The Tropical Fruit Forum
Citrus => Cold Hardy Citrus => Topic started by: Walt on November 04, 2021, 04:56:23 PM
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I've been thinking a lot about hardy citrus breeding for some years now. But new information and experience is changing my mind about several thing the last few weeks,
Ponciris trifoliata is hardy enough for my area, And it is the hardiest citrus relative I know of that is readily available. It crosses easily enough with good citrus, and I've always thought breeding from such crosses was the way to go. The ONLY way to go. People have told me they want to select within the pure P. trifoliata, and I thought that was stupid. There isn't enough variation to make that way successful, I thought.
But what is really the problem with P. trifoliata as a crop? The nasty-smelling resinous flavor, of course. But there is at least one mutant without that problem. Ponciris+. And P. trifoliata is mostly nucellular. Again Ponciris+ is zygotic so that is at least less of a problem. In addition, P. trifoliata, its F1 hybrids, and backcrosses to mandarins (mandarin x P. trifoliata) x mandarin, are too sour and lack sweetness. Granted, I've only tasted one mandarin backcross, Clemtriclem. It is (Clementine x P. trifoliata) x Clementine. And Clementine is not the sweetest mandarin. But I have not read of any improvement over Clemtriclem. Another problem is the size of Ponciris fruit. They are small. But that is a minor problem compared to flavor.
But all this means, really, is that more sugar (higher brix) and less acid (higher pH) is the whole breeding problem. Or at least most of it. Precocity, short time from seed to bloom, would be valuable, as with a certain set of breeding stock, progress will be set by population size, ability to measure brix and acid, and the number of generations. Keeping generation time short would be very valuable.
But to select within P. trifoliata seems a dead end. There isn't much variation in brix or acidity to select from. At least I haven't found information that would make me think otherwise. So crosses with other citrus is the only way to get the needed genes. Fortunately, such crosses have been made. Kumin and I and others have acquired such hybrids. US 1279, US 1281, US1282, Us 852, 5*, are useful as seed parents as well as pollen parents. Other varieties might be used as pollen parents if desired. Citrangequats can't be ruled out, though they wouldn't be my choice. Bringing in Kishu Seedless as a pollen parent seems worthwhile, as it has a dominant gene for seedless, and is said to be exceptionally sweet.
New hybrids could be worthwhile. Precocity might be brought in from Laaz's Fast Flowering Ponciris, Etrog, or Hong Kong kumquat. None of these are of proven value, but I am checking them out.
Hybrids of various citrus with Ponciris+ could speed up getting rid of the Ponciris flavor. Though a generation or two of selection should get rid of it where Ponciris+ isn't available.
The amount of Ponciris in a breeding population should be determined by your climate zone. Zone 8, maybe zone 7, 1/4 Ponciris could be enough. This would speed up the breeding in those areas. I plan to make such seeds available in a few years, when my breeding stock is older. Kumin, in zone 6, has had some success with 1/2 Ponciris in zone 6. What he does in the future is up to him. He has already done in one generation what I thought would take several generations, so I'm not the one to tell him what to do.
I'm also in zone 6, and will be working with 1/2 Ponciris. But I will also make some crosses of those 1/2 Ponciris with pure Ponciris. This will give me a big population that can be grown without protection. This population will include seedless plants from the Kishu Seedless mandarin ancestor, fruits lacking Ponciris famous flavor, various levels of brix and acid, and fruit size. Of course, I'll be working on the 1/2 Ponciris population, but I'll have to provide some protection to keep seedless and some other genes in the population in the early generations.
Breeding stock I now have on hand include:
Ponciris trifoliata
Ponciris+ which doesn't have the undesirable Ponciris flavor and does have zygotic seeds.
FFP, Laaz's Fast Flowering Ponciris, which doesn't pass on its fast flowering to its seedlings when crossed with other citrus.. But it may pass it on to its grandchildren. If so, it would speed up generation time.
B and J. Bigger and juicier P. trifoliata. 100 seeds from Kumin.
Many seeds from a wild population. Sent by orangedays. These trees give monozygotic seeds. These are to broaden the genetic diversity of my breeding population.
Mandarins
Kishu Seedless. Very small, but very sweet and has a dominant gene for seedless. It can only be used as a pollen parent. Half of its seedlings will be seedless.
