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Author Topic: Long term cold hardy citrus breeding project  (Read 4187 times)

Walt

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Long term cold hardy citrus breeding project
« on: December 18, 2017, 04:34:50 PM »
I've started a citrus breeding program about 3 years ago.  Goal is hardy edible citrus for zone 6.

The plan is to have 9 breeding populations, based mostly on P. trifoliata, oranges, and mandarins.  The populations are pop. 1, pure P. trifolata;  pop 2, 7/8 P. trifoliata 1/8 Citrus species, most orange and mandarin;  pop 3, 2/8 , 6/8 Citrus;  pop 4, 3/8 Citrus, etc, up to pop 9, 8/8 Citrus.
Pop 1 is to be only monoebryonic P. trifoliata x precocious P. trifoliata.  If the F1 isn't monoembryonic, then, it could take a couple more generations to give a monoembruonic, precocious P. trifoliata.  This will be useful in later breeding.
Pop9, at the other extreme, will be to produce good-tasting oranges or mandarins with as much hardiness as possible without poluting it with P. trifoliata.  Others are working on this, so I won't be working on it.
Pop 5 is where my energy has been so far.  Half P. trifoliata, half citrus.  I have about 25 Sanford open-pollinated seedlings, and 2 US 852 seedlings.  I have been promiced some open-pollinated C. ichangensis x P. trifoliata seeds. I have some other citranges which I'll be using for pollen, so my gene base will have some diversity. I am working mostly on this population at first because until these bloom, I can't do selection or crossing to make other populations.  Plans are to select only for precocity, monoembryony, cold hardiness, and flavor.
Flavor selection will only be against P. trifoliata  flavor.  It will still be too sour for most people, but until the P. trifoliata flavor is dealt with, lack of sweetness is a minor problem.
Selection for cold tolerance will be done by keeping cuttings in a freezer for a week and see which survive.  Each population will have its own temperature. which will change slightly in each generation.  I'm doing experiments now to see what temperatures I'll be starting with.
Precocity will be easy to detect, I think, as well as monoembryony.  I have read that one (or more) citrus variety makes monebryonic seeeds via appomixis.  I'll have to watch  out for that by checking that seedlings aren't too uniform.
When population 5 blooms, crossing it with populations 1 and 9 will give populations 3 and 7.
If any of population 3 can survive here in zone 6, then populations 1 and 2 will not be needed.  But I'm not counting on that.
If any of population 7 has good fruit, population 8 and 9 won't be needed.  But I'm not counting on that either.  I have been encouraged by  reading of Dr. Brown's work with cold hardy citrus.  Some of his would be like population 7.  But I haven't tasted any of his citrus, so I don't know how accurate the reports are.
Population 7 would be the place for Troyer citrangequat, which some people enjoy.  I read that its seedlings don't do well, and I am not planning to use it.  Comments about this are welcome.
Crossing populations 7 and 9 give pop. 8.  Some of these should be edible, if not really good.  I'm prepared to select for flavor for a several generations.  And selection for cold tolerance for several generations might give measurably more cold tolerance.
Crossing populations 7 and 9 will give pop 8.  I expect some to taste quite good even in the first generation.  Perhaps I'm too optimistic.  We'll see.  Likewise we'll see if 1/8 P. trifoliata will give any increased cold tolerance.
Crossing populations 5 and 7 will give population 6, 3/8 P. trifoliata and 5/8 citrus.  Selections will be as for pop. 5.
Crossing populations 3 and 5 will give population 4.    Selection will be as for pops 5 and 6.  Selections is most effective generally when genes are around 50% frequency.  So pops 4, 5, and 6 will give greatest improvement.  Pops 7, 8, and 9 will give good fruit sooner though and somewhat increase the range of good citrus.
Crossing pops 1 and 3 will give pop 2.  If pop 3 gives any winter-hardy seedlings, pop 2 will never exist.  And pop1 would be dropped.
I plan to grow out at least 200 plants per population per generation.  More would be better, of course, but space is limited.
Populations will be dropped, or better still, turned over to other people when they have served my purpose, or better still, as someone else sees their potential and wants to take them on.
Monoembryony should quit being an issue in 3 or 4 generations.
Precocity is very important and will always be selected for, but there will be a limit.
Flavor and winter-hardiness will need work longer than I expect to live, and I expect to live a long time.  That is why I'm hoping others with the means will take an interest in this.

