A High Density Genetic Linkage Map for Northern Red Oak (Quercus rubra L.)

Oaks (Quercus spp.) are ecologically significant components of hardwood forests in the northern hemisphere and are the most species-rich genus within the Fagaceae (oaks, chestnuts, and beeches). Q. rubra is the most wide-ranging species in Quercus section Lobatae, the oak section native only in the Americas. Despite the huge ecological and economic importance of Q. rubra, a dominant species in the oak forests of Eastern North America, genetic studies were quite limited until recently. Using parentage analysis, we have identified 509 full sib progeny from a single seed parent.  All progeny were genotyped with 37 gSSR and 39 EST-SSR derived from Q. rubra, 40 EST-SSR previously mapped in European pedunculate oak Q. robur L. (Quercus section Quercus) and one EST-SSR marker from Castanea mollissima Blume. A subset of the full sib family (225) was also genotyped with ddRADtag markers. Our current consensus map includes 117 gSSR and EST-SSR framework markers and 2736 ddRADtag markers with an average distance between markers of ~0.45 cM. We have the expected number of linkage groups (12), each of which is tagged to the Q. robur linkage map using the 40 EST-SSR markers mapped in both species. Our map reveals a high degree of marker colinearity between northern red oak and pedunculate oak, suggesting that these two species share quite similar genome architecture. This map will serve as a basic foundation for the study of the genetic architecture of adaptive traits and genome evolution in the genus Quercus.