The wtb mutation line is still a WTB.... so it has two blue egg genes.
every single WTG has one blue egg gene.
for all intents and purposes, they’re an olive egger.
it is theoretically possible to stabilize a green egg layer, but hard as heck. The only breed I think it’s been done in is Silveruud.
the brown egg color gene is really a white egg and there’s like 5-10 genes they think are in charge of the tones of the brown coating, so it’s a total mess to try and map out what genes you’re working on. But, I’m gonna call it a “brown egg gene” anyway.
Add to the mix that the WTG has a straight comb and it’s even harder. The pea comb is loosely linked to the blue egg gene so people cut in line sort of with test breeding to find a blue egg gene cockerel because if an EE or OE cockerel has a pea comb there’s a slightly higher chance they have a blue egg gene.
You would have WTG and you would breed them together. You would eliminate all male offspring. You would wait for the girls to lay, and then, you would eliminate all the blue layers and brown layers. You’re left with green only layers. Some of these would be 1 blue and 1 brown gene, and some (a very few) would be 2 blue genes with brown modifiers left over. I’d breed the females back to the father, the original WTG. We know because he is F1, he has a blue and a brown egg gene.
Then, you have the offspring of that mating, Im not sure if this is called F2 or F3 or what, I don’t really know the differences of those hybrid generations. Let’s call them F3, but, I am probably off. Anyway, you’ll need to start TEST breeding all the the F3 males AND the females. Females are slightly easier because once again, you can eliminate the blue and brown layers visually. Then, you are test breeding just the green layers. The boys of this mating, F3 boys, you have to test breed them ALL. This is because they could have picked up a brown gene from both parents.
To test breed, you take an F3 individual bird and mate them to a white layer breed. You then have to grow out at least 10 of the pullets from the single test mating to laying age. If ANY of the pullets of the test breeding offspring lay white or brown, that F3 individual has to be removed. If the F3 individual has two blue egg genes, all of the offspring will lay a shade of blue to green.
Im not so sure how you would determine, though, if the males carried just two blue egg genes OR carried two blue egg genes AND the brown modifiers (which is what you need). I suppose, but am just guessing here, that you would have to keep only F3 males that test bred to yield all green egg offspring when mated to a white layer…. BUT…. This is deep in these color genetics and I do not know.
Either way, the female test breeding is hard, yes, but, at least you’ve got pullets to deal with no matter what happens. Test breeding to find the roosters from your F3 that carry blue genes means growing out a LOT of birds.
