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Post by ilya11 on Jan 8, 2021 17:30:29 GMT -5
Indeed, I have few hundred seedlings of 5starXacidless_orangeGosset, but I am making primary selection by frost resistance.
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till
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Post by till on Jan 9, 2021 8:03:42 GMT -5
Mikkel, I have read the arcile from Ilya again and I see no contradiction to the articles I mentioned here. Some points: - The article mentioned by Ilya is mainly concerned with the Millsweet type of mutation. That is in the arrangement of "my" article a atypical form of acidless gene mutation and not a fully acidless one. This has to be taken into account. - "Ilyas" article identifies CitAN1 as the key factor for acidless fruits in non-pumelos. The grafic of this gene strongly resemples the NOEMI-gene of "my" article. CitAN1 and NOEMI seem to be more or less the same genes. But here my understanding is a bit incomplete. It seems, however, to me that CitAN1 in "Ilyas" article is only a part of what they call NOEMI in my article. So what the latter article summarizes under defective NOEMI is analysed more closely in "Ilyas" article. Correct me if I am wrong. - "Ilyas" article states that the differences of acidification in sweet non mutated varieties is still unknown. They should not be comfused with acidless varieties. - "Ilyas" article also states that acidless pummelos posses a different genetic constitution than for instance sweet lemons or oranges.
To sum up, according to my understanding everything that the articles that I mentioned at the beginning of my threat state remains valid, especially what regards the consequences for breeders. But the article introduced by Ilya has a closer view at some points.
I shall ad that I have the printed version of the articles of Cameron and Soost. There is a table with acidity levels of 82 backcrosses (Acidless pummelo x normal sweet citrus) x normal sweet citrus. The numbers there strongly support the view that acidless pummelos contain a single gene that regulates acidity. In homozygous form it is dominant in heterozygous form it can lower the acidity level.
Correct me if I am wrong. But I would say: Let us not make the matter more complicated than it is. And be cautious that you don't mix up acidic sweet types like Clementine with acidless types. The inheritance of acidless types seems to be relatively clear, the genes behind the different levels of acidity in acidic sweet types (like Clementine) may be more complicated and is still unknown.
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Post by ilya11 on Jan 9, 2021 10:00:02 GMT -5
Funny enough that we have no F1 hybrids of poncirus to any of these 3 (?) types of acidless citruses.
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Post by mikkel on Jan 9, 2021 11:18:37 GMT -5
I have 2 varieties of Acidless Oranges but I am still waiting for my Poncirus to flower.... Meanwhile I tried to pollinate with Ichang Papeda but the flowers were aborted.
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Post by mikkel on Jan 9, 2021 12:10:54 GMT -5
there is some overlap between the two articles. I will now write down my summary / understanding again, just for completeness: Ultimately, the first article assumes one gene and the nature article assumes 2 or 3 genes that regulate acidity but are themselves regulated by at least 3 other genes. with CitAN1 playing the key role in all non-pomelos. Consequently, there is only indirect regulation of acidity. Because at least 3 genes are involved, the normal rules of inheritance do not apply without restrictions. And there I see the main difference to the first article. in acid-free oranges and lemons, the gene CitAN1 plays the decisive role, it also influences the other two regulatory genes. if CitAN1 is not expressed, the entire regulatory mechanism is interrupted and no acid is accumulated. Hybrids of acid-free varieties are then always acidic. Because the gene variant in acid-free varieties is probably recessive. Only backcrosses with acid-free varieties can be acid-free again. There are some differences in acidless Oranges and Lemons. In "sweet" Lemons there is a gradient expression of acidity reagulatory gene (CitPH1 and CitPH5) depending on the grade of expression of CitAN1. In "sweet" Oranges only if CitAN1 is not expressed the variety is acidless. As soon as CitAN1 is expressed no matter at wich level (compare Ostia Orange in Fig 5) fruits are acidic (low pH ).