I know that cold tolerance alone doesn't give winter hardiness.  A winter-hardy plant must become cold tolerant before the first hard freeze of winter, and maintain cold tolerance in spite of mid-winter warm spells.  But the lower number populations should include winter survivers because they are mostly P. trifoliata, which survives well here.

Ilya11

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Re: Long term cold hardy citrus breeding project
« Reply #1 on: December 18, 2017, 05:45:04 PM »
From what I know precocious flowering gene in poncirus is recessive , you need two copies of it to express this feature.
There exist "edible" poncirus clones like Swamp Lemon and Poncirus+ that could be  better starting points at  your pop1 level to produce further F1 populations.
Another comment- since your breeding goal is hardiness for z6, you necessary should select for deciduous trait, even in your pop 5 population crossings.   
Best regards,
                       Ilya

Farmerche

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Re: Long term cold hardy citrus breeding project
« Reply #2 on: December 18, 2017, 05:58:30 PM »
Towards the goal of starting with more desirable poncirus, I can offer my flying dragon variety which originated as a seedling. It is very resilient and has a sour but not bitter, slightly floral taste. It is small and seedy though. I'm am actually beginning my own effort at breeding with it in which I hope to stick mainly to poncirus but maintain this seedlings flavor but get to a larger less seedy fruit.
If you are interested in cuttings from my variety in spring let me know.
Have you looked at the earliest fruiting mandarins for crossing efforts. This could be important for controlling for dormancy.

Isaac-1

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Re: Long term cold hardy citrus breeding project
« Reply #3 on: December 18, 2017, 06:08:02 PM »
Thanks for posting this somewhat detailed plan, I hope you keep us updated as it  progresses.    My one suggestion is that you actively work to find someone in your region to collaborate with.   All too often these sorts of long term individual projects get side track by unexpected life events of the originator. 

SoCal2warm

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Re: Long term cold hardy citrus breeding project
« Reply #4 on: December 18, 2017, 06:45:23 PM »
I'm also breeding cold-hardy citrus, but I'm focusing more on things that could survive in zone 8.

I believe zone 8 is pushing it, but still within the reasonable range of what something good tasting could grow in.

As for cold hardiness testing, my plan is just to breed everything to two generations and then, out of all the offspring, see which ones can survive. That's the fastest way to accelerate things. I'm also planning to propagate a clone of each sample before it undergoes testing for cold hardiness, that way if it survives the cutting will have been already growing the entire time, so there won't be any Winter setbacks in the breeding process. The drawback to this approach is having to grow more cultivars without knowing whether they're going to be cold-hardy.

If I can make a suggestion for you, zone 6 is going to be really difficult. You might try to make a backcross that contains more than 50% poncirus in its ancestry.
Something like this:
 ([citrumelo x mandarin] x poncirus) x (citrange x poncirus)
« Last Edit: December 18, 2017, 07:10:44 PM by SoCal2warm »

Walt

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Re: Long term cold hardy citrus breeding project
« Reply #5 on: December 19, 2017, 01:03:11 PM »
Thank you all for your useful replies.
Ilya11, I agree that the precocious trait is recessive.  But it is worth the wait since this a long term project. 
I didn't know about Swamp lemon and Poncirrus+.  Do you know where I can get them? I'll google as soon as I get done with this post.   It sounds like they would be worth having even if I wasn't breeding.  Any idea of the inheritance of the edible trait?
I agree that most of my work will be with deciduous stock.  Even the deciduous trees mostly won't be hardy here.  Evergreen trees are out of the question, except protected as breeding stock.

Farmche.  I am quite interested in your Flying Dragon seedling.  I am suprized at an edible fruit from that source.  Cutting and/or seed would be very usefull

Isaac-11.  I am looking for collaborators.  I expect this to take 30 years if I am very lucky.  Likely it will take longer.  And I am 67 years old.  So if I don't get collaborators,  I am only amusing myself, not really doing useful work.

SoCal2warm.  I'll be keeping a clone of each seedling to fruiting.  I'll want to cross the most cold hardy with the best fruit in each population in each generation.  My plan is to intercross the 10 best trees in each population in each generation.
As for your suggestion to backcross the F1 trees to P. trifoliata, that would be population 3 above.  Actually, I plan to make a second backcross to P. trifoliata if necessary.  That would be population 2.

So is anyone crossing Swamp Lemon, Poncirus+ or the Flying Dragon seedling with quality citrus or kumquats?  If not, times being wasted.   

