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by Seshata on 26/06/2013 | Cultivation

Cannabis Genetics 101: Stabilising a strain

Stabilising cannabis Procedures to stabilise cannabis strains are poorly understood, even by breeders producing commercial strains. Stability refers to the variability and predictability found in the offspring of a parent generation: when a strain is unstable, variability will be high and predictability low; with a stable strain, the reverse is true.


Variability & predictability

Variability in this case refers to the range of different phenotypes that will express when hybridising two different strains; predictability refers to the expected distribution ratio of the different phenotypes. When crossing stable parents, Mendelian inheritance dictates that: 50% of the offspring will resemble both parents equally, 25% will express traits closer to the mother and 25% closer to the father.

Usually, breeders will stabilise a strain over several generations. First, a healthy mother and father are selected, and bred to produce hybrid offspring that will be of varying predictability depending on parent stability. Hence, if the mother and father are both considered stable, their offspring would be expected to express three phenotypes as outlined above.

Stable vs. true-breeding

It is important to note that ‘stable’ does not equate to ‘true-breeding’. A true-breeding strain is one that will produce consistent offspring of one dominant phenotype (with few to no specimens unlike their siblings);  in cannabis, these are usually found among the landraces and traditional cultivars. Further, breeders may use the term true-breeding to refer to single traits that will always recur (such as purpling or webbed leaves), rather than for overall phenotypic expression.

Mendelian inheritance at its most simple - 25% of offspring have the type AA, 25% are aa and 50% are Aa
Mendelian inheritance at its most simple – 25% of offspring have the type AA, 25% are aa and 50% are Aa

Stable parents usually produce predictable, homozygous offspring, although with a greater degree of variation than found in true-breeding strains. However, if one or more parents is unstable, crossing them together results in a range of heterozygous offspring that can express any number of unpredictable traits, and which will not correspond to predictable Mendelian ratios.

The traits that are dominant in each parent are recombined to provide the genetic basis for the next generation. The initial crossing of two unrelated parents is known as the filial-1 (f1) hybrid. Usually, the best examples of the f1 hybrids will be crossed to produce the f2 generation, which is usually even more unstable than the f1.

Crossing & back-crossing

With several generations of crossing together brothers and sisters from the same parents—selecting on the basis of desirable traits—a greater degree of consistency and therefore predictability can be achieved. Desired traits become dominant and will always appear, while undesirable traits are gradually eliminated from the gene pool and are no longer expressed.

For some traits, back-crossing plants to previous generations allows traits to become stabilised more quickly. Many breeders erroneously believe that some degree of back-crossing is necessary to stabilise any strain, but in reality this technique is only required for certain characteristics.

Inbreeding depression

After crossing and possibly back-crossing for several generations, the desired traits should begin to express in all individuals. However, after many generations of essentially limiting and reducing the gene pool so that only desired traits express, the resulting paucity of genetic material can lead to a level of inbreeding that is detrimental to the overall health and sustainability of the strain.

A simple diagram showing the potential for inbreeding to render unwanted, recessive traits dominant
A simple diagram showing the potential for inbreeding to render unwanted, recessive traits dominant

Put simply, if two related parents both carry the same recessive allele, which happens to be defective or otherwise deleterious, the chances of two identical copies passing to the offspring are far higher than with unrelated parents. If two individuals carrying these faulty alleles then breed with each other, the undesirable trait will be dominant and breed true in all subsequent generations of the lineage.

Outbreeding for improved diversity

For this reason, when strains begin to experience such severe inbreeding (known as inbreeding depression), it is common to introduce a new, unrelated father in a process known as outbreeding.

Inbreeding depression will occur more slowly if there is an abundance of genetic material from which to form new offspring. Therefore, with smaller population sizes, inbreeding depression can occur rapidly. This is especially common in countries with a strong cannabis-using culture that have not decriminalised the means of production, such as the Netherlands where small libraries are maintained due to risk of discovery.

Comment Section

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Matt Heyn

Wow what a great article. Breeding Cannabis is quite comprehensive. I have learned a lot from Robert Clark and Green's, 'Cannabis Breeders Bible.' I remember some details over all well put Seshata.

We here in America look up to the Dutch and their laws. We have such a clandestine culture surrounding Cannabis here. With current laws changing we can hope that The Federal Government will realize that the war on drugs is a war on Cannabis solely. Once we do this we can move forward and perpetuate the plant in a fundamental way, I think. Perpetuate the plant we have grown to use for many ailments, in a positive way.

