Josephine was discovered by Samuel Miller in the late 1800s on the Missouri River. It’s also been distributed as (American) Honey due to its translucent yellow color when mature. As far as I know, Jerry never had it. It’s been MIA for many decades.
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For those of you interested in the history behind the Josephine, these articles give a pretty good background and even a couple of photographs
Growing Fruit and Nuts in the Southern Great Plains.pdf (4.1 MB)
Miller1894.pdf (304.9 KB)
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As I said, I see Josephine mentioned as a parent of JT-02. In the sheet, it is also listed as the parent of the non-existent JT-06. Did I miss any others?
I have a suspicion that the variety named Iowa Arboretum at Red Fern Farm may be the Josephine. I think it may also be the yellow persimmon depicted in this YouTube video.https://www.youtube.com/watch?v=YBQx55lHJoI
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Very often I see a reference to “embryo rescue”. I do not really understand how Jerry can send seeds to be grown out in Japan using the “embryo rescue” method.
The reason for using this technique is because in many difficult crosses the seed will abort while it matures in the fruit, leaving just an empty or shrunken seedshell while the content is for the largest part reabsorbed by the fruit. By removing the still green immature seed with jelly-like contents and letting it mature under sterile conditions in vitro and letting it germinate… still in vitro, a cross between two otherwise incompatible parents can be realised while in nature this would be impossible because of seed abortion.
This is just what was done when the first crosses were made in Yalta between D.kaki x D.virginiana.
It is a mystery to me how Jerry would have harvested and sent immature hybrid persimmon seed to Japan to be grown out in vitro…the green and jelly like seed is worthless as soon as it is removed from the fruit…
A second remark but nothing to do with the above…maybe more important is that the whole issue about hybrid PCNA persimmon is that the most important aspect of a persimmon worth growing is flavor/sweetness. Without that it make no sense to put all this effort in growing very hardy zone 5 or 6 hybrid PCNA persimmon.
In my experience the most difficult hurdle is getting sweetness in persimmon which is grown that far north under far from ideal circumstances. The fruit will almost always be bland…but perhaps nice to look at… A persimmon worth eating should have a brix reading of about 22° or more. In my experience fruit growing that far north doesn’t even get to 15-16° brix. The season is just to short and the small amount of accumulated heat hours is just not enough to obtain sufficient sugar in the fruit. In that respect I would focus on breeding short season varieties with little need for high accumulated heat hours. Once that is achieved the focus can be shifted towards non astringency…
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Thanks.
Re #1, I have no idea. I’d love for someone to explain what roles were played by Jerry Lehman and by his Japanese partners.
Re #2, I’m sure you’re right that heat matters. Z5 or Z6 can get hot enough. The question is whether the growing season is long enough. The correlation between winter low temperature and growing season is fairly loose. I know people growing figs (as I do) in Z6B (like here) with a growing season 2-4 weeks longer than mine. When it comes to ripening late-ripening figs or persimmons, those 2-4 weeks can make all the difference. But I think we have good evidence that much of Z6 has a long-enough growing season to ripen some PCNA varieties. More on this below.
So the development of a good hybrid for Z5-6 seems to be two-step: First, develop cold hardiness. [You skipped this step in your final sentences above; but this is sine qua non for the Z5-6 grower.] Second, develop early-ripening, which should bring sweetness. Third, get non-astringency when and where we can.
I’m very interested in JT-02 precisely because it already seems to have cold hardiness required for Z6 and it seems early enough to ripen in most Z6 locations. This year I ripened one (1) on a one-year old graft, finishing it indoors. It seemed excellent but I need more to be sure. Genetically JT-02 is 50% PCNA, so the Great Leap Forward would be a cross with Taishu or some other male-flowering PCNA that produces a fully PCNA offspring without losing the cold hardiness or delaying the ripening.
Some D Virginiana varieties ripen much earlier than D kaki. So if we’re willing to sacrifice non-astringency for now, it would seem important to pay more attention to early ripening in the selection of DV cultivars used to produce new hybrids. So the paradigm would be to get BOTH cold hardiness and early ripening from the DV parent and then other characteristics such as size, flavor, and possibly PCNA from the DK parent. The C-PCNA route to NA might be easier.
FWIW, while I did not measure Brix for my IKKJ fruit, subjectively (1) the ripe but still firm fruit was mildly sweet, (2) the ripe and soft fruit (ripened indoors) was moderately sweet, very edible; and (3) the dried fruit was intensely sweet. I’m happy with these results. But I am planning to experiment with Cardinal, which I believe to be a synonym for Soshu, which reportedly is the earliest-ripening PCNA produced by Japanese breeders.
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… unless the acid content is significantly reduced when ripe.
