RT Journal Article SR Electronic T1 A complete Cannabis chromosome assembly and adaptive admixture for elevated cannabidiol (CBD) content JF bioRxiv FD Cold Spring Harbor Laboratory SP 458083 DO 10.1101/458083 A1 Christopher J. Grassa A1 Jonathan P. Wenger A1 Clemon Dabney A1 Shane G. Poplawski A1 S. Timothy Motley A1 Todd P. Michael A1 C.J. Schwartz A1 George D. Weiblen YR 2018 UL http://biorxiv.org/content/early/2018/10/31/458083.abstract AB Cannabis has been cultivated for millennia with distinct cultivars providing either fiber and grain or tetrahydrocannabinol. Recent demand for cannabidiol rather than tetrahydrocannabinol has favored the breeding of admixed cultivars with extremely high cannabidiol content. Despite several draft Cannabis genomes, the genomic structure of cannabinoid synthase loci has remained elusive. A genetic map derived from a tetrahydrocannabinol/cannabidiol segregating population and a complete chromosome assembly from a high-cannabidiol cultivar together resolve the linkage of cannabidiolic and tetrahydrocannabinolic acid synthase gene clusters which are associated with transposable elements. High-cannabidiol cultivars appear to have been generated by integrating hemp-type cannabidiolic acid synthase gene clusters into a background of marijuana-type cannabis. Quantitative trait locus mapping suggests that overall drug potency, however, is associated with other genomic regions needing additional study.Summary A complete chromosome assembly and an ultra-high-density linkage map together identify the genetic mechanism responsible for the ratio of tetrahydrocannabinol (THC) to cannabidiol (CBD) in Cannabis cultivars, allowing paradigms for the evolution and inheritance of drug potency to be evaluated.