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Post by Joseph Lofthouse on Jun 1, 2012 20:09:28 GMT -5
Here's what some of the (presumably) homozygous se+ seed looked like yesterday just before planting: I planted 6X more seed than normal, so if it germinates adequately, then I'll have to thin. F2 cross between Blue Hopi and se+ F2 cross between Earthtones Dent and se+ Kernels from Frosted cobs that passed the density and soak tests. F2 of cross between mixed decorative corns and se+
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Post by Joseph Lofthouse on Sept 12, 2012 23:15:25 GMT -5
I harvested the se+ breeding patch today. I didn't get proper photos yet due to it being a market day, but here is a teaser photo. Between tasting so much sweet corn and eating so many watermelons, perhaps I'll go into a sugar coma tonight and die happy.
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Post by flowerpower on Sept 13, 2012 6:27:25 GMT -5
Nice, Joseph.
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Post by samyaza on Sept 16, 2012 15:55:32 GMT -5
I was interested in breeding for sky-reaching, big cob AND sweet corn this year.
I used Bloody Butcher ( that I think has all these qualities except sugar enhancement, with additional sexy color and my favourite variety so far ) and a commercial super sweet hybrid called Challenger.
For more security, I planted the two varieties very far from each other ( Bloody Butcher in the garden and Challenger in the field ), and manually pollinated a single female "flower" with Challenger pollen. Unfortunately and I don't know why, it failed and the resulting cob was completely empty. If I can grow again in 2013, I'll try to grow them next to each other with one of the two varieties emasculated.
Selecting for sweetness genes may not be as easy as selecting for a single recessive gene as recent varieties can segregate for until three sugar enhancement genes : the indian sweet su, sh2, and the famous se. Extra sweetness reaching candy sugar content is of that kind.
To keep the most heirloom genetics in your hybrids, you'll have to backcross several times your resulting homozygous F2+ with the heirloom parent, and select recursively for homozygous. I think the shrivel seed is a very good way to identify the homozygous embryos on the cob, but with several recessive genes for candy corn, it could get very difficult.
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Post by mayz on Sept 17, 2012 2:21:29 GMT -5
In same idea I have crossed Double red with Mirai white in the aim to create a red suse sweet corn. The cross was performed by detasseling DR plants inserted in the Mirai patch. Attachments:
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Post by mayz on Sept 17, 2012 2:25:18 GMT -5
In an other idea I have crossed a colombian flint (ae wx Y) with black mexican (su). A pic of the F2 seeds. Attachments:
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Post by Joseph Lofthouse on Dec 1, 2012 13:38:58 GMT -5
I want to mention a failure in my process of selecting se+ seed. First some background: I used a density separation technique (sugar water) to separate the denser kernels from the lighter kernels in my F2 seed of a cross between flint/flour corns and sugary enhanced sweet corns. The idea being that the densest kernels would be sugary enhanced, and the flint/flour kernels and some su kernels would float away. Then when ready for planting I soaked the kernels to separate the su kernels from the se kernels. It worked out pretty well for me, except for my mistake... I should have sorted the kernels after they came out of the sugar water solution, because there were a few flint/flour kernels that were carried through with the densest (se) seeds, and in the soak test they looked like they had swollen up when they really hadn't, so I carried some flint/flour corn through into my supposedly se+ patch. It was obvious during the taste testing which was which, but it slowed down my selection process more than necessary.
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Post by DarJones on Dec 3, 2012 1:49:42 GMT -5
Joseph, remember that there is also a flour gene that can cause a similar problem. So while the technique is useful, it is best to separate the kernels at each step of the process. The end result is more reliable.
BTW, I have a huge amount of segregating sweet kernels of which about 1/2 are se+. I need to do some experiments to see if your soaking procedure easily separates them from the other genotypes. How was I able to get to 1/2 se+? Well when I harvested the corn, I sampled the tip of each ear and kept only the the ears that tasted sweetest. This would have selected ears that were either su/su se/se or else su/su with 1 se gene.
