A chemotaxonomic analysis of cannabinoid variation in Cannabis (Cannabaceae)

Abstract

Cannabinoids are important chemotaxonomic markers unique to Cannabis. Previous studies show that a plant's dry-weight ratio of Δ(9)-tetrahydrocannabinol (THC) to cannabidiol (CBD) can be assigned to one of three chemotypes and that alleles B(D) and B(T) encode alloenzymes that catalyze the conversion of cannabigerol to CBD and THC, respectively. In the present study, the frequencies of B(D) and B(T) in sample populations of 157 Cannabis accessions were determined from CBD and THC banding patterns, visualized by starch gel electrophoresis. Gas chromatography was used to quantify cannabinoid levels in 96 of the same accessions. The data were interpreted with respect to previous analyses of genetic and morphological variation in the same germplasm collection. Two biotypes (infraspecific taxa of unassigned rank) of C. sativa and four biotypes of C. indica were recognized. Mean THC levels and the frequency of B(T) were significantly higher in C. indica than C. sativa. The proportion of high THC/CBD chemotype plants in most accessions assigned to C. sativa was <25% and in most accessions assigned to C. indica was >25%. Plants with relatively high levels of tetrahydrocannabivarin (THCV) and/or cannabidivarin (CBDV) were common only in C. indica. This study supports a two-species concept of Cannabis.

Characterisation of cannabinoid composition in a diverse Cannabis sativa L. germplasm collection

“…4). GC analysis of chemotype II has typically demonstrated a more narrow range skewed towards a high CBD total to THC total ratio (De Meijer et al 1992;Hillig and Mahlberg 2004;Weiblen et al 2015), although a low CBD total to THC total ratio similar to those reported here have been observed in Southeast Asian landraces (Tipparat et al 2012). Nevertheless, this is the first time that such a wide range in chemotype II variability has been unequivocally assigned to genotype and heterozygosity of THCAS and CBDAS.…”

“…However, this is unlikely to be the case, as the distributions of chemotypes I, II, and III appear to be sufficient to account for the variation observed within the gene pool (Fig. 3) (De Meijer et al 2003;Hillig and Mahlberg 2004;Pacifico et al 2006).…”

“…Given the extensive genetic (Faeti et al 1996;Gao et al 2014;Gilmore et al 2007;Hillig 2005) and chemotypic variability (Baker et al 1980;Hillig and Mahlberg 2004) which appears to exist, use of each approach in isolation may not be sufficient to account for the full extent of variation in cannabinoid composition within the species. In the present study, we carried out a representative survey from a wide range of geographically and genetically diverse accessions with differing domestication histories.…”

“…The pentyl-alkyl-cannabinoids THCA and cannabidiolic acid (CBDA) are the major constituents found in plants ( De Backer et al 2009;Swift et al 2013), although a series of propyl-alkyl-cannabinoid homologues [delta-9-tetrahydrocannabivarinic acid (THCVA) and cannabidivarinic acid (CBDVA)] also occur in plants from specific geographical regions (Baker et al 1980;Hillig and Mahlberg 2004). Pentyl-cannabinoids are formed from cannabigerolic acid (CBGA) (Taura et al 2007b), while propyl-cannabinoids are formed from cannabigerovarinic acid (CBGVA) (Shoyama et al 1984).…”

Botany: The cultivation of weed

“…Based on proportions of CBD and THC levels, they suggested that there are two species, C. sativa and C. indica, that contain six subspecies 1 . Hillig later published a broader study identifying three species -adding C. ruderalis to the mix 2 .…”