What Do F1, F2, S1, BXL, and IBL Seeds Mean?

Have you ever been caught in a conversation with friends where letters and numbers get thrown around, such as Bx, F1, S1, IBL, and just didn’t have a clue what they were talking about? Yes? Then this article is for you!

Cannabis breeding is entangled with trends, traits, context, and even geopolitical factors. Understanding breeding terminology and what different nomenclature means will enhance your knowledge of the cannabis plant, its history, and its development. Advancements in technology are paving the way for innovative methods in DNA-informed cannabis breeding. Below, we’ll provide a bit of historical context, break down the lingo, and present the pros and cons of different types of seeds.

TL/DR

• Cannabis breeding has been affected by nature and human geopolitics
• F1 Hybrids are “better than the best” of both their gene donors
• Learning breeding lingo improves our understanding of how new cultivars are made
• Changes in technology invite exciting new possibilities in DNA-informed cannabis breeding 

Basics of Breeding Cannabis Plants

Cannabis breeding is done by selecting a pollen donor (Male plant or staminate flower) and pollen recipient (Female plant or pistillate flower) with desirable traits. In unmanaged settings, the wind takes care of this task, spreading pollen for miles, hoping to land on a fertile bloom. This is also known as Anemophily or wind pollination.  

Humans and cannabis have been growing side by side throughout known history, and human fingerprints are all over cannabis genetics. Now, DNA analysis is being used to investigate which populations are actually unique from each other and how they differ. As we keep uncovering more about the biology of cannabis, breeding projects can focus on very specific traits.

Different Cannabis Breeding Techniques

In nature, after pollination, cannabis flowers develop seeds at the end of one fertility cycle (generally, spring to autumn). These mature seeds are shaken out of the dried plant’s heads by weather, animals, or merely gravity. Assuming they land in suitable conditions to survive and germinate, the population continues for another generation.

Traditional Cannabis Breeding 

Cultivators of any seed-bearing species generally look for desirable characteristics in the parents and prioritize saving and re-planting from the best. They select healthy and robust performers, fitting the needs of both the farmers and the end-users.

So this is how disease-resistant, local climate-adapted, and consumer-oriented types of cannabis were developed. Different strains served different needs. People who wanted the stalks for fiber focused on picking and improving those types. Folks with spiritual or other psychoactive aims chose to give preference to the most trichome-covered, aromatic flowers.

Modern Breeding Techniques

As you are probably aware, pistillate (“female”) plants that are never pollinated (“sinsemilla”) use the energy that would have gone into seed-making for the production of more THC, CBD, and other targeted phytochemicals, like terpenes. 

Breeding to harvest the maximum amount of these compounds made separating pollen donors and pollen receivers desirable.

Using reserved pollen or isolating a smaller group of plants in special breeding rooms, breeders can be much more specific about which plants donate their genes to future generations. 

When folks were able to pick genetics from more distant and distinct geographic regions, they could breed short-season (fast-flowering) or non-daylength dependent (autoflowering) plants with longer-season selections. This could reduce the time it would take for the cultivar (strain) to reach harvest time. 

Seed Breeding Lingo: What are all these acronyms? 

Knowing what people mean when they drop abbreviations like F1 Hybrid, IBL, etc, gives you insight into the history behind the plant you’re growing. When you do, you can really appreciate the collaborative, multi-generational efforts that secure and develop exceptional, exciting, and highly effective cannabis genetics for our own exploits in cultivation!

What is a True F1 Hybrid, and How are they Created?

When Parent A and Parent B are completely unrelated, the seeds they make together are known as True F1 Hybrids.   

A True F1 Hybrid, as opposed to any cross between any two plants with different names, is made by breeding genetic lines that are definitely distinct from one another. 

To be “true,” the lineage of each contributing partner in a cross must be known. Their DNA should differ to the point that their shared ancestry is untraceable (or ancient). 

In the legacy days, breeders sought out and crossed seeds that were from geographically distant places, sometimes called landraces. In isolation, nature and the local people developed inbred cannabis lines through a lack of available new genetics. But in many late-20th-century artificial breeding environments, a lot of people were working with the same basic building blocks. DNA analysis, and marker-assisted breeding, are now involved in the development process. People can look into the genetic profile of their selections to make informed choices about why certain plants could make excellent mates. 

What is an IBL? 

