The ancient roots of cannabis domestication

Knowing how the plant was domesticated will allow scientists to target varieties from specific genetic groups for breeding and increasing their genetic variability, explains evolutionary biologist Luca Fumagalli from the University of Lausanne in Switzerland. It also helps identify the specific genes that played an important role in causing fibre-producing varieties, used to spin products like ropes and textiles, to diverge from drug-producing ones, he adds. 

To trace the domestication history of cannabis plants, the scientists sequenced and analysed more than 100 genomes of different plant varieties collected from the field in China, India, Switzerland, Pakistan, Peru and Russia, and from agronomic companies, commercial shops and germplasm collections. 

“By looking at the DNA mutation rate and the number of differences between two DNA sequences, it is possible to date the time when these two sequences started to diverge,” says Fumagalli. 

The researchers say this molecular dating, supported by traces of cannabis plant-based artefacts at different archaeological sites, revealed that, after domestication in East Asia during the early Neolithic period, cannabis was likely used as a multipurpose plant before undergoing strong divergent selection for fibre production or for its psychoactive properties. 

The team, which included researchers from Qatar, China and India, also identified several genes related to flowering time, cellulose and lignin biosynthesis, branch formation and cannabinoid biosynthesis and potency that were selected for growing fibre-producing or drug-type varieties. 

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