Semi-coerulea?

[3rdMaestro]

Hey everyone,
I was just wondering something after viewing some different cattleyas. I see that there are alba forms of some species of orchids, and sometimes semi alba, but I’ve never seen semi coerulea. Is that because it can’t happen, perhaps being genetically impossible? I’m not sure how it’s possible to have semi alba either, yet I know I’ve seen that on certain listings/pictures.

[Louis_W]

I think it must be impossible. The genes must be mutually exclusive recessive genes.

I'm not a breeder but it seems to me that the pigments that make a cerulea are the same ones that must be silenced to make and alba or semi alba.

I could be wrong. Just a layman's guess

[Fairorchids]

It is a genetic issue.

Alba & Semi-Alba are both recessive. If you breed them, you should get Semi-Alba.

Coerulea is also recessive.

If you cross either Alba or Semi-Alba with Coerulea, the resulting seedlings will all be standard tipo, since they do not get a double dose of either recessive trait.

[Louis_W]

Hey Fairorchids

Does this mean that it is theoretically possible to have a plant that is recessive in both alleles? Both as semi-alba and coerulea?

If not, does that mean that the traits are determined by the same allele?

Do you know where we can go if we want to learn more about this?

[3rdMaestro]

Well I wasn’t necessarily looking for an alba coerulea. More like, could you have an orange orchid with only a coerulea lip? Sort of like how dendrobium parishii semi alba is mostly white but has that touch of purple still in it. Can you have something similar with coerulea where it’s mostly or partly bluish, but another color still present?

[Louis_W]

I dont think that is possible. Coerulea is a condition that affects the entire flower. The genes are linked up in a way that makes it impossible to isolate parts of the flower as coerulea.

It may however be possible to breed a flower that has a purple lip and orange petals and sepals. Perhaps such a flower already exists, I'm not sure

[Fairorchids]

My genetics adviser responds: alba & semi-alba are not compatible, if bred together they would produce plain tipo.

Comment on coerulea: Many coeruleas have near white flowers, and color primarily in the lip. For example, see Laelia anceps: