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Post by mikkel on Jan 7, 2021 12:39:40 GMT -5
It is apparently very complex but I think we can also just look at what crosses worked in the past from existing hybrids: I totally agree. It is best to try and take into mind what already has been achieved. I made crosses Vaniglia x Ichang Papeda and vice versa, only I P x Vaniglia are still around. US 119 has a sweet taste and it is cross: Citrumelo 80-9 (Duncan grapefruit x Poncirus "Gotha Road") x Succari (acidless orange)
It is clearly possible to get sweet fruit from crossing sour citrumelo with Acidless orange, despite it has not the full set of these "acidless genes". Theoretically explanations:
Premise: all 3 genes are considered as linked and handled as they were just the same. s: rezessive non sour S: dominant sour
(as sour is controlled by at least 3 genes it isn`t possible to write it this way but for simplification I suppose Ss for Duncan)
Duncan (Ss) x Poncirus (SS) results in 100% sour F1 hybrid seedlings but with 50 % with heterozygous sS allels.
F1 (sS) x Succari (ss) results in 50% sour hybrids with (sS) and 50% Sweet (ss) F2 hybrids US119 would be one of them.
But in fact acidity level is controlled by 3 genes (as mentioned in the paper) Due to the fact that US119 is not completely acidless (as supposed here) There must be a a gradient from sour to sourless due to the fact that it is controlled by multiple genes.
This would mean the chance of an hybrid like US119 is far less than 50% as expected when only 1 gene is involved. A practical issue is how to detect the most likely seedlings? Like Till wrote seedlings without any anthocyanin could be a good hint. But are there more ways to detect them?
Using less sour Poncirus and acid less Citrus varieties for crossing would be even better, the best pomelo variety for such a combination would be P2240 (taken from the nature article) as all 3 sour genes are not expressed. But sour is only one part of the problem there is still hardiness and bitterness in P.t.hybrids. I don`t write it to disencourage someone, but for finding the most probable way to reach our goals. SP Urban (Ichangensis x Acidless Rangpur) did not work and the result is sour taste, but maybe it is possible to found acidless F2 seedling, SP Urban also may have a short juvenile period, one seedling flowered after 4 years. If I.P is (SS) and Rangpur is (ss), SP Urban should be (Ss). Backcrosses with Rangpur or selfed should result in 50% (ss) or 25% (ss). (Again as are 3 genes involved percentage is much lower) If the resulting BC1 seedlings are not as desired it would be best to backcross it again with Rangpur. BC2. Each backcross generation has higher chances for expression of the desired trait. Beside the time which is needed I see recurrent backcrossing as the best way for introgression of desired traits. But breeding for multiple traits even this way is very hard and still lottery  Large numbers would solve it, but...
I had the idea it would be a good idea to breed several Poncirus and / or Ichang Papeda varieties e.g. via recurrent backcrossing with several desired traits. like "less sour", "bitter free" etc. for further breeding. Again due to the long periods until maturity it is hard to make it happen but if one know what is to be achieved it could be possible to do several of these at the same time....
my head is smoking.... Did I make any mistakes?
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jibro
Full Member
Czech Rep. | USDA 6b
Posts: 163
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Post by jibro on Jan 7, 2021 15:25:41 GMT -5
Thanks for explaining US 119, but Duncan should not have the same acidless genes as Succari. I suppose he could have other acidless genes inherited from the Pomelo ancestor, so does that means it is not necessary to be limited to just one acidless variety for crossing or backcrossing? I think backcrossing SP Urban to acidless Rangpur does not make much sense, because you would lose hardiness and you will end up with similar taste as acidless Rangpur, at this point Keraji and Changsha may be more hardy and they have better taste already...
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till
Full Member
Posts: 160
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Post by till on Jan 7, 2021 16:33:16 GMT -5
You can explain the sweet taste of US119 without dominant acidless genes. Given that the allel for normal sweetness (like in normal sweet oranges) from Duncan grapefruits meets the gene for acidless sweet oranges the acidless gene will be ruled out but still the allel for sweet orange fruits is present. An acidless orange is besides its acidless attribute just a sweet orange. Sweet x Sweet may well result in sweet offspring. The exact acidity level (low or moderately low) may depend on other factors still unknown.
