Corn cross pollination, ways to cross and avoid crossing

[JesseI (Jesse Ilonen)]

I have been growing sweetcorn for over a decade and graincorn for a few years, but so far haven’t done much crossing. Have grown sweet painted hills landrace for a few years so tecnically there is some crossing, but mainly it’s been about avoiding crossing. This year I though could introduce some other sweetcorns to sweet painted hills and start mixing graincorns as well, but keep them separate. My problem is that I haven’t got the distance to isolate nor do I have long enough growing season to isolate in time except with the fastest graincorns. Even then there is some overlap at the end. So far I have detasseled my graincorn to avoid cross pollination. There might have been some crossing the other way around because of this right at the tips of graincorns. Atleast there has been some off type kernels which I take is because of that? So far I have been able to just remove tips and it’s no issue, but if I want to breed I would like to sure that that doesn’t happen. So is it possible to desilk my graincorn to avoid mixing with sweetcorn? As I understand those silks work even if they are cut so maybe I need to tape them as well? This would be just to introduce new genes, later I would select by speed.

What about what’s the best way introducing new varieties to the mix (within types)? I was thinking that I could detassel those new varieties to have definite crosses and next year let them cross pollinate freely. Off type colours might tell crosses in some cases, but not all.

Since I don’t quite understand how corn genetics work there is one case that is still quite mysterious to me. I had one completely yellow cob in my atomic orange from seeds I purchased. I did not see any off types when I planted them, but there must have been a cross or possibly natural mutation. What I wonder is that some of the landraces I have grown have some single colour cobs despite not being covered. Yet there must have been some cross pollination. So is that single colour just dominant and isn’t affected by cross pollination, but is maybe affected some other ways that are not visible? If in my case cross doesn’t seem visible from kernel, but cob it produces is different colour, what has been dominant?

[stephane_rave]

I am trying again to restart this discussion, which is related to my question.

I also don’t know enough about corn genetics, and something intrigues me.

Why do the cobs of corn in some populations have uniform grain colors but with variations in hue from one plant to another, while in other populations each grain has a different color?

What will happen about the colors when these two populations are crossed?

Are some colors dominant and others recessive? Even if you don’t have a scientific explanation, tell us about your experiences.

example :

1/ Painted Mountain flour corn population

2/ North italian flour / polenta corn population (thank @marcela_v for this picture taken at a local seed exchange in Italy)

[MarkReed]

The color of corn is a bit complicated because it exists in three different places on in a kernel.

One - the endosperm is the starchy part inside. It can be either yellow or white and yellow is dominant. It is inherited from both sides and can vary from kernel to kernel on a single cob. It is what gives us the popular bicolor sweet corn. “I think” that the intensity of the yellow is a bit quantitative, meaning it could be light yellow or dark yellow, but I don’t know for sure how that is inherited. Anthocyanin in the sap or carotene “might” add purple or orange but I don’t think I have ever seen that.

Two - the aleurone is a thin layer of cells over the endosperm. “I think” it mostly bluish/purplish in varying intensities all the way up to appearing black. I don’t know the dominate/recessive nature, but it is most definitely widely variable. Actually, I do think it is recessive because it can show up when you don’t expect it. It can also be completely colorless and completely transparent or intensely colored and pretty much opaque or anything between. It is also inherited from both sides so again can vary a lot on the same ear.

Three - the pericarp is the outer coating of the seed. It is completely maternal tissue and is the same on all kernels on all cobs of a single mother plant. Unless you want to talk about the effect of transposons, which I don’t. It can also range from colorless and transparent to black, or nearly so and opaque.

If you look at that one ear in your photo of PM just left of center, it has some pure white kernels and some bright yellow kernels but also some dark kernels. You can tell from that that it has mixed endosperm, varying between kernels. On the white and yellow kernels, it has colorless and transparent aleurone, allowing you to see what’s underneath but very dark aleurone on the dark kernels. Pericarp on that ear is also colorless and transparent and the same on all kernels so you can see the differences in aleurone / endosperm. Aleurone or pericarp either one or both can be dark enough to obscure endosperm, or not. Pericarp alone can be dark enough to both aleurone and endosperm, or not.