Changsha. Good flavor, good size, more cold tolerant than most mandarins, zygotic seeds.
Citandarins
US 852 85% zygotic seeds
US 1279 More than 95% zygotic seeds
US 1281 More than 95% zygotic seeds
US 1282 More than 95% zygotic seeds
Bishop Citandarin Seedling of US 852. An improvement in flavor.
Citrange
010 Citrange Survived 3 winters in Pennsylvania. Zone 6 Fruit quality unknown. % zygotic unknown.
058 Citrange Survived 3 winters in Pennsylvania. Zone 6 Fruit quality unknown. % zygotic unknown.
067 Citrange Survived 3 winters in Pennsylvania. Zone 6 Fruit quality unknown. % zygotic unknown.
These 3 are seedlings from the same tree, C-35. Mother tree was 15% zygotic. These were all grown and selected by Kumin. He has reported his work elsewhere on this forum. Very impressive work.
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Kumin has been reporting on his citrus breeding. Of about 3,000 zygotic F2 seedlings from C-35 citrange, he had 12 survive in good health for the past 3 winters in Pennsyvania, zone 6. Others survived with serious damage. But lets look closer at those that survived in good health.
12 out of 3,000 is 1 in 250. The odds of getting a given plant is the odds of a suitable pollen x the odds of getting a suitable egg cell. We don't know the pollen parent of these seeds, but it seems likely they had been self pollinated. I'll assume they were. So 16 x 16 = 256. 256 is close enough to 250 for my use just now.
So C-35 citrange gametes have a 1 in 16 chance of giving hardy seedlings. I expect plain P. trifoliata gives 100% potentially hardy gametes. So if C-35 had been pollinated by P. trifoliata, 1 in 16 seedlings would hardy in Kumin's area. I am also in zone 6, but sudden temperature changes and lack of snow cover here might mean less survival here. But this is still good enough for what I'm saying.
So I'm thinking about crossing citandarins back to P. trifoliata and to mandarins. I want to get the seedless gene from Kishu Seedless into my breeding. There are a few ways to do this.
One is to pollinate a citandarin with Kishu pollen. But such seedlings couldn't be grown outside in my area, nor Kumin's, with any chance of survival.
Another way is to pollinate a zygotic P. trifoliata with Kishu pollen. Then use Pollen from those seedlings in further crosses with other citandarins, citranges, etc. This is a good way. but I don't know how soon this all could happen.
A third way would be to make the cross (citandarin x P. trifoliata) x (citandarin x Kishu). The resulting seedlings would still be 50% mandarin and 50% P. trifolitata. The advantage of this method would be that someone in zone 7 or 8 might be willing to grow out the citandarin x Kishu seedlings in hopes of getting hardier mandarin-like fruit. It could happen. How much improvement would be found remains to be seen. This would save me limited greenhouse space. And I could grow out the citandarin x P. trifoliata seedlings outside. Again, this would save me greenhouse space. And perhaps 1 out of 16 would survive.
Back to Kumin's citrange F2 plants that have done well through 3 winters. With such strict selection, I'm sure that they will produce more than 1 in 16 useful gametes. Using their pollen on citadarins is a logical plan. No one knows what fraction of such seedlings will survive, but it should be much better than 1 in 250.
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Thanks for your roadmap and report, Walt. Just a few comments on the citrandarins and selections 010, 058, and 067. This Winter will allow me to compare 1279, 1281, and 1282 in regards to cold resistance. Initial appearances are that 1281 and 1279 may be more cold resistant than 1282. 1281 shows the greatest Poncirus influence on the foliage.
Segentrange 010 is more cold hardy than 058 and 067. 010 shows more Poncirus influence, 058 and 067 are the most Citrus-like of all the trial survivors.
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The advantage of this method would be that someone in zone 7 or 8 might be willing to grow out the citandarin x Kishu seedlings in hopes of getting hardier mandarin-like fruit. It could happen.
Oooh! Oooh! Me! Pick me!
I'm currently trialling pretty much every variety of citrus that's reputed to be cold-hardy. Anyone needs a clay-soil, zone 7(b) test out here in north alabama across a few separate microclimates I prepare, just let me know :D
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Thanks for the offer. It will be at least a year, maybe more. W
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So far I've written only about mandarin breeding. But I've given thought about breeding other citrus too.
