Inheritance of ry (reddish yellow, ”bicolor”)

[Pippin]

I have some questions on the ry gene, the modifier of red colour of fruit flesh - often referred as bicolor in many cultivars.

There seems to be evidence that the phenotype of RR (red) x ryry (bicolor yellow) cross is red in F1. In F2, it shows a phenotype ratio of 3:1, i.e. 3 reds to 1 bicolor yellow. (https://tgc.ifas.ufl.edu/vol6/v6p33a.html)

There is also evidence that the phenotype of rr (yellow) x ryry (bicolor yellow) cross is yellow in F1. (https://tgc.ifas.ufl.edu/vol7/v7p14.html) My question is what can be expected in F2 phenotypes? Interestingly, the results seemed to be so confusing back in 1950’s that the researchers didn’t dare to publish all their data from their yellow bicolor x yellow-tangerine cross.

I am asking this because I have some F2 ryry (bicolor yellow) phenotypes from a cross between RR (red) x rr (yellow). The only way I can explain this to myself is that the phenotype of (rr)(ryry) must be yellow. So my rr (yellow) parent would actually carry also ryry that cannot be observed from the phenotype by eye. Is this possible?

If this is the case, the answer to my first question would be that the F2 from rr (yellow) x ryry (bicolor yellow) cross would show a ratio 3:1, i.e. 3 yellows to 1 bicolor yellow. r (yellow) would be acting like a dominant gene towards ry which would be funny because r is a recessive gene towards red itself. In other words, ry (yellow bicolor) could not be expressed with yellow (r), it would need something else like red (R) or tangerine (t). In a similar way than Beta requires red (R) to be expressed. It also means that the expression of ry (yellow bicolor) could ”disapear” in later Fn generations if heterozygous red/yellow (Rr) segregates in later generations to rr after the yellow bicolor (ryry) has already expressed. Has anyone made such observations in crosses where both r and ry genes are involved?

I would be interested in learning also any other experience on crosses involving ry. For example, crosses with tangerine seem to work just fine. But what about crossing with genes like Beta, for example?

[bower]

Hi Pippin.
I think the source of ry must have been your yellow parent in the original cross. If it was r/ry it would appear yellow but was not actually homozygous.
As I understand it, R, r, and ry are alleles of the same locus, and from what you said here, R is dominant to r which is then dominant to ry. Interesting finding!

I have not yet had the pleasure of growing out a bicolor cross, but finally this past fall I made a successful cross with Oaxacan Jewel as pollen donor to one of my determinate Skipper lines. As with everything else, there's likely more to learn in the process than you get from the books.

Crosses with Beta I wouldn't expect any expression of the Beta orange, since it nominally requires RR background to be expressed. However I've not seen that confirmed anywhere, so I could be wrong.

OTOH there are also a few other genes that cause additional coloring in the fruit. There are yellow OP's which have a little pink blush inside, for example, and is not a full bicolor effect but seems to be the effect of another gene (Zolotye Kupola iirc has this). And there is the little red marking typical of Jaune Flamme fruit, which is not explained, and that is in a Beta. If you explore TGRC genes effecting color you will see some odd ones described and shown, but I have never seen them confirmed or identified in an OP that I know or recognize, only in certain accessions which are numbered. So these genes are doubtless around in the OP gene pool but we don't know much about them. Their effects on color are more subtle than a full ry/ry.

More experiments and pics of your results would be lovely to see!

[Pippin]

I would not like to direct too much focus on my own cross. I don’t have urgent need to really know what the genetic is. I enjoy the mystery, and will enjoy even more next summer when experimenting more.

The problem is that there is not that much information available on ry genetics. For some reason, there has been quite little interest for it in research or by seed companies. This is the alley of hobbyist and small scale plant breeders.

My F2s are probably not the most typical examples of bicolor if they even represent that. I grew both the F1 and a sample of F2s during 2020 which means very little natural light for F2s at the time of ripening. I select only for plant architecture in F2, and in the end I had only 6 F2s left for fruits to ripe - others were rejected earlier. The cross is between two OP stable varieties, little more complex than just rr x RR. I got 4 RR/Rr, 2 reddish yellows and 0 yellows. Two had stripes and two had green flesh. Two (purple/brown and reddish yellow) will continue to next summer F3 growings.

My reddish yellow F2s start ripening from green to yellow, then they turn to orange and look ripe, however, they are still very hard. The amount of red seem to increase over time. BlushIng describes them well. The skin is clear which is important because the yellow of the skin does not contribute to the orange look and they have a very thin layer of red right under the skin (’red skin’). You can see the yellow stage in left background in the pic too, that yellow is not coming from the skin but the flesh. When I cut the first reddish open, I was surprised to see the pale yellow insides. Unfortunately, no pics on that. These are cherry size tomatoes, not easy to compare with large beefstakes or hearts. The pics below are after several weeks of ripening and I have to admit that they don’t look very yellow anymore. I still have few left - the taste is very acid, not really a pleasure to eat. As if one was eating vitamin C tablets. I am confident that the taste will improve with better growing conditions next season.

