The inheritance of chemical phenotype in Cannabis sativa L. (IV): cannabinoid-free plants

Abstract

A genetic factor that blocks the cannabinoid biosynthesis in Cannabis sativa has been investigated. Crosses between cannabinoid-free material and high content, pharmaceutical clones were performed. F 1 s were uniform and had cannabinoid contents much lower than the mean parental value. Inbred F 2 progenies segregated into discrete groups: a cannabinoid-free chemotype, a chemotype with relatively low cannabinoid content and one with relatively high content, in a monogenic 1:2:1 ratio. In our model the cannabinoid knockout factor is indicated as a recessive allele o, situated at locus O, which segregates independently from previously presented chemotype loci. The genotype o/o underlies the cannabinoid-free chemotype, O/o is expressed as an intermediate, low content chemotype, and O/O is the genotype of the high content chemotype. The data suggests that locus O governs a reaction in the pathway towards the phenolic cannabinoid precursors. The composition of terpenoids and various other compound classes of cannabinoid-free segregants remains unaffected. Backcrossing produced cannabinoid-free homologues of pharmaceutical production clones with potential applications in pharmacological research. A new variant of the previously presented allele 'B 0 ', that almost completely obstructs the conversion of CBG into CBD, was also selected from the source population of the cannabinoid knockout factor.

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

“…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).…”

“…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. In a single (B) locus model, chemotype II individuals are assumed to be heterozygote for the codominant B T (THCAS) and B D (CBDAS) alleles (De Meijer et al 2003). These alleles encode functional sequence variants of THCA and CBDA synthase, and therefore the efficiency (Pacifico et al 2006) with which CBG(V)A is converted to THC(V)A (B T ) and CBD(V)A (B D ) (Sirikantaramas et al 2004;Taura et al 2007b) (Fig.…”

“…Three main cannabinoid chemical phenotypes (chemotypes) are recognised based on CBD(V)A and THC(V)A composition (De Meijer et al 2003); Chemotype I (CBD(V)A: THC(V)A ratio [1), chemotype II (CBD(V)A: THC(V)A ratio close to 1:1), and chemotype III (CBD(V)A: THC(V)A: ratio \1) (De Meijer et al 1992). Additional chemotypes IV (CBG(V)A: CBD(V)A/THC(V)A [1) and V (total cannabinoid content \0.02 %) also occur at low levels within a subgroup of the C. sativa gene pool (Pacifico et al 2006).…”

“…Accurately characterising chemotypic variation offers the potential to identify allelic variation that can contribute to novel cultivars capable of meeting the demands of quality, safety, and efficacy necessary for the manufacture of cannabinoid-based pharmaceutical-grade botanical extracts (Potter 2014), or (De Meijer et al 2009). Black lines indicate alternative cannabinoid biosynthetic pathways.…”

“…The A pentyl allele is associated with the accumulation of pentylcannabinoid intermediate CBGA, while the A propyl allele is associated with the accumulation of propyl-cannabinoid intermediate CBGVA (Shoyama et al 1984). The B T and B D alleles encode functional THCA synthase and CBDA synthase homologs respectively (De Meijer et al 2003). The B T0 allele encodes a non-functional THCA synthase homolog, while B Dw , B D01 , and B D02 encode non-functional CBDA synthase homologs (Onofri et al 2015).…”