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Basic genetics applied to marijuana strains

To be able to create stable and top-quality marijuana strains, our breeding team always takes into account several basic plant genetic concepts that help us stabilizing the desired traits from our parents to their offspring. Mendel’s Laws (Gregor Mendel 1885-86)  were the foundations upon which plant genetics were based, explaining the inherintance  of different traits among individuals of the same species. Thanks to these Laws, nowadays we can create autoflowering, purple or high-CBD strains, besides the large number of possibilities that arise if they are correctly understood.  First, we all should know what is a landrace and what is an IBL (Inbred Line).

Mendel's Laws and chromosomes

Mendel’s Laws and chromosomes

Landrace marijuana strain from Philosopher Seeds

A landrace or purebred is the endemic cannabis strain of a specific area. Generally – as long as they are kept pure – these plants will be very homogeneous, so they will have almost the same growing and flowering patterns and their organoleptic properties will also be quite similar.  Our Early Maroc strain is the perfect example of a landrace or purebred.

Early Maroc

Early Maroc grown outdoors

Early Maroc

Early Maroc’s colas, grown outdoors

Marijuana hybrids from Philosopher seeds (IBL)

IBL (inbred line) is how stable hybrids are called, hybrids which have been stabilised and show little variations on their phenotypes. Achieving an IBL is hard and requires time and patience; just to mention a few examples, Skunk or Northern Lights are typical IBL lines, as well as other strains which have been highly stabilised during the years, like Blueberry or White Widow.

Sour Diesel IBL "Riri" cut, grown by amc98

Sour Diesel IBL “Riri” cut, grown by amc98

Knowing this, we can continue with the next step: F1’s, F2’s, etc… F1 is the first filial generation from the cross of two different parentals, whether landraces or IBL’s. This first offspring of the cross will show the so-called hybrid vigour, what means that we will have better individuals than their parents, being more vigorous and strong than those from the parental generation, with better flower production and very homogeneous. A F2, then, is the second filial generation, the result of crossing individuals from the first filial generation (F1). Probably, we’ll lose the “hybrid vigour” trait in this second generation, as well as the stability of the first one. The F2 offspring will show 50% individuals with similar traits to the father or mother, while the remaining 50% will show intermediate traits. By crossing the F2 generation we get the F3, and  so on. All autoflowering strains from Philosopher Seeds, like Cheesy Auto, have been developed with this technique, achieving autoflowering hybrids from the fourth filial generation (F4).

Cheesy Auto marihuana

Back-crossing marijuana strains

BX – or backcross – is the cross between a F1 individual and one of its original parentals. This technique is useful if we want to stabilize particular traits from the parental to its offspring (resistance to pests and diseases, yield, flowering time, etc…). Once we have this first BX1, we can cross it again with the original parental to fix more traits (or to reinforce the fixed ones, getting the second backcross or BX2). Backcrossing is often used to replicate clone-only strains in seed form, so we achieve plants from seed very similar to the clone-only specimen; in this case, we use a male plant called “donor”, which often has a trait that the clone-only strain lacks, and cross its offspring with the original mother as many times as needed (cubing).

Motherplant with very special traits

Motherplant with very special traits

S1 is the result of crossing a female plant with herself by sex reversal, so we use a single phenotype for the whole process and get feminised seeds only.  The Tropimango is a perfect example of this type of genetic cross. Like we mentioned before regarding back-crossing and cubing, the S1 is another way to replicate a clone-only female whose parentals are lost, in this case, without using any male plant or “donor”.

Tropimango bud

Tropimango bud

To close the post, we will explain what are poly-hybrids, the most common type of seeds found on the market today.

Marijuana Poly-hybrids

A poly-hybrid is a cross between two non-stabilised different hybrids. Most commercial cannabis varieties offered by seedbanks are poly-hybrids. They are not F1s since their parentals are neither landraces nor stabilised strains. The resulting plants are usually vigorous but rather unstable; through a hard process of selection, we’ll find good individuals, but this will depend on how stable are the landrace parentals chosen to create the hybrid, and also on how stable are the hybrid parentals themselves. After many different crosses among our genepool, we have finally achieved a great poly-hybrid with tropical smell and taste, the Jack el Frutero variety .

Fruity Jack / Jack El Frutero close-up view

Fruity Jack / Jack El Frutero close-up view

We hope this post has been interesting, see you soon!

The articles published by Philosopher Seeds are reserved for adult clients only. In France, the age of majority is set at 18 years old. Consult your country's legislation and obey it. Philosopher Seeds is a Spanish company governed by Spanish law and can not, in any case, be held responsible for any misuse or non-compliance with the laws and regulations specific to each country, in relation to the articles published on its Blog. We remind you that the cultivation of cannabis seeds on French territory is strongly prohibited by law. We do not encourage our customers to break the law in any way and are not responsible for their use.



Comments and questions about Basic genetics applied to marijuana strains

  • Jan

    I’m thinking of crossing a
    1.Male Pure Thai/Cambodia Border Landrace, with Auto Blueberry and Auto Skunk ,
    2 F1.Male Thai-Blueberry with Female Thai-Skunk and Male Thai-Skunk with Female Thai Blueberry
    3 F2,Male (TBS) Thai blueberry skunk with female (TSB) Thai skunk blueberry, and (TSB) Male skunk blueberry with Female (TBS) Thai Blueberry Skunk
    4 F3. Male (TSB) skunk blueberry with (TSB} Skunk blueberry female, and (TBS) Blueberry skunk male with (TBS) Thai blueberry skunk female
    5 F4. Male TSB and TBS with original blueberry Auto Female and Skunk Female Autos, i wonder if it would create 100% auto flowering characteristics in F5 as they wil be (TSBB) Thai/skunk/blueberry/blueberry Auto And (TBSS) Thai/blueberry/skunk/skunk Auto, any advice would be greatful

    • Dani

      Hi Jan,

      A nice breeding project you have mate, good for you!

      If everything is ok and you only use the autoflowering parents in each generation, you should get 100% autoflowering strains in F5 for sure!

      Best of luck! 😉

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