I got one pink as well, and the red in it is much more intence and bright than in these assumed bicolors.

The cross involves gf and gs too, the stripes were faintly visible in F1. Not sure if those could explain this unexpected look. Or can simply a Rr be expressed as this type of lighter red color?

4D258617-8387-493B-BF2F-70FDC8525177.jpeg

[Pippin]

Coming back to the original question of the inheritance of ry. I think the two references further above are pretty much the only research done on this topic. The cross between reddish yellow and yellow-tangerine confirmed the allelic nature of r and ry, I think. I copied some data below from the cross below. The evidence of r and ry being allelic basically is (in my opinion):

• F1 is yellow (which means that neither of the parents probably do not have fully functional RR gene to produce lycopene or something is still blocking the expression of it), and

• F2 did not produce any reds neither (which means that it is very unlikely that there is some unknown third factor that was blocking the expression of red in F1 because some combo in F2 should have made at least some reds visible again).

UI Acc. 29 x UI Acc. 36
ry ry t^+^t^+ rrtt
F1: yellow
F2: red (0), yellow (169), tangerine (57)

But the question still remains if a yellow stabilized OP phenotype from above type of cross can segregate ry phenotypes when used in further crosses with reds. It should not be possible in my mind - that is why I am asking observations from people who have been playing with bicolor ry gene.

I will grow F2s next summer from a cross between Aftershock and the same red parent I used in this mystery cross. AfterS should have some bicolor gene and I will hopefully be able to compare the colors. Just that AfterS red markings have been quite small, maybe it is a different gene or allel.

The ’yellow’ parent in my mystery cross was Green Sausage (green striped). Below some further pics from different seggregates (top left: pink striped, top right: purple/brown, bottom left: reddish yellow, bottom right: pink).

24EADAEA-3F19-44F7-A65D-460E8AD4C04A.jpeg

[bower]

Hmmm I wonder if your comment about low light for ripening the F2 may be the explanation. A possible cause of uneven ripening/uneven coloring as shown in your pic is potassium defects. I encountered this problem due to growing too many plants in a small greenhouse space - they did not get enough light and consequently ripened unevenly. The fruit look absolutely normal as long as they are green, but the problem with potassium metabolism is already present and does not show itself until the long awaited ripening.
Potassium defects in tomato can occur for multiple causes (too much light, not enough light, too cold to process K, too hot... etc) and susceptibility is also genetically determined to some extent.
So anyway, this is a non-genetic possibility, to explain what appears to be ry coloring in a line that had no ry parent.

[Pippin]

Whow, excellent theory, thank you Bower!

Did not come to my mind at all. I must be focusing too much into these interesting imaginary genes that I am skipping other essential factors. Good that I asked: imagine if my reddish yellows disappear next season, how confused would have been? What kinds of conspirasy theories (of the genes) I might be presenting in this forum then?

I think you are very likely correct. I have seen the potassium deficiency only caused by hot weather, didn’t know that e.g. cold could do the same. The plants were exposed to cold for a couple of weeks before I took them to warmer conditions. And yes, there was some strange whilting and damage on the leaves too. This was the first time ever I grew tomatoes out of season. This is a good lesson if I try to skip one season and F generation some time later. Maybe the better potassium balance would help with the flavor and sugars as well as. It would be sad to drop these lines because the flavor was so poor. They are actually very pretty.

Still interested in hands-on experiences on bicolor genetics if someone wants to share! No change on that.

[bower]

I'm glad you brought it up! I was mulling about starting my F1's now to try and get seeds in time for an F2 grow this summer looking for bicolor. The problem is, I would not get seeds before my usual starting time. Plants started late, not only will be later to mature but they also face the problem of bigger tomato plants which got a head start on them! So they have the same issue of getting shaded out and risking the ol K issues.
Guess I'll just grow the F1s this year after all, at the usual time with the others. It's okay, alright to have a few red tomatoes to eat as well.

[wykvlvr]

Me, being the type of person I am, had to google "how to get a bicolor" I found an old thread on Tville where they talked about it. Step 1 was start with a bicolor... however they also went on to show that Cherokee Green at that time tended to throw bicolors so they felt it could be a hidden bicolor. I couldn't see the photos of course but the information was interesting...

Problem I have is what is the definition of bicolor. IF you look at stores they tend to lump 3 distinct types of coloring under the term bi color... Type 1 is yellow or green but the core ripens red/pink, Type 2 is stripped red/pink on yellow or green, and Type 3 the whole tomato is blotched/swirled with patches of red/pink on a green or yellow background.

