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General Category => Nightshades => Plant Breeding => Tomatoes => Topic started by: Roland on 2021-08-29, 03:08:53 PM

Title: Dark green shoulders and Uniform ripening genes
Post by: Roland on 2021-08-29, 03:08:53 PM
Galahad F1 have very light green shoulders. It is heterozygous for the u gene (uniform ripening).
In the F2 I get some different phenotypes:
Very dark green shoulders

Light green shoulders

Uniform ripening.

Do u know if the u gene for uniform ripening and the U gene for dark green shoulders are incomplete dominant?

Hence the plants with dark green shoulders are homozygous for the U gene.
The plants with the light green shoulders are heterozygous for the U gene and u gene?
Title: Re: Dark green shoulders and Uniform ripening genes
Post by: Vesa Tee on 2021-08-31, 12:36:14 AM
Hi,

I haven’t experimented with u/U crosses myself to figure out the logic here. Just wanted to comment that there seems to be more than one gene (than just u/U) that may result such phenotypes, see e.g.

https://journals.ashs.org/jashs/view/journals/jashs/142/6/article-p444.xml (https://journals.ashs.org/jashs/view/journals/jashs/142/6/article-p444.xml)

Your observations are good and the incomplete dominance could explain what you see.

An alternative theory could be that the Galahad F1 is a cross involving two separate immature green fruit color modifying genes, e.g. uniform and medium green from the article above (see Table 1). The wild type U may not be directly involved in the original cross but will segregate if the two genes do not overlap. Similar thing happens sometimes with fruit shape genes when the wild (round fruit) type segregates suddenly in a cross that didn’t involve round fruit tomato.
Title: Re: Dark green shoulders and Uniform ripening genes
Post by: Adrian on 2021-08-31, 09:39:28 AM
Hi
You can see this link
http://svt.discipline.ac-lille.fr/ressources/lycee/terminale/la-plante-domestiquee/la-selection-de-la-tomate-sans-gout

Title: Re: Dark green shoulders and Uniform ripening genes
Post by: Vesa Tee on 2021-09-01, 12:54:08 AM
I am currently screening F2s from a cross between Aftershock and a uniform u tomato. One of the offsprings seems to express U very strongly, i.e. having very dark shoulders. I am not growing Aftershock this season but I doubt it had dark shoulders.

So, I am still proposing that one might get the wild type out from a cross that was between parents not expressing the wild type. In Galahad F1 context, it might be a cross between the light green shoulders and unform gene, not necessarily between U and u.
Title: Re: Dark green shoulders and Uniform ripening genes
Post by: Steph S on 2021-09-01, 06:21:56 AM
If Galahad F1 has light green shoulders and is U/u, which appears the case in the segregation, this could be interpreted as incomplete dominance, where the single u allele is reducing the expression of U.
But I agree with Vesa that more than one gene is likely involved.
I would expect green shoulders genetics to be a QTL, so that you would get a range of shoulder intensity from segregating material.
It could be that Galahad is also heterozygous for that trait and so the F2 present a range of green shoulders from both parents.  Keeping in mind that the u/u parent has complete suppression of green shoulders, doesn't mean those genetics are absent, they are simply suppressed.
Title: Re: Dark green shoulders and Uniform ripening genes
Post by: Roland on 2021-09-01, 01:06:52 PM
I expect the u gene (uniform ripening) is coming from NC 1 CELBR.

I expect it to be U gen (green shoulders) comming from Brandywine.

This is because these two breeds are in the Galahad F1 pedigree. Together with Mountain Merrit.

https://mountainhort.ces.ncsu.edu/fresh-market-tomato-breeding/tomato-seedlines/
Title: Re: Dark green shoulders and Uniform ripening genes
Post by: Roland on 2021-09-01, 01:10:11 PM
Unfortunately, Vesa's journal does not indicate the phenotype of the U+ crossing. (dark green shoulders) You? (average green shoulders) and u (uniform ripening)
Title: Re: Dark green shoulders and Uniform ripening genes
Post by: Roland on 2021-09-01, 01:21:24 PM
For those who are interested, of my 51 F2 Galahad plants I have found the following Serigation:
8/51 dark green shoulders (15%)
20/51 Average green shoulders (40%)
23/51 uniform ripening (45%)

This is not the Mendelian expected Serigation for a single heterozygous gene.
here you would expect 25-50-25%.
Title: Re: Dark green shoulders and Uniform ripening genes
Post by: Vesa Tee on 2021-09-01, 01:55:17 PM
Quote
... journal does not indicate the phenotype of the U+ crossing...

