# IBL

> 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.

- Canonical: https://genetixbay.com/knowledge/glossary/ibl.html
- Also written: IBLs, in-bred line, stabilised line, stabilized line, stable line
- 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"

IBL stands for [inbred line](https://genetixbay.com/knowledge/glossary/inbred-line.md). In cannabis it means a seed line taken through many generations of closely related crosses (sib crosses, backcrosses or selfing) with selection each generation, until it breeds true: its seed reliably produces plants of the same type. An IBL is [homozygous](https://genetixbay.com/knowledge/glossary/homozygous.md) at most of the loci that define its traits.

## In practice

A real IBL is slow, expensive work: typically six or more generations, large populations at each step, and strict culling for herms, weak vigour and off-types. The pay-off is a line you can rely on, and an ideal parent for making uniform [F1](https://genetixbay.com/knowledge/glossary/f1.md) [hybrids](https://genetixbay.com/knowledge/glossary/hybrid.md), because it passes the same alleles every time.

IBLs also preserve a type. Many classic lines and some [landraces](https://genetixbay.com/knowledge/glossary/landrace.md) survive only because someone kept them going as [open-pollinated](https://genetixbay.com/knowledge/glossary/open-pollinated.md) or inbred seed lines rather than chasing new crosses.

Ask for proof. A line called "IBL" should come with its generation history, population sizes and [herm rates](https://genetixbay.com/knowledge/glossary/herm-threshold.md) from tester grows.

## Don't confuse with

- **Landrace**: a traditional, locally adapted population, often more variable than an IBL.
- **Clone-only**: a single genotype kept by cuttings, not a seed line.
- **Polyhybrid**: a recent mix of many lines, the opposite of an IBL.
- **Inbreeding depression**: the risk inbreeding carries; good IBL work culls it.

## Related terms

[Inbred line](https://genetixbay.com/knowledge/glossary/inbred-line.md), [True breeding](https://genetixbay.com/knowledge/glossary/true-breeding.md), [Stabilisation](https://genetixbay.com/knowledge/glossary/stabilisation.md), [Homozygous](https://genetixbay.com/knowledge/glossary/homozygous.md), [F1](https://genetixbay.com/knowledge/glossary/f1.md), [Line breeding](https://genetixbay.com/knowledge/glossary/line-breeding.md)

## Read more

- [Backcrossing, IBLs and stabilisation](https://genetixbay.com/knowledge/breeding/backcrossing-ibl-stabilisation.md)

## Sources

1. Allard RW. 1999. Principles of Plant Breeding, 2nd edition. John Wiley & Sons, New York. ISBN 978-0-471-02309-0
2. Charlesworth D, Willis JH. 2009. The genetics of inbreeding depression. Nature Reviews Genetics 10:783-796. https://doi.org/10.1038/nrg2664