Author Topic: US-1279 and SuperSour 2, new and better zygotic parents for cold hardy breeding?  (Read 3551 times)

a_Vivaldi

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Browsing the literature, it seems the industry has started moving away from highly nucellar rootstocks, which is great news to those of us with breeding aspirations. Most of the new HLB resistant rootstocks have very high rates of zygotic seedlings, at least according to citrusrootstocks.org and the papers I found for the newer USDA releases.

While I haven't found specific cold hardiness data, just looking at perigee, two of the new ones, US-1279, Changsha x poncirus, and SuperSour 2, poncirus x (c. aurantium x c. ichangensis) ought to be very cold hardy. US-1279 is listed as 100% zygotic. Supersour 2 has not been determined yet, but one of the stated goals of the SuperSour program is to breed highly zygotic rootstocks, so it's likely this release will be very good for breeding as well.

And since these are USDA released rootstock plants, they should already have great disease residence, including some HLB resistance, vigor, and productivity. Assuming the hardiness is as good as it ought to be given their parents, I'm thinking these two might make great alternatives to the other poncirus and poncirus x varieties that are currently out there.

Pandan

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Great, are those available to us civilians though?

If not and assuming there's not proprietary rights on them I wonder if Madison Citrus would be open to offering them as they've done a great job dissemination some rarer scions (why not rootstocks too)

a_Vivaldi

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I haven't been about to determine that yet. I'm hoping yes, or at least soon, since I don't believe there are any restrictions on these like the are on that UGA series. Madison would be a good place to try getting them from, though I've not contacted them myself.

drymifolia

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From the USDA release statement in 2018 for SuperSour 2:

Quote
Seed has never been observed on the clone US SuperSour 2, so for propagating trees on this rootstock to be planted into the field, cuttings or micropropagation from the tested Florida Department of Agriculture & Consumers Services (FDACS) sources are the recommended methods of propagation, at this time. It is possible that seed of this rootstock may eventually be available, but suitability of this clone for uniform apomictic seed propagation has not been evaluated.

I take that to mean that they are generally seedless, but maybe they just mean they haven't looked at the seeds or analyzed them yet?

a_Vivaldi

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I had the same thought, but I think they just hadn't grown then out to friend size. I don't remember which publication now, but I did see one that mentioned that seed hadn't been evaluated yet because none had fruited. Since they're propagating by cuttings to speed up the program, I can imagine their plans don't get big enough to flower before getting chopped back for cuttings.

I did notice the original release for US-1279 said that seed hadn't been evaluated yet but that they were expecting high degree of nucellar seed, but if you look at the current University of Florida listing, it says in big red highlighted text: do not propagate from seed. And elsewhere they have it in a table showing less than 5% seedling uniformity, which I take to mean nucellar.

But yes, I agree that until we get more explicit information, it could be that there is just very low seed set.

Pandan

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I think it means the seeds of the cultivar haven't been observed in-depth.
These seem to be intended to be propagated asexually.

Supersour 1 say the same thing and I would find it odd for ALL of these to be seedless given the parents.

poncirsguy

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a_Vivaldi

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Thanks for the link @poncirusguy.

So the original release said no seed had been "observed" but the current UFl document says US-1279 has very low seedling uniformity, ie is highly zygotic. Supersour 2 seed hadn't been observed yet, but given the information in this article I think it's safe to say that it will be similarly extremely zygotic: https://www.frontiersin.org/articles/10.3389/fpls.2021.741009/full

Which is great news. Looks like the USDA has already done a lot of the hard work, they bred several zygotic, vigorous, disease resistant poncirus hybrids, most of which are some combination of mandarin, ichang, or other sour orange, so cold hardiness is highly likely. These should make excellent replacements for Swingle, Dunstan, the older US-____ rootstocks, and even, for some breeders, poncirus itself. Now, if we could just find a nursery that'll sell them retail...

kumin

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US 1279 shows better cold hardiness than Meyer lemon, but less than TaiTri or 5* Citrumelo. Bishop Citrandarin which likely has similar genetics shows greater cold resistance than 1279 does. Bishop has a good percentage of zygotic seedlings, I don't know the percentage, however.

Bishop Citrandarin grafted on Poncirus rootstock.


1279 flowers are small and are produced on new inflorescences rather than overwintering buds. The flowers are quite small and fragile in contrast to 5* Citrumelo flowers.
« Last Edit: May 16, 2023, 12:54:42 AM by kumin »

a_Vivaldi

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Tai-tri and 5* are mostly nucellar though, correct?

My impression had been that while there are a decent number of poncirus hybrids floating around, most of them are highly nucellar. These new ones from the USDA being nearly 100% zygotic struck me as exceptional. Curious about Bishop though, I've not heard of that one before aside from I think some of your posts kumin.

On related note, it'd be nice if there were, and there may well be, somewhere with data on these cold hardy hybrid varieties in a table. Would make trying to find the %nucellar, parentage, or estimated cold hardiness much easier to reference.

mikkel

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TaiTri is supposed to be nucellar, in my experience the seedlings are differently cold tolerant. I think this can be a sign of zygotic seedlings.
Yesterday I saw a picture of someone where every single seedling was clearly different from the others.
TaiTri could be zygotic at least sometimes.

kumin

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Tai-tri and 5* are mostly nucellar though, correct?

