HYB: pigment basics
iris@hort.net
  • Subject: HYB: pigment basics
  • From: L* M* <l*@lock-net.com>
  • Date: Sun, 24 Feb 2013 19:26:28 -0500
Tom Waters just posted this on FB, & I'm re-posting it here, so I can find it again. 
==============
Encouraged by Linda Mann's kind word in the Iris Lover's group, I thought I might offer a really basic concept for those completely new to iris genetics. Basic, but probably the single most important idea to make discussions of the genetics of color and pattern make sense.
There are two different types of pigment in our bearded irises: carotenoids, which produce yellow, orange, pink, and (in the beard) true red color; and anthocyanins, which produce blue, violet, and purple coloration. When both are present together, the result is a blend that usually appears brown, grayish, brick red, bright purple, or (rarely) greenish.
This matters because the genes controlling these two types of pigment and where they appear on the flower are quite separate from one another. So an iris flower can be thought of as an overlay of two separate components, like one color transparency on top of another. One is the yellow/orange/pink pattern, the other is the blue/violet pattern.
One of the best things you can do to train your eye for hybridizing for color is to look at an iris through these two "filters" - try to see how it would look with no carotenoids, and then how it would look with no anthocyanins.
Here's an example, chosen just because its name matches the theme of this post: 'Dualtone'. What do you see when you take away the anthocyanin? It's an iris with light peach-colored standards, warm peachy hafts, and otherwise nearly white falls. The beard is orange. What do you see when you take away the carotenoids? It's now an iris with white standards, light lavender-blue falls, and a little blue on the tips of the beard, especially at the end.
It's good to practice seeing the "two irises" in every iris you observe (sometimes one both of them will just be white!). When you get used to looking at irises this way, it becomes much easier to understand discussions about how colors and patterns are inherited. 

http://wiki.irises.org/bin/view/TbAthruE/TbDualtone

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