Submitted to: International Symposium of Molecular Breeding of Forage Turf
Publication Type: Abstract Only
Publication Acceptance Date: 6/4/2012
Publication Date: 6/4/2012
Citation: Xie, W., Bushman, B.S., Robins, J.G. 2012. A genetic linkage map of tetraploid orchardgrass (Dactylis glomerata L.) and quantitative trait loci for heading date. 7th Molecular Breeding of Forage and Turf Symposium, Salt Lake City, UT. International Symposium of Molecular Breeding of Forage Turf.
Technical Abstract: Orchardgrass (Dactyllis glomerata L.) is indigenous to Eurasia and northern Africa but has been naturalized on nearly every continent. Despite its distribution and uses, there is a need for improved late flowering germplasm for use in North American mixed pastures. Many candidate genes affecting flowering time exist in cereal grasses, including vernalization (Vrn), flowering time (Ft), and heading date (Hd) genes. To improve the understanding of genetic architecture of orchardgrass, and provide a template for a flowering time candidate gene search, the goals of the present study were to construct a tetraploid orchardgrass genetic linkage map and identify QTL associated with heading date. An F1 population of 284 individuals derived from a very late heading D. glomerata ssp. himalayensis parent and an early to mid-heading D. glomerata ssp. aschersoniana parent were measured over two years for heading date, and were genotyped using a combination of EST-derived SSR markers and AFLP markers. Two parental maps were constructed with 28 cosegregation groups and seven consenus linkage groups each. Parental linkage group lengths varied from 98 to 187 cM with an average distance between markers of 5.5 cM. Homologous linkage groups were tied together by 38 bridging markers. All but two mapped SSR markers had homologies to physically mapped rice (Oryza sativa L.) genes, and six of the seven orchardgrass linkage groups were assigned based on this putative synteny with rice. Quantitative trait loci were detected for heading date on linkage groups 2, 5, and 6 in both parental maps, explaining between 12 and 24% of the variation. Using cereal and ryegrass homologs for primer and bait design, orchardgrass sequences of candidate flowering time genes was obtained using a solution capture and amplicon sequencing methods. Of 30 candidate gene primers pairs, five showed polymorphism and were mapped in the two parent populations.