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Calling geneticists. How can this be?

Posted by mwedzi chicago (My Page) on
Fri, Feb 18, 05 at 16:39

I'm sorry for asking a simple question, but I just don't understand. There is a discussion going on elsewhere about selfing the yellow-flowered Episcia 'Suomi'. But it seems that all the offspring (at least the ones the people on the forum have grown out) always give red or orange flowers. Red/orange flowers are the most common for the genus Episcia. So my question is, how can it be that a yellow-flowered Episcia crossed with itself not produce any plants with yellow flowers?

Thanks so much.


Follow-Up Postings:

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RE: Calling geneticists. How can this be?

It is not unusual for "sports" or "mutations" to affect only the outer layer of tissue. Most flowering plants have three distinct layers in the meristem (growing tip), and the "mutation" may be preserved in only one of the layers.

It also often happens that the ova are produced by the inner-most layer while the pollen are produced by the outer-most layer. If this is the case with 'Suomi', then the inner layer of tissue (and the ova produced from it) carry the "gene for red" while only the outer layer (and the pollen) carry the non-red (yellow only) factor.

In other words, even though the flowers are self-pollinated, the seeds result from crosses between red x yellow.

There was a similar case of a thornless blackberry that turned out to be a chimera of a thornless dwarf over a thorny variety of normal size.

Roots do not maintain the three layered meristem, so if Episcias can be regenerated from root cuttings it might be possible to get a "pure" yellow that will breed true. Otherwise, the best shot would be to pollinate the orange seedlings of 'Suomi' by 'Suomi' itself. Some of the offspring could then inherit only the non-red factor.

Karl

Here is a link that might be useful: Sports and Chimeras


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RE: Calling geneticists. How can this be?

  • Posted by Jon_D Northern Calif. (My Page) on
    Wed, Feb 23, 05 at 11:50

I was a part of the original discussion of this quesion on Gesneriphiles, an email group. I just happened to chance by this thread. Thanks, Keking, for your explanation. Episcias have long been bred only for foliage, with the floral color and pattern being very limited in range--from orangy red, to reddish orange. Other species contribute a pink type, but those are sterile. I have long wondered how it would be possible to introduce a range of colors into episcias, such as are found in other gesneriads. For your information, I am adding a link to a photo of E. 'Suomi', which, by the way, was found in Finland, of unknown origin, by a gesneriad grower about five years ago. It is now widely distributed.

Jon

Here is a link that might be useful: E. 'Suomi'


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RE: Calling geneticists. How can this be?

Thanks Karl for the explanation. Someone on the discussion group had also mentioned crossing back to the parent in order to get yellow again. And thans for putting up the pic, Jon. I didn't know Suomi was so recent an introduction.


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RE: Calling geneticists. How can this be?

Mwedzi,

I hope someone follows up on this. I'd like to see whether backcrossing does the trick, and whether the direction of the cross makes a difference. My guess is that the yellow trait of 'Suomi' would be carried in the pollen rather than the ova, but I could be wrong.

Karl

Here is a link that might be useful: Bulb 'n' Rose


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