Assessing genetic diversity in Cannabis sativa using molecular approaches

Abstract

Cannabis sativa L. represents plants cultivated for their psychoactive and medicinal properties (marijuana) or as a source of fibre, seed and oil (hemp). Breeding and selection efforts have produced marijuana genotypes (strains) with a range of levels of the cannabinoid ?9-tetrahydrocannabinolic acid (THCA) and other non-psychoactive cannabinoids, e.g. cannabidiolic acid (CBDA). Hemp lines have been bred for high fibre content and seed production and have low/no THCA. There are currently hundreds of marijuana strains which differ in THCA:CBDA ratios, growth characteristics, morphological features, THCA and CBDA contents, disease resistance, as well as overall medicinal value. The extent of genetic diversity among these marijuana strains, as well as between marijuana and hemp, has been studied using a range of molecular approaches. The results from these studies have demonstrated that considerable genetic diversity exists among marijuana as well as hemp strains. Using ISSR markers, we have shown that distinct DNA banding patterns can allow for the initial discrimination between many of the strains tested, and provide an insight into the possible genetic relationships among strains. Some strains, e.g. 'Jack', 'Super Sour Skunk', 'Jilly Bean', exhibited unique patterns that can be used to develop strain-specific DNA fingerprints. In addition, a number of "landraces" and strains originating from remote geographic locations, showed unique and distinct ISSR patterns and morphologies. A very high degree of genetic diversity was exhibited among the strains studied. Additional molecular studies, including DNA sequencing approaches, should provide more insight into the genetic relationships that exist within strains of a complex plant species and could augment future breeding efforts for genetic improvement of C. Sativa.