Author Topic: Poncirus hybrid crosses  (Read 4894 times)

Walt

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Re: Poncirus hybrid crosses
« Reply #50 on: August 23, 2023, 12:29:31 PM »
Yeah, cold hardy citrus breeding is no walk in the park.

Again, one of the biggest roadblocks is high rates of nucellar seed. What probably needs to happen at some point is someone needs to make a dedicated effort to breed zygotic seed into cold hardy citrus.

To do that, you'd want to take a bunch of fully zygotic varieties like Meyer lemon, ichang papeda, one of the more cold hardy pomelos, rough Seville orange or some other zygotic sour orange, then some combination of (1) breed then with each other, using ichang papeda as your main source of cold hardiness and then screen your F2 generation for hardiness (2) cross them with the handful of zygotic poncirus hybrids (eg the SuperSour series of rootstocks) and again screen for cold hardiness in the F2 generation, (3) find out which fairly cold hardy hybrids have one fully zygotic patent, ichang lemon for example, and cross it with your zygotic varieties, then screen the F1 generation for zygotic seed, and (4) cross them or some of your good F1s and F2s with the nucellar but very hardy hybrids and varieties like 5*, Dunstan, Changsha, then backcross those F1s with your fully zygotic plants again so that hopefully you'll have some fully zygotic F2s.

Lots of options, but none of them would get you results in a single generation. You'd probably need another two generations to then select for the best cold hardiness. That's at least a lifetime of breeding work. However, were someone to do this, it would make cold hardy citrus breeding much, much easier. And if you went for an four options, and were sure to include a wide variety of sources of zygotic seed (lemon, pomelos, sour orange) you'd end up with a lot of genetic diversity to work with to get the fruit quality you'd need for something not just edible, but good.

8B is probably one of the better zones for attempting a project like this.


  Nothing against what was said above, if you want that much genetic variation in your population.  But there are already 4 mostly zygotic mandarin x Ponciris hybrids in use.  US 1279, 1281 and 1282 are more than 95% zygotic, and 852 is about 85% zygotic.  And Kumin has some F2 citranges that have survived 4 (or is it 5 now?)zone 6 winters.  And he has collected some citrimelos and such to bring into his population.  I think he is closer to success and will have an easier time than is being talked of here.
I am trying about the same way but I'm way behind him, in spite of his sharing his stock with me.  We are both in zone 6, but our climate and soil are different, and our time and space are different.
Also I am also working toward a hardy finger lime.  I didn't know that Australian citrus don't cross well with Ponciris.  However, at least one finger lime x Ponciris exists in Florida.  They aren't sharing it.  At least not with me.
I hope my saying this keeps others from trying to breed hardier citrus, and trying different methods, and working toward different goal.  I have been in touch with someone in Tennessee zone 7,  working on hardier kumquats via kumquat x Ponciris.  I think he will be successful in a few generations.
I wish success to all of us.  And have fun!

a_Vivaldi

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Re: Poncirus hybrid crosses
« Reply #51 on: August 23, 2023, 02:29:27 PM »
Quote
Nothing against what was said above, if you want that much genetic variation in your population.  But there are already 4 mostly zygotic mandarin x Ponciris hybrids in use.  US 1279, 1281 and 1282 are more than 95% zygotic, and 852 is about 85% zygotic.  And Kumin has some F2 citranges that have survived 4 (or is it 5 now?)zone 6 winters.  And he has collected some citrimelos and such to bring into his population.  I think he is closer to success and will have an easier time than is being talked of here.
I am trying about the same way but I'm way behind him, in spite of his sharing his stock with me.  We are both in zone 6, but our climate and soil are different, and our time and space are different.
Also I am also working toward a hardy finger lime.  I didn't know that Australian citrus don't cross well with Ponciris.  However, at least one finger lime x Ponciris exists in Florida.  They aren't sharing it.  At least not with me.
I hope my saying this keeps others from trying to breed hardier citrus, and trying different methods, and working toward different goal.  I have been in touch with someone in Tennessee zone 7,  working on hardier kumquats via kumquat x Ponciris.  I think he will be successful in a few generations.
I wish success to all of us.  And have fun!

These are very good points. In hindsight, my post was probably too pessimistic/daunting. I certainly would never want to drive someone away from citrus breeding.

The two issues I see with those USDA rootstocks are the limited genetics and the even more limited availability. All three of them are derived from the same Poncirus parent and mostly the same mandarin parent as well, and to date, I haven't seen anyone actually offer them, at least to use plebs. I do plan to ask Stan McKenzie about them when I get around to visiting his nursery (had planned the trip on two occasions this summer, but scuttled those plans were, twice...).

US852, and the child seedling the name of which is escaping me at the moment, that I believe kumin also has, do seem like good options, though the same mild criticism still applies, limited genetics and even more limited availability.

