A recessive allele shows in the phenotype only when the plant is homozygous for it (aa). A plant with one copy (Aa) looks like the dominant type but passes the recessive allele to about half its offspring.
In practice
Recessives are why seed lines surprise people. Two vigorous parents can both carry a hidden recessive for weak growth, odd leaves or a missing trait; about one in four of their offspring will show it. Selfing and close inbreeding bring recessives out fast because they push loci towards homozygosity. That works both ways: it can reveal a rare recessive aroma a breeder wants to fix, or a defect that has to be culled.
The autoflowering trait is recessive. So is the expression of many deleterious alleles that cause inbreeding depression. A breeder who wants to know whether a plant carries a recessive does a test cross with a known aa plant: any aa offspring prove the carrier.
Don't confuse with
- Rare: a recessive allele can be common in a population and still be hidden in most plants.
- Weak or bad: recessive describes inheritance, not value. Many desirable traits are recessive.
- Codominant: in codominance both alleles show; nothing is hidden.
The phenotype is what a plant visibly and measurably is (shape, colour, smell, chemistry, timing), the result of its genotype acting in a particular environment.A plant is homozygous at a locus when it carries two identical alleles there (AA or aa), so it passes the same allele to every offspring.A dominant allele is one whose effect shows in the phenotype even when only one copy is present, masking the other (recessive) allele at that locus.Inbreeding is mating between related plants, which raises homozygosity; an inbred line is the resulting population, measured by the inbreeding coefficient F.A day-neutral cannabis plant that starts flowering by age, usually a few weeks after germination, regardless of light schedule; the trait is mainly recessive.An allele is one version of a gene; a diploid cannabis plant carries two alleles at each locus, one from each parent, which may be the same or different.Inbreeding depression is the loss of vigour, fertility, yield or survival that follows mating between relatives, mainly because harmful recessive alleles become homozygous.A test cross mates a plant of unknown genotype with one that is homozygous recessive for a trait, so the offspring ratios reveal what the first plant carries.A plant is heterozygous at a locus when it carries two different alleles there (Aa), so its offspring can inherit either one and segregate.F2 is the second filial generation, made by crossing or selfing F1 plants; it shows the widest segregation, bringing back hidden recessives and new combinations.S1 is seed from a plant pollinated with its own pollen; every S1 seed is female and a new genotype, not a copy of the parent.