So say I decided I want to make a bicolor micro. My impression is that the Type 3 tomatoes are true bi colors. Not sure on the Type 2 but have realized from my reading that the Type 1 with only the core affected is a different gene. For my "bicolor" indet parent I could chose from Mr Stripey (one of those type 2 tomatoes) or Pineapple Fog (a type 3 tomato) then pick a yellow, any yellow or hmm I do have a green that is one of the new releases from Bunny Hop...
Of course I still haven't totally sorted my swap seeds so may have other choices in there... I am not being lazy, honestly I have been busy rearranging the room so I have a bigger and better place for my plants. including room for a small fan. PLUS I need to find room for my big RH loom... Beka needs a space about 4 ft square and the space I have is only 9 ft square...

[Pippin]

I think I found the discussion in the other forum, thanks for the hint! You must mean this one: http://www.tomatoville.com/showthread. ... 607&page=2 I am not familiar with the dosing effect but it seems to provide an alternative, genetic explanation for my reddish yellows. It sounds like something that cannot be stabilized as an OP phenotype. Need to investigate more.

Not sure if there is agreed definition of what bicolor is. Anything with two colors, I suppose.

If I was creating a bicolor micro from the parents that you mention, I would not use yellow as the micro parent. I think the Mr Stripey carries the ry gene that we are discussing here. If you use red or black (red+green) micro in the cross, then all yellows and greens in F2 will all be bicolors. You would not need to guess if the gene is there even if it didn’t express very well.

The same goes for the Pineapple Fog, I would use red or black micro parent. PF could be Beta which does not express on yellow background. In my experience, ripe Beta’s have typically red center - so there is not likely a separate bicolor gene involved at all. If you use yellow parent with Beta cross, all yellow F2s would be plane yellow, no orange, no red in the center. Note also that Beta and sp (determinate) genes are linked genes and you would not likely get determinate Beta out of the cross with PF. To create Beta micro determinate, I would use determinate Beta parent.

Pineapple Fog could also be tangerine with ry (tt+ryry). If this was the case, yellow would work well as the micro parent. But also red and black is good.

There are other genes than ry or Beta that gives two color phenotypes, like apricot or some of the ripening inhibitors (like Green Ripe).

[Rockoe10]

....
Not sure if there is agreed definition of what bicolor is. Anything with two colors, I suppose.
...

I'm definitely not the person with the answer, but i remember reading somewhere that s truly bi-color tomato is one who's flesh inside is also bi-color

[wykvlvr]

Yes that is the thread I was talking about

If you use red or black (red+green) micro in the cross, then all yellows and greens in F2 will all be bicolors. You would not need to guess if the gene is there even if it didn’t express very well.

DUH I really should have thought of that .. time to sit down and really think of what would be involved. For instance the size of F1 and F2 plants would be a limiting factor for me but if I use a dwarf like Wherokowhai as my bi color sire those will be dwarf not full size. I could raise them in buckets rather then taking room from my very limited trellis space. Okay someone tell me I don't need to do this...

[Pippin]

When you read my comments on making bicolor crosses, remember that I am just a bookworm without any experience on them. What confused me originally on this ry bicolor thing was that it is often described as a modifier of yellow flesh. So, it sounds like one would need the yellow (y) and the modifier (ry) to get the effect. But the crossing tables in my first references are telling something else, i.e. one only needs ry. The normal yellow flesh y might actually just make finding the bicolor phenotype more difficult. So, if one wants to call the ry as a modifier of something, one should call it a modifier of red (RR), not yellow (rr), in my opinion. It does not ”add” the red markings to a yellow tomato (if crossed with yellow) but it ”removes” some of the red parts from a red tomato (if crossed with red). Both r and ry should not co-exist in a stable OP variety. Only with tangerine or apricot background, ry kind of adds the red markings because it interferes with the carotenoid/lycopene pathway in some strange way. Based on the literature, that is.

I have screened one F2 on a cross between a dwarf (Lime Green Salad) and a plant with one of these other non-rugose dwarf genes, and I was able to visually pick the micro dwarfs (cf. Red Robin type and some more compact) very early. So, you don’t really need buckets at least for your F2s. You need to sow lots of F2 seeds and a trained eye to pick only the smallest ones. You probably need to see one or two of the true leaves to make the selection. But for the F1, yes, a larger container would be good.

[MrBig46]

Theoretically, crosses yellow and red should give orange. But it's not that simple, because the red gene is dominant over the yellow. But there are certainly people here, who could say more about that.

[Pippin]

Sorry to disagree.

In watercolors: yes, mixing red and yellow gives orange.

In tomatoes: no, crossing red and yellow does not give orange but only reds and yellows.

