Re: Re: HYB: orange, pigments

In a message dated 11/23/00 7:45:39 AM Mountain Standard Time, Linda Mann 
writes:

<< 
 Also (having read the chapter in TWOI for background for Sharon M's
 latest homework assignment), I see there are thought to be three
 separate (independent) genes that can give yellow color.  Do those three
 types of yellows look any different, either with or without combination
 with these other things (e.g., violet for orange, tangerine, other
 pigments?).  If all three are present does the color look any different
 than if just one or two are present?
>>

Oops -- I sure didn't mean to imply that it's this simple!  

Yes, carotenes that produce three different types of yellow and one type of 
pink have been identified.  They produce distinct effects, separately or in 
combination -- BUT it seems highly unlikely that this entire chemical pathway 
is governed by three separate, independent genes. 
 
<<
 And a bunch more questions resulting from all that wonderfully techical
 stuff!  Like, for example, what the heck colors are all of these
 pigments?  
>>

Alpha-carotene is "yellow".  This is the one most closely associated with 
lycopene, which can range from pink to orange-red depending on the intensity 
of its expression.

Gamma-carotene, which is considered primarily a precursor to beta-carotene, 
is also "yellow".  Apparently, it is much less apt to be noticeable in iris, 
but I have not found a clear description of the difference in color produced 
by alpha- and gamma-carotene so have to keep it in mind as a potential 
complicating factor.

Beta-carotene itself is yellow-orange.

The study summarized in TWOI found that the carotene pigments could be found 
separately or together and, yes, how many are present and in what dosage does 
affect the appearance.  Sometimes, though, the effect is rather subtle.

<<
 Sharon, for myself and those who don't have TWOI (The World of Iris),
 I'm going to try to make a little table of which pigments are in which
 color classes to start off my homework assignment and post it here.  I
 figure none of us really needs to know any of this stuff to start
 hybridizing, but like they say, knowledge is power & it adds to the iris
 fun during times of the year when some of us deprived geeks have no iris
 in bloom.
>>

Good plan.  Winter is coming in the northern hemisphere, and that's 
traditionally the time to curl up with books & records and gather information 
to be used the coming bloom season.
 
<<
 Based on what I've read and what's been said, it sounds like my orange
 GOLDEN APPLE X CRYSTAL GLITTERS seedlings probably combined yellow from
 GA with tangerine from CG; but if it needed violet to be orange, where
 did that come from?  Recessive violet???  Or ...aha, supression of the
 violet in one or the other of the parents, that didn't get picked up by
 all the seedlings....  Sooo, does that mean there are some plicata genes
 in there somewhere? 
>>

Maybe.  Maybe not.   An inhibitor is the simplest explanation, but it would 
take some detailed pedigree analysis to determine whether an inhibitor or 
accumulation of recessive genes is the most likely explanation.  And I'm NOT 
going to take the bait and do it for you! <G>

Sharon McAllister   

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