My impression had been that while there are a decent number of poncirus hybrids floating around, most of them are highly nucellar. These new ones from the USDA being nearly 100% zygotic struck me as exceptional. Curious about Bishop though, I've not heard of that one before aside from I think some of your posts kumin.

On related note, it'd be nice if there were, and there may well be, somewhere with data on these cold hardy hybrid varieties in a table. Would make trying to find the %nucellar, parentage, or estimated cold hardiness much easier to reference.
There are indeed cold hardiness tables, keeping them current to the latest introductions may be a challenge.
Bishop Citrandarin arose as a likely chance seedling among stock purchased from Stan McKenzie. The tree didn't fruit initially, but after a period it flower and fruit.
The initial discoverer provided me with fruit and grafting materials. It's seedlings show variability due to a degree of zygotic embryony.



Overripe Bishop Citrandarin fruits.






1rainman

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What's wrong with swingle or Dunstan? Dunstan is probably the most edible of the cold hardy citrus. I'm more interested in hlb tolerance though. Swingle has really good cold tolerance and almost edible fruit.

kumin

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The objective is to find highly, or totally zygotic selections as seed parents. Pollen donor parents may be either zygotic, or nucellar. In the pursuit of advanced generation breeding selections, having zygotic breeding lines provides greater flexibility, as any desirable selection can serve as a seed parent.

Zitrusgaertner

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What's wrong with swingle or Dunstan? Dunstan is probably the most edible of the cold hardy citrus. I'm more interested in hlb tolerance though. Swingle has really good cold tolerance and almost edible fruit.
I would not state that Swingle had edible fruits. Dunstan is slightly better but still not edible. The best citrumelo seems to be stock number 82 at Reto Eisenhut's vivaio in Switzerland. I did not have fruit yet but everybody who could compare says so. Trifolis is also quite nice but seems to be F2 and is probably less hardy than F1 Citrumelo. But in fact Swingle is not that hardy. 5* ist much better.

Walt

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The relative hardiness of different cultivars can vary from year to year or place to place.  One variety could better survive mid winter cold but another might better take early fall or late spring cold.

a_Vivaldi

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True, it's not a binary distinction, but then again, neither is zygotic vs nucellar.


1rainman

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Swingle is a great root stock in Florida. Could probably produce edible fruit if crossed again it's not too bad but not good enough to eat. I'd like something 1/8 poncirus or something so it might be edible but may have hlb tolerance.

a_Vivaldi

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I may be misremembering, but Swingle is highly nucellar, so you'd either have to use it as a make parent or do something crazy like embryo rescue. At that point though, why bother? Dunstan tastes better, does great on its own roots, and is extremely cold hardy (there's one growing at the JC Raulston arboretum in Raleigh NC unprotected that has taken single digit lows many times). The arboretum has buckets of fruit that they give out in late fall/early winter.

1rainman

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Wouldn't citrus glauca be better for hybridizing? It goes into dormancy. Tolerates temps below zero fahrenheit. Salt tolerant, drought tolerant, hlb tolerant. It's cold tolerance isn't as high but it's close to poncirus. But the fruit is actually edible. And there are hybrids with oranges and lemons out there. It's also relatively small in size. The only negative is fruits fall off the tree pretty soon after ripening.

Hopefully I'll get some eremoorange and erenolemon seeds. I mainly want disease resistant stuff.

1rainman

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I would take the best poncirus hybrid then cross it with an eremoorange or erenolemon. But not rootstock. They have the one poncirus x orange that is an edible f1 hybrid. Then there's the complex hybrids that are edible the FL whatever the number. The erenolemon or orange cross could significantly reduce the undesirable poncirus oils without having much impact on cold tolerance. Of course the key would be selective breeding finding the best seeds.

mikkel

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They have the one poncirus x orange that is an edible f1 hybrid.

Which one do you mean?

a_Vivaldi

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Citrus glauca seems cool, but hardy to only about -10 C is an issue, at least for my area. 

Perplexed

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Wouldn't citrus glauca be better for hybridizing? It goes into dormancy. Tolerates temps below zero fahrenheit. Salt tolerant, drought tolerant, hlb tolerant. It's cold tolerance isn't as high but it's close to poncirus. But the fruit is actually edible. And there are hybrids with oranges and lemons out there. It's also relatively small in size. The only negative is fruits fall off the tree pretty soon after ripening.

Hopefully I'll get some eremoorange and erenolemon seeds. I mainly want disease resistant stuff.

Citrus glauca doesn't tolerate temps below zero Fahrenheit, correct me if I'm wrong I've just heard of it being hardy to just about -10. But I do plan on using microcitrus (inodora and australis) for crossing with zygotic trifoliate hybrids like US 852, or the others mentioned if I can ever source them

bussone

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Wouldn't citrus glauca be better for hybridizing? It goes into dormancy. Tolerates temps below zero fahrenheit.

Everything I've heard about glauca suggests zero Celsius, not zero Fahrenheit. Poncirus is the only citrus member really comfortable at 0 F.

Citrangeremos (poncirus and glauca ancestry) exist; I've had one. I've only even heard of one of them flowering, though.

\I had it in a pot, which means its fate was already sealed

 

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