When these things get mixed up it’s like stacking pieces of colored glass of varying opacity on top of each other, the color you end up seeing isn’t originating with just one of them and in the case of corn isn’t inherited singularly. It’s complicated. In a sense there is no such thing as what may be described as red corn or blue corn.

In your other photo it looks like most of those ears have varied white/yellow endosperm and mostly uniform aleurone. The very dark ones look to have a very dark pericarp and probably the same mix-up under it. That one ear that is mostly red but with a much darker top may be an example of the previously mentioned transposons where the same pericarp genetics express in different ways.

I’ve grown and seen a lot of corn but most of what I have written here comes from how Carol Deppe explained it to me. It’s been a while but “I think” I got it mostly right and “I think” she also covered it in one of her books. I highly recommend Carol’s books.

[stephane_rave]

Thank you for this detailed response .

Now, I have a better understanding of how it works, and the image of colored glasses is the best possible example you could have given to illustrate the interactions between the different layers.

I would like to take advantage of your expertise on the subject to ask another question.
In which part of the grain does the color heterogeneity occur to obtain grains with patterns like these?

Is it a good idea to cross all these flour corn varieties with such beautiful and interesting color profiles? Isn’t there a risk, as in painting, that by mixing colors we will end up with an ugly brown that erases the specific characteristics of each variety?

[MarkReed]

I think the color in both of those is mostly from the aleurone layer. I’ve seen photos of the first one but can’t remember the name of it. I think it is a flour corn from the neighborhood of the Dakotas in the US. I suspect with it, that it would have to be kept purely inbred to keep that pattern. Mixing in any different aleurone or pericarp color would ruin it, maybe forever. That is, if I’m right that the color is from aleurone, the pericarp is colorless and transparent, and the endosperm is uniformly white. I could speculate but can’t really explain the solid white kernel.

You can soak a corn kernel in warm water for a few minutes and prick the pericarp with a sharp knife to get it started and then peel it off. That will show if the color is in the pericarp or under it. I don’t remember if it is all or just some, but Carol Deppe warned that the color can be water soluble. So, for example, if it is in pericarp, it might stain the aleurone when you soak it, or the other way around. Still if you experiment and soak it just long enough to get the pericarp off and do several kernels you can get a pretty good idea of where the color is coming from.

If I’m wrong on that one and the purple splotch is in the pericarp instead of the aleurone it should be pretty easy to tell by dissecting the kernels and also pretty easy to preserve it or even transfer it to other corns by breeding.

The second one is a bit easier because of the green color in some of the kernels. I think green only comes from transparent bluish/purple aleurone over yellow endosperm. I’ve seen the splotchy or spotted patterns before, but I have no idea how it is inherited. It’s hard to tell much when the kernels are off the cob unless you are sure they all came from the same cob.

Aleurone in general is hard because it is so ridiculously variable and I don’t know if it is from one gene or from a group of genes. I don’t remember the term for that but if it is multiple genes, I don’t know how many and I’m guessing they each have their own dominant/recessive nature.

@stephane_rave

Isn’t there a risk, as in painting, that by mixing colors we will end up with an ugly brown that erases the specific characteristics of each variety

I don’t think that mixing lots of different corns together will result in them blending into an ugly brown or any other uniform appearance. I think instead you would just end up with something like an ornamental corn where every ear is different.

On that first one though, I think mixing it up with pretty much anything else would probably be saying so long to that cool purple splotch on a snow-white background. I can’t begin to imagine what combination of genes managed to stabilize or how long it took to arrive at corn like that, no way I could imagine to ever recover it if it was lost.

[stephane_rave]

The first is Montana Cudu, a modern reinvention of a vanished Native American corn variety.

So I got some seeds that I’m going to grow separately from PM for this first year. I might do a test with one or two plants in my cornfield to see what happens.

The second is gneis corn, which resembles the stone of the same name. There is no information about where it comes from, but the few seeds will also be grown in isolation during the first year.

We’ll see how to make the psychedelic color mix later on!