# Polyhybrids vs landraces: what each gives a breeder

> A landrace is a locally adapted, farmer-maintained population with a regional history; it is variable but coherent, and a reservoir of diversity. A polyhybrid is a modern line with many ancestors from different gene pools; it can be highly productive but is heterozygous and segregates unpredictably. Breeders use landraces as sources of new traits and polyhybrids as elite starting material.

- Canonical: https://genetixbay.com/knowledge/breeding/polyhybrids-vs-landraces.html
- Category: Breeding · Level: Advanced
- Evidence: Supported · Status: Draft: awaiting expert review (some figures are being checked)
- Stage: Any stage · Systems: Any system
- Updated: 2026-10-31 · Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay Knowledge Base (genetixbay.com/knowledge)"

## Questions and answers

**What is a [landrace strain](https://genetixbay.com/knowledge/glossary/landrace.md)?** A landrace cannabis strain is a regional population shaped over many generations by local farmers and climate. Plant-genetic-resources literature defines it by historical origin, distinct identity, local adaptation and links to traditional farming, usually without formal improvement. Landraces are variable but coherent, and many are now endangered by replacement with [hybrids](https://genetixbay.com/knowledge/glossary/hybrid.md).

**What is a polyhybrid?** A polyhybrid is a cannabis line whose pedigree combines many unrelated ancestors, which describes most commercial strains today. Polyhybrids are often productive indoors and bred for flowering in about 8-10 weeks, but each plant is highly [heterozygous](https://genetixbay.com/knowledge/glossary/heterozygous.md). Genetic studies show their reported ancestry and actual genetic structure only partly agree.

**Are landraces more stable than hybrids?** Landraces are usually more uniform from seed than polyhybrids, though not perfectly uniform. A landrace in its region has moderate to high but coherent variation, while polyhybrid seed shows low uniformity because each parent is heterozygous at many genes. A landrace's variation is part of its value, not a defect, and imports often lose some through [bottlenecks](https://genetixbay.com/knowledge/glossary/genetic-bottleneck.md).

**Why are my polyhybrid seeds so variable?** Polyhybrid cannabis seeds are variable because each parent clone is heterozygous at a large share of its genes. Crossing two such plants reshuffles many alleles at once, so the so-called [F1](https://genetixbay.com/knowledge/glossary/f1.md) behaves like an [F2](https://genetixbay.com/knowledge/glossary/f2.md) and throws many different phenotypes. Uniform seed would require more inbred, stabilised parent lines.

**How should a landrace be preserved?** Preserve a cannabis landrace by keeping population size up, ideally 20-50 or more females and 10-20 or more males per generation, pooling pollen from many males, and isolating it from other cannabis. Avoid selecting for your own preferences; remove only diseased or off-type plants. Document its origin and regenerate stored seed before [germination](https://genetixbay.com/knowledge/glossary/germination.md) falls.

**Is an heirloom the same as a landrace?** No, an heirloom is not the same as a landrace. An heirloom or heritage cannabis line has been kept for decades, often outside its origin, by growers or seed collectors. It may descend from a landrace but has been through new selection and founder bottlenecks, losing some adaptation. Many 1990s seed-bank 'pure landraces' are really heirlooms.

**Short answer.** Landraces are regional populations shaped by local farmers and climate over many generations: variable, adapted, and genetically distinct from each other. Polyhybrids are modern mixes of many such sources: often more productive in indoor conditions, but heterozygous, so their seed scatters. Neither is "better". Landraces are where new traits live; polyhybrids are where most modern selection happens.

## Definitions

- **Landrace:** a dynamic population with historical origin, distinct identity, local adaptation and association with traditional farming, usually lacking formal improvement [1].
- **Heirloom / heritage line:** a line kept for decades (often outside its origin) by growers or seed collectors. It may descend from a landrace but has been through new selection and bottlenecks. Not the same thing.
- **Polyhybrid:** a line whose pedigree combines many unrelated ancestors. Most commercial "strains" today [3][6].

