SNP in Potentially Defunct Tetrahydrocannabinolic Acid Synthase Is a Marker for Cannabigerolic Acid Dominance in Cannabis sativa L

Abstract

The regulation of cannabinoid synthesis in Cannabis sativa is of increasing research interest as restrictions around the globe loosen to allow the plant's legal cultivation. Of the major cannabinoids, the regulation of cannabigerolic acid (CBGA) production is the least understood. The purpose of this study was to elucidate the inheritance of CBGA dominance in C. sativa and describe a marker related to this chemotype. We produced two crossing populations, one between a CBGA dominant cultivar and a tetrahydrocannabinolic acid (THCA) dominant cultivar, and one between a CBGA dominant cultivar and a cannabidiolic acid (CBDA) cultivar. Chemical and genotyping analyses confirmed that CBGA dominance is inherited as a single recessive gene, potentially governed by a non-functioning allelic variant of the THCA synthase. The "null" THCAS synthase contains a single nucleotide polymorphism (SNP) that may render the synthase unable to convert CBGA to THCA leading to the accumulation of CBGA. This SNP can be reliably used as a molecular marker for CBGA dominance in the selection and breeding of C. sativa.

Keywords: CBG; cannabinoid synthesis; cannabinoids; hemp.

Figure 1

Distribution of CBDA:CBGA ratios in Cross TE, a backcrossed F₂ population of 102 individuals resulting from an F₁ cross between a Type III (CBDA-dominant) plant and a Type IV (CBGA-dominant) C. sativa plant. The arithmetic mean is indicated with a diamond. Whiskers indicate 1.5 × the inner quartile range and open circles are observations that fall outside of this parameter.

Figure 2

Distribution of THCA(V):CBGA(V) ratios in Cross FH, a selfed F₂ population of 99 individuals resulting from an F₁ cross between a Type I (THCA(V)-dominant) plant and a Type IV (CBGA-dominant) C. sativa plant. The arithmetic mean is indicated with a diamond. Whiskers indicate 1.5 × the inner quartile range and open circles are observations that fall outside of this parameter.