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Post by mikkel on Jan 7, 2021 16:53:24 GMT -5
I think backcrossing SP Urban to acidless Rangpur does not make much sense, because you would lose hardiness and you will end up with similar taste as acidless Rangpur, at this point Keraji and Changsha may be more hardy and they have better taste already... This is what I am thinking of the most. Theoretically it should be possible to breed coldhardiness into Rangpur or any other variety while keeping fruit characteristics of Rangpur by backcrossing but I see many limitations to do so.
a good example for recurrent backcrossing and the introgression for 2 resistancy genes are the both NC Celbr tomato varieties
but tomatoes are annuals and resistency is caused by only 2 genes (Ph-2 and Ph-3) Much different from situation in Citrus. But still good for clarification. |
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Post by ilya11 on Jan 7, 2021 17:34:34 GMT -5
Was this tomato breeding assisted by genotyping or disease induction?
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Post by ilya11 on Jan 7, 2021 17:39:37 GMT -5
You can explain the sweet taste of US119 without dominant acidless genes. Given that the allel for normal sweetness (like in normal sweet oranges) from Duncan grapefruits meets the gene for acidless sweet oranges the acidless gene will be ruled out but still the allel for sweet orange fruits is present. An acidless orange is besides its acidless attribute just a sweet orange. Sweet x Sweet may well result in sweet offspring. The exact acidity level (low or moderately low) may depend on other factors still unknown. US119 has been selected out of population of ~200 seedlings. At these numbers level some rare events like gene conversion, rearrangements, gene amplification are possible. |
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Post by ilya11 on Jan 7, 2021 18:29:27 GMT -5
Jibro, that is why I have produced Kucle x Poncirus crosses, Calamondin x Poncirus crosses and tried last year Limquat x Swingle 5 Star and Meiwa x Poncirus (seed are germinating at the moment). My hope is especially in Kucle x Poncirus because Kucle definitely contains genes for sweet taste besides Kumquat genes. Leaf taste of Calamondin x Poncirus is remiscent of Poncirus (weakly so) but has also a strong mandarin aroma (see my post on Calamondin x Poncirus). Leaves of Yuzu x Poncirus have no Poncirus taste at all. I have also a mainly monofoliate seedling of Kucle x Poncirus with leaves without any Poncirus aroma. It is certainly worthwile to try these and other crosses. And we should keep in mind that we do not need acidless citrus in order to get sweet Poncirus hybrids (cf. 5Star x Keraji, Sanford Curafora and certain US852 seedlings). I am only interested in acidless citrus because I hope that they make it easier to trace the gene for sweetness through the generations. Hybridizing citrus is a lot of work. So it would be good when we could focus on the more promising combinations which are, among others, Acidless pummelo x Poncirus. What is promising depends of cause not only on theoretical considerations but sometimes simply on everyones individual possibilities. I first wanted to produce cicitranges out of good reasons but had no flowering Poncirus hybrid for some years. So I tried other combinations first, even ones in which I did not really believe. I got interesting results while others came up with other good and unexpected results. So my plans changed a bit and I believe it is good so. Yet, it is good to have reasonable plans. Many years ago I made KucleX5star cross,
After 8 years of open ground only two seedlings survived, one of them- 1104004 flowered for the first time this year  [/div] No bitterness, internal oils or poncirus aftertaste |
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Post by mikkel on Jan 7, 2021 18:51:10 GMT -5
Was this tomato breeding assisted by genotyping or disease induction? good question, I couldn`t find out. In tomatoes it is very easy to find resistent plants as Late Blight is letal in most cases only the time span is varying when the pressure is high. So disease induction while high pressure would be an easy way to find out. But these both varieties are from a breeding programm of the University of NC and are now the parental lines of most of the resistent F1 hybrids available at the moment. I would suppose they used genotyping. Or a combination of both disease induction and only genotyping the most promising plants to save resources... My guess
edit: at least for the last step, the combination of both genes in one line, genotyping had to be done, otherwise it would not have been possible to find out which plants are homozygous for both genes.
