Sequence-based genetic mapping of Cynodon dactylon Pers.

Bermudagrass (Cynodon dactylon Pers.) is an important warm-season perennial used extensively for turf, forage, soil conservation and remediation worldwide. However, limited genomic information has hindered the application of molecular tools towards understanding genome evolution and in breeding new cultivars. In this study, we genotyped a first-generation selfed population derived from a tetraploid (4x=36) genotype using genotyping-by-sequencing. A high density genetic map of 18 linkage groups (LGs) was constructed with 3,544 markers. Comparative genomic analyses revealed that each of nine homeologous LG pairs of C. dactylon corresponded to one of the first nine chromosomes of Oropetium thomaeum. Two nested paleo-ancestor chromosome fusions might have resulted in a 12-to-10 chromosome reduction. A segmental dissemination of O. thomaeum chromosome 10 into C. dactylon genome (LGs 3 &4, and 5 &6) led to the 10-to-9 chromosome reduction. The genetic map will assist in an ongoing whole genome sequence assembly and facilitate marker assisted selection (MAS) in developing new cultivars.