glaciata (was Re: Yellow "Plicata" Pattern)
- To: i*@rt66.com
- Subject: glaciata (was Re: Yellow "Plicata" Pattern)
- From: t*@lanl.gov (Tom Tadfor Little)
- Date: Tue, 3 Sep 1996 09:05:03 -0600
Arnold writes
:Help!!!! Now it is "glaciata", and that term is a total mystery?
:What does it mean?
:
A glaciata is a special type of iris without the dark anthocyanin
(blue, violet) pigments. It may be yellow, cream, pink, orange, or
white.
I say a "special type" because there are several ways (genetically
speaking) for a tall bearded irises to be without anthocyanin pigments.
The most common genetic cause is the presence of an inhibitor gene
(given the symbol I) that suppresses the expression of these pigments.
This is a dominant gene, and most white, yellow, pink (etc.) irises
have this inhibitor.
Another way for an iris to be without anthocyanin pigment is that
the gene that is responsible for that pigment in the first place is
not present. There are apparently several such genes, each with a
recessive allele (written w1, w2, ...?) that causes the anthocyanin
to be absent.
A third gene that can make an iris without dark pigmentation is the
glaciata (or "all-white") allele (written pl-a) at the plicata locus.
Whereas the plicata and luminata alleles causes the anthocyanin to be
restricted to a particular part of the petal surface, the glaciata allele
restricts it completely, leaving a bloom without any dark coloring
at all.
Although there are perhaps some subtle differences in appearance
between light-colored irises of these three types, the difference is
really of interest mostly to breeders. Most of us wouldn't care if
an iris is pink because it has the dominant inhibitor (VANITY, say)
or because it has the recessive glaciata gene (GODDESS, say). It's
pink either way.
Cheers, Tom.
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Tom Tadfor Little tlittle@lanl.gov -or- telp@Rt66.com
technical writer/editor Los Alamos National Laboratory
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Telperion Productions http://www.rt66.com/~telp/
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