Walt

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Re: Long term cold hardy citrus breeding project
« Reply #6 on: December 19, 2017, 01:07:16 PM »
I read a paper written way back that said the Citrus x  P. trifoliata F2 is less winter hardy than the F1., and that hardiness is less in each generration.
I think I know the explanation. 
In the  F1, all the genes for winter hardiness are there, but only one copy of each.  We all knew that.
In the F2, 25% of those genes are there with 2 copies.  Good.  And 50% of the genes are there with single copies like the F1.  No further loss there from the F1.  But 25% of the genes for winter hardiness are not in a given F2 plant.  And in the F3 25% of the genes  hetrozygous in the F2 are gone, and so one.
It is not just that genes are being lost, the genes have co-evolved and some of the genes remaining won't work well without the genes that are gone. 
If I just worked selecting in the F2, F3, F4, etc., selection won't be effective on those genes that require those genes that are missing.  So selecting only in population 5 won't be effectively selecting for all genes involved in winter hardiness.  Only as some of the genes that have some effect alone are selected will the others start becoming effective and be acted on by selection.
That is why I'll backcross the F1 to P. trifoliata, to have more of the hardiness genes present.  This will allow selection to work on those genes that need other genes to interact with.  A second backcross, Pop 2, may be needed to get the majority of genes available for selections.  That remains to be seen

In the same way,  flavor is the result of many genes interacting.  Population 8 will at first only be able to use cold hardy genes that have significant effect without all those other genes which will be missing,  But it will have all the genes necessary for good flavor, plus some genes for bad flavor which will be discarded.

Walt

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Re: Long term cold hardy citrus breeding project
« Reply #7 on: December 19, 2017, 01:22:33 PM »
Farmche.  You mentioned early fruiting mandarins.  I haven't looked into them.  I should.
So far, I have been collecting and growing only pre-existing poncirus hybrids so I could get on with the breeding.  I plan to aquire Clementine this spring as it makes sexual seeds.  I realize that a problem I'm not addressing yet is the short season here. 

Ilya11

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Re: Long term cold hardy citrus breeding project
« Reply #8 on: December 19, 2017, 02:39:45 PM »
Walt,
Both Swamp Lemon and Poncirus+ were described on defunct CitrusGrowers forum.
Below is an extract of this discussion presented by Sylvain on the AgrumesPassion French forum
http://www.agrumes-passion.com/poncirus-citranges-porte-greffes-rustiques-f67/topic5861.html

Poncirus+ have essentially no internal sticky oils and it seems that its seeds contain a single embryo.
On the left is  juice of the regular poncirus, on the right that of Poncirus+


Next spring I am planning  to cross them in  a hope of obtaining even better quality of fruits.
I shall be glad to provide you  hybrid seeds, if you are interested.

I am not fully agree with your reasoning for rejection of of the progeny of direct hybrids between poncirus and edible citrus.
Of course, if you consider all the plants in F2, F3 and so on generations, they become more and more heterogeneous in respect of the presence of genes for hardiness, but due to the chromosome crossing-overs the two genomes will be progressively  present in the smaller and smaller intermingled fragments finally resulting in the separation of genes for bad the quality of poncirus fruits from the genes of hardiness in particular plants. This will be less possible in your pop3 and pop2 populations.

If you select for extreme hardiness ( comparable to that of poncirus ) in each subsequent generation of intercrossing inside pop5 population, and simultaneously keep selection for better and better  hardiness, discarding the rest, you will produce hardy plants with higher and higher proportion of edible citrus genome.
Best regards,
                       Ilya

SoCal2warm

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Re: Long term cold hardy citrus breeding project
« Reply #9 on: December 19, 2017, 02:42:34 PM »
Walt, I'll collaborate with you.

It's true I have no interest in something that is mostly trifoliate in its ancestry, but maybe I can use what you develop to hybridize something and you can take what I develop and cross that with trifoliate.

