# Genotype by environment interaction

> Genotype by environment interaction (GxE) is when different genotypes respond differently to the same change in conditions, so the best cultivar in one room may not be best in another.

- Canonical: https://genetixbay.com/knowledge/glossary/genotype-by-environment.html
- Also written: GxE, G×E, GxE interaction, genotype-environment interaction, phenotypic plasticity
- 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"

Genotype by environment interaction (GxE) means the effect of the environment depends on the [genotype](https://genetixbay.com/knowledge/glossary/genotype.md). Two cultivars may rank one way under one light, feed or climate and the other way under another. Phenotypic plasticity is the related idea that one genotype can produce different [phenotypes](https://genetixbay.com/knowledge/glossary/phenotype.md) in different conditions.

## In practice

GxE is why "test your cultivar" is GenetixBay's stance. One clone may love [24/0](https://genetixbay.com/knowledge/glossary/24-0.md) veg and [13/11](https://genetixbay.com/knowledge/glossary/13-11.md) flower; another stalls. Some cultivars thrive with a mild late [dry-back](https://genetixbay.com/knowledge/glossary/dryback.md); others lose yield. One mother handles [heavy defoliation](https://genetixbay.com/knowledge/glossary/schwazzing.md); her sister sulks. Ca and Mg demand also varies by cultivar, more than by light type.

For breeders, GxE means selections should be tested in more than one environment before release. A keeper selected under one grower's lights in one climate may disappoint in a cooler, more humid room. Tester grows across many members are a practical way to see GxE.

## Don't confuse with

- **Genotype**: the DNA, which does not change between rooms.
- **Environmental effect**: when every genotype shifts the same way (all plants yield less in a cold room), that is not GxE.
- **Genetic drift**: clones do not drift genetically because they are moved to a new room.

## Related terms

[Genotype](https://genetixbay.com/knowledge/glossary/genotype.md), [Phenotype](https://genetixbay.com/knowledge/glossary/phenotype.md), [Heritability](https://genetixbay.com/knowledge/glossary/heritability.md), [Test grow](https://genetixbay.com/knowledge/glossary/test-grow.md), [Quantitative trait](https://genetixbay.com/knowledge/glossary/quantitative-trait.md)

## Read more

- [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. Acquaah G. 2012. Principles of Plant Genetics and Breeding, 2nd edition. Wiley-Blackwell. https://doi.org/10.1002/9781118313718