Cultivar

ˈkəltəˌvär | Noun

A group of plants that carry common, distinguishable characteristics that have been selected in a process of breeding during commercial cultivation. Cultivar is synonymous with variety. The term strain is often used to refer to a cultivar of cannabis, however, the term strain is not strictly correct in the field of botany, though it is used in other fields of biology. 

 

This cultivar of cannabis has a floral aroma.

 

It may be wise to use a dehumidifier, since the cultivar you are growing is susceptible to mold.

 

Cultivar is a term used in botany to describe plants that are cultivated to have distinct characteristics, as applied to, for example, apples (Pink Lady, Fuji, etc.). Notwithstanding, the term strain was adopted to ascribe this same concept for cannabis (Amnesia, SFV OG, Tangie, etc.). While the term strain does not officially indicate taxonomic rank in the field of plant biology, it has been adopted by convention and is used extensively in popular culture and scientific literature alike. 

How is Cannabis Classified?

The classification of the varieties present in the species Cannabis sativa has been a subject of significant debate for well over 500 years. One of the first mentions of cannabis is in an Herbarium, a collection of plant specimens, in the 16th century that describes domesticated hemp cultivated for fiber, and “wild” hemp postulated to exist but never observed. Swedish scientist Carl Linnaeus, the father of modern taxonomy, described all variations of cannabis to exist as one species in his monumental “Species Plantarum” in 1753. To this day, the current taxonomical classification Cannabis sativa L. bears his name. His mention of the plant’s “habitat in India,” was a nod at the commonly held belief that cannabis was native to this area. 

 

French biologist Jean-Baptiste Lamarck was the first to propose that Cannabis was a genus consisting of two distinct species in 1785. The separation of Cannabis sativa, non-intoxicating hemp, from Cannabis indica, the inebriating herb, was the first time this dichotomy was put in place. The idea of speciation was tossed back by British botanist John Lindley in his “Flora Medica” in 1838. The Irish physician William O’Shaughnessy, known for introducing the medical use of cannabis to Western medicine, also agreed with the notion that cannabis is a single species, but spread the usage of the term indica to refer to the highly intoxicating herb. 

Photo via Gina Coleman/WM News

Different varieties of cannabis growing all across central and eastern Asia were described in the 20th century (japonicus, kafiristanica, etc.), some were even attributed as representing different species, such as Cannabis ruderalis by Russian botanist Dmitri Janischevsky in 1924. In the 1970s Richard Evans Schultes, an eminent botanist at Harvard University proposed three distinct species of cannabis: C. sativa, C. indica, and C. ruderalis. A drawing depicting this interpretation was published by Harvard botanist Loran C. Anderson and has been widely distributed on the internet despite its roots in a since-disproven classification. Canadian botanist Ernest Small refuted Schultes’ three-species classification scheme, and along with the famous American botanist Arthur Cronquist, introduced a taxonomical breakdown for cannabis that has been in place since it was first proposed in 1976. Small’s and Cronquist’s system defines cannabis as one species (C. sativa L.), but separates two subspecies: sativa and indica. Each subspecies, in turn, has two varieties:

  • C. sativa subspecies sativa variety sativa: domesticated with low THC (hemp)
  • C. sativa subspecies sativa variety spontanea: wild cannabis with low THC
  • C. sativa subspecies indica variety indica: domesticated with high THC
  • C. sativa subspecies indica variety kafiristanica: wild cannabis with high THC.

However, even the renowned cannabis botanist Robert Connell Clarke at the moment still contends cannabis is divided into two separate species: C. sativa and C. indica. 

 

High-THC domesticated cannabis has undergone a great degree of hybridization. So-called narrow leaf drug varieties and broad leaf drug varieties became known as sativa and indica respectively in the vernacular of cannabis culture. Select accessions wild high-THC varieties were inbred to create breeding stock strains such as Afghani #1, Thai, or Acapulco Gold. Despite the extensive hybridization, the dichotomy indica and sativa (i.e., broad leaf and narrow leaf drug still exists and, while inaccurate and obsolete, is still used to describe the plants’ euphoric effects: Indicas are relaxing (“couch lock”), and sativas are uplifting (“head high”). 