Working with the more distant citruses, like the Aussie ones and kumquats, seems to me like it would be a bit riskier, since the wide genetic crosses could lead to trouble down the road (correct me if I'm wrong, but isn't Thomasville basically sterile, only able to clone itself? I feel like that kind of dead-end will turn up more often for those wide crosses). Not saying people shouldn't be doing it, not at all, I hope people are doing it, and I hope they succeed. I just strikes me as a riskier path.

Ilya11

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Re: Poncirus hybrid crosses
« Reply #52 on: August 23, 2023, 04:27:24 PM »
Thomasville is fertile as a pollen partner.
Best regards,
                       Ilya

kumin

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Re: Poncirus hybrid crosses
« Reply #53 on: August 23, 2023, 04:27:51 PM »
Crossing Citrandarins with Citranges and Citrumelos should broaden the genetic base while conserving genes for palatability as well as cold hardiness. In the F² generation there appears to already be a lowering of vigor in a percentage of the zygotic seedlings. In the Meyer Lemon x Conestoga 026 hybrids there appear to be fewer weak seedlings.
I would expect the depression of vigor to likely worsen in the F³ selfed generation.
Further trials should shed more light on this matter.

bussone

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Re: Poncirus hybrid crosses
« Reply #54 on: August 23, 2023, 04:44:28 PM »
I didn't know that Australian citrus don't cross well with Ponciris.  However, at least one finger lime x Ponciris exists in Florida.  They aren't sharing it.  At least not with me.

I understand the Australians have one as well, but it's noted to struggle. Not so much that it dies, but it's not exactly happy about it, either.


1rainman

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Re: Poncirus hybrid crosses
« Reply #55 on: August 27, 2023, 03:40:10 PM »
When you backcross to the 1/4 level fertility is restored pretty much other than a few low vigor seeds. It's like that with grapes muscadine x euviris. First generation hybrids have low fertility many have low vigor. It just needs crossed again.

But if you are dealing with three or more distant species that is more problems.

mikkel

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Re: Poncirus hybrid crosses
« Reply #56 on: August 27, 2023, 04:30:09 PM »
I understand the Australians have one as well, but it's noted to struggle. Not so much that it dies, but it's not exactly happy about it, either.

Microcitrus australasica x Poncirus hybrids also have been done in Florida by Ethan Nielsen. @ethane

The Microcitrus x Poncirus hybrids


Walt

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Re: Poncirus hybrid crosses
« Reply #57 on: August 28, 2023, 12:44:35 PM »
1rainman.  That is what I thought likely.  Make the cross both directions, if I can.  Then backcross in both directions, if I can, and see what I get.  And go from there.

Mikkel. 

Curiousgardener23

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Re: Poncirus hybrid crosses
« Reply #58 on: September 16, 2023, 02:52:10 PM »
Is there good information on favorable/interesting citrus traits in cultivated citrus that are dominant? This might be helpful when considering potential Poncirus hybrid outcomes. For example, given that many kumquat hybrids have thin edible skin, it might be the case that this trait is dominant. I'm sure this will depend on the genetics involved with the cross but it might be useful information when considering potential crosses. I think other trails that would be interesting to understand would be pigmentation (blood oranges) and sweetness. I know that sweetness (acidless) might be partially dominant when looking at the pummelo trait but recessive when looking at the orange trait (https://citrusgrowersv2.proboards.com/thread/728/inheritance-low-acidity). That being said, the low acid citrus genetics might be diverse so this might depend on the specific varieties in the cross.

Walt

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Re: Poncirus hybrid crosses
« Reply #59 on: December 10, 2023, 04:43:51 PM »
This thread brought up inbreeding.  Since then I've done lots of thinking, and more importantly, lots of reading about inbreeding.
Corn breeders in areas where hybrid corn isn't used often use synthetic varieties.  These are varieties that can be re-synthisised if the varieties are lost.  These varieties are created by test-crossing many inbred breeding lines of corn.  Then those lines with the best hybrid seedlings are intercrossed to make the new variety.
The more breeding lines that are put into the synthetic variety, the less inbreeding will take place in future generation.  On the other hand, if they start with the pest line based on the test crosses, each added line will be less good.  Experimental results show that the best number of lines vary between 8 and 12.  After all, if one uses the best 8 best, number 9 will not be as good as the first 8, though the new variety will have less inbreeding.  Somewhere between 8 and 12 the balance between degree of inbreeding and the value of more lines reaches the break even point.
So it would be desirable to start with about 8 citrus clones to not be concerned about inbreeding.
So what to start with? 
Kumin's selections, of course top the list.  But being all seedlings of C-35, They count as a group as more than one but less than 2 I think.  US 852, US 1279, US 1281, and US 1282 are all good to include but 2 of them are P. trifoliata x Changsha and 2 of them are P. trifoliata x Clementine.  I don't know if the same P. trifoliata was used in making those crosses.  But as a group they could count as somewhere between 2 and 4, because I don't know how related they are.
As has been mentioned elsewhere, citromelos should be useful in breeding hardy citrus.  I don't know the pedigrees of any citrmelos so I don't have a good guess at how many to count this group as,
P. trifoliata+ can be used in further breeding and counts as one.
I think Troyer citrangequat has potential and can count as one.
So this list can be used as a guide to estimate the inbreeding in future generation.  I counted 6 or more, probably 8 or more.  It means the germplasm exists for breeding hardy non-inbred citrus  without going back and making new F1 hybrids, which would take more time.  Not that I would discourage from making new F1 hybrids.  They have there place and will be used if someone makes them.

