Rapid Isolation of a Disease Resistance Gene in Hexaploid Wheat By Generating a Cultivar-Specific Long-Range Chromosome Assembly

A better understanding of genes that control agriculturally important traits will be paramount to breed high-yielding and stress-tolerant cereals. Many cereals however have large and complex genomes, which hampered the isolation of genes in the past. ‘Positional cloning’ or ‘map-based’ cloning is a frequently used approach to isolate genes that does not require prior knowledge about the gene product or the strategy of gene validation. One of the most critical steps during positional cloning is the generation of high-quality sequence information that spans the region of the gene of interest. Because gene content and gene order can differ dramatically between cultivars of the same cereal species, this sequence information needs to be generated from a donor line that carries the gene of interest. This requirement represented a major obstacle for many gene cloning projects in the past, particularly in cereals with large and complex genomes. Here, we combined lossless genome complexity reduction and long-range scaffolding to rapidly and inexpensively obtain sequence information from a hexaploid wheat cultivar containing a leaf rust resistance gene.