Re: HYB: recessive yellow and genetics
iris@hort.net
  • Subject: Re: HYB: recessive yellow and genetics
  • From: C* C* <i*@aim.com>
  • Date: Sun, 24 Apr 2011 08:55:42 -0400
In terms of pigments, there is no difference. You can speculate on the
differences in gene pathway, and there are  two pathways. One is as outlined
in "World Of Iris" which has been  reevaluated.  Revised pathway is  lycopene
coming  before beta carotene. This is the main pathway in flowers.

There is a study in tomato plants of a yellow tomato  that  has lycopene
production blocked, so the pathway of lycopene to beta carotene isn't
functioning, yet there is  beta carotene  making fruit yellow. This study  was
done some time ago. I can't find any follow up on it.

The data for  a recessive pathway  involves studying  orange  flowers in iris,
which have both lycopene and  beta carotene. This yellow is recessive in this
case.  If you cross an orange  iris to a pink(which doesn't have a recessive
yellow gene)  you get all seedlings as pink. If the yellow was dominant, half
of the seedlings would be orange, and the other half would be pink.

When you have a yellow with tangerine red beards, the yellow is recessive.  In
this case the lycopene is blocked from production in petals, but you still
have yellow.  Normally when lycopene is blocked from petals, you have white
flowers with red beard. So you can't have a lycopene producing a yellow
pigment, as you don't have production of lycopene  in petals. Thus an
alternate  route  to production of beta carotene.

The other possibility, genetically, is that there is a modifier gene that only
partially converts lycopene to beta-carotene. And multiple dosages of this
gene completely converts lycopene to beta carotene, but only in petals, not in
beard.  This explanation seems less likely to me.

Chuck Chapman











---- Original Message ----
From: Paul Archer <pharcher@mindspring.com>
To: iris@hort.net
Sent: Sun, Apr 24, 2011 2:38 am
Subject: Re: [iris] HYB: recessive yellow and genetics


We've seen the topic of recessive yellow (and red beards) batted around a bit,
but I've haven't seen any mention of the actual difference between that and a
dominant yellow in relation to the pigment difference in the yellow or how the
gene pathway is different.

Did I miss it (and a recap would be nice) or we just don't know as yet what
the
difference is?

I'm thinking his would apply to cultivars like 'Pulsar' and probably 'Yes'?
I'm
guessing 'Crackling Caldera' is a recessive yellow as well, it's just has pink
in the petals as well creating an orange effect?

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