sweetcorn genetics question

[blueadzuki]

Hi,
I was wondering if anyone out there can explain something to me that's been bugging me.

again and again I have read on this forum (and in most other sites) that the gene that makes sweetcorn is recessive, that if you see a mature kernel of corn, and it has the wrinkles and shrivelings of a sweetcorn kernel, it has to be double recessive. all fine all good, my question is as follows, if that is the case then why does one quite often finds errant sweetcorn kernels on otherwise non sweet cobs (such as the ornamental "indian corns" found in farmers markets and stores during the autum). I could understand what would cause the reverse (non sweetcorn kernels on sweetcorn cobs) the result of errant pollen from a non-sweet, but wouln't the presence of sweet kernels on a largely nonsweet cob only work if the orginal nonsweet plant was heterozygously half sweet itself? and if that is the case why doesn't one get large numbers of sweet kernels when you take the non-sweet kernels from such a cob and cross them back to themselves? I've seed errant sweets in all kinds of ornametal flins and dents (incuding a beutifu lone i saved that is white with blue polkadots) I evne have a sample of sweet kernels that I removed from a cob of chinmarked cancha corn (at first it though they were just withered, but they are fully mature kernels and quite tellingly give that normal cancha is a flour (they let light through) andone able to shed some light on this mystery?

[Alan]

Corn is a strange animal.

The easiest way to explain it is that whatever type of pollen lands on each strand of silk, the corresponding kernal attached to that silk will when husked represent the type of corn that pollinated it which is why you will ocassionally see sweet seed on dent, flint, flour or wax varieties. It's important to realize that this kernal is only the F1 Seed and not a segregate like you will see in the f2. As an example, if you plant that f1 seed it will give rise to f1 sweet corn, save the seed from the f1 cob and plant it and in the f2 you will see the types revert back to about 80-95% kernels of whatever original corn was the parent (flint, dent, flour, wax) and 5-20% sweet kernels, select and plant the sweet kernels and in the f3 generation you will find 50% sweet.......keep going and you'll find an OP sweet corn. Hope that helps.

[blueadzuki]

In terms of an explination it helps a lot. Of course it does sort of stymie my plans to get that blue polka dotted sweetcorn out anytime soon; by the time I got something I can trust to make sweetcorn, I'll probably have lost the dots completely. On the bright side I proably meas that I dont have to hold onto all of non-sweet kernels from the chinmarked cancha cob, the're probably all flour genetically and I know a lot of people who have been baying for seed from that cob

[Alan]

I'll tell you how you can pull that off fairly easily if you want to make a "polka dot" type corn.


I have noticed that chinmarks do appear in sweet corn when crossed to certain varieties of chinmarked flint, but you also get those nice little "polka dot" kernals from time to time. My suggestion would be to select a chinmarked flint or flints that conform to the color that you want, plant a block of this flint next to a block of white sweet corn, detassle the flint corn and allow the sweet corn to pollinate it, save your seed, plant it back and as you know select for the sweet kernels with chinmarks or polka dots yearly, this would be an easy set of traits to pick out visually, you could have a fairly stable line in about 4 or 5 years.

[blueadzuki]

actually I've got a pretty large quantity of polka dotted flint as well (from my polka dot corn project) would that be even better having BOTH parents with the polka dot gene?

[Alan]

Yes, that would greatly increase your chances. I have a couple of sweet corns, one from Native Seeds and one a selection from Rainbow inca which are really chinmarked for sweet corn, I've been trying to select for more apparent chinmark coloring than what they have with some success but it's still a few years out.

[canadamike]

There is a canadian frenchie in search of a definition of chinmark here, no luck in the dictionary ;D ;D

[blueadzuki]

I think I can field this one.

"chinmark" in corn terms refers to a phenomenon that can happen in corns that have thhe trait of pigment in thier "skin" (the outmost layer of the kernel, which is actually I believe the seed coat) If a corn has the "chinmark" trait the outermost laver will not be pure red, pink, purple,or brown (those being the colors generally available for the outermost layer), rather the kernel develops streaks of clored and uncolored outside resuting in a "starburst" or "sunburst" effect on the kernel surface. The name is supposedly Native American in origin; one tribe thought the straks resembled the ritual chin tatoos of a neighboring tribe. Hope this helps

[canadamike]

Thanks blue

[grunt]

I think he means like this

[blueadzuki]

Yep. here's a sample from mine

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[bunkie]

fascinating thread! grunt and blue, awesome pics...

[Alan]

For those interested in working with chinmarked sweet corn selections Rainbow Inca is a good starting point, I warn you though, increasing the contrast in the sripes in sweet corn is a pain and probably not particularly useful except for an aesthetics sense.

[blueadzuki]

here's a selection of my speckeld corn. My apologies for leaving it in the box (which no doubt makes the picture a bit fuzzier) but it takes a long time to sort the stuff out, and I really don't want to do it again

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[blueadzuki]

sorry but I can't seem to figure out how to attach more than one picture to a message

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