Comparative Genetic Mapping in American and European Oaks

We report progress on a densely populated genetic map for northern red oak (Q. rubra) and relate these linkage groups with those reported for Q. robur.  Our mapping population consists of 320 full sib progeny, 250 of which are now clonally replicated in two different locations.  Marker types include gSSR from Q. rubra, EST-SSR from Q. rubra, EST-SSR mapped in Q. robur and SNPs from RAD-tag sequences.  Our population structure and replicated design will enable us to map QTL for bud burst, leaf morphology and marcescence, three characters for which the parents differ and can be scored reliably in juveniles. The red oaks of the Americas (Quercus section Lobatae) occur in sympatry with white oaks (Quercus section Quercus) across a wide array of forest communities and ecological niches.  Unlike the white oaks of Eastern North America and Northern Europe, which share a recent common ancestry and hybridize readily with each other, the red oaks are limited to North and Central America and are not proven to hybridize with any white oak, despite rampant interspecific hybridization within their own section.  This suggests that the barrier between the sections is genetic, not ecological. We will use our genetic map, as well as the other tools we are generating for North American hardwoods, to study interspecific hybridization within sections, infer chromosome evolution, detect stress resistance QTL and determine the extent of synteny and colinearity between section Quercus and section Lobatae, the two most speciose sections of the Quercus genus.