If I can make a suggestion, you should consider using an indoor grow tent to accelerate growth. I believe it's possible to go from seed to fruit in as little as 3 to 4 years if the temperature is constantly kept above 75 degrees and the humidity is contained (and the potting soil is kept consistently watered, makes sure the plant containers allow plenty of root space as well). You may be able to find a grow tent on the internet for under $45 (2.5 x 2.5 ft or 2 x 4 ft seem to be economical sizes). I usually use incandescent/halogen bulbs inside during the Winter, and have one tent with a little 250W heater on a thermostat temperature control outlet. (I put a gallon container of water right in front of where the heater blows to help keep the temperature moderated, and block the path of dry air to help avoid it causing any of the plants to get dried out)

I hope to breed something that is going to be supermarket quality in taste but survives without much trouble in a zone 8 climate (not just zone 8 but a cool zone 8 climate where the period of summer heat is not that long). This could be pretty useful to someone trying to breed cold hardier citrus because you would already having something that could survive a fair level of cold and tastes good, so it would be a shorter jump for you to get something with extreme cold tolerance that tastes acceptable.

Anyway, hope to stay in touch over the next few years.

SoCal2warm

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Re: Long term cold hardy citrus breeding project
« Reply #10 on: December 19, 2017, 03:09:27 PM »
I agree with you about those recessive genes, Walt.
Something I've been thinking of, you might try making crosses between hybrids that are 50% trifoliate and hybrids that are 25% trifoliate, hoping that some of the recessive genes were retained in the 25% hybrid. If you do crosses with enough different hybrids, you're bound to eventually get something that expresses the full (or closely so) trifoliate cold hardiness phenotype even though it's slightly less than 50% trifoliate in its ancestry.

I know someone who breeds reptiles and he often has to resort to second generation backcrossing to obtain offspring that express recessive traits.

Another thing to be aware of is that some citrus varieties produce more nucellar seeds than other varieties. (nucellar = true to seed, genetic clones)
So if you're making a cross, you might select a variety more likely to produce zygotic seeds as the female parent, and then grow those seeds. Citranges only rarely produce zygotic seeds, so not a good choice for the female parent. In some cases you might just have to grow the seeds to full plants without knowing whether they were true to seed yet.

Millet

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Re: Long term cold hardy citrus breeding project
« Reply #11 on: December 19, 2017, 03:11:20 PM »
Ilya11, could you please explain what is a poncirus+.  I am not familiar with that term.  Thanks.

Walt

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Re: Long term cold hardy citrus breeding project
« Reply #12 on: December 19, 2017, 03:49:38 PM »
Poncirus+ is new to me too.  And google doesn't have anything on it.

Walt

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Re: Long term cold hardy citrus breeding project
« Reply #13 on: December 19, 2017, 04:10:27 PM »
SoCal2warm.  I am aware of the nucellar seedlings.  I am using seedlings of Sandford citramagee. which is said to be completely zygotic, and US 852 citandarin which is said to be 50% zygotic.
I have about 25 seedlings of an open pollinated pure P. trifoliata that has zygotic seeds.
The 50% zygotic citandarin is the most nucellar seed source I plan on using.  I have decided to use use pollen fromcitandarins and citranges that are nucellar for a couple of generations because I don't want to limit the genetic diversity.  But I will be limiting use of non-zygotic plants after that.
I have a 200 sq. ft. greenhouse.  That is a little less than 20 sq. meters.  I plan on building more.  In spite of the cold spells we get here, it is sunny enough that I have overwintered tomatoes in sunken unheated greenhouses.  I plan to build more.
I am investigating venting my hot water heater into my greenhouse to add CO2, as well as heat.  I'll be installing a CO monitor too.  Neither I nor my citrus like carbon monoxide.

Yes, stay in touch.  It will be a couple more years before My next generation starting.

Walt

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Re: Long term cold hardy citrus breeding project
« Reply #14 on: December 19, 2017, 04:16:58 PM »
I agree with you about those recessive genes, Walt.
Something I've been thinking of, you might try making crosses between hybrids that are 50% trifoliate and hybrids that are 25% trifoliate, hoping that some of the recessive genes were retained in the 25% hybrid. If you do crosses with enough different hybrids, you're bound to eventually get something that expresses the full (or closely so) trifoliate cold hardiness phenotype even though it's slightly less than 50% trifoliate in its ancestry.
.

That would be pop 4 in my first post.

