Re: RE:HYB pink genetics

--- In iris-talk@y..., irischapman@n... wrote:
> I'm currently looking for information re the genetics of pink..."

Chuck, on the violet pigment, you have one too many letters, by the 
way.  There's no "r" in "antho..."   Re the genetics of pinks, there 
are several interacting factors.  One--the production of a carotene, 
normally yellow, that is a dominant, and shows dosage effects. A 
single "Y" produces, usually, a light yellow or cream.  Increasing 
the dosage is one of the means by which yellow becomes deeper 
colored.  There are other factors co-acting usually also.
  Distribution of the yellow (the pattern) appears to be governed by 
a couple--or more--other factors.  There is more than one carotene in 
irises, I think, and there are yellows that are not converted to 
pink, but the particular carotene that may become pink instead of 
yellow is converted with a recessive "epifactor."  At least that was 
the interepretation at one time of how this works.  This particular 
carotene is converted to a lycopene pigment, the same as tomato red.  
In tomatoes, I believe, the factor is dominant.  In iris it is not.

The presence or absense of anthocyanin violet/blue pigment is 
complex.  There is a dominant inhibitor (I), a selective inhibitor 
that affects standards, the influence most strongly present at the 
top of the flower and progressively weaker the lower in the standard 
one looks, and the falls much less or not at all affected.  The 
result would be pink standards (with some violet flush in the base of 
the standards) and violet falls.  That one was primarily introduced 
into modern bearded irises through the work of Paul Cook and his 
hybrid Progenitor.

The lack of anthocyanin can also be due to a recessive absense of the 
pigment.

The distribution of the violet pigment also may be governed by the 
presence of plicata alleles of various sorts.

Pink x pink does not give ALL pink in all crosses, but in many, the 
seedling count may be too small to reveal the violets that might (or 
might not) be possible.  If both parents are duplex for the 
inhibitor, very few violets will appear in large progenies.  I 
believe that triplex "I" does not often occur.  The speculation has 
been made that the factor may be lethal in more than duplex level of 
the four possible...  I have not seen recent work in this matter.

Pink x violet (with tangerine beard) will give theoretically half 
pink, half violet if the pink has one dose of "I."  If two, five of 
six of the progeny will be non-violet, one would be violet 
(theoretically).  Distance from the centromere makes some difference, 
and whether or not tri- or quadri-valent associations occuring during 
meiosis also can be a factor in seedling ratios.

Is this helpful?

Regards,
Neil Mogensen    7a in western North Carolina


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