A High Density GBS Map of Bread Wheat and Its Application for Genetic Improvement of the Crop

Genotyping-by-sequencing (GBS) is a high-throughput genotyping approach starting to be used in several crop species, including bread wheat. CIMMYT’s Seeds of discovery project has characterized more than 40,000 wheat gene bank accessions through this method. Therefore, anchoring GBS tags on chromosomes is an important step to utilize them for the wheat genetic improvement. Here we use genetic linkage mapping to construct a consensus map containing 20,490 markers including more than 19,000 GBS tags, some hybridization-based DArT and SSRs. Three RIL populations: PBW343 × Kingbird, PBW343 × Kenya Swara and PBW343 × Muu were used which shared a common parent to minimize the impact of potential structural genomic variation on consensus-map quality. Consensus map comprises 2,852 unique positions and covers a total genetic distance of 5,699 cM. Significant variation of recombination frequency and segregation distortion was observed. The consensus map was validated through comparing positions of the known rust resistance genes. The map was also compared with recently published wheat reference genome sequence and ratio of genetic and physical distance was estimated to be around 0.34cM/Mb. Further, comparison of the chromosome arm length of wheat variety “Chinese spring” with genetic distance covered by the map resulted in to ratio of 25.23 cM/µm averagely. The consensus map should provide a useful basis for analyzing genome-wide variation of complex traits.