[wykvlvr]

Yes it is the F1 that I would need buckets for since NORMALY the results are micro x indet = indet F1, micro x dwarf= dwarf F1, micro x micro = micro F1 but some have had micro x micro = indet size F1!

F2 are a bit more problematic. Leaf size and internode distance are not always true indicators of how big a plant will be. One plant in my current batch has larger leaves, was my tallest most rangy seedling but stopped growing and is now one of the plants I will continue with, while the small carrot leaf just kept growing and growing and acts more like an indet plant. It is currently pushing 14 inches tall and still growing. AND these are a micro x micro cross.
Which is actually a long winded way of saying that I may still grow selected F2 plants in buckets or large grow bags to be sure the plant is small due to genetics and not the size of the pot it grew in.

Of course we are talking color also, I do agree the red x bi color could be the easiest. Looking over tomato seeds I have I think these two crosses could be nice to play with...

Pygmy x Wherokowhai - Pygmy is an upright mini dwarf like plant . Last year Pygmy was very prolific for me, nice sized red cherries and I liked their flavor. And of course Wherokowhai would bring in some very good flavor.

Baby x Mr Stripey would be my second cross. Baby is a low growing plant with huge leaves that you have to hunt through for the tomatoes. This was my favorite of the micro dwarfs as far as flavor went.

[Rockoe10]

...
some have had micro x micro = indet size F1!
...

That's very strange. Sometimes the simplest answer is the correct one. Could it be that it was accidently crossed with an Indeterminate?

[wykvlvr]

An accidental cross is possible but I tend to I think it has more to do with the genetics of the micro dwarfs. Unlike dwarf tomatoes that have a set look and genetics that make developing more dwarf varieties fairly easy, Micro dwarfs are defined by their lack of height not by any specific genetics. I have noticed 3 very distinct types in the ones I have grown. Flat sprawling big leafed plants that rarely top 4 inches tall. Stout trunks with rugose leaves that resemble tiny dwarf plants. A bit rangier and often taller are the ones that look like small determinate plants but are under 20 inches tall regardless of pot size. I think is is possible when crossing different types you could break the linkages causing the small size and oops full size plants happen. I don't have any proof but the theory does make sense.

[MrBig46]

Sorry to disagree.

In watercolors: yes, mixing red and yellow gives orange.

In tomatoes: no, crossing red and yellow does not give orange but only reds and yellows.

I didn't want to say that crossing red and yellow tomatoes should produce orange. But I wanted to point out that red genes are dominant in tomatoes. I don't see much yellow in your crosses. "I guess in the next generation it will probably be red tomatoes. This is my opinion.
Vladimír

[Pippin]

Hi Vladimir,

Seems that I totally misread you then, sorry about that.

I tend to think that there is something special in Green Sausage, similar to what was discussed in Twille on Cherokee Green (here the link again http://www.tomatoville.com/showthread.php?t=42607). I woud expect to see reds from these ’bicolors’ in next generation too, however, the Twille discussion also hints that the ’salmon bicolors’ could be stabilized as one has been maintained successfully for several years. My pink F2 could also be described as ’candy apple red’, mentioned as one potential segregate in Twille discussion. Never seen such bright red color, the pic does not give it justice.

I suppose the simplified model of dominant and recessive allels is only the general rule of what can be expected in these types of crosses, then there are the exceptions. Will sure be interesting to see how these segregates in the next generation.

[Pippin]

I still wonder if an extra copy of r gene could be yet another explanation for the bicolor coming out of non-bicolor parent cross. This could be a result of natural polyploidy that exists in many plants, colchicine treatment often used in early plant breeding (in 1940’s or so) or crosses with wild tomato speaces.

Seems that some tomato varieties may have an additional 13th chromosome (compared to the normal 12), e.g. Floradade well adapted to hot, humid subtropical conditions. https://tgc.ifas.ufl.edu/vol34/v34p3.html Not claiming that such additional gene would have an extra copy of r gene, just that it could.

Also found the below description of tomato phenotype with three copies of the R gene. It is saying that Rrr phenotype resembles sunburn (that I think is also similar to symptoms of Potassium deficiency discussed earlier).

The flesh color of the fruit of triplo-I suggests the presence of the locus of the Rr gene pair in an unexpected manner. Rrr plants, grown in the field or in the greenhouse, have slightly paler red flesh than Rr diploids, especially at the proximal and distal ends. In the field, pale areas occur on the fruit which resemble externally those caused by sunburn. Appar- ently R is completely dominant over r, but is incompletely dominant over rr. A similar paleness of flesh color was often seen in the fruits of RRR and RRr plants. Apparently modifying genes are present in the I chromo- some, whose effectupon color is cumulative and opposed to that of R. The flesh color of rrr plants is yellow like that of rr diploids.

https://www.genetics.org/content/genet ... 5.full.pdf