Genetic tools weed out misconceptions of strain reliability in Cannabis sativa: implications for a budding industry

Abstract

Background Unlike other plants, Cannabis sativa is excluded from regulation by the United States Department of Agriculture (USDA). Distinctive Cannabis varieties are ostracized from registration and therefore nearly impossible to verify. As Cannabis has become legal for medical and recreational consumption in many states, consumers have been exposed to a wave of novel Cannabis products with many distinctive names. Despite more than 2000 named strains being available to consumers, questions about the consistency of commercially available strains have not been investigated through scientific methodologies. As Cannabis legalization and consumption increases, the need to provide consumers with consistent products becomes more pressing. In this research, we examined commercially available, drug-type Cannabis strains using genetic methods to determine if the commonly referenced distinctions are supported and if samples with the same strain name are consistent when obtained from different facilities. Methods We developed ten de-novo microsatellite markers using the “Purple Kush” genome to investigate potential genetic variation within 30 strains obtained from dispensaries in three states. Samples were examined to determine if there is any genetic distinction separating the commonly referenced Sativa, Indica and Hybrid types and if there is consistent genetic identity found within strain accessions obtained from different facilities. Results Although there was strong statistical support dividing the samples into two genetic groups, the groups did not correspond to commonly reported Sativa/Hybrid/Indica types. The analyses revealed genetic inconsistencies within strains, with most strains containing at least one genetic outlier. However, after the removal of obvious outliers, many strains showed considerable genetic stability. Conclusions We failed to find clear genetic support for commonly referenced Sativa, Indica and Hybrid types as described in online databases. Significant genetic differences within samples of the same strain were observed indicating that consumers could be provided inconsistent products. These differences have the potential to lead to phenotypic differences and unexpected effects, which could be surprising for the recreational user, but have more serious implications for patients relying on strains that alleviate specific medical symptoms. Electronic supplementary material The online version of this article (10.1186/s42238-019-0001-1) contains supplementary material, which is available to authorized users.

Research grade marijuana supplied by the National Institute on Drug Abuse is genetically divergent from commercially availableCannabis

“…Commercially available Cannabis has come to market through non-traditional means leading to many inconsistencies. We have previously documented 55 that there is substantial genetic divergence among samples within named strains, which only exacerbates questions about the impacts of Cannabis consumption. These results emphasize the need to increase consistency within the Cannabis marketplace, and the need for research grade Cannabis to accurately represent what is accessible to consumers.…”

“…DNA was extracted using a modified CTAB extraction protocol 57 with 0.035-0.100 grams of dried flower tissue per extraction. Ten variable microsatellite loci developed by Schwabe and McGlaughlin 55 were used in this study following their previously described procedures.…”

The Past, Present and Future of Cannabis sativa Tissue Culture

“…Due to their low levels of cannabinoids, male plants are generally not consumed as a medicinal or recreational drug and will not be extensively discussed in this review. The taxonomy of the genus Cannabis is a matter of spirited debate and no consensus has emerged on whether it is a monospecific or polyspecific genus [32][33][34]. The ability to distinguish between hemp and drug-type Cannabis has been the subject of much interest by law-enforcement, which relies on THC content for distinction [35].…”

“…The taxonomy of drug-type Cannabis is complicated by years of prohibition, which resulted in informal, clandestine breeding programs which caused decades of interbreeding and hybridization without records of parentage [40,46]. The ability to consistently and reliably distinguish between sativa and indica types of Cannabis has been scrutinized [35] and as a result of these underground breeding programs, establishing the pedigree of Cannabis is incredibly challenging and has resulted in unpredictability for consumers of C. sativa products [33]. Concerns have also been raised that this ever-increasing introgression is leading to a decline of biodiversity in the species and a loss of native indigenous C. sativa varieties [46].…”

A Single Nucleotide Polymorphism assay sheds light on the extent and distribution of genetic diversity, population structure and functional basis of key traits in cultivated North American Cannabis

“…Taxonomic classification of the Cannabis genus has been delineated through three main types: sativa (long and less branched plant with long and narrow leaves), indica (short but highly branched plant with broader leaves) and ruderalis (wild type with short stature, less branching and small thick leaves). While still under discussion, particularly whether the genus is polytypic or monotypic, this broad classification reflects a putative geographical origin of each group (Clarke and Merlin 2017; Lynch et al, 2016, Schwabe et al, 2019). Consequently, there is no structured horticultural registration system available for Cannabis and cultivars or varieties, instead these are often awarded the epithet “strains”, which are likely the outcome of extensive hybridization of the original botanical descriptors (Henry, 2015).…”