A High-Density, Sequence-Enriched Genetic Map of Hordeum bulbosum and Its Collinearity to H-vulgare

Hordeum bulbosum L., a wild grass and close relative of cultivated barley (Hordeum vulgare L.), gained importance in plant breeding as inducer of haploid plants in crosses with barley and also as a genetic resource for introgression of disease resistance/tolerance genes into cultivated barley. Genetic mapping of genes introgressed from H. bulbosum is a prerequisite for their efficient utilization in barley breeding, but often hindered due to repressed recombination. The mechanism underlying the reduced frequency or lack of meiotic recombination between H. bulbosum and H. vulgare chromatin in introgressed segments is not understood. It may be explained by lack of genome collinearity or other structural differences between both genomes. In the present study, two F-1 mapping populations of H. bulbosum were analyzed by genotyping-by-sequencing (GBS) and four dense H. bulbosum genetic maps containing 1449, 996, 720, and 943 SNP markers, respectively, revealed overall a high degree of collinearity for all seven homeologous linkage groups of H. vulgare and H. bulbosum. The patterns of distribution of recombination along chromosomes differed between barley and H. bulbosum, indicating organizational differences between both genomes.