I am imagine you are right, Joe, but where did you learn how many replication the Japanese make of each cross? You mentioned that you understand they make about 2000 replications of each cross.
Weston – I’m not sure where I read it (or even whether I just inferred it). After seeing your question, I skimmed various articles that I had saved.
This article from 1993 discusses the release of Suruga in 1959 and Izu in 1970. In that context, it states that “The total number of progenies examined at Okitsu was approximately 2,500.”
Apparently the breeding program shifted to Akitsu in 1968. The releases of Shinshuu and Youhou in 1990 came after the testing of ~1,000 progenies. And the cumulative number of progenies tested at Akitsu but 1993 was ~5,000.
Of course, these numbers (e.g., 2000, 5000) must represent numerous different crosses. So the actual number of progenies per cross must be much less.
Persimmon Breeding in Japan Yamada 93.pdf (846.8 KB)
We know that a PCNA x PCA cross will be astringent. This second article states that ~15% of 2nd generation back-crosses of [PCNA x PCA] x PNCA will be nonastringent. So if, for example, we want 15 PCNA offspring that we will test for flavor, ripening time, splitting, etc. then we will need ~100 offspring. Of course, the more offspring, the better the chance of a good cultivar.
Persimmon Breeding Japan PCNA.pdf (717.3 KB)
This final article, reporting the release of the Korean variety Romang, states that 260 2nd generation seedlings were tested to produce that one release.
Romang Korean Persimmon APS_Apr18.pdf (6.7 MB)
Looking at all of this information, absent better evidence I’d infer that maybe 250-500 2nd generation progenies would be more typical than 2000. Of course, if each 1st generation cross produces multiple 1st generation progenies, then we could get to ~2000 2nd generation (e.g., 8 x 250) very quickly.
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Ok. That makes sense.
Cliff told me that the proposed backcross of JT-02 would require at least 1000 replications to really sort out the genetics.
Weston
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I suppose it depends on how well you want to optimize the outcome. Roughly 1/6 (theoretically 16.7% but papers go with 15%) of the crosses of JT-02 x PCNA will be PCNA. But you’d want to ensure the cold-hardiness of JT-02, which I’m guessing only 1/2 would inherit. So that gets you to 8% both PCNA and cold hardy. And if you can cross with a PCNA that is relatively early-ripening, maybe that earliness will show up in 1/4 - 1/2 of the offspring – 2 to 4%. And maybe you want the size of the PCNA, no cracking / splitting of the skin, some other traits related to vigor, etc. It’s easy to see how even under optimal conditions maybe only 1% or less of the offspring will be optimized. It’s not obvious to me that 1000 would be required but I’d think 200-500. Unless you do fewer and get really lucky.
Note that nowadays breeders are not growing the seedlings to maturity. Instead they are grafting them onto mature rootstock. That produces a crop quicker. Also they are using genetic markers to test for the presence of the traits they want rather than waiting for the traits to actually show up in their developed trees.
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Yeah. Makes sense.
Help me with the math a little bit here. I keep seeing this 15% number show up.
We’ve got 6 chromosomes coming together, and each one must contain the recessive allele for the phenotype to be PCNA.
The alleles from the PCNA parent will all be PCNA alleles. The alleles from JT-02 could be PCNA, astringent, or (in most cases) a combo of the two. So here are the probabilities that each of the six alleles in the hybrid offspring would be PCNA. The first three have a probability of “1” since a PCNA parent can only donate PCNA alleles.
So now the math:
1 x 1 x 1 x 3/6 x 2/5 x 1/4 = 0.05. If you multiply these probabilities together to find the likelihood of the ALL occurring AT THE SAME TIME, you get 0.05 or 5%.
Seems like folks were talking about this 5% number earlier in the forum, so I don’t understand how 15% can be correct from a genetic perspective. It seems that we’re looking at 5% of the progeny being PCNA, and of that, roughly 75% would be male.
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I think you are almost exactly right.
The math that gets us to 5% assumes that (1) the PCNA grandparent has 6 PCNA genes, which is sensible since the trait is recessive; and (2) the PCA grandparent has 6 PCA genes, which would be true if its PCA parent is homozygous. I believe that I endorsed this analysis above.
More generally, I would say that 5% represents the probability that a 2nd generation PCNA results from any PCNA x [PCNA x PCA] cross, provided that the ancestors are all homozygous.
Unfortunately, I wrote 16.7% above. That was an error. I was letting the published 15% influence what I wrote, lamely “remembering” that the probability was 1/6 because there are 6 genes. So please ignore those comments. You are correct.
So your question remains – how does 5% become 15%? Note that 15% is presented not as a theoretical result but as an empirical result – it’s what happened.
One possibility (I’m speculating here) is that some of the PCA varieties used in the referenced breeding programs are heterozygous. Perhaps one or more of the gene’s in these PCA varieties are the recessive PCNA gene, perhaps picked up in the wild. In this scenario, the odds of 2nd generation PCNA progeny would rise.
Another possibility would be that the seeds / progeny of a PCNA x [PCNA x PCA] cross that is homozygous for PCNA has a survival advantage. So in this scenario, the odds of PCNA genetics match our analysis, but fewer of the heterozygous PCAs survive.