I didn’t find this info there neither directly. But there is the Table 7 that lists the parents and most F1 colors, e.g. the phenotype of green shoulder (Walter) x uniform green (NC 84173) is ”green shoulder”. Medium green is only listed when one of the parents is 8033 (medium green).
Title: Re: Dark green shoulders and Uniform ripening genes
Post by: Roland on 2021-09-01, 02:11:05 PM
Yes, but i am curious for the phenotype Walter x 8033.
Title: Re: Dark green shoulders and Uniform ripening genes
Post by: Steph S on 2021-09-01, 04:40:39 PM
Just for comparison, I grew 6 F2's this season that are segregating for u.   2 of 6 were u/u completely uniform, and the other 4 had green shoulders - I didn't pay attention which one had more shoulder or less so can't comment on the variation.
But this is what I would expect (more or less) from the simple mendelian segregation of a recessive trait.

I wonder why the breeders wanted a single u allele in their F1 Galahad.
This almost implies that there is some benefit to the heterozygous u or is there another closely linked trait, such as firmness perhaps? which brought u along with it in the parent line.
Title: Re: Dark green shoulders and Uniform ripening genes
Post by: Garrett Schantz on 2021-09-01, 09:44:30 PM
Galahad doesn't have early blight resistance but Johnny's seeds lists "exceptional" late blight resistance. "High resistance to Fusarium wilt (races 1, 2, and 3), gray leaf spot, late blight, nematodes, tomato spotted wilt virus, and Verticillium wilt." Also apparently has a decent taste according to Johnny's and some blogs. Don't really see too many tomatoes with all of these different high resistances. Figured I would mention it here.

Figured I would quote my old post, Galahad has a lot of different disease / pest resistances - this probably required a lot of breeding work.

The breeders may have only had a single u allele in the F1 because it was already hard enough cramming the other resistances in. Normally tomatoes don't have this many resistances.

Also assuming that there are a bunch of wild traits floating around in Galahad, the green shoulders could be influenced by multiple genes and/or an uncommon gene.
Title: Re: Dark green shoulders and Uniform ripening genes
Post by: Vesa Tee on 2021-09-02, 12:04:57 AM
The segregation ratio resembles the complementary gene action (9:7) if you consider only the uniform versus ”non-uniform”:

8+20=28 non-uniform (9)
23 uniform (7)

The original cross could be between two different ”uniform” phenotypes and the expression of uniform requires at least one of the two being homozygote, i.e. aaBB, aaBb, AAbb, Aabb, aabb (where a and b are recessive uniform genes). The F1 is not uniform because it is AaBb, and does not have any homozygote uniform gene.

See e.g.  https://www.ndsu.edu/pubweb/~mcclean/plsc431/mendel/mendel6.htm (https://www.ndsu.edu/pubweb/~mcclean/plsc431/mendel/mendel6.htm), Example 2: 9:7 Ratio.

Compare ”no anthocyanin produced” with ”uniform” in your Galahad F2 segregation.
Title: Re: Dark green shoulders and Uniform ripening genes
Post by: Roland on 2021-10-10, 07:27:21 AM
Maybe the dark green shoulders are the result of the U gene (Homozygous or heterozygous) in combination with the recessive high pigment genes hp-1 or hp-2?

If this is the case the F1 is carrying:
U/u = Green shoulders
+/hp = no extra high pigment.

The F2 with dark green shoulder is carrying:
U/u or U/U = Green shoulders
hp/hp = extra high pigment.
If this is the case there is no reason to think the U gene is incomplete dominant.

https://www.researchgate.net/publication/259184640_High_pigment_tomato_mutants_-_More_than_just_lycopene_a_review

Title: Re: Dark green shoulders and Uniform ripening genes
Post by: Adrian on 2021-10-19, 10:15:49 AM
Do you think that the vigor of the plant and the color of the leaf can influence the expression  of the gene U? I have note the better expression of U in the most vigorous andine cornue plant.