The sequenced genome of Corymbia citriodora subsp. Variegata

Eucalypts (genera Eucalyptus, Corymbia and Angophora) are the most widely planted hardwood trees in the world, prized for their fast growth rate, timber and fibre quality, and environmental adaptability. Corymbia (bloodwood taxa), having adapted to arid conditions and low quality soil types, have become an important forestry resource, grown for timber and essential oil production. Given their economic importance, the Corymbia genome consortium has sequenced the genome of C. citriodora subspecies variegata (CCV). The high-quality CCV genome is a result of combining Illumina and long-read PacBio technologies, along with a high-density DaRT-Seq genetic map to generate the 11 chromosome, 408 Mb assembly. Comparison of the CCV genome with Eucalyptus grandis found differing repeat content among the two species, with several large structural chromosomal rearrangements. Syntenic and orthologous gene analyses found 3981 shared eucalypt genes among the two species, as well as evidence of the eudicot specific paleotetraploidy event. Unique to Corymbia were several gene families related to pollen recognition and zinc-ion binding, as well as several gene families related to terpene synthesis and abiotic/biotic stress response that underwent expansion through tandem gene duplication. These data suggest that the genome of CCV has been shaped through adaptation to arid and stress-prone conditions throughout its evolutionary history.