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Post by plantsnobin on Aug 11, 2009 15:39:00 GMT -5
Welcome to Homegrown Jonathan. I don't have a clue what you guys are talking about, but I like to read along anyway....
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Post by Alan on Aug 11, 2009 20:14:46 GMT -5
Man, I wish I did know a better way Sperro, the way you mention is the best that I know of, well that and a refractometer, I've heard that back in the "old" days they used to actually carry around notebooks and pop kernels in the milk stage and make note of the amount of pressure it took to pop them, with the more tender kernels being SE types.
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Post by canadamike on Dec 2, 2009 19:11:03 GMT -5
I am not sure the refractometer ( I have one) would be really useful if you pick a bunch of grains and squeeze the juice out, as you will end up with an average result. And since a squeezed kernel is destroyed, how do you deal with the next. Kernels are independant fruits, each one of them might be different from the neighbor. Unless there is some visual identification clue/observation, that could be followed by refractometry used based on having differentiated the kernels, I cannot see the use of the refractometer other than to confirm presence of both types on an ear, unless you get lucky and get full se or su ears, in wich case I would gladly travel down to wash and kiss your feet
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Post by Andre on Sept 18, 2013 19:17:00 GMT -5
It should by all means segregate out, your working with three seperate types of corn in one hybrid or "grex", two of the genes are located in the same place... , To answer your question above, the reason SU and SH2 don't work very well together is because they are on different chromosomes. So the typical SH2 corn happens to have a starchy gene on chromosome 4 which is dominant over the su gene. The result of crossing su and sh2 will always be a starchy kernel. Where it gets kinky is when you cross an se variety with an sh2. The se gene is on chromosome 2, sh2 is on chromosome 3, and su is on chromosome 4. DarJones So where's the truth ?
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Post by DarJones on Sept 18, 2013 19:53:06 GMT -5
The truth is usually somewhere in the middle.
More seriously, a synergistic corn is what you get from a combination of genes including su, se, and sh2. If you get all three genes to homozygous state, then the problem of starchy kernels can only occur if there is a cross with field corn. The disadvantages are mostly from the sh2 gene which causes serious degradation of flavor.
Most synergistics are not homozygous for all three genes. They might be homozygous for su and se but heterozygous for sh2. This gives a corn with 3/4 of the kernels expressing an se+ phenotype and 1/4 expressing sh2. In other words, a good flavored corn with a few extra sweet kernels to boost the sweetness.
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Post by Andre on Sept 19, 2013 1:47:03 GMT -5
Thank you !
I was talking about this statement "two of the genes are located in the same place..." which seems false and you are right ! The se gene is on chromosome 2, sh2 is on chromosome 3, and su is on chromosome 4. We can also add bt1 on chromosome 5, bt2 on 4 and du1 on 10.
Some other precisions :
The su1 allele, contrary to its name, does not have exceptionally higher levels of sugars, but instead results in greatly increased levels of Water soluble polysaccharide (WSP). Mature endosperm of nonsweet corn contains about 2% WSP, while endosperm homozygous for su1 may contain up to 35% WSP. Water soluble polysaccharide is a highly branched polysaccharide consisting of α-(1-4) glucans with α-(1-6) branch points. WSP gives su1 endosperm the smooth texture and creaminess, characteristic of traditional sweet corn varieties. While high levels of phytoglycogen appear to be unique to su1, elevated levels are maintained when su1 is combined with either wx1, du1, or bt1. When su1 is combined with ae1, bt2, or sh2 phytoglycogen production is suppressed.
The presence of se1 maybe difficult to detect. In some backcrossing programs, the pale yellow kernel color associated with se1 has been used as an indicator for the presence of the gene, although the lighter color is background dependent and, in general, undesirable. Other indicators used for se1 are slower drydown rates, and more wrinkled kernels, both of which are also background dependent. Thus, incorporation of se1 into commercial varieties via the backcross method has been difficult in some instances. Taste testing during inbreeding is the most reliable method of obtaining high quality se1 inbreds.