With respect to JT-02 specifically, we must keep in mind that JT-02 is not a cross between two Asian parents, as in the Japanese and Korean breeding programs. It is a cross between a male Asian PCNA [Taishu] and a female American [Josephine]. By far the most likely scenario would seem to be that both parents are homozygous. Taishu is almost certainly homozygous for the Asian PCNA gene. Josephine its likely homozygous for some astringency. Josephine could not possibly have any Asian PCA genes or any Asian PCNA genes. So as a cross of Taishu x Josephine, JT-02 would have 3 Asian PCNA genes and 3 American A genes. The objective of a back-cross of JT-02 x Taishu (or some other PCNA male) would be to create an offspring with 6 Asian PCNA genes. As noted, the probability of such a cross seems to be 5%. Whether the 15% result observed for purely ASIAN hybrids applies here is unknowable.
Please understand that I am NOT a biologist. I’m certainly not a geneticist. So this is rank amateur’s speculation.
p.s. I edited this to correct some errors.
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From some of the documentation, if 5 of the genes are PCNA, the overall effect on the fruit is very close to the results if 6 genes are PCNA.
Genetics often do not meet mathematical rules.
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Great info. Where do you see this?
Do a deep dive into the articles and documentation that have been posted about persimmons in this and the other persimmon thread.
OK, I’m trying. Tell me this – Does any of the documentation pertain to the American gene for astringency. Like are there 5 Asian PCNA genes and 1 American astringency gene?
This matters because the astringency of JT-02 comes from its American mother.
p.s. I am reminded in earlier posts that whereas Japanese astringency is qualitative (all or none), American astringency appears quantitative (more or less). Reducing the number of American genes from 6 (Josephine) to 3 (JT-02) doesn’t seem to have substantially reduced astringency. But maybe a further reduction to 2 or 1 would help.
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<<From some of the documentation, if 5 of the genes are PCNA, the overall effect on the fruit is very close to the results if 6 genes are PCNA.>>
OK, I reread this entire thread and came up blank. I see no support for this statement. So now that I’ve paid some dues, you can help me not waste more time. Please point me to the documentation that you reference.
The only discussion that comes ANYWHERE close relates to Morris Burton, an American variety (NOT Asian PCNA). I agreed months ago that I might have been better if Jerry Lehman had used Morris Burton as the female crossed with Taishu. But since we have JT-02 in hand, that’s water under the bridge.
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It would be very interesting to one day cross it with male Oku Gosho flowers.
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@PharmerDrewee – Agreed. If I had the capability, I’d cross JT-02 with every Asian PCNA that I could get to produce male flowers. So Taishu, Oku Gosho, Hana Gosho, whatever.
As I wrote in the OP: << Bottom line: Shouldn’t we – and I use the pronoun “we” loosely – be back-crossing the crap out of JT-02 / Mikkusu with Taishu and/or any Japanese PCNAs with pollen? >>
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Simply prune heavy, so dense canopy.
Leaf pull north side of canopy to get yellow indirect sunlight on fruit.
Use sugar mover to accelerate ripping.
Graft male pollinator branches into the canopy.
Pollinated fruit have seeds, yet have reduced astringency.
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Andrew should be able to cross his JT-02 with some of the male flowers that he has. My 2 dugged up and potted JT-02 had no flowers this year probably due to transplant shocked.
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I crossed JT-02 with Nishimura Wase so the best I could hope for is PVNA (also larger fruit and earlier ripening). Hopefully I will have those male Oku Gosho flowers one day.
A male hybrid with PCNA as one of the parents would be a perfect pollen donor for my many PCNA trees. Surely one of the resulting seedlings would be a PCNA hybrid. I think Cliff England might have such a male tree.
I am very adamant about using JT-02 to derive a PCNA hybrid though because it has shown exceptional cold tolerance. I think cold tolerance would be my main goal, because it would be unique for a PCNA as of now. Then the next goal of less priority would be earlier ripening. Many colder places have shorter growing seasons, but this isn’t always true. It wouldn’t make sense to grow something that could survive your winters if it couldn’t ripen in your climate. Then increased fruit size would be an additional aim.
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I can’t tell you where to find the documentation on the effect of 5 PCNA genes vs 6. It was in some of the Japanese research. It was definitely NOT associated with American genetics. I read it roughly 6 months ago and clearly remember the details. The essential fact was that having 5 PCNA genes had nearly the same effect as having 6.
Re crossing with American varieties, I 100% agree Morris Burton would have been a better cross. It is a cross that could still be made if someone wanted to do a bit of embryo rescue. There is also the possibility of crossing one of the complex hybrid males to Morris Burton and recovering useful progeny.
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I am crossing my MB#3 with Jerry Lehman Nikita’s Gift male offspring. There will be plenty of seeds from the MB#3. It will be interesting to see how good the offsprings fruits of these two. Andrew, I will send you some seeds to grow them out like the Tam Kam crossed with Chocolate male flowers @PharmerDrewee.
No doubt that MB#3 fruits are excellent with the dark red color and taste sweet similar to Asian persimmon but on a medium size.
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Have you heard of the Korean Black Persimmon?
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I hope to cross the (Texas Black Persimmon x Izu)
Izu is probably the earliest ripening least astringent of all Persimmon.
Similar to Fuyu but ripens 2 months earlier.
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