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Breeding Cannabis, F1 and F2 Explained

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Breeding Cannabis, F1 and F2 Explained

Breeding Cannabis, F1 and F2 Explained

 Breeding Cannabis, F1 and F2 Explained

Cannabis Breeding Genetics F1 and F2 Generations
In common with orchids and prize roses, Cannabis seeds strains are grown and cross-bred by botanists to create new cannabis breeds with different characteristics. The most important characteristics manipulated through cross-breeding are the size of the plant, bud to leaf ratio, yield, taste, effect, and acclimatization to western growing conditions.

Breeding Cannabis, F1 and F2 Explained
Breeding Cannabis, F1 and F2 Explained

Sativa/Indica Differences
Breeding Cannabis, F1 and F2 ExplainedThere are two main varieties of Cannabis found in the world: Cannabis sativa and Cannabis indica. Cannabis sativa is a large “pine-tree like” plant with light green foliage. It is indigenous to Mexico, Columbia, Thailand, India, and Africa.

Cannabis Indica on the other hand is a smaller plant with wide, dark green foliage. It matures earlier and produces more potent, fatter, resinous flowers. Cannabis indica is indigenous to the high northern mountain ranges of the Afghani Hindu Kush, Pakistani Kara Korams, Russian Pamirs and Indian Himalayas.

There are many strains of each of the Cannabis varieties. cannabis indica and cannabis sativa.

Breeding Cannabis, F1 and F2 Explained

Until the last few decades, there had been very little crossbreeding of these Cannabis varieties because of this natural geographic segregation. However, in the 1960s and 70s seeds from different strains of the two varieties were collected from around the world. The strains were cross-bred by fertilizing isolated flowers from one variety with pollen from a strain of the other variety, creating offspring strains that were superior to the parents in terms of resistance to disease, yield, and levels of THC (the psychoactive ingredient in Cannabis), and could be grown better in northern latitudes.

Breeding Cannabis, F1 and F2 Explained
Breeding Cannabis, F1 and F2 Explained

A term used to describe strains produced by crossbreeding two different “true-breeding” strains.

True-breeding strains will produce true to type if reproduced from their own seeds, so different generations will share similar characteristics. True-breeding strains are either:

traditional land races that have only interbred with similar strains and so have almost identical genes


Stabilized Hybrids
Hybrids that have been created by breeders but then continually inbred until their characteristics are stabilized from generation to generation. There are very few strains of stabilized hybrids as the process takes a number of generations, over several years, to achieve.


F1” denotes that the seeds or plants have two true-breeding parents. The crossing of F1 hybrid strains produces plants whose characteristics won’t be the same as the original true-breeding parents, though they may share some. Plant quality is lost because the variation in genes is extended and making it less easy to foresee characteristics. The process is endless; F2s can be bred with other F2s creating F3s, with a further loss of quality.


Breeding Cannabis, F1 and F2 Explained


As you are probably aware of mendles peas, and the fact that an F2 made from two F1s give…
50% F1 trait for a given attribute.
25% Parent one trait for a given attribute.
25% Parent two trait for a given attribute.


However, if you back cross your F1 with Parent one again your F2’s turn out like this…
50% F1 trait for a given attribute.
50% Parent one trait for a given attribute.



Now, this is the bit that I suppose is the magic of back crossing, when you breed your F2 back cross with Parent one yet again you get either..
100% F1 trait or you get..
100% Parent one trait.
These are sometimes called F3 back cross-squared and at the best thing about doing it this way is this actually LOCKS a high percentage of the genes down. you can then carry on breeding you F3 squared back crosses with each other and you should not get too much fluctuation in the type. Really after this point you are really trying to select the best and strongest in the hope that you eliminate any weakness.


You might, and probably will find, at this point, that the F3 back cross-squared isnt what you were looking for when you started your project. It is then back to the drawing board to do it all over again in the hope that this time the genes fall a bit better.


It can, and often does, take years or even decades before a professional, well, TOP professional breeder has the seed that he was hoping to get when he started the project. He will not use the back cross route always, but will use it occasionally, He will not release any seeds until he is 100% happy and he knows that the only way he can really get to this point is by massive sampling rates selecting the best from hundreds of individuals for numerous qualities. (note where I put above that you get 100% F1 it should have read 100% F2 (50% F1 + 50% Parent one).



The point I was trying to make was that, although you read on various FAQs (including one around here somewhere) that 75% of your seeds with F3 back cross squared will be of the correct trait, is basically incorrect, and while it shows a great understanding of basic maths it totally misses dominant genes and the various theories behind back cross breeding.

They also make out that F4 back cross cubed your seeds will be 87.5% parent one trait. This is again incorrect. at F3 back cross squared your seeds will either be 100% F2 (50% F1 and 50% Parent One dominant, or 100% Parent One Dominant. at F4 back cross squared your seeds will be 100% as F3

The difference is that where as with an F3 back cross squared will stand a 50% chance of being 100% Parent One Dominant, the F4 has a 75% chance of being 100% Parent One Dominant. (50% chance of stabilizing at F3, and 50% of 50% at F4) in reality this isnt worth doing unless you have noticed something about one of the F3s that you really like but wasnt expecting. It is much more viable to do another back cross squared using F2 x Parent One than it is to do F3 x Parent One as it is just as likely to be Parent One dominant for the strain you want just with more chance of keeping a few of the Parent Two traits that you were after .

Now the very observant of you may be asking a few questions, the most viable of these is…
So how does a trait that I want to keep from an Parent Two female make it to the final product if we have only made F1 and Parent One traits available to it?
Well, remember back to mendles peas? you see, if we want to stabilize the “two weeks to flower” gene and manage to do it with our F3 back cross squares, that doesn’t mean that every single trait of the F1s will also stabilize.

Take my little project, that ive decided im going to do. SWT#3 x LR are the seeds I got. now if I back cross square it, only breeding the traits I want to keep… FAST TO AUTO-FLOWER and TIGHTER BUDS THAN A STANDARD LR.

Eventually, I will achieve an F3 that is Lowryder Dominant in the vegging pattern, but still F1 typical in its Bud density.

Now, this is the time when I will stop back crossing and start to breed the F3s together, remember that 25% of these will show the SWT#3 trait for dense buds, although because we have stabilized the FAST TO AUTO-FLOWER trait it will have that too.

Then starts the long winded process of trying to stabilize the dense bud gene, this can only really be done by years and years of cross breeding the F3s together and then selectively breeding these off sprig together too until the genes regarding bud density become dominant.

In practice, because this is a hobby, I wont do it, and will instead accept defeat and make do with 25% of my plants being the same bud density as LR, 50% of them being slightly higher than LR, and the other 25% being high bud density. This is usually where you see phenotypes, things the breeder decided were worth passing by as the main achievement (to make a LR with SWT#3 attributes too) has been reached and it wasn’t worth going through a decade or two to remove the problem.

The other thing a breeder can do at this time of course is to select the medium bud density plants, and cross it with the high bud density plants. A blumming hard trick as they are both females but it is possible if you can force hermie on one of them (not easy with a fast-to-flower plant) and keep the hermie trait from moving across too. I hope you enjoyed  Breeding Cannabis, F1 and F2 Explained

as always comments are more than welcome!


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