University of Northern Colorado
Type of Resources
Place of Publication
University of Northern Colorado
For thousands of years, humans have cultivated and dispersed Cannabis sativa L. across the globe. Although Cannabis has been largely illegal worldwide for decades, public perceptions and attitudes are changing. Increasing interest in potential Cannabis usage worldwide and nationwide is leading to less restrictions to make way for an expanding and lucrative industry with numerous applications. Although only one species is formally recognized in the Cannabis genus, thousands of years of artificial selection for diverse phenotypes and uses have resulted in two major usage groups; hemp-types which are defined worldwide as having very low levels of THC (< 1.0%), and drug-types which exceed a specified level of THC that varies among nations. The drug-type category includes three commonly used subcategories including Sativa, Indica and Hybrid types, and newly developed high CBD varieties that have more THC than hemp-types but are not bred for high THC. The quality of federally produced Cannabis for medical studies in the U.S. has recently been brought into question, and we included samples to determine the genetic relationship to these groups. Phenotypic variation in Cannabis gives rise to commonly referenced categories, but sources of variation are unclear and understudied. Phenotypes are observable characteristics that results from a combination of both genotype and the environment. The preferred method of propagation for Cannabis is cloning, and therefore variation within varietals should be from differences in environmental factors. Ten microsatellite markers were developed de-novo to investigate four aims: (1) genetic variation within strains, (2) genetic relationships among the common categories, (3) if genetic variation is detectable through olfactory sensation, and (4) how genetic variation is reflected in phytochemical levels. This dissertation includes four manuscript chapters representing each aim and uses a genetic basis for a multifaceted approach to investigate variation in Cannabis sativa. Substantial genetic variation was found within strains from obtained from different facilities. Genetic divergence between hemp and drug-types was genetically supported, but the Sativa, Indica, and Hybrid subcategories were not genetically well defined. The high CBD strains appear to bridge the genetic gap between hemp and drug-types, and federally grown research grade marijuana was genetically more similar to hemp than Cannabis available through the legal cannabis market. Genetic imposters within a strain had measurable aromatic differences, but there was considerable variation in aromas among samples with identical genetic identity. Analyses of both terpene and cannabinoid profiles among individuals with identical genotypes acquired from different sources varied considerably indicating environmental variation has a substantial impact on phenotype in Cannabis. Together these results show a need for the Cannabis industry to implement regulatory checks in the form of genetic testing in order to provide consistency, especially for medical applications. These results demonstrate the need for genotyping in order for phenotypic consistency to be achieved if standard growing conditions can be established. When genetic verification and standard protocols are established, deviations in phenotypic changes can be identified and disclosed to consumers so they are aware that there may be abnormal effects. This investigation highlights the need for additional research to provide consistent products, which is especially important for medical marijuana flower products. In order to provide consumers consistent products, it is imperative to understand sources of variation. Consumers deserve to be provided with quality consistent products as the industry continues to grow on a global scale.
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