A relatively small number of genetic regions appear to control much of the variation in major cannabinoids and monoterpenes found in marijuana, according to a new preprint study. Although the pathways plants use to produce these compounds are relatively well understood, researchers said knowledge of the genetic variation controlling their concentrations remains limited. To investigate that genetic control, researchers crossed two chemically and genetically distinct Cannabis sativa landraces. The THC-dominant parent had higher concentrations of myrcene and limonene but contained no detectable alpha-terpinolene, alpha-terpinene or gamma-terpinene. Despite those environmental differences, the study’s major genetic findings remained consistent across both growing conditions.