Peach:: The model genome for Rosaceae

For genome comparative studies and identification of important genes, it is critical to have adequate genomic resources in key model species. These resources include saturated genetic maps, large-insert genomic libraries, and physicalmaps that are integrated with the genetic maps. Such resources exist for Brassicaceae (Arabidopsis), Solanaceae (tomato) and the Poaceae (rice), but not for Rosaceae. In Rosaceae, we are building genomic resources in a tree species (peach) with a genome size only twice that of Arabidopsis. Our goal is to develop peach as a model for identification, characterization, and cloning of important genes of Rosaceae species. Consequently, we have produced saturated molecular marker linkage maps in several peach crosses segregating for important traits, both simple and complex. Because fruit quality is the single most important character to scion breeders, we have concentrated on mapping important fruit quality traits. The mapped molecular markers serve as landmarks for isolation of genes associated with important traits, and facilitate their maintenance during introgression of other tree characters, such as disease and pest resistance. They can also be used to align genetic maps in related species, facilitating gene marking and gene discovery. We are constructing a BAC physical map for peach and are integrating this map with genetic maps from other Rosaceae and key model species. These initial physical mapping studies will be presented.