IBL stands for In-Bred Line. IBLs are bred with the intention to make a truly new and predictable cultivar (strain). 

As mentioned before, landraces were genetically distinct through geographic exclusion, they were so far apart from each other that they never mixed. Breeders nowadays will use IBLs in the same way they used to use landraces. Breeders will isolate specific traits through inbreeding to stabilize them in a plant’s genetics. 

A lot of care and investment goes into developing cannabis IBLs. The breeders make a choice about what characteristics they want to be passed down (let’s say, a high THC:CBD ratio, a distinct terpene profile, and a dependable days-to-harvest timeline), and they only breed the plants exhibiting those features. 

They continue to grow out populations, season after season, evaluating and selecting the “best” plants, those that exhibit the selected features the most. The goal has been reached when all the seeds of a generation grow very similar plants, very similarly resembling their parents. 

IBLs are usually a minimum of an F5, but some breeders will grow out 20 generations if they arent sure of the parentage.

Recognizable modern classic cannabis varietals, like White Widow,  Jack Herrer, and Northern Lights, resulted from such efforts. 

Are F1 Cannabis Seeds Better?

In short, Yes! True F1 Hybrids display what is known as Heterosis or “Hybrid Vigor.” Plants generally demonstrate increased growth rates, biomass (size), and more stress tolerance than their parentage.

Evaluations of Good, Better, and Best are, of course, subjective. Many people like to grow (and sell) F1 seeds because the batch will be fairly consistent and an improvement on either side of the family. 

As a consequence, a breeder can make certain claims about the taste and potency potential based on the harvested results of their first crop of the F1s. The preferred traits are usually ones that have been both naturally (in evolutionary history) and artificially (by the hands of human-assisted breeding) preferred. Two great gene donors should make even better children (at least in theory)! 

Are all F1 Hybrid Cannabis Seeds Identical? 

The term F1 comes from “Filial” (child or offspring, by extension) #1: it means it’s the first generation produced by two specific genetic donors (Plant A and Plant B). 

Just like siblings aren’t identical to one another, F1 seeds resemble their parents. Still, they are also their own individual packages of DNA. As they grow, nature and nurture play their part, and plants express some natural variations that support the survivability of the species. 

Isn’t Hybrid just a combination of Indica and Sativa? 

It is conventional in cannabis culture to classify weed into three main types: Indica (your “body stone”), Sativa (“head stone”), and Hybrid (some of both). 

Unfortunately, this doesn’t really shake out in the science; in fact, a pure sativa or pure indica landrace is very hard to find nowadays; therefore, modern breeding guesses these traits, and the language gives us a clue as to what characteristics we can expect from a named cultivar. We can understand that the breeder aimed to strike a balance between things we would call “Sativa traits” (commonly associated with tropical varieties) and “Indica traits” (usually thought of as smaller, bushy plants with shorter flowering seasons). 

What are Poly-Hybrid Cannabis Seeds?

Many of the new hot cultivars that are coming out these days are not True F1 hybrids but are, in fact, “poly”-hybrids. When you take two excellent plants from reputable sources and combine their genetics, you do get a hybrid, and they can be great. But this practice, sometimes called “pollen-chucking,” doesn’t guarantee quality and repeatability.  

Many new or trendy varietals have fairly close relatives, not that far back in their family trees, because of the genetic bottleneck created during prohibition. As mentioned earlier, this period was characterized by the lack of new distinct genetics. 

Risk-taking cannabis breeders had to experiment to enhance certain features. As they bred ideal flavor, potency, yield, and adaptability to different growing conditions, they did not always know “how related” their two genetic lines actually were. This caused them to create unstable lines. 

What Is the Difference Between F1 and F2, F3, etc?

If F1 means Filial 1, you’ve probably figured out that F2 means Filial 2, and so on. F2 seeds result from breeding two plants from an F1 generation (essentially, siblings). 

The downside to F2s is that they do not have the “vigor” of the F1 hybrids. 

F2 seeds are interesting because the plants in the population are more diverse. Instead of each seed displaying the most dominant traits from each donor, now, the statistics favor a greater likelihood of other combinations showing up in the mix. 

In human cultures, we tend to have social norms that attempt to prevent relatives from mating, partly because there are unpredictable and often undesirable genetic outcomes for the offspring (like certain genetic-based disorders that only occur if the gene is passed from both parents). 

