Any test I do to determine sugar content on the mother
cob would be a small sample, say around 10 to 20 kernels.
Yes the earwigs will attack like crazy as soon as I open
the husk, but they don't take much.
If I end up allowing the starch to settle in the field or if I use
a centrifuge I would open up the husk while it is still on the stalk
and cut open something like 20 kernels and collect the juice
into a small container.
Those kernels are gone forever and we cannot plant them and
expect a harvest... What we get out of the measurement is
an approximation of the average sugar content of the
kernels on the cob. If I only measure one kernel it doesn't say
much about the cob, so I have to take enough kernels to
get a solid average.
Assuming we started with a homozygous se+ parent
crossed with an Indian corn...
In the F2 generation I expect the following distribution of genes
in the mother kernels (if I do no selection on the F1 other
than select for the su1 sweet corn gene).
1/4 of the kernels have zero se genes.
1/2 of the kernels have one se gene.
1/4 of the kernels have two se genes.
50% of the pollen is expected to contain the se gene.
So I expect the following:
25% of the seed has zero se genes and will produce a
cob that has the sugar content of regular sweet corn.
It doesn't matter if the embryo gets an se gene from
the pollen it will be inactive so the sugar in this cob
is expected to be around 9% to 13%.
25% of the seed has two se genes and will produce a
cob in which 50% of the kernels on the cob are
sugary enhanced and 50% are regular sweet corn.
So sugar in these cobs is expected to be around
15% to 26%.
Heck, I bet that many peoples taste buds are good
enough to tell the difference between them.
Any seed with only one se gene will produce a
sugar level somewhere in between. I am attaching a
graph that shows expected sugar levels.
So we select the 10% or 15% of cobs with the most
sugar from each cross, and never more than 25%.
I recognize that there are issues with maturity, and
that the sugar levels overlap... But even if the only
thing we are able to accomplish is to eliminate the
mother cobs without an se gene, then we have skewed
the gene pool in our favor.
Technically, this method is not really selecting for the
se gene it is selecting for high sugar content... So we
might inadvertently find a different gene or combination
of genes that manifests itself as higher sugar.
If I end up cooking kernels I'd cut a
sample from near the tip of the stalk.
I have small tubes that we use in the chemistry lab or in a
centrifuge that hold about 1/3 teaspoon of liquid. I hope that's
enough for a brix-meter.
And finally, for what it's worth...
I just won a small centrifuge on eBay for less than $20.
(Thanks for not bidding against me...)
I figure I'll disconnect one of the batteries from my solar array
and take it out into the field with an inverter...
Regards,
Joseph
p.s. My favorite ear of corn this year was from my Indian corn
patch... One side of the ear was yellow, and the other side
was red... I guess I could do that for market if I was willing
to hand pollinate.
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