Development of molecular tools for the identification of powdery mildew-resistant Cannabis sativa strains through a genomics-based approach

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OrganiGram is one of ~15 licensed producers of medical marijuana under the Marihuana for Medical Purposes Regulations (MMPR). As for any agricultural crop, plant diseases play a major limiting role in Cannabis production, for which OrganiGram is looking for control methods. Control of plant diseases using pesticides raises serious health and environmental concerns, which have dictated the need for organic pest management techniques, such as the use of disease-resistant strains. Powdery mildew is a major disease of Cannabis, but variation in resistance is known to exist between strains. In crops as diverse as barley, tomatoes or peas, durable control of powdery mildew is conferred by loss-of-function mutations in the Mlo gene. The availability of the Cannabis sativa genome enables the identification and study of Mlo orthologues, and the development of screening assays for naturally occurring loss-of-function mlo variants in marijuana strains. In order to confidently identify all potential Mlo orthologues, the Cannabis genome will first be improved by sequencing additional DNA libraries using the long-read sequencing platform Pacific Biosciences. PCR primers will then be developed to allow specific and reliable amplification of Mlo orthologues suspected to be involved in powdery mildew resistance, and primers will be tested against different strains to ensure sensitivity. Ultimately, these primers could be used to screen hundreds of Cannabis sativa strains or breeding material to uncover genomic variants encoding Mlo orthologues with loss-of-function mutations, e.g. powdery mildew-resistant plants.