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Post by mikkel on Jan 7, 2021 19:02:36 GMT -5
Many years ago I made KucleX5star cross,
After 8 years of open ground only two seedlings survived, one of them- 1104004 flowered for the first time this year
No bitterness, internal oils or poncirus aftertaste
good work! Incredible long time but it was worth it. I couldn`t even remember what I was doing at that time What about the inside?
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till
Full Member
Posts: 160
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Post by till on Jan 8, 2021 2:31:27 GMT -5
You can explain the sweet taste of US119 without dominant acidless genes. Given that the allel for normal sweetness (like in normal sweet oranges) from Duncan grapefruits meets the gene for acidless sweet oranges the acidless gene will be ruled out but still the allel for sweet orange fruits is present. An acidless orange is besides its acidless attribute just a sweet orange. Sweet x Sweet may well result in sweet offspring. The exact acidity level (low or moderately low) may depend on other factors still unknown. US119 has been selected out of population of ~200 seedlings. At these numbers level some rare events like gene conversion, rearrangements, gene amplification are possible. Sure, but the number 200 may also just show that they were discriminating with regard to fruit quality. Thank you for sharing your experience with Kucle x Swingle5Star! Gratulation! I hope seeds are zygotic. How does the peel taste? |
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Post by ilya11 on Jan 8, 2021 4:42:34 GMT -5
Internally for the moment it does not look not so good.
But of course, it is the first flowering and because of extreme dry summer the nearby plants have also large peel.
Moderately acid inside, albedo slightly sweet, no bitter taste. Flavedo is pleasantly but faintly aromatic, a little bit bitter. No seeds.
 [/div] |
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till
Full Member
Posts: 160
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Post by till on Jan 8, 2021 11:10:02 GMT -5
Thank you, Ilya. I could imagine that fruits are better next year. I had a year with drought stress for some plants. Kucle was nearly completely seedless then and Poncirus tended to taste so flat that it was almost tolerable out of hand. My Chandler suffered from perodical root rod. It was always seedless then as was Keraji mandarin under drought stress.
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Post by mikkel on Jan 8, 2021 12:33:54 GMT -5
Sure, but the number 200 may also just show that they were discriminating with regard to fruit quality. One could also say that large numbers are necessary to find desired traits. The parentage of US119 gives a lot of possible combinations in terms of bitterness, sweetness and low acidity in the fruits. If the low acidity was controlled by only one gene, there would be a 50% chance of hybrids with low acidity, F1 Citrumelo ( sS) x Succari ( ss) wouöd result in 50% acid hybrids with ( sS) and 50% sourless ( ss) F2 hybrids. actually it should be controlled by at least 3 genes. This massively lowers the chance of low acidity in the hybrids. Considering the other traits needed and all possible combinations of traits, I'd say finding it within just 200 seedlings was pretty lucky.... Apart from the fact that these numbers are only approximately correct, they show a tendency: the more, the better But never rule out that you may be lucky or even prove that previous assumptions were wrong....
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Post by mikkel on Jan 8, 2021 14:02:30 GMT -5
... but Duncan should not have the same acidless genes as Succari. I suppose he could have other acidless genes inherited from the Pomelo ancestor, so does that means it is not necessary to be limited to just one acidless variety for crossing or backcrossing? yes, due to the information given by Till sour should be controlled by the NOEMI gene and it is different in Pomelos and all other Citrus. due to the paper from nature sour is controlled by al least 3 TF which are lowered by 3 to 4 different genes or disfunctional versions of these genes. So the genes for sour are not expressed. I cannot see a link between the 2 papers. Any idea? |
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jibro
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Czech Rep. | USDA 6b
Posts: 163
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Post by jibro on Jan 8, 2021 15:24:19 GMT -5
Mikkel, I have no idea
I just checked this paper: US 119, An Intergeneric HybridCitrus Scion Breeding Line
journals.ashs.org/hortsci/view/journals/hortsci/25/12/article-p1670.xmlThey wanted to combine many traits: cold hardiness, CTV resistance, flavor, fruit size, color, etc I guess that US 119 was selected because it checked all the boxes, but that does not mean it was the only one with a sweet taste from 175 others... I believe there is a decent chance to get sweet fruit from citrumelo x acidless / sweet orange, mandarine or pomelo. I think Ilya may have several similar crosses already so we will see in the future...
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