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Post by Walk on Sept 7, 2013 8:38:13 GMT -5
We're harvesting our seed crop of Midnight Snack Sweet Corn. We bought our seed this spring from Sandhill but haven't grown this variety for over 30 years. I thought the kernels would be all purple, but some cobs have a "calico" mix of purple, yellow, white, and lavender splotchy. We're going for the purple but wondering if we should select purple seed from the mixed cobs or exclude them entirely from the gene pool we're saving? I'm wondering if they caught the tail end of the pollen from our Roy's Abenaki Flint or maybe they had some crossing to start with? Anyway, we're really happy with this variety as we were looking for a slightly shorter and earlier version of Reverend Morrow's Purple sweet corn and the Midnight Snack fits the bill, so we want to do a good job of maintaining its genetics.
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Post by Joseph Lofthouse on Sept 7, 2013 20:38:44 GMT -5
If the kernels were pollinated by a flint corn in your garden they will dry down to be smooth flint kernels. If the cross occurred in the fields of your supplier then they will dry down to be wrinkled sweet corn kernels.
If it were me, I would exclude saving seed from any cob with white kernels, because it has recessive traits that do not match the phenotype of the variety (all purple) as described by the seed catalogs.
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Post by Walk on Sept 8, 2013 8:22:09 GMT -5
Thanks Joseph. I'll exclude the "calico" cobs. It will mean that I'll have less than 100 cobs for seed, but the patch had nearly 400 plants so the pollen contribution was a bit more diverse. My plan is to keep this variety going by adding seed produced each year to the remains of prior years so I can bump up the diversity from our small plot. Hopefully I'll be able to keep up the quality without too much inbreeding depression. Do you think a population of 400-450 plants is sufficient over time if managed this way?
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Post by Joseph Lofthouse on Sept 8, 2013 11:31:48 GMT -5
Thanks Joseph. I'll exclude the "calico" cobs. It will mean that I'll have less than 100 cobs for seed, but the patch had nearly 400 plants so the pollen contribution was a bit more diverse. My plan is to keep this variety going by adding seed produced each year to the remains of prior years so I can bump up the diversity from our small plot. Hopefully I'll be able to keep up the quality without too much inbreeding depression. Do you think a population of 400-450 plants is sufficient over time if managed this way? That is a good strategy to maintain diversity if there was diversity to start with... A lot of heirlooms have been inbred for 50 to 100 generations before we start growing them in our individual gardens, and the genetic diversity can be quite low before we ever get the seed. Another thing that helps to maintain diversity is what I call "sharing seed with the neighbors". In other words if I import seed from time to time from other people that are also growing this same variety. Of course only if they are properly maintaining the line. Often times when I import foreign corn into my garden I detassel the new corn so that it is pollinated by my existing population. That way, it does no harm if I decide I don't like it. But if I do like it, then it has been fully integrated into my population. Last time you grew the corn were there many calico cobs? Only 1 in 4 cobs conformed to the description in the seed catalog? I'm trying to get a feel for whether the corn has always been a calico corn with a few purple cobs, or whether at one time it only had purple cobs. I couldn't find any photos of it, only text in seed catalogs. What is Sandhill Preservation's reputation regarding maintaining the purity of corn varieties? I imagine just looking at the logistics of their operation, that it would be impossible to grow more than 140 varieties of corn on 10 acres and keep them genetically pure, in spite of (or especially with) hand pollination. There are competing interests here: To maintain the line as purple only, you have to throw away the diversity that causes calico cobs to appear. If you are only interested in maintaining the purple cobs aspect of the phenotype, (the primary trait that defines it as a variety?), then you can cross it with small doses of other corns and reselect for the purple cobs trait. Edit: On further reflection... How many hours are available during a growing season? How long does it take to bag corn tassels, and corn silks. How impossible is it for Sandhill Preservation to avoid inbreeding depression on any variety of corn that they grow if they are hand pollinating?
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Post by blueadzuki on Sept 8, 2013 12:39:48 GMT -5
I can't speak for how pure any of Sandhill's corn seed is, but I can testify that a the seed of lot of the varieties they offer do not look AT ALL like seed of the same varieties if you buy it from some other purveyor.
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Post by DarJones on Sept 9, 2013 13:13:29 GMT -5
I can get a lot closer to a good answer on this. I grow corn for Sandhill. I make a point to grow at most 3 varieties timed to tassel at different times. I also make use of the "g" gene in popcorn which prevents pollination by other varieties. I also aggressively rogue the plants for off types. There is still a lot of variation in Sandhill's original seed and most of it can be attributed to crossing.
