Cannabis Sativa L., of the Cannabinaceae family, is a diploid plant used for millennia in the manufacture of fibers, oils, and medicines. It grows unhindered in the wild as well as in greenhouses.
The botanic type of cannabis are the flowering plants, which may be divided to two species: Cannabis sativa and Cannabis indica. While Cannabis sativa plants are usually tall with narrow leaves, Cannabis indica plants are usually characterized with shorter with wider leaves.
The plant is also known as hemp; however, this term is generally referring to cannabis strains that are cultivated for industrial (non-drug) uses. Hemp has a substantially lower concentration of THC (tetrahydrocannabinol) and it is mainly used in the production of fibers and grains.
Other strains of cannabis have higher concentrations of THC and CBD (cannabidiol), and may be used for medicinal purposes thanks to the immense therapeutic potential of cannabinoids. Despite its medicinal potential, growing cannabis is restricted around the globe, primarily due to UN Single Convention on Narcotic Drugs. However, the regulatory environment is currently in flux while more and more jurisdictions acknowledge the enormous potential of cannabis.
Cannabis varieties with a high THC:CBD ratio are generally prohibited for commercial use in most countries, while varieties with a low THC:CBD ratio may be eligible for commercial use. For example, a cannabis plant with a THC count of less than 0.2% of the plant’s total dry weight is considered to be legal under the European standards. A conventional method of distinguishing between cannabis strains lies in the difference in the chemical ratios of THC to CBD. Although this ratio is used to distinguish between cannabis varieties and their different morphologies, such morphologic difference between cannabis strains is minuscule, and the use of the THC to CBD ratio has not proven itself as a sufficient differentiator.
Cannabis Genetic Research
Distinguishing between the different cannabis genotypes is indeed a key factor in every plant nurturing venture, and different methods of molecular identification have been experimented for this purpose. RAPD markers were already used in 1995, ISSR markers in 2002, and AFLP markers in 2003, although these outdated markers expectedly suffered from a lack of accuracy (Houston et al. 2016; Valverde et al.2014).
SNP markers are currently used primarily for the identification of traits in specific genes, while much work has been done with STR markers over an almost two decade period. A first draft for the cannabis genome was published in 2011, although this data has not been expanded on or properly analyzed (Baker et al. 2011). In 2015, using 14,000 SNPs, scientists were able to show that the differences between the varieties are not simply based on genetic differences in the THCA synthase gene, but genome-wide level differences exist as well (Weiblen et al. 2015).
In 2017, using 13 STRs that were tested on 1300 cannabis samples from over 48 varieties (Booth et al. 2017), it was concluded that:
- It is possible to distinguish between the genetic structure of hemp and cannabis by using 13 markers for forensic purposes.
- Unidentified samples were attributed to one of the groups (hemp or cannabis).
- The inter-variety difference was tested, with hemp having a Fst value of 0.15 and cannabis with a higher variability of Fst of 0.36.
In conclusion, over the past decade ample information has been gathered about cannabis varieties, as well as about inherent differences in their active metabolic level and their influence on medical ailments. Notwithstanding, the molecular information available at the DNA or RNA level is still substantially lacking, and the molecular connection between active cannabinoids and genetic variety differences has yet to be comprehensively concluded.
Indeed, hundreds of clinical experiments tested the different effects of cannabinoids on pathologies and different ailments, yet the majority of the experimentations have centered around the effects on patients without a connection to the source of the material, i.e. the plant variety-level.
To fully benefit from the healing potential of cannabis, the following steps should be implemented:
- Molecular identification/profiling of varieties for the purpose of nurturing processes.
- Identification of active genes and the level of their activity.
- Based on the aforementioned information, to study the bio-synthetic paths that stand at the base of production of the cannabinoids.