Talk:Cannabis genetics

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Discussion for: Cannabis genetics • View • Links • Related changes

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Page scope

Cannabis genetics covers the study of heredity and genetic variation in cannabis as a whole: the genome and its assemblies, how sex, chemotype and quantitative traits are inherited, how variation is divided among hemp, drug-type, feral and landrace populations, what domestication and breeding did to it, and the genetics of conserving it. The heritable characters themselves, trait by trait, belong to Genetic traits. The measurement and patterns of variation belong to Genetic diversity, the evolutionary tree of the genus to Phylogenetics of Cannabis and the dates and places of domestication to Domestication.

Data verification

Record source conflicts, figures that differ between studies and sources not used here. Keep narrative content on the article.

Discussion

Sources

Divashuk and colleagues (2014), PLoS ONE 9: e85118: the karyotype, 2n = 20, nine pairs of autosomes and the XX/XY sex chromosomes.
van Bakel and colleagues (2011), Genome Biology 12: R102: the first draft genome (Purple Kush), the transcriptome and the THCA and CBDA synthase comparison with Finola; the legal limits on growing the plant for research.
Laverty and colleagues (2019), Genome Research 29: 146–156: the physical and genetic map of Purple Kush × Finola, recombination at the chromosome ends and the rearranged synthase region.
Grassa and colleagues (2021), New Phytologist 230: 1665–1679: the CBDRx assembly, the synthase arrays, the loci for the THC to CBD ratio and for total cannabinoid content, and hemp CBDA synthase introgressed into a drug-type background.
Lynch and colleagues (2025), Nature 643: 1001–1010: the pangenome of 193 genomes, its variation, its transposable elements, wild relatives and the sampling needed for the history of domestication.
de Meijer and colleagues (2003), Genetics 163: 335–346: the 1:2:1 segregation of chemotype and the B locus.
Woods and colleagues (2021), Genetics 219: iyab099: the 69 loci in the Carmagnola × USO31 cross.
Mohan Ram and Sett (1982), Theoretical and Applied Genetics 62: 369–375: male flowers induced on female plants by silver compounds, and all-female seed.
Sawler and colleagues (2015), PLoS ONE 10: e0133292: hemp and drug-type differentiation, strain names and the state of germplasm collections.
Zhang and colleagues (2018), Frontiers in Plant Science 9: 1876: the three latitudinal chloroplast lineages and day length.
Soorni and colleagues (2017), Scientific Reports 7: 15668: the partition of variation in Iranian landraces.
Ren and colleagues (2021), Science Advances 7: eabg2286: the domestication history from 110 genomes, the feral plants as escapes, the dates of about 12,000 and 4,000 years and the genes under selection; the legal restrictions on research.
McPartland and Small (2020), PhytoKeys 144: 81–112: introgressive hybridisation and the endangered drug-type domesticates.
Davinack (2024), Molecular Ecology & Evolution: An Introduction, an open textbook: effective population size and conservation genetics.

Source discrepancies

Genome size. The figures differ by what they measure. The 2011 draft assembled 534 Mb of sequence. Its authors cited estimates from flow cytometry of 818 Mb for the haploid genome of female plants and 843 Mb for males, the difference being the larger Y chromosome; Divashuk and colleagues cite the same estimates. The CBDRx assembly is 736 Mb, and the 2025 pangenome study puts the haploid genome at around 750 Mb.
Chromosome numbers. The THCA and CBDA synthase region lies on chromosome 6 in the numbering of the Purple Kush × Finola map (2019) and on chromosome 7 in that of the CBDRx assembly (2021). The two studies number the chromosomes differently.
The sex-determining mechanism. The 2011 draft genome paper describes sex determination as an X-to-autosome balance system, citing earlier work. Divashuk and colleagues (2014) describe an XY system; the competing readings are set out on Sex determination in cannabis.
Ren and colleagues on wild plants. Ren and colleagues (2021) suggested that pure wild progenitors of the species have died out. The 2025 pangenome study judged that wild relatives probably still exist in remote parts of Asia, on the evidence of one wild genome from Tibet.
Heritability of biochemical traits. Woods and colleagues state that biochemical traits are more heritable than agronomic ones in cannabis, citing an earlier field trial of hemp cultivars (Campbell and colleagues, 2019).

Terms

Chemotype is the chemical type of a plant, here the balance of THC and CBD.
F_ST measures how far two groups differ in allele frequencies, from 0 (identical) towards 1 (fixed for different alleles).
A quantitative trait locus is a region of the genome linked to variation in a trait that varies continuously.

Images reserved in the article

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File:Cannabis-sativa-male-karyotype.jpg (The genome): the chromosomes of a male plant laid out in pairs, nine pairs of autosomes and the X and Y, as seen under fluorescence in situ hybridisation. Wikimedia Commons holds such a karyotype, "Karyotype of Hemp (Cannabis sativa).png", from Divashuk and colleagues (2014), under the Creative Commons Attribution 2.5 licence.