The Polyploid History of Cultivated Dahlia

The cultivated dahlia has a complex evolutionary history that is likely the driver for its diverse floral forms. Previous studies have proposed cultivated dahlia as an allotetraploid, autotetraploid, and in one study an auto-allooctoploid. Here, we used PacBio HiFi long-reads and Dovetail Omni-C reads to assemble and annotate a genome for a tetraploid Dahlia variabilis cultivar Edna C. We identified Edna C as a segmental tetraploid with signature of auto- and allo-polyploidy events based on subgenome-specific repeat partitioning and single-copy gene tree construction within homoeologous groups. Additionally, we identified a cultivated dahlia-specific centromeric monomer shared between Dahlia variabilis Edna C and the Dahlia pinnata Kelvin Floodlight. Based on finding three major chromosome clusters, we propose that Dahlia variabilis Edna C is a segmental tetraploid with evidence of auto- and allopolyploidy.