Addressing microbial-induced pre- and post-harvest quality reduction in cannabis

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Following legalization of cannabis (Cannabis sativa L., marijuana) in Canada in October, 2018, production and supply of dried cannabis flowers (buds) and cannabis-derived products for medicinal and recreational markets have increased. Most cannabis production (90%) occurs in greenhouses, and each crop cycle requires a 10 week period to harvest. After harvest, cannabis flowers are dried to a moisture content of 10-12% (by weight). The greatest challenge facing licensed producers (LPs) is pre-and post-harvest losses due to microbial and pathogen invasion of flowers and unpredictable flower quality due to environmental perturbations. In addition, the increasing prevalence of viral pathogens is causing as-yet-undetermined losses in quality. The total yeast and mold (TYM) levels is a critical factor for final value of cannabis products - high levels of microbes during production can result in downgrading or rejection of product, potentially leading to millions of dollars in losses annually. In addition, poor flower development due to environmental stress, diseases or post-harvest damage can reduce flower quality and levels of medicinal and psychotropic chemicals in trichomes. Measurements of pre-and post-harvest flower quality are difficult to make as appropriate methods have not been developed to assess them. The proposed research will provide a number of significant scientific and technological advancements that can be implemented as innovative processes and technologies to improve cannabis quality in Canada, as follows: (i) a predictable culture and molecular based method to estimate TYM in cannabis production facilities to guide producers in optimal usage of resources to minimize post-harvest losses; (ii) identification of environmental conditions, cannabis genotypes and post-harvest handling methods that minimize TYM; (iii) a computer-assisted visual method based on trichome maturation analysis to assess optimal flower quality; (iv) a better understanding of the viral disease complex in cannabis. A number of novel research methodologies that can be utilized by other research institutions and cannabis producers across Canada to benefit Canadians will be an important outcome of this 3-year research project.