Benefiting froma Robust Cannabis Genetic Diversity
The discovery of the DNA double helix by Watson and Crick in 1953 opened the door to a revolution in our understanding of the cellular mechanisms of replication. This understanding guided huge technological advancements. Today, scientists are able to not only sequence every base pair in the entire DNA content (genome) of any given cell, but also to directly hack that DNA. This has given rise to the multi-billion dollar genetically-modified organism industry.
Selective pressures have driven evolutionary changes in organisms since the dawn of life on Earth. These forces of natural selection give rise to speciation and genetic diversity. Domestication, however, reduces these pressures. There are usually very specific traits that humans desire when tending their livestock, or growing their plants. Over time, this artificial selection reduces genetic diversity by removing unwanted traitsfrom the gene pool (represented by allelic homogeny in the DNA).
The erosion of Cannabis genetic resources and itslimited genetic improvement is mainly due to its contraband status over the past century1. Databases containing genetic information have been erased; seed banks confiscated or put to the torch; and bureaucratic red-tape created neigh-insurmountable obstacles to the scientific propagation and dissemination of verifiable, high-quality information.
Some data, however is still available. The general observable trend in cannabis worldwide has been an increase in dry-weight THC content. The mean THC values across many genetic sources obtained from reviewing the scientific literature found a four-fold increase between 1970 and 20092. One reason for this change is that the consumer market during that time drove genetic variation that favored high-THC cultivars for recreational use. Another reason was that economically, cultivating high-THC strains means using less grow space per kilo of THC produced, a variable that is extremly imporant in the black market, where grow space is extremely limited.
Understanding genetic diversity isn’t just economical; it also helps law enforcement agencies. Forensic scientists have exploited the growing availability of Cannabis whole-genome sequencing to develop techinques that distinguish between different species in the Cannabis genus3. This technology focuses on sequencing 13 microsatellite loci (STRs), and has been shown to accurately detect sufficient differences between C. sativa and C. savita L. species to satisfy judicial evidence threshhold.
This helps the state identify whether cultivars found on a farm or greenhouse are obeying state law or not. It also assists the Border Patrol in verify the source of hemp products coming from overseas. With the advent of genetic modification to the cannabis industry and following the lead of the food and beverage industry, novel sources of cannabis genetics can be patented under California and US law. Therefore, we can also see a potential application to patent law.
Genetic sourcing is important for the cannabis industry for a variety of reasons, not the least of them being the ability to choose cultivars appropriate for particular climate or growing technique. Another factor that has become more important in recent years is the selection of medicinal strains with desired cannabinoid expression levels. As cannabinoid science becomes more advanced, the medicinal levels of each cannabinoid are investigated for their role in therapeutic efficacy. Genetic sources that express variate expression profiles of these cannabinoids can be selected and grown to address specific ailments and pharmaceutical goals.
Instead of the Iron Curtain, the cannabis industry in many ways had experienced a Genetic Curtain, forbidding the dissemination of alternate genotypes and culling the genetic resources of the species. However, as more scientists, technology, and funds enter this hemisphere, we can expect the variety of genetic sources to increase. The only result of this increase will be positive therapeutic outcomes that will change the lives of generations of patients to come.
- Welling et al. A Belated Green Revolution for Cannabis: Virtual Genetic Resources to Fast-Track Cultivar Development.Front Plant Sci. 2016;7:1113. DOI: 10.3389/fpls.2016.01113.
- Cascini et al. Increasing Delta-9-Tetrahydrocannabinol (Δ-9-THC) Content in Herbal Cannabis Over Time: Systematic Review and Meta-Analysis.Curr Drug Abuse Rev. 2012;5(1):32-40.
- Duresnes et al. Broad-Scale Genetic Diversity of Cannabis for Forensic Applications. PLoS One. 2017;12(1):e0170522. DOI: 10.1371/journal.pone.0170522.