Talk:Genetic traits

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Discussion for: Genetic traits • View • Links • Related changes

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Page scope

Genetic traits covers the heritable characters of cannabis and what is known of their genetic basis, grouped by kind of inheritance: characters that segregate as single loci (sex, chemotype, insensitivity to day length), polygenic characters (flowering time, height and yield, cannabinoid content) and the characters most shaped by the growing environment. The study of heredity in cannabis as a whole, with the genome and the variation among populations, belongs to Cannabis genetics. The mechanism of sex determination belongs to Sex determination in cannabis, the chemical classes and their measurement to Chemotype and the plastic response to the environment to Phenotypic plasticity.

Data verification

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

Discussion

Sources

de Meijer and colleagues (2003), Genetics 163: 335–346: crosses of pure-THC and pure-CBD plants, the mixed F1, the 1:2:1 segregation in the F2 and the B locus with two codominant alleles.
Laverty and colleagues (2019), Genome Research 29: 146–156: the Purple Kush × Finola map; THCA synthase and CBDA synthase at separate loci in a region of suppressed recombination; no THCA synthase in Finola; the hemp gene resembling THCA synthase identified as CBCA synthase; a marker for total cannabinoid content near aromatic prenyltransferase.
Grassa and colleagues (2021), New Phytologist 230: 1665–1679: the CBDRx assembly and its synthase arrays; the Skunk No. 1 × Carmen cross, with one QTL for the THC:CBD ratio and six for total cannabinoid content.
Wenger and colleagues (2020), American Journal of Botany 107: 1423–1432: functional and non-functional CBDA synthase alleles predicting the THC:CBD ratio in feral, clinical and grain cannabis.
Divashuk and colleagues (2014), PLoS ONE 9: e85118: the XX/XY sex chromosome pair.
Faux and colleagues (2014), Euphytica 196: 183–197: monoecious cultivars as XX, and the degree of monoecy as a quantitative, cultivar-specific character.
Faux and colleagues (2016), Euphytica 209: 357–376: sex mapped as a marker in dioecious crosses, and five QTLs for sex expression in each of three crosses.
Petit and colleagues (2020), Frontiers in Plant Science 11: 102: variance components and broad-sense heritability of 28 traits in 123 hemp accessions at three sites in Europe.
Petit and colleagues (2020), Frontiers in Plant Science 11: 569958: the association study of the same panel, with QTLs for flowering time and sex determination.
Toth and colleagues (2022), Frontiers in Plant Science 13: 991680: Autoflower1 as a recessive single locus and Early1 as a major flowering-time locus, both on chromosome 1.
Woods and colleagues (2021), Genetics 219: iyab099: QTLs for agronomic and biochemical traits in a Carmagnola × USO31 cross.
Naim-Feil and colleagues (2023), Plants 12: 493: broad-sense heritability of cannabinoid, phenological and morphological traits in 119 drug-type genotypes grown as clones.
Beleggia and colleagues (2023), International Journal of Molecular Sciences 24: 8969: the shares of genotype, year and their interaction in the metabolites of six hemp cultivars over three years.
Beavis and colleagues (2023), in Suza and Lamkey (eds), Quantitative Genetics for Plant Breeding: the model of phenotypic value, broad- and narrow-sense heritability, and genotype-by-environment interaction.

Where the sources disagree

What the B locus is. de Meijer and colleagues proposed one locus with two alleles coding for forms of one synthase. Laverty and colleagues and Grassa and colleagues place THCA synthase and CBDA synthase at separate, closely linked loci and explain the single-locus pattern by that linkage. Wenger and colleagues score the locus by the CBDA synthase gene alone, as functional and non-functional alleles. The three accounts predict the same 1:2:1 segregation.
Where the autoflowering trait came from. The trait is widely attributed to Cannabis ruderalis. Toth and colleagues, who mapped Autoflower1, state that recent genomic studies do not support the existence of that group, and leave the origin of the locus open.
Which chromosome holds the synthase genes. The 2019 Purple Kush × Finola map places the synthase loci on its chromosome 6; the 2021 CBDRx assembly places its synthase arrays on its chromosome 7. Grassa and colleagues relate their chromosomes to those of Purple Kush and Finola in a supplementary table.

Terms

Trait and character are used as synonyms: a feature that differs among plants and can be measured or scored.
Chemotype in the inheritance studies means the ratio classes of THC and CBD (THC-type, intermediate and CBD-type), the classes the crosses scored.
Sex and sex expression. Sex is the plant's chromosomal constitution (XX or XY). Sex expression is the balance of male and female flowers it bears, which can vary in an XX plant.
Total cannabinoid content, which Grassa and colleagues call potency, is the summed concentration of all cannabinoids in the dried inflorescence, as distinct from the ratio between them.
Heritability figures are broad-sense estimates for the material and sites of each study: 123 hemp accessions at three European sites, or 119 drug-type genotypes in one controlled-environment facility. They describe those trials and are not fixed values for the species.

Images reserved in the article

Two images have places in the article but are not yet uploaded:

File:Cannabis-chemotype-B-locus-inheritance.jpg (lead), a diagram to be drawn: a cross between a pure-THC and a pure-CBD parent; the mixed F1 plant; an F2 row of one pure-CBD, two mixed and one pure-THC plant (de Meijer and colleagues 2003); and, beside it, a chromosome segment with THCA synthase and CBDA synthase as two neighbouring genes inside a shaded block where crossing over is rare (Laverty and colleagues 2019; Grassa and colleagues 2021). No chromosome number and no scale.
File:Cannabis-Autoflower1-photoperiod-insensitive-plants.jpg (Insensitivity to day length): a photograph of three photoperiod-insensitive female plants after 85 days under 16-hour days, the grain hemp Picolo, a Le Crème plant homozygous for Autoflower1 and their hybrid. Figure 3 of Toth and colleagues (2022), published under the CC BY 4.0 licence, shows them.