a_Vivaldi

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Re: Poncirus hybrid crosses
« Reply #60 on: December 10, 2023, 10:36:53 PM »
At least according to this the cultivars were P. trifoliata ‘English Large’ for 852, and P. trifoliata 'Gotha Road' for the other three. P. 'Gotha Road' shows up in a lot of places, OGW says US119 is a grandchild of it, for example, and a bunch of the US-xxxx rootstocks have it. UC Riverside says C-35 is from some P. trifoliata called "Webber-Fawcett."

Inbreeding seems like it could be an issue, especially with lots of crossing and backcrossing with varieties that are all children or grandchildren of maybe two P. trifoliata varieties. Which would perhaps be a decent enough reason to try and bring in genetics from Yuzu, Ichang lemon, etc. It would also help that in order to get something more than just edible, some genetics from non-cold hardy citrus need to be brought in.

Part of the appeal of making new F1 crosses is the availability now of non-hardy parents that might prove more useful than the old sweet orange and mandarins that produced the legacy F1s. Parents with low-acidity, with very early ripening or good ripening in cool or short summers, more zygotic seed, or whatever, are much easier to get ahold of now. Actually making that cross is as hard as ever, of course, but...

bussone

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Re: Poncirus hybrid crosses
« Reply #61 on: December 10, 2023, 10:49:44 PM »
At least according to this the cultivars were P. trifoliata ‘English Large’ for 852, and P. trifoliata 'Gotha Road' for the other three. P. 'Gotha Road' shows up in a lot of places, OGW says US119 is a grandchild of it, for example, and a bunch of the US-xxxx rootstocks have it. UC Riverside says C-35 is from some P. trifoliata called "Webber-Fawcett."

Inbreeding seems like it could be an issue, especially with lots of crossing and backcrossing with varieties that are all children or grandchildren of maybe two P. trifoliata varieties. Which would perhaps be a decent enough reason to try and bring in genetics from Yuzu, Ichang lemon, etc. It would also help that in order to get something more than just edible, some genetics from non-cold hardy citrus need to be brought in.

Part of the appeal of making new F1 crosses is the availability now of non-hardy parents that might prove more useful than the old sweet orange and mandarins that produced the legacy F1s. Parents with low-acidity, with very early ripening or good ripening in cool or short summers, more zygotic seed, or whatever, are much easier to get ahold of now. Actually making that cross is as hard as ever, of course, but...

I’ve never been entirely certain what was so great about Gotha Road and English Large and why they were varieties, per se.

I think it’s also worth remembering most of this effort was aimed at rootstocks more so than edible varieties. Although with greening that has changed a bit recently.

a_Vivaldi

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Re: Poncirus hybrid crosses
« Reply #62 on: December 11, 2023, 10:32:13 AM »
Gotha Road is supposed to be very vigorous, but that's about all I know.

That's a good point. And probably is another argument in favor of creating new F1 hybrids.
« Last Edit: December 11, 2023, 10:33:50 AM by a_Vivaldi »

Walt

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Re: Poncirus hybrid crosses
« Reply #63 on: December 11, 2023, 12:26:00 PM »
Thanks for the information on the Ponciris parents of some of the Ponciris hybrids.  So I can relax even more about inbreeding.
Something I should mention is that since it takes time and effort to make controled pollinations, getting F1 seeds in quantity, hundreds or thousands isn't easy.  But it is ok to grow out the slightly inbred F2 seeds where F1 trees have produced lots of seeds.  It would be good to make controled pollinations every second generation.  If one keeps seedlings from each F1 tree seperate, flowers on each F1 tree could be crossed with an unrelated, or at least noy closely related, tree.Since seedkings take a few years to bloom, some polllinations can be made each year and every year there would several seedlings growing and, at least in my situation, my acre could be kept full all the time.

I said above that new F1 crosses still have their place.  For example if you want to breed hardy kumquats, not much F1 breeding stock is easy to find.  Another such is finger lime which I have mentioned elsewhere that an F1 finger lime x Ponciris+ could be useful in zone 8 or perhaps zone 7 in sheltered spots.
Also I have bought Kishu Seedless for its dominant gene for seedless.  It can be crossed as a pollen parent and half the resulting seedlings will be seedless.  It can pollinate seeded seedlings in a breeding program, and its seedless F1 plants crossed back to your best seeded trees in your breeding population, and repeat again and soon your seedless seedlings will be as good as your seeded trees.  And since in this seedless breeding you are only trying to bring in the one gene, only a small population of the Kishu decendents will be needed.

 

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