27/06/2013

Deano

Marry me Seshata xo

12/05/2014

Why

How is an f2 that you choose a selected mother that will pass on desired traits become more unstable.....I'm sorry you choose a male that has similar traits then you would have a much more stable strain!!!!! "F2"&"F3" .....etc. Along with natural selection is how mother nature stabilizes strains.....wake up ppl and just observe nature

22/06/2015

Thee D.Spencer

F2 and even subsequent offspring can easily be more unstable because that's when recessive genes will appear. The first offspring of an unrelated pairing are F1 and if only one side carries a recessive gene it will carry on to a small percentage of the F2 generation. If both original patents carry a recessive gene it will show in a F2 generation but if only oneof the originals carries the recessive gene it won't show in the F2 generation. So you'd have what you think to be a more stable strain until F3 and subsequent generations with low percentage of plants with wild genetic variants. It's also a good way to find "hidden" recessive traits that you may desire in your strain but there is a give and take in every breeding between becoming more stable and inbreeding more recessive unwanted traits.

02/05/2016

calz

Hey there, awesome read for those starting on a breeding project. Myself; i already understand most of that as am in the feild of horticulture, already have the basics of crossing and inbreeding and have successfuly done both producing both an F1 and linebreeding from stable IBL. Would like to see bit more on the outcrossing (namely using hybrids or 'double-crossing') and also on top crossing or '3-ways'.

15/07/2015

calz

Also this for 'Why'. F2 is highly unpredictable n varied because it shows phenos of parents, grandparents plus great grandparents. F3-F5 wil also show recessive genes, once 7th generation is reached it should be fairly true-breeding providing good practice and selection is involved. If trying to create an IBL note taking and photos are a huge help.

15/07/2015

Thee D.Spencer

Well put

02/05/2016

Jason Murray

I am a grower out of oregon.Been growing for 20 years. Study cannabis botany for 5 years or more.I understood ur breeding medellain scale and it was thefirst time i saw that scale.u guys explained things well! Thank you!

26/09/2015

Haylo

It is so funny you guys actually arguing about stability, assuming the heredity mechanism is Mendelian.
~99% of the desired traits are quantitative, breeding and stabilizing is relevant in terms of populations, GWA, and is usually acquired by mass selection.

18/07/2016

NuggyNic

Reading that tells me why my Cali connection GSC seeds are all so different. 6 seeds. 1 never cracked. 1 damped off (my fault), the other 4 are all totally different. CCs GSC seeds are crap! Beware!

19/09/2016

jane doe

I have been growing cannabis for 15 years, received
about 30 seeds from a breeder friend o mine, most crap
seeds or died, 1 damped off small runt to darn, but the
3 seedlings I did grow are as follows. Plant#1 I broke the tap
root unfortunately, but has been fed organic liquid karma
i think has built a new tap root now, she is the best cannabis
strain i have ever seen in 15 years now, but is secret will not tell,
But i did name the strain CLEOPATRA is a pure indica though,with long fuzzy white hairs, at only 7 inches tall and
STINKS, will post up some photos
on the forums sometime, I AM THE ONLY PERSON WITH THIS INDICA
STRAIN OR TYPE OF CANNABIS, WHICH I BELIEVE IS EXTINCT, MOST
LIKELY EVEN THE NATIVE COUNTRY IT IS FROM DUE TO WARS ETC. Plant #2 She is a BERRY cocktail odor.they have been growin in 50% perlite,
and a 50% vermiculite mix I make myself, for ex. drainage,
Plant number #3 is a burnt rubber ORANGE, and is a MALE PLANT
BUT REALLY STINKS, AND ALL 3 STRAINS ARE SO CHRONIC.
AND ARE F-2 OR F-3, OR HIGHER? THEY ARE MY OLDEST SEEDS
FROM 4-5 YEARS SAVED FROM MEDICAL COLLECTIVES, THE
CROSSED BREED BY MY FRIEND, I PLAN ON STABLIZING,
ALL 3 PLANTS, THEY HAVE MISSING PARTS ON SOME LEAVES.
I TRIM THESE WITH MY CLIPPERS, and they seedlings
start growing some what more normal for themselves.
I will take cuts of all 3 strains, Cleopatra is my favorite,
because of the plants odor which as i said is a secret,
and is the strain i have been searching for 15 years now,
i have never seen so much resin in a cannabis plant like
these 3 strains just really old clone INDICA STRAINS,
JUST UNBELIVABLE QUALITY, I HAVE CROSSED A PURE
SATIVA MALE. WHICH WAS VERY TALL BUT SPICE ODOR
AND THE FEMALE DONOR PLANT WAS A PINEAPPLE, MOSTLY
SATIVA. ALL HAND POLLANTED BY ME, ON 1 BRANCH,
1 1/2 2 WEEKS INTO 12/12 -JUST SPRINKLED MALE POLLEN
AND MARKED W/PLASTIC BAG, AND
GARDEN TIE, TURNED ON MY FAN AT PLANT, 3 WEEKS
LATER SEEDS WHERE DONE, AND FLOWERS DONE AND NO MALE PLANTS LATER
ALL FEMALE AND DONE IN 2001-0R 2002 BEFORE PEOPLE
IN HOLLAND LEARNED-HOW TO FEMINIZE THEIR SEEDS?
I DO HAND POLLANTE THEM THROUGH, GREENHOUSE
SEED CO. LET THE MALE POLLANATE IN THE SAME ROOM,

MY MALE PLANTS WHERE OUTDOORS AND MY FEMALE DONOR INDOORS, UNDER MY
400 HIGH PRESSURE SODIUM VAPOR BULB.

