Cannabis Chemotypes I, II, III, IV, & V

Cannabis sativa, which includes Hemp, as well as all drug varieties, consists of different chemical variants. These variants differ in their chemical makeup as well as their morphology. Initially, three main chemotypes were identified. The first one, Type I, was defined as the “drug type” because of its high THC content and low CBD:THC ratio. The second chemotype, Type II, was defined as the “intermediate,” which consists of near equal parts of the two main cannabinoids, THC and CBD. Among Type II’s, CBD tends to be slightly more prevalent, while THC dominant Type II’s can be somewhat rare. The third one, Type III, is called the “fiber” or “non-drug type” and is mainly CBD. We often use the definition of hemp, with a THC amount lower than 0.3%, to classify type III chemotypes. There are also two additional chemotypes. Type IV, which is predominantly CBG, with some CBD present, and Type V, which was proposed to classify any material with undetectable amounts of any cannabinoids.

Source: https://www.slideshare.net/Adrienna/the-future-of-cannabis-genetics

We now understood that the inheritance of the three main chemotypes (I, II, and III) is due to the occurrence at B locus of two co-dominant alleles BD, responsible for CBD and BT, which is the allele responsible for the presence of THC. You can achieve all three main chemotypes by breeding two different chemotype parents, resulting in a segregation of the single locus (B) in the offspring. For example, a Type I drug variety crossed with a Type III hemp variety, will produce Type II chemotypes in the offspring. In this case, two homozygous parents of separate chemotypes (I and III) are crossed and the resulting progeny are a 50/50 of both parents. Since, these are all heterozygous at those alleles, when you inbreed them, the F2 progeny will exhibit all three chemotypes in a 1:2:1 genotypic ratio of chemotypes I, II, and III respectively.

While types I, II, and III are fairly straightforward to breed, things get more complicated as you dive into type IV’s and beyond. According to OregonCBD, there is evidence of three specific routes to create type IVs. The first is a double deletion of the THCAS and CBDAS synthases, such as in the case of Santhica 27. The second, is an abnormal “nonfunctional” CBDAS synthase in the presence of a normal nonfunctional THCAS synthase and third, an abnormal “nonfunctional” THCAS synthase in the presence of a normal nonfunctional CBDAS synthase. Other theoretical methods might include introducing exogenous forces to shutdown protein expression, such as gene silencing through a virus.

Source: https://www.slideshare.net/Adrienna/the-future-of-cannabis-genetics

Apart from these common chemotypes, we are now seeing new varietals on the market such as THCV-rich Black Beauty and Doug’s Varin. There are also, sure to come, new minor-rich varieties of which additional chemotypes may need to be created. With the passage of the 2018 Farm Bill, we are now moving into a world where type I drug varieties no longer dominate the cannabis market. In this new market, the cannabis type classification system is needed more than ever. Without a consistent language to differentiate the chemical makeup of cannabis chemotypes, consumers and industry insiders will struggle to communicate on the same level.