Cannabinoid synthase genes are responsible for converting precursor chemicals into the cannabinoids we all love and benefit from. The genes are classified based on their nucleotide sequence similarity and the resulting compounds produced--CBGA, CBDA, THCA, and CBCA. Onofri et al. (2015) genetically cataloged the largest collection of CBDA and THCA synthases and reported the relative proportion of the namesake compounds produced by each. Genes can also serve as one piece of a "DNA fingerprint." Ben Holmes's OttoII/BaOx lines are most similar to an old German fiber variety. All of the type II and type III plants from Spain over the past decade (Cannatonic, etc.) are identical to a known type II Afghan hash variety. Ringo's work is related to a Chinese fiber variety. Nearly every current variety produced in the US is a relative of these synthase families.
The authors also demonstrated that specific changes in synthase coding--in both CBDA and THCA genes--could weaken or altogether block the conversion of CBGA and lead to accumulation of that compound instead. Two known CBDA genes (5/1 and 6/4) are partially functional, leading to 2/3 CBDA and 1/3 CBGA in the 5/1 gene and 1/3 CBDA and 2/3 CBGA in the 6/4 gene, respectively. The 6/1 gene (Italian fiber variety) only accumulates 6% of its total cannabinoid fraction as CBDA; most of the rest is CBGA.
One THCA gene (1/3) was identified as a major CBGA accumulator (11.1% is THCA); its significant loss of function is driven by a single nucleotide change at position 706 (G->C). The germplasm originated in Malawi. The single site change occurred after multiple generations of self-pollinating.
The "Oregon CBD THCA synthase" (it emerged in our breeding program through self-pollination and we have spent the past 4 years characterizing its structure/function) is unique. It shares 100% identical similarity with several THC varieties known to accumulate 1%-2% CBGA (Animal Cookies etc.), with the exception of a single nucleotide change at position 1064 (G->A).
Guess which gene is present in all of the “new” CBG varieties released this year?