A polyhybrid is a cultivar built from many different parent lines in recent generations: a hybrid crossed with another hybrid crossed with a third. Its genome is a patchwork, heterozygous at many loci, and its seed segregates widely.
In practice
Most current market cultivars are polyhybrids. That explains common grower experiences: a pack of seed from a famous cross produces plants that look and smell very different from each other; seed saved from a great polyhybrid clone throws a scatter of types; and "the same name" from two sources behaves differently.
Polyhybrids are not bad. They can be vigorous, productive and full of variation to select from. But they are poor material for anyone who wants a predictable seed line, and they are part of why commercial cannabis is converging on similar profiles. Breeding polyhybrids from polyhybrids, with little stabilisation, multiplies the problem.
Don't confuse with
- Polyploid: extra chromosome sets; unrelated, despite the similar word.
- F1 hybrid: a single cross, possibly uniform if the parents were inbred.
- Landrace: a population with a long local history and coherent type.
- IBL: stabilised by inbreeding and selection, the opposite end of the scale.
A plant is heterozygous at a locus when it carries two different alleles there (Aa), so its offspring can inherit either one and segregate.Segregation is the separation of a plant's two alleles at each locus into different gametes, so offspring of a heterozygous parent vary in which allele they get.Stabilisation is breeding a seed line over several generations, with selection each time, until it reliably reproduces the chosen traits from seed.A chromosome is one long DNA molecule packaged with proteins that carries many genes; cannabis normally has 10 pairs, nine autosome pairs plus an X/Y sex pair.F1 is the first generation of offspring from crossing two parents; if the parents are inbred and different, F1 plants are uniform and often show hybrid vigour.A landrace is a traditional, locally adapted cannabis population kept by farmers in one region over many generations, with its own type and plenty of internal variation.An IBL (inbred line) is a seed line that has been inbred and selected over many generations until it breeds true for its main traits, giving uniform offspring.Inbreeding is mating between related plants, which raises homozygosity; an inbred line is the resulting population, measured by the inbreeding coefficient F.A hybrid is the offspring of two genetically different parents; almost all modern cannabis is hybrid, built from crosses between landrace-derived and other lines.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.
