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University of Saskatchewan scientists believe they have made a key discovery about Cannabis sativa, the plant species for hemp and marijuana. (CBC)

Researchers at the University of Saskatchewan have identified the process that marijuana plants use to create tetrahydrocannabinol (THC) — the active ingredient in pot that gets smokers high —and say it could help breeders create pot plants that contain no traces of the drug and can be freely used in fibres or pharmaceuticals.

It turns out the chemical pathway to THC production involves two enzymes that are used in a unique way in cannabis plants, according to University of Saskatchewan biologist Jon Page.

"What cannabis has done is take a rare fatty acid with a simple, six-carbon chain and use it as a building block to make something chemically complex and pharmacologically active," Page said in a news release.

The research, published online Monday in the Proceedings of the National Academy of Sciences (PNAS), paves the way for the development of marijuana varieties that can produce substances for pharmaceutical use or industrial hemp that is completely drug-free, the scientists say.

Currently, industrial hemp — the cannabis strains used to make rope and textiles — contains only residual quantities of THC, but even trace amounts can be problematic when it comes to export markets and drug regulators.

The way to get around this problem, the U of S scientists say, could be to essentially switch off the chemical pathway.

"As breeders try to develop new varieties, they always struggle with this sort of residual or small amount of THC that always seems to leak through," Page said. "So, we might not just get really, really low levels of THC; we'd get zero levels of THC."

The researchers are also looking at ways to produce THC-like substances using yeast or other micro-organisms, something that would have applications in the manufacture of pharmaceuticals.

As far as using their discoveries to "turn up" the level of THC in cannabis?

Page says it's unlikely his and his colleagues' work will have applications for recreational drug users. That's because there already exist potent strains of marijuana through conventional production methods, he said.