—possibly monogenic. For more information regarding the differences between
quantity and quality, see this book’s chapter by Grassi and McPartland. The
THC/CBD ratio, a dimentionless ratio, cancels two quantities (THC%, CBD%), and
provides a more valid comparison between plants cultivated in different
environments.
Hillig and Mahlberg ( 2004 ) published an exemplary CGE: 157 Cannabis
accessions from around the world, with passport data regarding provenance.
Accessions were classified into seven biotypes, witha priorisegregation based on
geographic origins and a genetic analysis (Hillig2005a). We will focus on two
populations in their study: the WLD biotype (n = 12 from Afghanistan, the
North-West Frontier Province of Pakistan, and Uzbekistan) and the NLD biotype
(n = 27 from India, Thailand, Cambodia, Mexico, Colombia, Jamaica, South- and
East Africa).
They prepared a voucher specimen of each accession, deposited in a herbarium.
Voucher specimens are critical for authenticating the identification of a taxon;
vouchers allow other researchers to retrospectively analyse accessions (Culley
2013 ). Hillig and Mahlberg made a great effort to exclude hybrids. For example,
“Not everything from Afghanistan is Afghani”(Hillig, pers. commun., 2006). An
examination of their vouchers reveals that a few hybrids snuck into their analysis.
They cultivated plants in a glasshouse under natural and supplemental light, and
staggered the harvest to sample each accession at peak, uniform maturity.
Cannabinoids were measured in individual plants, rather than in bulked samples.
Results obtained from NLD and WLD biotypes are presented in Table4.1.
Hillig and Mahlberg reported a statistical difference in CBD%, but no statistical
difference in THC% (Table4.1). They depicted cannabinoid profiles in graphs
(histograms and Cartesian graphs), but they did not present actual numerical data.
We calculated cannabinoid profiles of NLD and WLD biotypes from their data in
Table4.1, as the quotient of THC/CBD. NLD biotype = 5.48/0.02 = 274.0, WLD
biotype = 6.49/1.21 = 5.4. The order of magnitude difference between 274.0 and
5.4 is significant, although statistical inferences cannot be calculated for n = 2.
The WLD biotype produced a much greater concentration of cannabinoids
(represented by THC% + CBD% in Table4.1). This is likely due to the WLD
biotype’s greater density of perigonal bracts, and greater expression of CSG tri-
chomes onfloral leaves, compared to NLD plants. The size of resin heads (gland
heads) may also differ. Small and Naraine (2015b) measured resin head size in ten
strains of“high-THC medical marijuana”(WLD-NLD hybrids), which averaged
129 μm in diameter. Seven cultivars of low-THC industrial hemp averaged 81μm.
Table 4.1 Cannabinoid content (mean±standard deviation) in twoCannabisbiotypes, data
from Hillig and Mahlberg ( 2004 )
THC% CBD%a THC% + CBD%a THCV% + CBDV%a
NLD biotype 5.48±2.41 0.02±0.02 5.50±2.42 0.25±0.40
WLD biotype 6.49±4.09 1.21±2.78 7.70±3.45 0.14±0.30
aMeans in this column are statistically different using Student’s pairwisettest (p0.05)
108 J.M. McPartland