Author Topic: Selecting for endosperm color in corn  (Read 371 times)

reed

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Selecting for endosperm color in corn
« on: 2019-05-10, 05:59:22 AM »
From what I'v read here on the forum and elsewhere I think that soft flour endosperm is always white so any true flour corn will be white. Flint endosperm though is white or yellow and in different shades. The gene for that is called y or Y and it is triploid with two sets from the father and one from the mother. And white (y) is recessive.

If I understand it right only (yy) (yy) (yy) will make truly white flint. Is that correct?

Is it quantitative? And if so is this correct, (Yy) (yy) (yy) would be light yellow and (YY) (YY) (YY) would be dark yellow?

Or is that all a gross over simplification?

Mike Jennings

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Re: Selecting for endosperm color in corn
« Reply #1 on: 2019-05-11, 02:18:25 PM »
From what I'v read here on the forum and elsewhere I think that soft flour endosperm is always white so any true flour corn will be white. Flint endosperm though is white or yellow and in different shades. The gene for that is called y or Y and it is triploid with two sets from the father and one from the mother. And white (y) is recessive.

If I understand it right only (yy) (yy) (yy) will make truly white flint. Is that correct?

Is it quantitative? And if so is this correct, (Yy) (yy) (yy) would be light yellow and (YY) (YY) (YY) would be dark yellow?

Or is that all a gross over simplification?

That is mostly my understanding as well. Although in my experience even the purest flour corn still has a very thin layer of flinty endosperm surrounding the floury. So even a pure flour corn can have dark yellow kernels, but only that outer flint layer will be yellow most of the endosperm will be floury and white. I believe Painted Mountain has examples of this (I haven't grown it -- only seen photos).

Also I think the endosperm color receives 2 identical alleles from the mother and 1 allele from the father.

I usually see the the triploid endosperm genotype written as YYY (dark yellow), YYy (light yellow), yyY (pale yellow), yyy (white). And this represents the 4 possible endosperm color phenotypes (or degrees of yellow color intensity). When you write it as (Yy) (yy) (yy) that makes it look like it has 6 sets of chromosomes (hexaploid) and like there would be 7 different color genotypes/phenotypes.

Of course, the embryo is diploid and only carries 2 alleles for endosperm color. For example: Yy (heterozygous). When that heterozygous embryo grows into a corn plant, the cob (female inflorescence) it produces will have a roughly even number of white allele ovules and yellow allele ovules. I think that the genes carried by each ovule will contribute 2 identical alleles to the triploid endosperm which, when combined with the 1 allele delivered by the pollen, will determine the phenotype of the endosperm.

I think that's how it works. I'm not totally sure I have it right.

Here is a paper on corn color inheritance.

Also that old HG thread on Understanding Corn Genetics is has a lot of info.

These have been 2 of my main sources on this subject.

Reed, I'm working on a flour corn project similar to yours, with colorless endosperm and aleurone, but variable pericarp color. Last year I crossed in some day-neutral Maize Morado, in an attempt to add the black/very-dark-red pericarp color (similar to your Big Red corn by the way). Of course with that dark coloration you can't see if there is colored endosperm or aleurone. So, I sat down and used a file on a bunch of the dark pericarp kernels to see what was underneath before planting. The Maize Morado had a lot of different colors under the pericarp, but I was able to cull those kernels. I only spent about 15 minutes or so. Since the colorless genes are recessive, I shouldn't have to keep doing the filing for very many generations to cull out all the unwanted colors.

The filing also works well for seeing how thick the flinty endosperm is surrounding a floury kernel. I also culled anything with too much flint over the flour. The slight damage to the kernels did not seem to affect germination at all.
« Last Edit: 2019-05-12, 12:10:57 AM by Mike Jennings »

reed

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Re: Selecting for endosperm color in corn
« Reply #2 on: 2019-05-12, 04:27:17 AM »
So regardless of how we write it or what the true scientific mechanism and explanation is, if the dominant Y is expressed even once there will be some yellow shade to the endosperm?