In principle, the same genes act in pomelos as in all other varieties, including the acid-free varieties. However, it is striking that Siamese Sweet has an active CitAN1 gene and yet is acid-free. Attention: this is only speculation: There may be another gene (or allele at the CitAN1 gene locus) which, unlike in other citrus varieties, can shut down the entire regulatory mechanism (even if CitAN1 is expressed). This mechanism would have to be dominant and heterozygous in Siamese Sweet, which would at least explain why the cross Rangpur x Siamese Sweet does not express the genes CitPH1 and CitPH5 (acid-free) and in a second cross, these genes are expressed normally (acidic).
till Can you post the table from the Cameron and Soost article? This might help to understand it ia little bit more. This particular gene seems to be reserved for acid-free pomelos like Siamese Sweet. What this does not explain, however, is why Chandler is intermediate in terms of acidity. (Which is why this explanation cannot be entirely correct). But this is "only" genetics, for practical breeding I interpret it like this: that for acid-free hybrids Siamese Sweet would be probably best suited. simply because one can concentrate on the other traits, because (only IF Siamese Sweet is dominant heterozygous) half of the hybrids would then be acid-free. It is interesting that semi-acidic varieties (e.g. Pineapple Orange) have the same pH value as acidic varieties, but form a much less amount of acid and therefore taste sweeter... In any case, the whole story is multifactorial and not fully researched, (and of course not fully understood by me ) so trial and error is still the best way for amateur breeders. but a few hints as to which combinations might be the most promising can already be extracted.
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till
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Post by till on Jan 10, 2021 4:18:53 GMT -5
This is how I read the articles. Would agree with your interpretation. But where do you see that Rangpur x Siamese Sweet is acidfree? From where do you have this information?
Here the table from Cammeron and Soost:
Cross Trees sampled 0.1% acids 0.4% acids 0.5-0.9% acids 1.0-1.6% acids >1.6% acids
(Acidless pummelo x Kinnow) selfed 40 12 0 4 16 8
(Acidless pummelo x Frua) x Clementine 27 0 4 10 12 1
(Acidless pummelo x Dweet) x Frua 15 0 0 4 8 3
The articles are not long. I can send them via email to those who are interested. I think that should be ok. But posting everything here is probable against copyright laws.
We must carefully interpret the data in the table because he gives certain ranges of acidity. He might perhaps have grouped it a bit differently. Then the hereditary rules might have become a bit more apparent.
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till
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Post by till on Jan 10, 2021 6:22:46 GMT -5
It is indeed funny that we have no Poncirus hybrids of these acidless types. I think that is telling. Cameron and Soost presented their data in 1963 and 1975. They worked in Riverside, so to say in the center or citrus breeding. 45 years later there are still no hybrids. It is not that good hybrids are impossible. There is simply no (economic) interest in producing them. Even the last 100 years passed away largely unused. It is not that breeding is so difficult that nothing could have been archieved in 100 years. A little bit has been archieved but most by hobby breeders with very limited resources. For the small resources the results are not bad I would say. Anyway, I have pollinated my Vainiglia Sanguigno with Poncirus again. Hope it was successfull.
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Post by ilya11 on Jan 10, 2021 11:19:22 GMT -5
Many years ago Bernhardt Voss made this cross:
M23 citroncirus xmaxima"Chandler" ****** Citrangelo Voß 1 -8? j Mono-Bi-und Trifoliate Blätter,sehr wüchsig.
This ChandlerTri potentially could have an acidless gene but his plant has not flowered yet.
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Post by mikkel on Jan 10, 2021 11:31:00 GMT -5
ilya11 do you have M23 citroncirus xmaxima"Chandler" ****** Citrangelo?
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Post by ilya11 on Jan 10, 2021 11:48:23 GMT -5
Probably not, but yesterday was trying to resolve one enigma with Bernhardt, will keep you posted.
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Post by mikkel on Jan 10, 2021 11:49:32 GMT -5
Pummelo x rangpur : interpretation from down right to down left to upper left to upper middle to upper right
6C-32-01 CitAN1 expression level 2,5 --> CitPH1 and CitPH5 are expressed --> pH level : 3 (sour)--> 15mg/ml acid concentration --> Brix the same as the 2nd hybrid
6C-32-02 CitAN1 expression level around 0,25 --> CitPH1 and CitPH5 are not expressed ---> pH level: 5,5 (not sour)--> 0,1mg/ml acid concentartion (nearly absent / acidfree ) ---> brix is the same as in other hybrids
I just noticed that Weirick Rangpur has the highest expression of CitAN1 but no expression of CitPH3 but in opposite to the thesis that CitAN1 can regulate the expression of the "SOUR" genes it is less sour and considered as sweet in the table
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till
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Post by till on Jan 11, 2021 3:49:21 GMT -5
Indeed. Thank you for reminding me. I should have paid more attention to that. So we have even more options to breed sweet citrus.
