Cannabis species

Payment, Josephine & Cvetkovska, Marina Cvetkovska Marina, 2023, The responses of Cannabis sativa to environmental stress: a balancing act, Botany 101 (8), pp. 318-332 : 319

Cannabis species, strains, cultivars, or chemovars?

Much of the available scientific insight on cannabis is complicated by the inconsistent classification of cannabis varieties. Both the species name ( C. sativa ) and the colloquial name (cannabis) are widely used in the scientific literature. In this manuscript, we will refer to C. sativa when indicating the plant species while the word “cannabis” will refer to the colloquial use of the plant. Cannabis sativa is the only member of the Cannabis genus, which is often divided into three subspecies with distinct phenotypic differences: ssp. sativa, ssp. indica , and ssp. ruderalis ; however, this taxonomy has been questioned and extensive interbreeding has tangled any distinctions still further ( Sawler et al. 2015; Lynch et al. 2016; McPartland 2018; Barcaccia et al. 2020).

Cannabis varieties are often described as “strains” conceptually equivalent to “cultivars” ( McPartland and Small 2020), a term that has largely been appropriated by commercial and hobby breeders. For instance, the online database SeedFinder (https://en.seedfinder.eu) currently lists>29 000 distinct cannabis varieties, but these often reflect clandestine parentage. The genetic lineage of many of commercially used varieties is often unclear, does not always correspond to the advertized chemical profile and, in some cases, may originate from the black market. Unregulated domestication and hybridization of cannabis varieties has even been associated loss of chemical diversity in the modern cannabis landscape ( Mudge et al. 2018). Thus, a given strain name may not reflect its actual genetic background or chemical profile ( Hazekamp and Fischedick 2012; Pusiak et al. 2021; Smith et al. 2022). Defining the usage of the term “strain” has been proposed ( Pollio 2016), but this nomenclature has not been standardized yet.

Agricultural and plant sciences define plant cultivars as varieties developed over long periods of breeding and selection for desirable traits. Agricultural cultivars are internationally accredited and have well-defined phenotypic and chemical characteristics, which can be consistently reproduced either asexually through cloning or sexually through seed production. For legislative purposes of C. sativa production, the most important classification is that of drug-type (marijuana) with>0.3% THC and fiber-type (hemp) with <0.3% THC on basis of dry plant tissue. Commercial hemp cultivars have already been accredited (e.g., 84 approved cultivars for the 2022 Growing Season in Canada; Government of Canada 2023), but accreditation has not been achieved for drug-type C. sativa with higher THC levels.

More recently, the term chemovar/chemotype has been applied to cannabis varieties based on cannabinoid levels and profiles: (1) type I (THCA/CBDA >> 1), type II (CBDA/THCA ≈ 1), type III (THCA/CBDA « 1), type IV (cannabigerol (CBGA)-dominant, with very low THC + CBD content), and type V (very low cannabinoid content overall). Types I and II are considered as medical (or drug-type) cannabis, while chemotypes III–V are described as hemp ( Hillig and Mahlberg 2004; Pacifico et al. 2006; Schilling et al. 2021). It must be noted that classification based on cannabinoid levels is somewhat misleading. The C. sativa plant is very phenotypically diverse in traits other than cannabinoid levels, including height, leaf shape, photoperiod, and highly variable responses to environmental stimuli (discussed in more detail below). Furthermore, chemotypes do not necessarily constitute a phylogenetic classification based on evolutionary relationship. The dioecy of the plant leads to high levels of heterozygosity even within a single cannabis variety ( Clarke and Merlin 2016; Schilling et al. 2021) and, unlike previously assumed, many morphological traits (e.g., leaf shape) do not correlate with phytochemistry ( Vergara et al. 2021). Many traits important for plant growth, development, and stress resilience have not been examined in detail.

To summarize, the vast amount of C. sativa variants coupled with a lack of defined genetic pedigrees poses a question as to the comparability of studies looking at different lineages. For instance, the literature surveyed here involved no less than 52 different hemp and 35 different medical cannabis varieties, inconsistently defined as cultivars, strains, or chemovars. When directly compared, many varieties display different responses to the same stressor, hinting to vastly different genetics within the species. For consistency, in this manuscript we use the terms “variety, cultivar, strain, and chemovar” interchangeably and as they appear in the original cited work. In addition to clearly defining the nomenclature, it may be relevant to consider utilizing a smaller number of standardized and genetically stable varieties in the future to ensure verifiable results that can be systematically applied to larger growth operations.