Crossbreeding 101: Filial Generations (Gene Strengthening)
Credits to: Thailand Crossbreed Club for this lucid documentation.
Crossbreeding 101: Filial Generations- "Introducing the F0 generations and working them up to perfect your bloodlines in hybrid fish crossbreeding".
(F0): Pure blood wild fish. The F0 is the base of the foundation for any crossbreeding to be done. Choosing your F0 is very important when it comes to what true bloodlines you will be introducing into your cross. From this base line genetics we will begin to crossbreed in new bloodlines and strains to begin our project.
(F1): The F1 generation of hybrid crossbreeding is when u cross two F0 x F0 of two different species of cichlids etc... a good example of this would be the synspillium x hart-wedgie which gives us what we call in the Flowerhorn world the "Classic Kamfa".... sometimes in your F1 breeding project you'll find that your F1 looks very similar to your F0 this is actually a very good thing because now you can clearly identify a dominant trait in that fish which you can then use to perfect what your looking for in your f2 line... Clearly identifying dominant traits being pushed onto the fry is very important in perfecting your new generation fry. Once you know which genes are dominant this will help you to identify recessive genes at which later you will work back into your project etc... A good example of this would be flowerlines, pearls, eye color, body structure, finnage etc.
(F2): is the result of crossing the F1 x F1 you now have reached the next generation congratulations ! Most breeder's start to crossbreed new genes into this mix of different F1's strains to start to pull together there perfect f2 strain, a variety of crossbreeding, line breeding, and inbreeding start happening in the is the f2 generation. Many people in the Flowerhorn world will agree that the f2 generation of King Kamfa is the highest quality Kamfa known to date. The F2 King Kamfa has nice rectangular synspillium body's, majority will have the white eyes gene...massive pearling on the body,face and kok, and a big beautiful wrap tail gained from the synpillium crossbreeding ...Breeding the F1 male that looks most like your original strain and which also has the new characteristic you want to females from your original strain produces the F2 generation. You continue to do this, using only females from your original strain, because you must keep working the new characteristic back into that original strain. (This is Key)
(F3): If a special feature you want (and which was present in one of the strains used in the out-cross) does not show up in the F2 generations, you must take brother and sister from an F1 fry batch and inbreed them together to find out if the trait is recessive. If it is recessive, it should show up in 25% of the offspring from this sibling breeding. Assuming that the feature is a recessive, and it shows. This new F3 generation will now show the recessive trait. Please keep in mind that really what we mean when we say a trait is recessive is that an individual will not display a recessive trait unless he (or she) got the necessary genes from both parents. This F3 generation had and F2 male which did have the recessive trait for their father and their mother was from your original strain which does not carry the recessive; therefore, the F3's got the recessive genes from only one parent. Each offspring in the F3 generation carries the recessive genes, but there will not be visible evidence of it. The next step is to breed brother to sister from the F3 to give offspring, 25% of which will again show the recessive trait.
You can see that when you are breeding a recessive trait back into an established strain which does not carry the recessive, you have to use a two generation cycle for a while. In other words, every other generation you will breed siblings and in the alternate generations you will breed back to your pure strain females.
You remember we said there might be another reason why a trait would not show up in the first generation. It might be that the new trait was passed to the F1 females, but not the F1 males. But you never know.
Therefore, besides breeding brother to sister from the F1 generation to see if the missing trait is recessive, you must also breed some of the F1 females to males from your original strain to see if the trait you are working for is not recessive, but just carried by the females. If you get the new trait by breeding F females to your original strain males, you are off and running. That is, you would breed the males from your original strain into the hybrid females, which will be getting closer, genetically to your original strain after each generation of breeding.
In summary, when an out-cross is used to try to add a feature to an established strain, one of three things will happen in the fifth generation: 1) the desired trait is dominant; 2) it will not show in the first generation because it is recessive, or 3) it will not show in the first generation because it is carried by the females. The dominant trait and the trait carried by the females are the easiest to handle. The recessive trait is more difficult. But in all three your whole purpose is to breed the new trait into your original strain as often as possible.
This breeding back to your original strain will mean that you are purifying the hybrids, but it also means that the hybrids will be getting more and more like your original strain. You may start losing the feature you made the initial out-cross for and which you got in the first generations after the initial out-cross. You have to watch out for that. If things start going the wrong way, then you begin mating brother to sister within the hybrids to see what happens up in the F2 generation (from breeding F1 brother to sister), you pick an F2 male that looks most like your original strain and which has the new feature and then breed him to females from your original, pure strain which you have kept pure for exactly this purpose. This gives you the F3 generation from the initial out-cross
Credits to: Thailand Crossbreed Club for this lucid documentation.