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What is an IBL?

Defining Inbred Lines
By Colin Gordon & Ben Owens

In cannabis, it has become increasingly common to hear the term "IBL,” especially when referring to specific varieties.

An IBL (inbred line) is a genetic line that has been intentionally bred over multiple generations for consistency and homogeneity of expression. At its most basic level, inbreeding involves two or more parents that share DNA. By definition, even filial breeding (F1 -> FX) is inbreeding.

A line is classified as an IBL when a specific genotype has been isolated and stabilized for consistent, uniform reproduction.

What is an IBL?

By definition, an IBL is a homogenous, genetically-stable variety that has been developed through multiple generations of breeding between related parents.

In most cases, an IBL is accomplished through backcrossing. For this reason, IBLs may also be referred to as IBCs (inbred backcross line). We use the term IBL to refer to cannabis genetics whose expressions have been stabilized through backcrossing. 

In some cases, a mixture of the two interpretations exists. Most commonly, this is referred to as an IBL or IX (inbred cross). This is typically used to refer to a filial offspring that is backcrossed into a prior filial, rather than back into the original parent, or when parents share significant genetic overlap. (F1 x Bx2 instead of P1 x Bx2, for example).

With each backcross to the original parent, shared expressions will become more pronounced, and recessive traits (or those of the original donor parent) will be suppressed.

Achieving IBL Status

IBLs are achieved through two processes: outdoor, self-pollinating landraces, and selective breeding.

In nature, the environment decides which expressions are naturally fit for survival. With each cycle, the most fit plants survive, and pollinate one another over generations until a relatively homogenous crop continues to exist through self-pollination. 

This is also how autoflower lines are stabilized, as it is not possible to maintain a mom of the initial parent.

With breeding projects, seed makers choose which expressions are desirable and breed in a direction that selects plants with that expression.

The number of generations it takes to reach IBL status varies, but agricultural breeders typically begin to release inbred lines after six or more generations.1,2

From parent to IBL

[insert chart here]

Image source:

Advantages of IBL

The biggest advantage that IBL varieties offer—regardless of whether you're a grower, breeder, or researcher—is predictability.

As a grower, predictability means that you will be able to rely on your seed stock to perform consistently from plant-to-plant and crop-to-crop with the same environment and care.

As a breeder, predictability allows for a controlled baseline. Expressions that are consistently dominant can be predicted among offspring, expediting the selection and stabilization process with each generation.

As a researcher, the generalizability of a study relies upon the stability of inputs; if you are working with unstable, non-IBL varieties, the results seen could be the result of a specific expression, rather than the experiment at hand. Additionally, with an IBL, further research can be done on the genotypes with varying degrees of genetic similarity with a high confidence level that could not be accomplished with unstable poly-hybrids.

Once a genetic reaches a point where a single phenotype is isolated and consistently replicated, a backcross is classified as an IBL.

The standards of cannabis are well behind those of commercial agriculture as far as IBLs and homogenized seed. Most cultivars in this industry are not stable by agricultural standards, but there are people in the industry who are slowly moving these types of projects forward. 

IBL In Practice

At ETHOS, I use IBL to refer to lines that have been worked until there is only one phenotype.

[ETHOS KUSH: Graphic of Black Fire Face Off x TK Afghan] - Pic 6/15

Caption: Ethos Kush IBL –– Black Fire  is the offspring of WiFi and The Black (a 1990s-2000s Afghan variety that came out of British Columbia). This genetic won 3rd Place in the 2015 national High Times Cup. Fletcher's Face-Off OG was then selected for its genetic similarity and sexual stability, and reversed into the Black Fire F1. This cross came out primarily OG Kush-dominant in expression, losing much of the Afghan quality. TK Afghan was then crossed into these offspring due to its gassier, chunkier, and faster-finishing nature than OGs.

In the world I operate in, genetics that are highly-related are enough to consider backcrosses.

WiFi is almost a Bx in itself. Face-Off is a Bx, and is genetically close enough to the OG lineage of Black Fire for their cross to be a Bx. The TK Afghan is a Bx (Afghan OG into an Afghan OG). But all of these "backcrosses" aren't technically backcrosses, because they do not involve the original parents.

In the above lineage, the only non-Bx cross in there is WiFi into the Black (the first actual cross). So what do you call it?

The reason that I went with IBL was that after several rounds of directional breeding, the seeds exhibited only one phenotype.

Simply put: if there are still multiple phenos, it's a backcross; if there's only one, it's an IBL.

This can be seen in our Super Lemon Haze IBL.

[Chart of SLH]

Caption: Super Lemon Haze IBL (LV Lemon Skunk x Male 94 Jack Herer) –– P->F1->Bx1->Bx1F2->Bx2F2->Bx2f3 – I ran 60 of the SLH F1 seeds and found them all to be very lemon skunk dominant. I took a random male that was a little more towards lemon skunk as far as morphology (not as monstrous) and made the F2 off of this. Still having the original SLH cut, I took the F2 and backcrossed it into the original SLH, and continued to cross until I narrowed her down to one pheno.

Looking at this chart, it may seem complicated, and people may wonder what the thought process is behind having so many partially-related crosses.

Often, when making new crosses, I will throw a few random mates in the room to create these partially-related lines that can be used as multiple tools within the same realm. This is what was done with the Super Lemon Haze. I already had the SLH, having made the seeds in 2010, and having a variety of partially related SLH gave me the tools to work the line further.

At this point, none of nomenclature adds up, so I'm going with the most accurate, looking at the SLH as a Bx6 or an IBL, and it's definitely down to one pheno.

Due to the confusion it can cause, we sometimes don't put the full crosses on the labels because it becomes so convoluted. I don't want to put out information that is not easily digestible; it mostly causes more questions.

With the SLH, I didn’t strategize this direction intentionally. I just kept crossing it to get various versions and ended up homogenizing it into the primary pheno.

I like SLH as a crosser; its most desirable traits are dominant and breed consistently. I use it in our Lemon OG Haze lines and Lilac Diesel, and in multiple backcrosses across the catalog. 

ETHOS basically has three different potential IBLs at this point: Ethos Haze, SLH and Ethos Kush.

With autoflowers, because we are always breeding from seed, each generation gets closer to an IBL.

Each iteration of an autoflower represents one step further down the genetic tree. When breeding autoflowers, it is not possible to maintain clones of the original parents, and new pollen donors and recipients must be chosen from each successive generation. By the sixth or seventh iteration of an autoflower, it is much closer to its IBL state.


1. Lee, M. (1994). Inbred Lines of Maize and Their Molecular Markers. In: Freeling, M., Walbot, V. (eds) The Maize Handbook. Springer Lab Manuals. Springer, New York, NY.

2. Robbins, M. (2019, November 14). Inbred Backcross (IBC) Lines and Populations. Plant Breeding and Genomics.

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