22/09/2016

Youaredelusional

I couldn't get through the first few sentences before realizing this dude is delusional. Lol.

01/03/2017

peace khalifa

hi Dear . i have question
if we have 2 Clones from 1 Single (superStrain)
and Trying to polinate one of them with using collodial silver for sexing with other one ? what is future results ? can this seeds apear Exactly as mother-father plants?
can seeds have genetics problems?

03/12/2016

Scarlet Palmer

Hello Peace,

Thank you for your comment ? Unfortunately we cannot respond to grow questions on the blog, but we do have the Sensi Seeds Forum where you can ask a thriving community of gardening fans for advice, share your experiences, and see if your question has already been covered. I hope this helps.

With best wishes

Scarlet

05/12/2016

DRM Ranch

Successive selfing and selection of desirable phenotypes that are as identical to the founding mother as possible works toward stabilizing a strain.

Each generation will carry less and less undesirable genetic characteristics as those that do show up are removed from the breeding project.

Once the strain is reduced to as near a true breeding line as one desires the project can be called complete.

If the breeder desires the near true breeding phenotype can be then back crossed to the original mother plant and the process completed again as many times as desired.

It should be noted that any out breeding or back cross to the original and desired phenotype will result in an increase in genetic diversity requiring additional breeder selection and removal of undesirable traits.

While this process involves much inbreeding, any negative results are likely to be easily identified and removed from future use. Once bad genetics are found and removed they are gone, this is ultimately a good thing.

DRM Ranch

06/12/2016

Guess Work

I dont think ANY of you know what youre talking about. Great speculation though!!

18/03/2017

tony

send me your email bro, if you really do this and you're good at it and you know about it we can help each other out. I breed the best strains and select only the best phenomes, mostly the afghan indica dominant phenomtypes of all my strains

25/03/2017

bob

Talking of genetics becomes very complex. Although the mendelian square is a good ground to start, we are truly opening up a diverse selection of many different allele that are either closely related or situated upon differing loci upon the DNA strand. The combinations of these allele in pairing can either be expressed or switched off depending upon the allele itself. The back crossing becomes the stabilizing element, and even introducing a completely different strain can produce a hybrid of stronger growth and bigger yield. Creating a phenotype that breeds true having characteristics that are desired is a very lengthy process and careful thought along with detailed notes to review so as to deeper understand the process involved which is hidden in the genetic coding. Letting natural selection to take place without any human intervention then the phenotypes revert back to their original strains. I learn this from breeding show guppies.

25/03/2017

tony

this article helped a lot towards my knowledge of breeding and creating a reliable strain with only the best genetics, I had a general idea but wasn't sure. I'm going to be crossing some really bomb strains, like cup material

25/03/2017

mother nature

Imagine that the plants are people.
First, you have sex with a sibling. F1.
Then, your inbred offspring do the same. F2.
And then those even more inbred offspring do the same again. F3.
Imagine how genetically superior we could all be, completely severed from Nature.
How beautiful. How potent. Really ??
Stabilized hybrid horticulture is a good example of how myopic, greedy and sick humans have become.
And yes, stabilized hybrid cannabis culture started here at Sensi Seed Bank. Yes, you are the experts.
I have been growing organic, open pollinated cannabis outdoors for 40 years, growing with Nature, not against it.
My weed is sweeter, higher and genetically stronger than any inbred mutant will ever be.
When you take away the Sun, take away the earth and the wind and the rain and abuse the sexual integrity of the medicine, all you have left is a drug that makes you even more stupid than you already are.
Nature knows best, You can work with it, selective breeding is natural, progressive. Engineering a genetic cul-de-sac is not.

03/07/2017

Lotus buds

So true. Nature took care, is taking care, and will always take care. Humans only pollute.

24/08/2017

youroutsidebudisswagweed

you are a toxic person

09/10/2017

phoenix108

Well said! Kudos

28/03/2018

Joe

as far as breeding goes,can feminized plants pollen if there sprayed with the silver collidal spray and collected and then used to pollinate another feminized plant create only female seeds?in theory ..

04/08/2017

dave isaryk

thanks for a great article

09/10/2017

Winkin Sun

Thanks for sharing this knowledge. Just getting a grasp on breeding. Lots to consider, track and log and "TIME"
Cant help but hear @MotherNatures points about Sun Rain wind Organic outdoor altruism but science doesn't stop.

26/12/2017

Jeffrey

Wouldn't feminized seed production count as back-crossing? Of course it would. How many generations before inbreeding depression sets in? 3? 5? Some growers are headed toward a brick wall.

26/02/2018

phoenix108

Well said! Kudos

28/03/2018

WesternMass420

99% of everything written here is crap. Get your facts straight.

07/06/2018

Kevin Lee Smith

Well sounds like true grit.im going with mother nature and jamaica

13/09/2018

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