All sugar genes in the same corn kernel

[Roland]

For sugar corn there are 3 tipes of genes. Each gene have to be homozygous in the corn kernel to give a sweet corn.
SU gene
SE gene
SH2 gene

Is it possible to combine all 3 genes homozygous in one corn kernel?

And if so, why do we not have corn varieties that have all these 3 genes in the corn kernel?

[Jeremy Weiss]

Considering that each of the sugary genes comes with heavily decreased seed viability and seedling vigor, it is possible that a plant that had all three wouldn't be able to survive, or even germinate.

[Joseph Lofthouse]

I concur with Jeremy's assessment.

When I plant commercial su/se corn without it's typical poisons, germination is around 5%.

I gave up working on a homozygous se sweet corn because germination was too unreliable.

Adding in the sh2 gene would make things even worse. There are varieties with all three genes, they are marketed as "synergistic". They basically end up being a shell of poison with a tiny, fragile corn seed inside.

[Roland]

Im Growing the Op variety Damaun. It seems it's the first Europe variety homoyzygous for SH2.
75% of the seeds germinate.

I seeded the cornkernels in P9 pots in the greenhouse.

You guys have problems with the germination of sh2?

[Roland]

https://www.saemereien.ch/maissamen-kaufen-zuckermais-ks-zea-mays-bio-samen

[Roland]

A homozygous sh2 cornel is completely wrinkled. Can you tell by its appearance whether a cornel is homozygous for both su and sh2?

[darjones]

If you do due diligence, there are far more than 3 sweet corn genes.  One I recall offhand is "dull" which was used back in the 1940's to breed enhanced su type sweet corn.  Narrow Leaf Evergreen is the corn line which provided se.  See "Corn improvement, seed production and uses" by Jugenheimer.  Sugar enhanced is a very particular gene which does not properly express except in the presence of su.  By default, all se corn - whether heterozygous or homozygous for se - is always homozygous for su.

If you look closely at sweet corn, you will find that it is always in a background of a "flint" type corn.  Dent type corn has soft starch near the core which turns out to reduce sweetness when combined with the usual sweet genes.  If you go back a very long way, the original su sweet corn was grown by the Iroquois who happened to grow flint type corn.  But the story does not end there as the mutation for su has also occurred anywhere corn has been grown if grown long enough.

[Ocimum]

[...]
If you look closely at sweet corn, you will find that it is always in a background of a "flint" type corn.  Dent type corn has soft starch near the core which turns out to reduce sweetness when combined with the usual sweet genes.  If you go back a very long way, the original su sweet corn was grown by the Iroquois who happened to grow flint type corn.  But the story does not end there as the mutation for su has also occurred anywhere corn has been grown if grown long enough.

Interesting DarJones. Do you know what happens when a four corn has the sweet genes?

[darjones]

It produces a very floury kernel which tastes pretty bad.  Yes, I made a cross with Cherokee White flour corn.  Give it a few minutes thought and this will make sense.  Floury starch follows a different biopath therefore is not affected by su/se/sh2. (need to verify this, I'm going on memory)  So a standard floury kernel would have very little if any hard starch and therefore would not taste sweet.  A qualified exception, I'm not certain where sh2 impacts starch formation, it might also affect floury.  I don't think so, but worth checking if you are interested.

[Roland]

The sh2 gene will give shrunken kernels.

Do u think the maize Double red on the picture contain the sh2 gene?

[Joseph Lofthouse]

The Double red looks like old-fashioned su sweet corn to me. Not shrunken.

[AndrewB]

Double Red was bred by Alan Kapuler, so it likely is the oldest SU gene.

SE at best, but not likely,  but is not SH2.

As a side note,  I just planted a few seeds for double red and some dark purple seeds from old Astonomy Domine corn to try and cross together.

[AndrewB]

Also,  there is an interesting paper on Google scholar somewhere that talks about combining sweet corn (Sh2?) With wax corn.

I can't remember if they were able combine or if the double ressive mutant deactivated the sweet corn gene.

[reed]

Kapuler's Double Red Sweet is fine corn. Years ago, I crossed it with Aunt Mary's, a very old, all white Ohio heirloom. I also crossed in two early white SE hybrids and made the crosses in all directions I could. The result was wonderful. I have some seed from it in the freezer, it's the only seed I kept from my sweet corn breeding days and one of few things I devote freezer space to. 

[AndrewB]

Kapuler's Double Red Sweet is fine corn. Years ago, I crossed it with Aunt Mary's, a very old, all white Ohio heirloom. I also crossed in two early white SE hybrids and made the crosses in all directions I could. The result was wonderful. I have some seed from it in the freezer, it's the only seed I kept from my sweet corn breeding days and one of few things I devote freezer space to. 

That might be something worth sharing! Perhaps OSSI pledged?