Source : "Specialty corns". Hallauer - 2001
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Post by mayz on Sept 19, 2013 3:09:56 GMT -5
To answer your question above, the reason SU and SH2 don't work very well together is because they are on different chromosomes. So the typical SH2 corn happens to have a starchy gene on chromosome 4 which is dominant over the su gene. The result of crossing su and sh2 will always be a starchy kernel. Where it gets kinky is when you cross an se variety with an sh2. The se gene is on chromosome 2, sh2 is on chromosome 3, and su is on chromosome 4. sorry but the reason for which su and sh don't work together has nothing to do with chromosomal location. The only implication of loci interaction is linkage and its consequences in term of segregation. (No linkage in this particular case.) The reason is in enzymatic interaction. Sh2 codes for an enzyme (ADP-glucose-pyrophosphorylase) that "prepare" oses before the polymerisation. If the deficient gene sh2 is in homozygous state, the cell doesn't have de possibility to synthetise polyoses such as amidon or water soluble polysaccharides. Thus no possibility for su1 to act on the starch synthesis pathway.
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Post by hortusbrambonii on Sept 19, 2013 4:14:30 GMT -5
Wow
I thought I understood the basics of plant genetics. Until I read this thread that is...
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Post by Andre on Sept 19, 2013 4:31:04 GMT -5
Thank you Mayz ! Great explanation as usual !
One more question. If I understood well, Synergistic varieties carry the dominant Sh2 only on the su or se kernels (because the sh2 kernels are mandatory homozygous sh2/sh2), that's the reason why they should not be grown near sh2 varieties (or the off spring will be Sh2 and not sh2). Am I right ?
To make it clearer, on sweet corns we need at least one sugary gene :
1 / su kernels must at least carry the genes su/su and Sh2/Sh2 or Sh2/sh2 2 / se kernels must at least carry the genes se/se and Sh2/Sh2 or Sh2/sh2 3 / sh2 kernels must at least carry the genes sh2/sh2
And the only variety that have all the sugary genes homozygous is Mirai which must be su/su, se/se and sh2/sh2
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Post by mayz on Sept 19, 2013 6:01:45 GMT -5
One more question. If I understood well, Synergistic varieties carry the dominant Sh2 only on the su or se kernels (because the sh2 kernels are mandatory homozygous sh2/sh2), that's the reason why they should not be grown near sh2 varieties (or the off spring will be Sh2 and not sh2). Am I right ? If heterozygous se synergistic (susuSeseShsh) is pollinated with the pollen of shrunken corn (SuSesh), it will produce two types of endosperm on the synergistic ear 50% Su_ _Se_ _Sh_ _ field type phenotype 50% Su_ _Se_ _shshsh shrunken phenotype To make it clearer, on sweet corns we need at least one sugary gene : 1 / su kernels must at least carry the genes su/su and Sh2/Sh2 or Sh2/sh2 2 / se kernels must at least carry the genes se/se and Sh2/Sh2 or Sh2/sh2 3 / sh2 kernels must at least carry the genes sh2/sh2 And the only variety that have all the sugary genes homozygous is Mirai which must be su/su, se/se and sh2/sh2 To make it clearer, on sweet corns we need at least one sugary gene ...at homozygous state. It's right for su1 and sh2 Exception for se as it needs the presence of su at homozygous state susu Se_ Sh_ = sugary corn susu sese = augmented sugary corn Su_ Se_ shsh = shrunken corn
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Post by Joseph Lofthouse on Sept 19, 2013 11:27:47 GMT -5
"Other indicators used for se1 are slower drydown rates... both of which are also background dependent." Source : "Specialty corns". Hallauer - 2001 I continue to believe that se+ kernels dry down quicker than non-se+ kernels. I guess I can let the author off the hook because he also claims that it is background dependent. "Taste testing during inbreeding is the most reliable method of obtaining high quality se1 inbreds." Source : "Specialty corns". Hallauer - 2001 Taste testing during mass selection has been very effective for me even without inbreeding. I made a determination a long time ago that the sh2 gene is too troublesome and too unpleasant tasting to work with, so forgive me if I don't participate in that part of the discussion. I don't want to devote the time to understand the interactions of sh2 gene with other genes because it will not be invited into my garden. And if it arrives inadertently it will be eliminated.
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