This year, I grew Buhl sweet corn getting a crop that will shell out about 5 gallons of seed. Most of the ears produced match the desired type. There is a small sub-population that shows influence by a variety with larger ears and different starch ratio. There was also an ear or two that had a few white kernels. Please note that these traits were present in the source seed I got from Glenn.
I have grown several of his varieties over the years and have not found any of them to be pure, but the variety does tend to match closely to the source type that Glenn received.
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Post by Walk on Sept 9, 2013 15:55:37 GMT -5
I looked at the corn we've got drying on the wire shelves. The majority of the cobs are dark purple. Less than a dozen are the extreme calico type shown in the photo. Many of the purple cobs have the occasional white, yellow, or lavender kernel. The picture shows a red and a yellow Roy's Abenkaki Calais Flint for comparison. I'm hoping that I can save dark kernels from cobs like the 2nd and 3rd from the left as well as the completely purple cobs. I think the 1st cob on the left is too mixed to include. The kernels aren't dry enough to see if they are all wrinkly or not. They were being picked as soon as the birds started pecking through the husks and brought indoors to dry. I did notice this color variation to a lesser extent when we grew Reverend Morrow's Purple Sweet, so thought it might be related to yellow sweet kernels that turn purple in maturity. I'm thinking that the white sweet corn that matures purple may have less of this variability. But I also expect some variation in Sandhill's seed stock as they're in Iowa and getting all of these corns to mature and miss out on the GMO pollen has got to be a challenge. Just want to keep the variety mostly intact enough for us to enjoy it's production for many years to come.
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Post by Joseph Lofthouse on Sept 9, 2013 19:48:40 GMT -5
I'm hoping that I can save dark kernels from cobs like the 2nd and 3rd from the left as well as the completely purple cobs. I think the 1st cob on the left is too mixed to include. Great photo. If it were my seed crop, I would save purple seeds from cobs like the 2nd and 3rd from the left, but not from the "too mixed" cob.
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Post by blueadzuki on Sept 9, 2013 20:41:06 GMT -5
The second from the left might be a little iffy as well. While I have never grown this particular corn I assume that, if the cob 3rd from the right is what a "type" cob for the variety is supposed to look like, I assume that the corn is supposed to be all one shade. While most of the kernels on the second to the left are purple, they are all different shades of purple. I get the feeling that if you put too many of the lighter purple kernels in your seed stock, you'll begin getting kernels that are progressively paler and paler shade, until at least some of them turn white again and will have to be rouged out. If getting all of your corn to look like the 3rd from the right is your goal, you probably only want to save those kernels that match it in shade to keep the purple that intense.
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Post by Andre on Sept 10, 2013 5:49:47 GMT -5
Do you think a population of 400-450 plants is sufficient over time if managed this way? Maize populations are usually maintained by hand sib-pollinations that require extensive supplies and labor, and only a limited number of plants may be included for each population. Hence the problems of expenses, genetic drift, seed supplies, and contamination can arise. Omolo and Russell (1971) propagated by handcontrolled pollinations 500, 200, 80, 32, and 18 plant populations for five successive generations of the open-pollinated variety Krug. They wanted to determine what size of population was required in order to maintain itself without causing significant genetic changes. Significant yield decrease was obtained as sample size decreased, and they concluded that a sample of 200 plants was adequate to maintain a heterogeneous population by hand sib-pollination. Only if some inbreeding could be tolerated and reproduction was infrequent would an 80-plant sample be adequate.Source : "Quantitative Genetics in Maize Breeding" - Arnel R. Hallauer· Marcelo J. Carena·J.B. Miranda Filho - 1981 I also make use of the "g" gene in popcorn which prevents pollination by other varieties. Do you have more informations on this "g" gene ? Didn't find anything with Google.
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Post by Walk on Sept 11, 2013 9:26:52 GMT -5
I'm still struggling with the population size issue. If I grow 400 corn plants and save out 50 nice cobs for seed, does that mean that the seed has enough diversity represented, in other words is my population 50 or 400? The other random element I'm trying to grasp is that next year I'll only plant out about 400 seeds again. Would it be better to take 8 seeds from each of 50 cobs and use that as my planting stock? Perhaps when seed selecting do 8 seeds/cob in each of 4 batches so as to have 3 backup batches of equal diversity? I'm thinking of the ear to row methods of doing corn planting I've read about, only on a much smaller scale. When I acquired the original seed stock from Sandhill I got 4 packets then sat at the table and visually selected out the nicest looking kernels. If I did that from a smaller lot of seed I might inadvertently be picking out seed that would skew towards only a few cobs, therefore reducing the size of the population being planted out. Am I being too anal in this process or just being extra careful? My goal is to keep this variety strong and healthy, with early, medium size plants, and yellow sweet kernels turning purple when mature.
