Comparative mapping in the Solanaceae

A genetic map of Capsicum (pepper) was constructed using tomato-derived DNA probes in RFLP and other anonymous markers. The pepper map consists of 11 large and 2 small linkage groups covering 1245 cM. Comparison of the pepper map to published tomato maps shows that 98.1% of the tomato genome and 95.0% of the mapped pepper genome can be represented by eighteen homoeologous segments, that apparently have undergone common cytological rearrangements to create the unique karyotypes of each genus. These data were used to further characterize the rearrangements that differentiate the tomato, potato, and pepper genomes. A theoretical mapping study was also undertaken to test the validity of genetic maps generated in populations with structural rearrangements. This study found that marker orders within the conserved segments of a translocation were maintained and identifiable, although associations between segments remained indiscernible. The map of pepper chromosome 1 was found to be most similar to simulated datasets from parents with a translocation and inversion of the translocated segment. Finally, the comparative map of pepper and tomato was used to compare locations of pepper QTL identified in a small dataset to tomato QTL for phenotypically similar horticultural traits. This study identified at least eight putative QTL in pepper where QTL had been identified in the syntenic regions of the tomato genome.