« Last Edit: 2019-05-12, 04:31:13 AM by reed »

Mike Jennings

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Re: Selecting for endosperm color in corn
« Reply #3 on: 2019-05-12, 09:15:32 AM »
So regardless of how we write it or what the true scientific mechanism and explanation is, if the dominant Y is expressed even once there will be some yellow shade to the endosperm?

Right, it has to be homozygous recessive (yyy) for the kernel to be white, regardless of flint/flour composition of the endosperm, and each dominant Y allele will add to the intensity of yellow.

I supposed it would be easier to select for a homozygous pure white than a homozygous dark yellow phenotype (from a mixed population). Because the dominant Y alleles will always show themselves as some shade of yellow to be culled out to get white.
« Last Edit: 2019-05-12, 12:07:31 PM by Mike Jennings »

reed

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Re: Selecting for endosperm color in corn
« Reply #4 on: 2019-05-12, 03:40:22 PM »
Right, it has to be homozygous recessive (yyy) for the kernel to be white, regardless of flint/flour composition of the endosperm, and each dominant Y allele will add to the intensity of yellow.

I supposed it would be easier to select for a homozygous pure white than a homozygous dark yellow phenotype (from a mixed population). Because the dominant Y alleles will always show themselves as some shade of yellow to be culled out to get white.

Thanks Mike,
That's what I'm counting on in my FLOUR patch where I'v decided I'm keeping all the diversity I'v collected over these past several years even though it will slow the task of arriving at a fully flour crop. It also will have variable colored pericarp but white endsperm in the end; but a small amount of it at first may be contaminated with yellow.

I only have one year where this will work but the original crosses will have some white varieties with colorless endosperm and pericarp so using those as mothers all I got to do is cull anything yellow that shows up.

Next year though the variable pericarp will be intergrated and it will be a little harder. Still for example if a I have an ear with light enough pericarp it might show different shades and assuming I'v been successful at keeping aleurone color out of the mix  all I got to do is cull the darker ones and disproportionately plant them along with seeds from  the darker pericarp ears. I'll use basically the same but opposite strategy in my FLINT patch.
« Last Edit: 2019-05-12, 03:46:18 PM by reed »

spacecase0

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Re: Selecting for endosperm color in corn
« Reply #5 on: 2019-05-25, 12:17:44 AM »
I like white flower corn because can easily keep it pure
if the sweet corn crosses, I can tell from the shrunken kernels
if any other corn crosses I can see in the color
I have seen blue flower corn, and it grinds up to look almost like my white flour corn,
but a harder to keep the blue corn pure (especially the yellow the blows in with the wind from far away)
I get that each color of corn has a flavor, guess I don't care that much about flavor

Olaf Nurlif

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Re: Selecting for endosperm color in corn
« Reply #6 on: 2019-05-29, 02:38:31 AM »
@spacecase0
but you won't see it if any flour corns with coloured pericarps and pure white endosperm pollinate your white flour corn!
But I guess red or brown flour corns are not grown that often and if they cross into variety only good things can come out of it :)

reed

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Re: Selecting for endosperm color in corn
« Reply #7 on: 2019-05-29, 04:02:26 AM »
I think soft flour endosperm only comes in white so if you select for soft kernels it will eventually just be white regardless of what color the kernel looks. Other colors like blue, brown, pink or whatever come form the aleurone and or pericarp. If you get rid of aleurone color like I want to do you can end up with multi colored ears but any single ear will be all the same color. Variable color in the aleurone will cause multiple colors on the same ear.

Flint endosperm is different, it can be white or yellow, so it's a little harder to select for single color ears there. Sweet corn is like that too, that's what makes bi-color sweet corn. No color in the aleurone or pericarp but variable white / yellow endosperm.

In my flint I'm looking for no aleruone color, variable pericarp color and yellow endosperm color. On ears with light or no pericarp color I'll be able to see a difference in endosperm but on those with dark pericarp I may not be able to. I figure I'll select heavily from ears with light pericarp but always include some of the darker so as to keep wide variation.

I don't want multi-color on a single ear so I'm starting out with no aleurone color and if I have the option I will cull any ear where it shows up. So I won't have any blue or purple.
« Last Edit: 2019-05-29, 04:10:26 AM by reed »