For millennia, humans have grown Cannabis for fiber, food, oil and — yes — for that telltale buzz. And today, Cannabis is a booming business. Marijuana is legal in ten states and Washington, D.C. An additional 33 states and four territories sport medical marijuana programs. Last year, Canada legalized recreational marijuana outright, and the U.S. Food & Drug administration approved the first drug containing a Cannabis-derived compound.
THC, or not THC
Despite the upsurge, Cannabis cultivators have little firm knowledge about the genetic innards of the devil’s lettuce — particularly about the genetic variations responsible for the differences between Cannabis strains. Cannabis comes in many varieties — from Skunk to Carmen to Acapulco Gold. Today’s pot aficionados are generally on the prowl for strains that produce high levels of cannabinoidcompounds — especially the infamous tetrahydrocannabinol, or THC. Other Cannabis varieties, such as hemp strains, produce almost no THC, but are valued for their fiber.
Knots to you
Studies show that gene copy number could explain some of the differences between Cannabis strains, such as levels of THC production. But fully unlocking the genetic secrets of Cannabis traits like cannabinoid production ultimately requires wading headlong into a mire more unpleasant than a dirty bong: the Cannabis genome itself. By all accounts, it is a sticky, complex realm of repeats, duplications and AT-rich mazes spread among 10 chromosome pairs. The half-dozen or so Cannabis genome assemblies that have come out since 2011 are complex collections of 2,000 to 300,000 contigs, depending on assembly.
But advancements like Proximo Hi-C have revived hope that it’s possible to build increasingly longer and more complete assemblies of the Cannabis genome — moving the field away from fragmented assemblies and toward the highly complete chromosome-length scaffolds that are key to building a better bud.
“A refined genome assembly will enable molecular breeding programs to deploy marker-assisted selection for yield, flowering time, pest resistance and rare cannabinoid expression,” said Kevin McKernan of Medicinal Genomics.
Read more at geneticliteracyproject.org