Ilya11

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Re: Long term cold hardy citrus breeding project
« Reply #15 on: December 19, 2017, 05:39:40 PM »
Poncirus+ is a chance seedling of trifoliata growing near Yalta, Crimea.
It was found by Forward,  the old  member of CitrusGrowers forum. He posted some photos of it on the  Ukrainian citrus forum.

http://citrusforum.org.ua/viewtopic.php?f=57&t=86&start=210

Google translation ;D
http://translate.google.com/translate?hl=fr&sl=auto&tl=en&u=http%3A%2F%2Fcitrusforum.org.ua%2Fviewtopic.php%3Ff%3D57%26t%3D86%26start%3D210&sandbox=1
« Last Edit: December 20, 2017, 02:54:19 PM by Ilya11 »
Best regards,
                       Ilya

Millet

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Re: Long term cold hardy citrus breeding project
« Reply #16 on: December 19, 2017, 10:18:00 PM »
Thanks Ilya11 for the explanation. Seems to me Forward could make a lot of money on Poncirus+.

Walt

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Re: Long term cold hardy citrus breeding project
« Reply #17 on: December 20, 2017, 01:21:01 PM »
I googled poncirus+ and got nothing.  Thank you Ilya for the information you provided.
I googled Swamp Lemon.  I got only one hit, a blog at

http://hardycitrus.blogspot.com/2017/06/swamp-lemon.html

I found no commercial source, but the blog does have a source.
 "only growing wild along the west side of Rte. 74 where it crosses the Livingston Creek. "
That's in North Carolina, USA.  Quite a drive from Kansas, but if no other source is available I might do it.
Who do I know who lives in North Carolina?

Walt

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Re: Long term cold hardy citrus breeding project
« Reply #18 on: December 20, 2017, 01:26:51 PM »
I didn't sleep much last night.  The 3 variations on P. trifoliata have me excited, thinking about how they could shorten my breeding plans.  Without the evil flavor of P. trifoliata F1 hybrids, citranges, citandarins, citanything, would be much better.  No substitute for the best southern grown citrus, but enough to thrill me.  Thanks to everyone!

Millet

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Re: Long term cold hardy citrus breeding project
« Reply #19 on: December 20, 2017, 03:01:10 PM »
There was some talk about using early maturing citrus. The earliest maturing mandarin I know of is the Xie Shan satsuma (which can easily be purchased in the USA).  Xie Shan can mature as early as mid-September

Ilya11

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Re: Long term cold hardy citrus breeding project
« Reply #20 on: December 20, 2017, 03:06:34 PM »
Walt,
Bernhard Voss from Hamburg succeeded to produce a deciduous hybrid between Ichangensis and Poncirus that resist to -21C (USDA zone 6b).
It is listed as  "Neuzüchtung" at his site, also has a name N2tri.
I have it, not flowering yet, but it is shredding all leaves in early November.
Best regards,
                       Ilya

Citradia

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Re: Long term cold hardy citrus breeding project
« Reply #21 on: December 20, 2017, 08:32:02 PM »
Walt, I looked up Livingston Creek in NC: it's crossing hwy 74 just west of Delco in Columbus county, on the south coast of NC just one county east of Wilmington. I've driven through there several times this year. I'd love to look for swamp lemons over there, but since that's 4.5 hours from where I live, don't know when I'll be able to go out there. My husband's father grew up in Whiteville in Columbus county, and he tells me he used to season fish they caught from local rivers with a small wild citrus that grew there, but he says he didn't call it a lemon.

Farmerche

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Re: Long term cold hardy citrus breeding project
« Reply #22 on: December 20, 2017, 08:37:02 PM »
I think two new varieties Iwasaki and Nichinan are slightly earlier than Xie Shan.

Walt I can send you a cutting from my FD now if you think you can work with it but if not we can wait until later in spring.

Any chance we can get poncirus + into the US?

mikkel

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Re: Long term cold hardy citrus breeding project
« Reply #23 on: December 21, 2017, 02:05:13 AM »
Walt, I looked up Livingston Creek in NC: it's crossing hwy 74 just west of Delco in Columbus county, on the south coast of NC just one county east of Wilmington. I've driven through there several times this year. I'd love to look for swamp lemons over there, but since that's 4.5 hours from where I live, don't know when I'll be able to go out there. My husband's father grew up in Whiteville in Columbus county, and he tells me he used to season fish they caught from local rivers with a small wild citrus that grew there, but he says he didn't call it a lemon.

hardyvermont did some research. He might know the place... I think he is on this forum too.

Millet

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Re: Long term cold hardy citrus breeding project
« Reply #24 on: December 21, 2017, 10:20:14 AM »
Farmerche, getting permission to import poncirus+ into the USA, would have to go through the USDA, and that would be a BIG BIG BIG nightmare.  Especially with all the present citrus problems going on in this country.

 

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