Article by Randy Shore, Vancouver Sun
University of B.C. researchers are on the hunt for genes that protect cannabis from the destructive ravages of powdery mildew, which will be a game-changer for commercial growers.
Loren Rieseberg and Marco Todesco are comparing the natural resistance with four mildew strains in about 500 different cannabis cultivars maintained by Aurora Cannabis.
“These are the strains of mildew that are commonly found in Canadian greenhouses,” said Rieseberg.
Grey mould — known in the industry as bud rot — can quickly devastate a cannabis crop. Only a tiny fraction of infected plants will recover from an infection.
Although the project will require massive computing power to sort through genetic information, finding candidate cultivars is relatively simple.
“You just infect the plants by sprinkling them with mildew spores and see if they become diseased,” he said.
Once the researchers identify the most resistant cannabis varieties, they will sequence the genomes of the best candidates and compare them with identified genes and genetic variants associated with resistance. The genetic variants that are strongly associated with broad resistance to mildew and specific resistance to the most damaging mildew strains can quickly be incorporated into Aurora’s breeding program.
“Cannabis is a terrible crop in the sense that it’s not particularly resistant to disease and insects,” said Rieseberg.
The focus of breeders has always been to make cannabis a more potent intoxicant rather than making a resilient plant. As a result, the most highly prized strains of cannabis are relatively feeble plants, requiring strict control of light and humidity usually in a greenhouse-like environment.
Better cannabis strains would greatly reduce losses due to disease, according to a statement from Genome B.C.
The $4.2-million project — Fast-Track Breeding of Powdery Mildew-Resistant Cannabis — is jointly funded by Aurora, Genome B.C. and Genome Canada.
Because cannabis is ingested or inhaled, commercial growers are forbidden from using most chemical pesticides, and testing for residues of those products is strict.
“For something like powdery mildew, there is a strong incentive to develop really strong genetic resistance,” he said.
Studies of illicit cannabis have found pesticide residues, heavy metals and microbes in products intended to be smoked or eaten.