Wheat is one of the most important food crops in the world and its continued breeding is essential to achieve the production goals set by FAO in 2050. Breeding programs benefit from the development of genomic resources that reduce time and costs of selection of suitable varieties. Recent evidence has suggested that an important fraction of crop plant genomes exhibits presence-absence variation and cannot be exploited following the single reference paradigm. Pangenomic studies aim to fill this vacuum by creating a complete catalogue of genes in a species and characterizing them. With the release of the first wheat draft genome for cultivar Chinese Spring, we are able to explore the wheat pangenome. In the first chapter I performed a review of the current status of wheat genomics and pangenomic studies. In the second chapter the public wheat reference is assessed for its suitability as the basis of a pangenomic study. Extensive uncollapsed duplicated sequences and the absence of support for some gene models prompted us to reassemble the genome. Both assemblies were then compared and the new assembly was selected for further study. In the third chapter, eighteen wheat cultivars were used to extend the Chinese Spring reference. A metagenomics assembly approach was employed and 350 Mbp of additional sequence absent from the Chinese Spring reference were assembled. These sequences contained over 20,000 additional genes which were classified into core and variable genes and later characterized. The pangenome size was modelled as a function of the number of genomes and functional enrichment of the variable genes showed that these were enriched with genes involved in response to biotic and abiotic stress. In chapter 4, we use the new pangenome to identify over 34.6 million SNPs and further use these SNPs to characterize core and variable genes, to construct a high density genetic map and to assess the relatedness of the cultivars used in this study. We show that the variable genes have a higher SNP density particularly for non-synonymous SNPs. The results show that the synthetic cultivar W7984 is the most divergent accession alongside Chinese Spring. Finally, in chapter 5, the future of pangenomic studies is evaluated with a critique and suggestions to improve the current wheat pangenome.
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