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Post by raymondo on Sept 11, 2013 16:05:58 GMT -5
From what I've read, I don't think you're being too anal. I'm creating a sweet corn that works well in my climate. Last season I grew only 50 or so plants but it was a mixed population to begin with. I saved 4 or 5 kernels from one cob from each plant for planting this season so my population will be about 200. I'll save a few seeds from one cob from each plant again so that my population next season will be around the 200 to 300 mark. I will try to keep it that way. Selection will only be for colour really. The corns I'm using all produce well already in my garden and all are sweet corns, a mix of su and se.
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Post by Walk on Sept 12, 2013 14:33:02 GMT -5
Thanks for the answers everyone. I think I'm on the right path with this corn. Just wanted to share a picture of one corn I won't be including in my seed stock. We had one plant of Midnight Snack that was a miniature. Here's a picture of the entire stalk (2' tall), it's one ear with 3 kernels (3" long), and a "normal" cob (8" long) for size comparison.
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Post by Joseph Lofthouse on Sept 12, 2013 15:22:49 GMT -5
From a statistical perspective... If you save bulk seed from any cob that produces acceptable seed, then over the years you will be selecting for plants that produce more cobs and/or more seeds per cob. If you save seed from individual plants (only one cob saved per plant) and the same number of seeds per cob, then you will not be selecting for seediness. With most of my corn varieties I save multiple cobs per plant into the bulk lot of seed. That skews the population towards plants that produce more cobs.
I'm currently fussing over this issue with beans. If I harvest whatever the field produces, the population becomes skewed towards whichever varieties produce the most seeds. I plant most of the patch for bulk beans. These are primarily used for eating and secondarily for seed. Then I plant a separate patch as type-to-row, which is saved for seed. That keeps all the different kinds in my population while at the same time allowing the population as a whole to move towards better adapted plants.
I do a lot of my planting ear-to-row for corn, and fruit-to-row for other things. I might only plant 7 to 10 seeds from each mother. Even if multiple fathers are involved, it gives a really good idea of the strengths and weaknesses of each sibling group.
At the start of a breeding program I depend more heavily on ear-to-row planting. That gets me quicker selection in the early years. Later on I become more inclined to do mostly mass selection on bulk seed because it's less work: So I'll do mostly mass selection with a few fruit-to-row selections/plantings of things that have extra desirable traits.
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Post by petitvilaincanard on Sept 12, 2013 17:04:42 GMT -5
From a statistical perspective... If you save bulk seed from any cob that produces acceptable seed, then over the years you will be selecting for plants that produce more cobs and/or more seeds per cob. If you save seed from individual plants (only one cob saved per plant) and the same number of seeds per cob, then you will not be selecting for seediness. With most of my corn varieties I save multiple cobs per plant into the bulk lot of seed. That skews the population towards plants that produce more cobs. I'm currently fussing over this issue with beans. If I harvest whatever the field produces, the population becomes skewed towards whichever varieties produce the most seeds. I plant most of the patch for bulk beans. These are primarily used for eating and secondarily for seed. Then I plant a separate patch as type-to-row, which is saved for seed. That keeps all the different kinds in my population while at the same time allowing the population as a whole to move towards better adapted plants. I do a lot of my planting ear-to-row for corn, and fruit-to-row for other things. I might only plant 7 to 10 seeds from each mother. Even if multiple fathers are involved, it gives a really good idea of the strengths and weaknesses of each sibling group. At the start of a breeding program I depend more heavily on ear-to-row planting. That gets me quicker selection in the early years. Later on I become more inclined to do mostly mass selection on bulk seed because it's less work: So I'll do mostly mass selection with a few fruit-to-row selections/plantings of things that have extra desirable traits. I think in some cases some plants can produce more but smaller seeds,with the same yield.So,if you take your seeds from the mass of grain,it can be a good idea to discard the smaller grains to avoid selection towards smaller grains.I f you take a fixed number per plant,selection toward smaller seeds is not likely.If you take a number per cob(in the case of corn),you should take care not to select toward smaller grain(when there can be more or less cobs/plant),on the other hand you should take more seeds from a cob that produce more seeds. In the case of taking seeds from the bulk it's important to mix the whole lot very well,before taking the grains,or having a good sample method.Not that easy for bigger fields
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