DarJones
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Post by Joseph Lofthouse on Dec 3, 2012 2:49:39 GMT -5
How was I able to get to 1/2 se+? Well when I harvested the corn, I sampled the tip of each ear and kept only the the ears that tasted sweetest. This would have selected ears that were either su/su se/se or else su/su with 1 se gene. Good strategy. This late at night, with a foggy brain, when I attempt the math, it seems to me like it would be closer to 1/3 se+, if the patch was open pollinated, and not sorted before planting, because the pollen would have only been 50% se. In the F3 seed that holly returned to me, the percentage of kernels that pass the soak test is lower than predicted by Mendelian ratios. I attribute that to the se+ seed not germinating as well as the other seeds in the population. When I harvested my F3 seed this year, I also tasted each cob, and I saved each cob into it's own seed packet, (and labeled them). I intend to do the soak test on each cob. I'm thinking that doing so will allow me to sort the cobs into mothers that were se+ and mothers that were Se/se. That won't give me a homozygous se+ population, because there was some non se pollen running around the patch, (because of my failure to sort the seed before the soak test), but it will be another step in the right direction, and it may give me a way to mathematically model the homozygosity of the se locus. There may not have been much wind in my garden while the corn was flowering so some of the plants may have been more or less selfed, or the flowering times may have been staggered, because many of the cobs did not have any flint/flour kernels in them even though I planted some.
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Post by DarJones on Dec 3, 2012 17:20:42 GMT -5
Remember I was only selecting the sweetest ears. That means I was biasing the selection for mother plants that were su/su se/se. Since I was deliberately trying to save seed only from this genotype, the result should be at least 50% of the kernels are the desired genotype.
DarJones
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Post by adamus on Dec 16, 2012 23:44:31 GMT -5
It's the same here I figure. people here rarely get the opportunity to eat fresh corn of any variety. When i bring my "normal" sweet corn to the market, it's snapped up really quickly. I get comments about how amazing it tastes etc. But i doubt to Supersweets would be liked here.
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Post by nathanp on Mar 10, 2013 23:37:16 GMT -5
Can I ask some general theoretical questions about generational selection if you do not cross to other SE+ types? It's been more than a few years since I've read Mangelsdorf, and I'm trying to wrap my head around the methodology in crossing corn types that I see from various people.
Is hybridizing with another SE+ type on a yearly level necessary to maintain corn with SE+ sugar content? If you do not select for SE+ kernals, will each successive seed crop have lower and lower sugar? If you do not cross to other SE+ types on a yearly basis, will the resulting seed have lower sugar content? After several years of either of these and not crossing with known SE+ hybrid types, will the sugar level eventually stabilize at only SU or SU/SE levels? F2, F3, F4, etc...
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Post by Joseph Lofthouse on Mar 11, 2013 1:58:48 GMT -5
Sugary Enhanced sweet corn does not grow as reliably as old-fashioned sweet corn. Germination percentages can be very low. The commercial seed industry solves that problem by applying poison to the seed to aid in germination.
The typical home gardener and small scale farmer that is saving seed does not coat their seed with poison before planting. What this means from a practical standpoint is that if there is even a slight amount of non-se in the patch that it quickly comes to dominate the patch because it germinates at high percentages and swamps out the se+ seed which germinates at low percentages. The gene isn't spontaneously disappearing, its just at a huge reproductive disadvantage compared to the non-se gene.
Some type of mechanism is required to keep the corn in or near the se+ state. I do that by tasting cobs, and then by selecting individual kernels from the sweetest cobs for replanting.
My preferred method, if I can ever get it done, would be to grow hybrid corn as my main crop: [plain old fashioned landrace sweet corn X se+ sweet corn]. That would give me the traditional reliability of sweet corn with the added sweetness of sugary enhanced. su/se corn germinates reliably. Crossing is not required to maintain the se gene in a population, but it may be the easiest and most reliable way to assure that it is there. My selection methods are prone to errors.
In promiscuously pollinated mixed populations, if there is any su or su/se in the population the se gene will get swamped out fairly quickly (within a couple years) without active selection for se or routine infusions of the se gene. One or the other is required, but not both.
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Post by raymondo on Mar 11, 2013 2:02:33 GMT -5
If se+ means homozygous for se, then if a corn is se+, all subsequent generations will also be se+, barring mutations. In such a population, you do not need to select for se+ because all kernels are se+.
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Post by Joseph Lofthouse on Mar 11, 2013 2:18:12 GMT -5
If se+ means homozygous for se, then if a corn is se+, all subsequent generations will also be se+, barring mutations. In such a population, you do not need to select for se+ because all kernels are se+. Correct. I wish that there was an open pollinated se+ strain of sweet corn available. As far as I can tell, there is nothing like that on the commercial market, nor available for swap in the informal market. Due to the germination issue, even the slightest contamination from non-se+ sweet corn will lead to quick deterioration of any se+ variety. Blah... Maybe I'll have to get serious this summer about this project and self a bunch of corn: to definitively separate the se+ from the su/se.
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