Rosaceae conserved orthologous set (RosCOS) markers as a tool to assess genome synteny between Malus and Fragaria

Intertribal comparisons of genome synteny between phylogenetically distant genera in Rosaceae, such as Malus (apple) and Fragaria (strawberry), have previously been hampered by a lack of transferable markers that can be used as anchor points between genetic maps. The availability of conserved orthologous set (COS) markers recently developed for this family, coupled with the release of the Malus x domestica and Fragaria vesca draft genome sequences, provide new tools for comprehensive pairwise comparisons. The genetic mapping of 56 Rosaceae COS (RosCOS) markers revealed 21 regions of genomic synteny between apple and strawberry. Information concerning the location of RosCOS markers on 15 of 17 apple linkage groups (LG) and all seven LG of strawberry was used to assess the ancestral relationships between the two genera. Four differences in orientation of ancestral chromosome fragments on extant LG were identified in comparison with previous studies, as well as two potential insertions, two potential translocations, and two potential inversions. The set of orthologous markers developed for use in genetic mapping in Rosaceae, in combination with high-throughput analysis, will allow the exploration of chromosome evolution and refinement of ancestral relationships within the family, orientation, and anchoring of genome sequences as they become available and provide resources to develop markers for nonsequenced genomes within the family.