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The most tractable solution to multiparameter optimization problems is rarely through pursuit of a single parameter at a time. This is especially true in breeding.
Thanks Dax. I did read that post after typing my question. I now wonder if I’ll see the same results in my area. I heard somewhere heat influences astringency (in addition to pollination) in some PVNA varieties like coffee cake. Gora Roman Kosh is not PVNA and clearly Stan’s pic shows that it’s not pollinated.
I also read that Stan hates Jiro! So, that’s another reason I need to do the comparison on my own 
Yeah, I agree with this. “Step” might have been the wrong word because it sounds too discrete. Development of a good variety addresses multiple objectives simultaneously. Really I’m laying out priorities. My point, however unclearly articulated, was that for Z5-6 growers, cold hardiness must be the #1 priority. This seems to imply that crosses intended to produce hybrids suitable for Z5-Z6 growers should probably include a cold hardy parent. Of course, any F1 DV x DK hybrid would meet this requirement. But there are lots of F2 (and beyond) hybrids where one parent is a hybrid with mediocre cold hardiness and the other parent is a kaki with poor cold hardiness. These crosses seem unlikely to produce more cold hardy offspring.
Establishing clear priorities also helps us take full advantage of serendipity. Consider JT-02. This variety seems extraordinarily cold-hardy given its Kaki parent, Taishu. It’s hard to imagine a more cold-hardy persimmon with 50% kaki parentage, at least not soon. Furthermore, if anyone starts to develop a cold-hardy PCNA, then they will probably start by crossing the Kaki PCNA with a cold-hardy but astringent Virginiana. The goals of non-astringency and cold-hardiness seem very difficult to achieve simultaneously. Through sheer good luck, JT-02 seems to provide an optimal place to start.
One of these days I’m turning off the spicket of scionwood here. 
I’ve never had a fruit except a peach and a plum I think. I’ve managed to cut all the branches off my trees every single year.
Get on it is my advice!
Dax
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That comports with my experience here in “zone 5b” Vermont. My best performer year over year has been the virginiana variety ‘Mohler’, which starts dropping about Sept. 1 here, and finishes by Oct. 1, peaking about in the middle. Not only is frost of no concern for me then, but there is plenty of heat and sunlight. That was part of my reason for inquiring about the logistics of producing F-1’s, as I would tend to want to use a variety like ‘Mohler’ as the starting point.
As to the logistics of embryo rescue, my impression is that in these cases, embryos tend to be viable in mature seed (thus ripe-ish fruit), but have limited viablility that tends to Peter out. Excising the embryo from the seed saves it having to force its way out of the seed coat, and gives it a leg up to begin mitosis. That said, I really have only a vague notion what’s really entailed, so strictly a guess.
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I did not skip the cold hardiness issue… it comes with naturally when hybridizing kaki with virginia. The more the resulting hybrid leans towards virginia, the hardier it gets and vice versa… It is like crossing hardy citrus (Poncirus trifoliata) with any other citrus to obtain a hardy citrus with palatable fruit. The hardiness is linked to the resin that is found in this species and makes it hardy. Only hybrids with noticeable resin flavor are really hardy. The less resin taste, the less hardy it is. And when finally, in crossing further, the resin taste has completely vanished…so has the hardiness. I believe the same to be true when crossing kaki x virginiana…
Anyway that was not the point I wanted to make… I have about 30 years of experience growing (and crossing) Asian and American persimmon in a less favorable climate and my conclusion is that both species, but Asian persimmon specifically, need a lot of ACCUMULATED heat hours (400+). (1 heat hour = 1hour of +/-77F). I am not referring to how hot it gets in a certain growing area but how many hours of warm temp you get in one growing season = accumulated heat hours. This is what makes the sugars from in a persimmon. E.g. in Ukraine it can get really cold, to cold for kaki to survive, but summer has enough accumulated heat hours for kaki fruit to ripen and be sweet enough to be palatable. In my climate (Belgium) I have absolutely no problem with hardiness but we just don’t get enough accumulated heat hours during the growing season although temp can rise to 100F+ on some occasions. Very few kaki varieties will produce (really) sweet fruit here but all kaki fruit will ripen and look very handsome… I presume many of you growers will know what I’m talking about
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Neither do they here in southern-most coastal California. But if left on the tree long after leaf-fall they become soft and the acid drops significantly while the Brix remains around 10-12 (by digital meter). At this point they are absolutely delicious. Extra sweetness would spoil the taste.
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Richard, are you sure you are only at 10-12 brix?
I let my Jiro get quite soft before picking and the brix climbs above 20. It is very tasty then.
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My digital meter returns values significantly lower than people report with handheld devices. I haven’t done a side-by-side comparison.
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