Cannabis Strain Finder by Genetics: Lineage and Chemotype

A cannabis strain finder by genetics matches a cultivar's genotype and lab-tested chemotype against a database of parent lines. It does not sort by name. Strain names repeat across unrelated plants, so genetic finders use three inputs: recorded lineage, cannabinoid ratios, and terpene results from a batch test.

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One locus sets the THC to CBD ratio

The balance of THC and CBD is inherited at a single locus. Two alleles, Bt and Bd, govern the activity of THCA synthase and CBDA synthase. Plants with two Bt copies make THC as the main cannabinoid. Plants with two Bd copies make CBD. Plants with one of each make a mixed profile. Breeders label these Type I, Type II and Type III chemovars.

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A finder that lists chemotype first removes much of the guesswork. Two cultivars sold under the same name but carrying different alleles land in different chemotype groups.

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Lineage terms used in the database

• Landrace: a population grown in one region for many generations. Examples include Afghani, Thai and Colombian lines.
• IBL (inbred line): a line stabilized by repeated selfing or sibling crossing. Offspring from an IBL show little variation.
• F1: the first cross of two inbred parents. Plants from an F1 seed lot are uniform at many loci.
• Backcross (BX): a cross back to one parent to move a trait, such as a CBD to THC ratio, into a line.
• S1: seed from one plant forced to self-pollinate. S1 lines vary more than IBLs.
• Polyhybrid: a cross of two hybrids. Parentage is hard to trace past two generations.

Names do not track genetics

Sawler and colleagues genotyped 81 marijuana and 43 hemp samples and reported in PLOS ONE in 2015 that sample names did not match genetic clusters. Related work found the labels indica and sativa have little genetic basis in cultivated drug-type plants. A finder that ranks by genetic distance sidesteps the naming problem.

How to run a search

1. Pick the chemotype you want: Type I, Type II or Type III.
2. Filter by lineage. Enter a parent name, a landrace, or a breeder line.
3. Read the parent list. One known parent gives a weaker prediction than two.
4. Open the certificate of analysis for the batch. Check total THC, total CBD and the terpene panel.
5. Save the batch number. Lab results differ between harvests of the same cultivar.

Limits of genetic prediction

Public genotype databases hold a few thousand samples. A plant grown from seed is a unique genotype even when both parents are known. A finder returns a probability range, not a fixed result. Terpene content also shifts with light, temperature, harvest date and cure.

US legal threshold

Federal law defines hemp as cannabis with 0.3% delta-9 THC or less on a dry weight basis. Cannabis above that limit is a Schedule I substance under the Controlled Substances Act. State programs set their own testing and labeling rules.