Attempting to Classify Cultivars

The decriminalization of cannabis cultivation and the solidification of a legal cannabis market throughout Europe and the Americas has been a boon to breeders. Market saturation has motivated many to distinguish their newly developed cultivars through selective breeding chiefly via hybridization to develop uniquely fragrant strains such as Tangie or Blueberry, or outcrossing to develop strains with distinct cannabinoid profiles such as Cannatonic (high CBD) or Willie Nelson (high THCV). 

Photo via Gina Coleman/WM News

The publishing of Dr. Ethan B. Russo’s theory on the entourage effect in the British Journal of Pharmacology in 2011 represented an important first step in the mainstream medical community accepting the idea that different cannabis cultivars have different effects on the body. Several attempts have been made at providing a systematic method for mapping the relationships between cannabis cultivars and providing a system for validating their identity. Three general tactics have been employed: chemical profiling, genome sequencing, and most recently, RNA sequencing.

Chemical Profiling

Chemical analysis of cannabis has been an important tool for cannabis botanists and forensic scientists alike for the better part of the 20th century. The Small and Cronquist system outlined above largely relies on differential THC or CBD expression by the two cannabis subspecies sativa and indica. While chemical profiling proved useful for differentiating the broad strokes of the cannabis genome, it more recently has been successfully applied as a tool that can differentiate between cultivars. 

 

Cannabis analytical scientist Arno Hazekamp proposed the cannabis industry move away from the botanically based cultivar classification system to a component-based system of chemovars. The research published by Hazekamp used a statistical data processing method drawing on levels of 28 cannabinoid and terpene components averaged between different accessions acquired at coffee shops around the Netherlands. They showed it was possible to differentiate two strains, Amnesia and White Widow, by chemical profiling alone. 

Genome Sequencing

Mapping the cannabis genome proved useful for differentiating between subspecies of cannabis and is being implemented as a tool for understanding the metabolic pathways that govern cannabinoid production. A collaborative effort led by researchers at the University of Toronto performed gene sequencing on a high-THC cultivar Purple Kush and a hemp cultivar Finola, and were able to identify genes associated with THC or CBD production in each case. The data have important implications for the evolutionary history of the plant. Gene sequencing applied to the question of classifying high-THC cultivars has been undertaken by only a handful of private companies in the cannabis industry, as this technique is costly and time-consuming.

RNA Sequencing

Researchers at Washington State University in a collaboration with Evio Labs, a company that does cannabis potency and quality screening, recently published a study which was able to fully differentiate nine market-available strains by sequencing ribonucleic acids (RNA) extracted from trichomes. Not only did their method differentiate between strains, it was also able to show that strains colloquially classified as indica or sativa grouped together in their model. 

 

While genome sequencing relies on high-resolution, fully sequenced genomes, RNA sequencing does not depend on previous sequencing data. It was expected that RNA sequencing would result in a detailed dataset of cultivar-specific information, given that RNA is responsible for transcribing the information coded in the genome, which goes on the synthesize cellular proteins that carry out the metabolism of terpenes and cannabinoids. Further study may lead to the identification of characteristic single nucleotide polymorphisms (SNPs) in cannabis, which opens the door to SNP-based genotyping that is already widely employed for other commercial crops such as corn. 

 

 

Sources

Erkelens, J. L.; Hazekamp, A. (2014) That which we call Indica, by any other name would smell as sweet. Cannabinoids, 9 (1), 9-15.

McPartland, J. M. (2018). Cannabis Systematics at the Levels of Family, Genus, and Species. Cannabis and Cannabinoid Research, 3.1, 2018.

Hillig, K. W. (2004). A chemotaxonomic analysis of terpenoid variation in Cannabis. Biochemical Systematics and Ecology, 32, 875-891.

Small, E.; Cronquist, A. (1976). A Practical and Natural Taxonomy for Cannabis. Taxon, 25 (4), 405-435.

Hillig, K. W.; Mahlberg, P. G. (2004). A Chemotaxonomic Analysis of Cannabinoid Variation in Cannabis (Cannabaceae). American Journal of Botany, 91 (6), 966-975.

Clarke, R. C.; Merlin, M. D. (2016). Cannabis Domestication, Breeding History, Present-day Genetic Diversity, and Future Prospects. Critical Reviews in Plant Science, 35 (5-6), 293-327.

Meijer, E. P. M.; Bagatta, M.; Carboni, A; Crucitti, P.; Molinterni, C. V. M.; Ranalli, P.; Mandolino, G. (2003). The Inheritance of Chemical Phenotype in Cannabis sativa L. Genetics, 163, 335-346.