# Selection

> Selection in breeding is choosing which plants become parents, so that alleles behind the chosen traits become more common in the next generation.

- Canonical: https://genetixbay.com/knowledge/glossary/selection.html
- Also written: artificial selection, breeder selection, selecting, mass selection, phenotypic selection
- Glossary category: Genetics and breeding · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

Selection is deciding which plants get to reproduce. In breeding it is deliberate (artificial selection): the breeder grows a population, judges it, and uses only the best plants as parents. Over generations, the [alleles](https://genetixbay.com/knowledge/glossary/allele.md) behind the chosen traits become more frequent.

## In practice

Selection works on whatever the breeder measures, and only as fast as [heritability](https://genetixbay.com/knowledge/glossary/heritability.md) allows. High-heritability traits (flowering time, [chemotype](https://genetixbay.com/knowledge/glossary/chemotype.md), leaf shape) shift in a generation or two. Low-heritability traits (yield, potency percentage) need large populations, uniform conditions and repeated testing of clones or offspring.

Selection also works on both sexes. Choosing the female carefully and grabbing any male wastes half the opportunity. Breeders evaluate males by structure, vigour, smell of stems and early flowers, and above all by the offspring they produce.

Culling is the other half: removing every plant with [intersex](https://genetixbay.com/knowledge/glossary/hermaphrodite.md) flowers, weak roots, poor pest resistance or off-types, whatever its other virtues.

## Units and formula

Breeder's equation: R = h² × S. The response (R) equals narrow-sense heritability times the [selection differential](https://genetixbay.com/knowledge/glossary/selection-pressure.md) (S: how far the chosen parents are above the population average).

## Don't confuse with

- **Natural selection**: survival in the wild or a field without a breeder choosing.
- **A pheno hunt**: one round of selection among [seedlings](https://genetixbay.com/knowledge/glossary/seedling.md).

## Related terms

[Selection pressure](https://genetixbay.com/knowledge/glossary/selection-pressure.md), [Pheno hunt](https://genetixbay.com/knowledge/glossary/pheno-hunt.md), [Heritability](https://genetixbay.com/knowledge/glossary/heritability.md), [Male selection](https://genetixbay.com/knowledge/glossary/male-selection.md), [Progeny test](https://genetixbay.com/knowledge/glossary/progeny-test.md), [Stabilisation](https://genetixbay.com/knowledge/glossary/stabilisation.md)

## Read more

- [Selection and pheno hunting: sample sizes and scoring rubrics](https://genetixbay.com/knowledge/breeding/selection-pheno-hunting.md)
- [Quantitative traits and heritability: why most good traits are hard to fix](https://genetixbay.com/knowledge/breeding/quantitative-traits-heritability.md)

## Sources

1. Falconer DS, Mackay TFC. 1996. Introduction to Quantitative Genetics, 4th edition. Longman, Harlow. ISBN 978-0-582-24302-6
2. Allard RW. 1999. Principles of Plant Breeding, 2nd edition. John Wiley & Sons, New York. ISBN 978-0-471-02309-0