A sib cross is a cross between siblings. Full sibs share both parents; half sibs share one. In cannabis it usually means crossing a selected female with a selected male from the same seed batch, which is how F2, F3 and later generations are made.
In practice
Sib crossing is the standard way to advance a line without bringing in outside genetics. With selection each generation, it gradually raises homozygosity and makes the line more uniform. It is slower and gentler than selfing.
Done with tiny populations (one female, one male, every generation), sib crossing narrows the gene pool quickly and can lead to inbreeding depression. Breeders reduce this by selecting from more plants, keeping several parallel families, and crossing families occasionally.
Unlike selfing, a sib cross uses a real male. GenetixBay prefers it for exactly that reason: males are part of breeding, and a selected male carries information the female alone cannot.
Inbreeding coefficient after one generation of full-sib mating from unrelated parents: F = 0.25. Half-sib: F = 0.125.
Don't confuse with
- Selfing: the same plant as both parents (F = 0.5 in one generation).
- Outcross: crossing outside the family.
A seed run is a dedicated grow in which selected parents are crossed to produce a batch of seed, as opposed to growing for flower.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.Filial generations (F1, F2, F3 and on) count generations of offspring from an original cross, each made by crossing plants of the previous generation together.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.Selfing is pollinating a plant with its own pollen, in cannabis usually by reversing part of a female to make pollen; it is the most intense form of inbreeding.The gene pool is the total set of alleles present in a population, cultivar group or species; a narrow gene pool limits what breeders can select from.Inbreeding depression is the loss of vigour, fertility, yield or survival that follows mating between relatives, mainly because harmful recessive alleles become homozygous.Inbreeding is mating between related plants, which raises homozygosity; an inbred line is the resulting population, measured by the inbreeding coefficient F.Line breeding is a mild form of inbreeding in which plants are mated within a family, often back towards one outstanding ancestor, to concentrate its traits while limiting inbreeding.
