The Genetic Structure of Marijuana and Hemp

Summary & key facts

Researchers compared the DNA of many cultivated Cannabis plants to see how hemp and drug-type marijuana are related. They checked about 14,000 genetic markers in 81 marijuana plants and 43 hemp plants. They found that hemp and marijuana are clearly different across the whole genome, that common labels like “C. sativa” and “C. indica” only partly match real genetic differences, and that hemp is genetically closer to indica-type marijuana than to sativa strains. This matters because it shows plant labels and strain names do not always reflect true genetic relationships.

Key facts:

• The team tested about 14,000 genetic markers in 124 plants: 81 marijuana samples and 43 hemp samples.
• Marijuana and hemp are significantly different across the whole genome, not just in the genes that make the psychoactive chemical THC.
• Labels people use like C. sativa and C. indica only moderately match the plants' actual genetic structure.
• Marijuana strain names often do not reflect a clear or meaningful genetic identity.
• Hemp plants in this study were genetically more similar to indica-type marijuana than to sativa strains.

Abstract

Despite its cultivation as a source of food, fibre and medicine, and its global status as the most used illicit drug, the genus Cannabis has an inconclusive taxonomic organization and evolutionary history. Drug types of Cannabis (marijuana), which contain high amounts of the psychoactive cannabinoid Δ9-tetrahydrocannabinol (THC), are used for medical purposes and as a recreational drug. Hemp types are grown for the production of seed and fibre, and contain low amounts of THC. Two species or gene pools (C. sativa and C. indica) are widely used in describing the pedigree or appearance of cultivated Cannabis plants. Using 14,031 single-nucleotide polymorphisms (SNPs) genotyped in 81 marijuana and 43 hemp samples, we show that marijuana and hemp are significantly differentiated at a genome-wide level, demonstrating that the distinction between these populations is not limited to genes underlying THC production. We find a moderate correlation between the genetic structure of marijuana strains and their reported C. sativa and C. indica ancestry and show that marijuana strain names often do not reflect a meaningful genetic identity. We also provide evidence that hemp is genetically more similar to C. indica type marijuana than to C. sativa strains.

Topics

Cannabis and Cannabinoid Research

Categories

Health Sciences Medicine Pharmacology

Tags

Biology Biotechnology Botany Cannabinoid Cannabis Cannabis sativa Drug Gene Genetics Genome Genotype Medicine Pharmacology Psychiatry Receptor Recreational Drug Single-nucleotide polymorphism Tetrahydrocannabinol

Substances

Cannabis