauschii from the perspective of the 7DL chromosome, which contribute to better understanding of the evolution of wheat, and supports wheat crop improvement.
Highlights
Bread wheat (Triticum aestivum L.) is one of the most important staple crops worldwide, providing around 19% of the total calories for humankind (FAO, www.fao.org/faostat)
The aim of this study was to provide insights into the sequence, structure and gene organization differences between bread wheat and Ae. tauschii from the perspective of the 7DL chromosome arm, which will lead to get a better understanding of the formation and evolution of wheat, and support wheat crop improvement
A 7DL BAC library was constructed from DNA of flow-sorted 7DL chromosome arms and comprises 50 304 clones with an average insert size of 116 kb, representing 14.9-fold coverage of the predicted size of 346 Mb of 7DL (Simkova et al, 2011)
Summary
Bread wheat (Triticum aestivum L.) is one of the most important staple crops worldwide, providing around 19% of the total calories for humankind (FAO, www.fao.org/faostat). With the global population continuing to grow and climate change negatively impacting agricultural productivity, more efficient and systematic approaches are urgently required to breed improved wheat cultivars with a stable yield and are well-adapted to diverse environmental stresses. The genome sequence of bread wheat is needed to better interpret the genetic variation and regulatory processes underlying key traits and to support the development of more effective breeding strategies (IWGSC, 2018). Derived from a spontaneous hybridization of diploid Aegilops tauschii (2n = 14; DD) with tetraploid wheat Triticum turgidum
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