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till
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Post by till on Jan 12, 2021 5:29:35 GMT -5
Ilya, where do you get M23 from Bernhard Voss? I have found nothing in the internet about it?
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Post by ilya11 on Jan 12, 2021 7:36:25 GMT -5
I ordered it in 2002, but there was apparently some problem with tags,entirely my fault. Recently discussed this with Bernhardt, it is possible that I still have it under another name.
Citrus_nursery>ColdHardyHybrids
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jibro
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Czech Rep. | USDA 6b
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Post by jibro on Jan 12, 2021 8:16:16 GMT -5
In citrus, organic acids accumulate in the juice sac cells of developing fruits and are catabolized thereafter during ripening. Aconitase, that transforms citrate to isocitrate, is the first step of citric acid catabolism and a major component of the citrate utilization machinery. In this work, the citrus aconitase gene family was first characterized... Gene expression analyses of the citrus aconitase family were subsequently performed in several acidic and acidless genotypes... identified in citrus 3 transcription units coding for putatively active aconitate hydratase proteins, named as CcAco1, CcAco2 and CcAco3.
Real-time RT-PCR expression analyses of the three aconitase citrus genes were performed in pulp tissues along fruit development in acidic and acidless citrus varieties such as mandarins, oranges and lemons. While CcAco3 expression was always low, CcAco1 and CcAco2 genes were generally induced during the rapid phase of fruit growth along with the maximum in acidity and the beginning of the acid reduction. Two exceptions to this general pattern were found:
1) Clemenules mandarin failed inducing CcAco2 although acid levels were rapidly reduced 2) the acidless "Sucreña" orange showed unusually high levels of expression of both aconitases, an observation correlating with the acidless phenotype.
However, in the acidless "Dulce" lemon aconitase expression was normal suggesting that the acidless trait in this variety is not dependent upon aconitases. Phylogenetic studies showed the occurrence of five different subfamilies of aconitate hydratase in plants and sequence analyses identified three active genes in citrus. The pattern of expression of two of these genes, CcAco1 and CcAco2, was normally associated with the timing of acid content reduction in most genotypes. Two exceptions to this general observation suggest the occurrence of additional regulatory steps of citrate homeostasis in citrus.
Clemenules fruits did not show CcAco2 induction, an observation suggesting a possible mutation in the regulatory regions of this gene, since no alteration was detected in the coding sequence... Thus, differences in citric acid content between these two varieties(Clemenules and Fortune) may be related to additional regulatory steps such as the activity of the membrane transporters m ediating citrate efflux from the vacuole during ripening .
Acidless orange Sucreña
The highest mRNA levels of CcAco1 and CcAco2 genes were found in the pulp of acidless Sucreña orange and these levels were already high at the onset of phase II, when the expression of these genes was still arrestedin normal acidity oranges (Comuna and Valencia Late) mandarins and lemons.
The overexpression of these genes when citric acid is being produced in the mitochondrial matrix, released to the cytosol and exported to the vacuole may be responsible for the acidless phenotype of the variety, since a higher aconitase activity would degrade citric acid, avoiding its vacuolar.
Sweet lemon Dulce
The comparison of Dulce, an acidless lemon variety with Fino, a normal acidity lemon, showed no significant differences in the expression of the aconitase genes.
This suggests that different mechanisms are responsible for the phenotypes of orange (Sucreña) and lemon (Dulce ).
Sweet Lime
This activity decrease was correlated with a previously reported increase in citramalate, a competitive inhibitor of aconitase activity. In acidless sweet lime, citramalate level was lower suggesting that the acid-less phenotype of this variety mostly related to citric acid production instead of citric acid removal. This possibility is compatible with the observation that in acidless Dulce lemon.
It looks like this is another confirmation that there are different mechanism how to reduce acidity in each of the acidless varieties, only sweet lemon and sweet lime may be similar...For me is interesing also low acidity in clementines, I will use early maturing variety Oronules and maybe Clemenrubi (if I get it) for crossing. I am also thinking that one of the genes that reduce acidity may be the same in some poncirus with low acidity, so I may try cross acidless lime, lemon, orange with PT Tachov and Flying Dragon VS (it had only Brix 8 but the taste was still much less sour than in others Poncirus, so I assume it may have reduced acidity too) maybe there wil be some compatibility in one combination.
I also found the famous acidless pummelo Siamesse sweet CRC 2240 in IVIA collection as IVIA-685 Siamesse Acidless any idea how to get it?
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