## Comparison

| Feature | Landrace (in origin) | Heirloom import | Polyhybrid |
|---|---|---|---|
| Genetic variation within | Moderate to high, but coherent | Often reduced (founder bottleneck) | High heterozygosity per plant |
| Uniformity from seed | Moderate | Variable | Low |
| Adaptation | Local climate, [day length](https://genetixbay.com/knowledge/glossary/photoperiod.md), pests | Partly lost outside origin | Indoor production |
| Flowering time | Often long (tropical) or short (high latitude) | As origin | Bred for 8-10 weeks typically |
| Value to breeders | Novel alleles, resistance, unusual chemistry | Historical reference | Elite combinations to select from |
| Conservation status | Many endangered by hybrid replacement [2] | Small populations, drift | Abundant |

McPartland and Small (2020) describe several high-THC landrace groups as critically endangered [germplasm](https://genetixbay.com/knowledge/glossary/germplasm.md) and note that widespread hybridisation over the past 50 years has blurred distinctions [2] (*Supported*).

## Why polyhybrid seed scatters

A polyhybrid clone may be heterozygous at a large share of its genes. Crossing two such clones produces offspring that reshuffle many alleles at once, so the "F1" behaves like an F2 (see [F1, F2, F3](https://genetixbay.com/knowledge/breeding/f1-f2-f3-explained.md)). Genetic studies show commercial drug-type cannabis is a mixed [gene pool](https://genetixbay.com/knowledge/glossary/gene-pool.md) in which reported ancestry and genetic structure only partly agree [6] (*Supported*).

## Preserving a landrace properly

1. **Keep population size up.** Grow and cross as many plants as you can, ideally ≥20-50 females and ≥10-20 males per generation; bottlenecks lose rare alleles (*Supported* by general conservation genetics) [5].
2. **Avoid strong selection** for your own preferences; you are conserving, not improving. Remove only diseased or off-type plants (pollen contamination).
3. **Pool pollen** from many males, or do many pair crosses and bulk the seed.
4. **Isolate** from other cannabis.
5. **Document origin claims**: where collected, when, by whom, and how many seeds, as GB-DOCs. Unverified origin = L1 at best.
6. **Store seed** properly and regenerate before germination falls (see [seed testing](https://genetixbay.com/knowledge/breeding/seed-germination-testing-qc.md)).

## Using a landrace in breeding

- Cross landrace x elite, then [backcross](https://genetixbay.com/knowledge/glossary/backcross.md) to the elite while selecting for the landrace trait (see [backcrossing](https://genetixbay.com/knowledge/breeding/backcrossing-ibl-stabilisation.md)).
- Expect long flowering, tall stretch or different chemistry in early generations.
- Check legality and [benefit-sharing](https://genetixbay.com/knowledge/glossary/benefit-sharing.md) rules for collected material from other countries.

## Common mistakes

- Calling a 1990s seed-bank line a "pure landrace". Usually it is an heirloom with its own history.
- "Preserving" a landrace by keeping one female and one male.
- Treating a landrace's variation as a defect. It is the point.

## Evidence

- Landrace definition: *Established* (plant genetic resources literature) [1].
- Endangered status of cannabis landraces: *Supported* [2].
- Commercial cannabis as a mixed, heterozygous gene pool: *Supported* [3][6].
- East Asian domestication origin: *Contested* [4].
- Population-size guidance: *Supported* by general genetics [5]; exact numbers are rules of thumb.

## Sources

1. Villa TCC, Maxted N, Scholten M, Ford-Lloyd B. 2005. Defining and identifying crop landraces. Plant Genetic Resources 3(3):373-384. https://doi.org/10.1079/PGR200591
2. McPartland JM, Small E. 2020. A classification of endangered high-THC cannabis (Cannabis sativa subsp. indica) domesticates and their wild relatives. PhytoKeys 144:81-112. https://doi.org/10.3897/phytokeys.144.46700
3. Lynch RC, Vergara D, Tittes S, et al. 2016. Genomic and chemical diversity in Cannabis. Critical Reviews in Plant Sciences 35(5-6):349-363. https://doi.org/10.1080/07352689.2016.1265363
4. Ren G, Zhang X, Li Y, et al. 2021. Large-scale whole-genome resequencing unravels the domestication history of Cannabis sativa. Science Advances 7(29):eabg2286. https://doi.org/10.1126/sciadv.abg2286
5. Charlesworth D, Willis JH. 2009. The genetics of inbreeding depression. Nature Reviews Genetics 10:783-796. https://doi.org/10.1038/nrg2664
6. Sawler J, Stout JM, Gardner KM, et al. 2015. The genetic structure of marijuana and hemp. PLoS ONE 10(8):e0133292. https://doi.org/10.1371/journal.pone.0133292