Quote:
Originally Posted by gary
Beautiful. Could you explain a little about the genetics and breeding of an intermedia peloric alba?
Thanks,
Gary
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Hi Gary! I’m no expert in this field, but I can try to put it in simple words (those of you who are biologists, molecular scientists or have similar formal education, this is a simplification, but please fell free to correct me if my general approach fails).
Peloria is an abnormality that appears in some flowers modifying its spatial structure. A monstrosity, if you prefer. Most of times, among orchids, this monstrosity is represented by the repetition of the lip spatial conformation and color patterns in the petals, but this can also occur in the sepals.
To try to understand the peloric traits in an alba, lets take before a regularly colored C. intermedia as an example and see how an alba appears. At least two sets of genes are involved: one controlling whether the colors of the lip show up or not, and another controlling whether the color of the side petals and sepals shows up or not.
To facilitate, lets assume that:
“A” is the set of genes controlling the appearance of colors in the lip;
“B” is the set of genes controlling the appearance of the color in the sepals and side petals;
These two sets can assume three states:
- A and B are turned on, and then the regular colors of the flower appear;
- B is turned off and A is turned on, and then the semi alba variety appears;
- both sets are turned off, and then the alba variety appears.
There’s also a set of genes controlling how to physically construct a lip and where it should be located in the flower structure. This set of genes and the preceding ones work together to built up a normally structured and colored lip.
When a disorder occurs with this last set of genes, it sends information to build up not one, but three lips, one in the normal place and the others in the petals.
Let’s make “C” be the disorder that acts on the set of genes responsible for the construction of the lip, obliging it to send information to build up three lips.
Now, we can integrate all these three sets, which can assume the following states:
A, B and C are turned on – the regularly colored peloric form appears (three colored lips, rest of the flower also colored);
A and C are turned on, B is turned off – the peloric semi alba form appears (three colored lips, rest of the flower white);
A and B are turned off, C is turned on – the peloric alba form appears
Again, this is just a simplification, but serves to the purpose of a general understanding of the process.
To artificially breed a peloric alba form the best way, in my opinion, is to start with a peloric semi alba, because you have there two sets of genes already in the state you want – B turned off and C turned on. All you need is to try to turn off the set A. And you can try to achieve that by crossing the peloric semi alba with a true alba and observe the resulting F1 generation. By intercrossing carefully selected clones of the F1 generation, backcrossing some of them with the alba parent and so on, it is possible that, somewhere in the future generations, one of the plants appears with the A set of genes also turned off.
Something similar occurred with the breeding of the Cattleya intermedia caerulea aquini, the peloric form that has blue instead of the regular purple. It took at least seven generations of carefully studied intercrossings before the blue could be transposed from the lip of a regular caerulea variety (white with blue lip) to the petals of a peloric form.
Hope this helps a little.
By the way, in my opinion, these are the few situations where the term ‘form’ (or ‘forma’) is correctly employed, because actually there is a modification in the normal shape of the flower, in its spatial conformation. Why some organizations are recommending using the term ‘form’ to designate simple color variations is something hard to understand. The etymology of the term form (or ‘forma’ in Latin), sends to the idea of shape, not color… I’d like to say that I am not a reactionary, of course
. I can accept changes, and I can do it gladly since they have at least one foot on the ground
! Changing only for the sake of changing can be fun in things like fashion, but not in this kind of activity that affects several thousands of other people worldwide. But, sometimes, it looks like if there’s nothing new, let’s invent then, regardless of what, as long as we are the ones to do it.
Hybrid Mode