Variance among phenotypes increases in the F2 generation. A phenohunt is when someone grows out a population of seeds to find specific plants for further breeding. 

This includes exposing the recessive genes that, unlike dominant genes, need to be passed down from both sides of a breeding pair to show up in their offspring.

Breeders grow and select their favorites from each generation of seeds they make, sometimes sharing these seeds or trading “cuts” (cuttings for cloning) with other breeders. 

Each person’s opinions on the best and most interesting genetic combinations become the parents for future generations. Then, through inbreeding, they are developed into stable genetic lines (IBLs) whose reputations last decades. 

Pros and Cons of Different Cannabis Seeds

What Does S1 Mean?

S1 means the seeds are known as “Selfed,” and they’re the First generation of seeds made in this process. 

A “selfed” seed comes from a female mother plant that has been literally bred with itself. To make this happen with cannabis requires some “fertility clinic”-type intervention. 

A pistil-bearing plant (“female”) is exposed to an organic chemical (usually Silver Thiosulfate), which causes it to grow some pollen-bearing reproductive parts. 

Unlike other forms of self-pollination, the resulting seeds don’t have the genetic programming to produce staminate (“male”) flowers. Instead it took a third party, the scientist/breeder, to manipulate it to happen. 

So that’s where we get the first batch of Feminized seeds. You can think of S1 seeds as the closest thing to a clone in seed form. S1s will grow fairly uniformly, displaying the same traits as their original “mother” plant. 

How do you get a Feminized F1 Hybrid? 

When you take pollen from the process of making an S1 (sometimes called “female pollen”) and use it to pollinate a plant that is truly genetically distinct, you will produce unique cannabis seeds. These feminised seeds will have both the Hybrid Vigour of an F1 and the sex-expression predictability of an S1. 

So, for example, Plant A and Plant B are entirely unrelated.  Someone treated Plant A with silver thiosulfate and pollinated Plant B: the seeds harvested from Plant B would be a Feminized F1 Hybrid. 

What Does Bx Mean?

The B stands for “Back,” and the X stands for “cross”. Backcrossed cannabis has been bred with a member of its own family from a previous generation. 

Breeders do backcrossing to raise the statistical likelihood the resulting crop will closely resemble its forebears. It’s an intentional shallowing of the gene pool.  

In the wrong hands, inbreeding and backcrossing can exacerbate problematic inheritances (for example, poor stress tolerance). This is known as “inbreeding depression”.

Novel and Future-Focused Cannabis Breeding Methods

Today, plant breeding is increasingly informed by refinement in laboratory techniques and technologies. 

Using DNA analysis, breeders are empowered to discover the true heritage of their plants and understand how many generations separate them. They can see which individuals are, in fact, distant cousins and which ones are entirely distinct. 

Plants exhibiting specific traits identified in exceptional phenotypes can be selected as genetic donors for subsequent generations.  

Better post-harvest analysis enables growers to detect the presence of smaller quantities of rare cannabinoids and other, possibly highly specific and therapeutically important, compounds.

Isolation of gene pools hosting certain undesirable characteristics, like unhelpful mutations or viruses, is also more achievable. 

Cryopreservation of cannabis genetics for future production (through micropropagation – also known as “tissue culture propagation” – which you can think of as test-tube clone) is creating opportunities that were previously unimaginable. A special plant can be held in suspended animation practically indefinitely and resurrected for breeding with others that were unavailable or unknown at the time of its storage.

Now that the genetic supply chain has added these new links, exchanges of material between interested breeders are better informed with quantified data.

Conclusion

We are in a rich era of cannabis breeding. Mainly because craft growers continue to refine and specialize their in-house cultivars. And they are increasingly able to provide the best conditions both nature and human innovation have to offer. 

Empowered by DNA analysis, breeders can dive deep into their trait selection process, creating a dynamic generation of new cannabis cultivars. 

In a world of diverse interests and desires, the discernment of cannabis consumers has increased dramatically. Sharing the ideals of identifying and preserving unique genetics while at the same time making access to the plant more universal, breeding serves these interests both where they intersect and diverge. 

This might be your first time thinking about your favorite cultivar’s family tree. Or perhaps you’re a longtime appreciator of the incredible interchanges of culture that led to that seed sitting in your hand. Give a moment of gratitude to the growers and scientists who’ve gone before: it’s been a labor of love!

Until next time, may you and your garden keep growing together ever higher!

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