Interspecific hybridization and the analysis of meiotic chromosome pairing in Dahlia (Asteraceae-Heliantheae) species with x=6

The successful production of a large number of artificial hybrids between Dahlia species based on x=16 has allowed a detailed study of their genomic relationships. Chromosome behaviour in these artificial hybrids was extremely similar to that observed in parental species suggesting that there is a considerable degree of homology between the genomes of these Dahlia species. Using GISH it can be demonstrated that in these hybrids bivalent formation involved pairing only between parental genomes. The ability of GISH to differentiate between parental genomes in artificial hybrids was variable, indicating that molecular divergence of highly repeated sequences has accompanied the evolution of these species. However, the extent of chromosome pairing and chiasma formation in the hybrids does not reflect the differences that can be detected by GISH. Several of the new hybrid combinations have resulted in horticulturally interesting plants.