-I like having finger limes around. They aren't the greatest, but those little balls of flavor are nice in some things. I've read that when it is crossed with other citrus, the seedlings' fruit have the same little balls of flavor, but they taste like the other parent. I doubt that's exactly true. But I don't doubt that when crossed with various other citrus, you will get lots of variation in flavor, and some of them will be good.
It seems that all finger lime's seeds are zygotic. Good. A single cross with a P. trifoliata would likely extend its range greatly. Not zone 6, but it would give it another zone or two. If the P. trifoliata parent was Ponciris+, the F1 might give fruits with the little balls of flavor that taste like sour orange. Already it would be liked by some people. Tastes differ.
But beyond the F1, possibly a backcross to Ponciris+ would put some seedlings into zone 6. And some of them might have those little round bursts of sour flavor, instead of the elongated shape common to most citrus. Selection for less sour and higher brix would increase the number of people who would like it. I've got to get on this. This is the only hardy citrus breeding plan that could succeed in only 2 generations. Of course if anyone else wants to get on it, do it. Its not that I have lots of time and space and nothing else to do. And it would take some extra generations to get the gene for seedless into it. But one could use the seeded ones until seedless ones are developed.
-Kumquats are one of my favorite citrus. Like finger limes, they are all zygotic. Unlike finger limes, I doubt many would like the F1 kumquat x P. trifoliata no matter which P. trifoliata is used. Big populations and several generations might be needed. Still it can be done. Unlike the other citrus I've written about, the flavor and texture of the peel matters. Well, the zest of the other citrus is used, but it is less important to many people.
-For grapefruit, 5* is one of the most used P. trifoliata hybrids. A good start. A cross back to grapefruit or pummelo would give a population that would include some that are good grapefruit. Getting them into zone 7 or 6 would be several more generations. And part of the problem is that grapefruit need a long season. Zones 6 and 7 don't have long seasons.
-Lemons and limes I'll lump together. Neither have zygotic seeds. None of them as far as I know have zygotic seeds. So pollinate Ponciris+ with pollen from lemons (or limes, which can be treated the same way. But I'll just say lemons to save time and space.) whichever you want to work with. The fruits from F1 plants won't taste like lemons. It will be sour, but the lemon flavor won't stand out. Sure, the genes for the complex flaveres in lemons will be jumbled with the orange flavors on P. trifoliata. So how to sort them out. Sure, one could select based on subjective taste. But I wouldn't be able to make out which is a liitle more lemony and a little less orangy. So one possibility is to use s gas chromatology machine and find out what seperates the lemon flavor from the orange flavor. Run a sample of orange juice and a sample of lemon juice. Record the blips on the graph or screen for each. Then run a sample of juice from each seedling. Select those seedlings with the most lemon pattern. So gas chromotology machines aren't cheap. But I knew a professor at Emporia State U. that built his own because he wanted to be able to carry it to the field to run really fresh root samples. It can be done. Or one could find a lab that would do it for you. That could be very expensive. Or you might find someone who would do it to get a good publication with their name on it. That happens. Infra red spectrscopy might also work. Those machines have been home built. It's been over 30 years since I've known of a homebuilt one, but it would't be any harder now.
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I keep seeing mention of “poncirus+” - what is this? I’ve got a gazillion standard poncirus, as well as lucky enough to have been able to get an early fruiting poncirus from Laaz. But I’m clueless about poncirus+.
My home is *filled* with finger limes in pots (red and green), so if there’s a potential way to extend their range and actually get them outside here in 7b, I’d love to hear it.
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Ilya may have a clearer history of Poncirus+, but my understanding is that it was selected in Eastern Europe, perhaps Ukraine. There appears to be a little uncertainty as to whether it's fully as hardy as common Poncirus. Local Winters haven't been super cold during the past 2 years, so no real challenges in that respect. My trees are too young to have fruited so I have no personal experience with fruit characteristics.
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Ponciris+ iseported to lack the acrid flavor of other ponciris and to have at least some zygotic seeds.
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So a poncirus that doesn’t taste terrible? Or just tastes less-terrible? Is there a source for this? I’d love to compare to the normal poncirus and precocious poncirus I have.
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I have found that P.t and all of its hybrids and backcrosses to citrus I've tasted are very sour. I expect P+ is also sour. But add water and sweetener and they have all tasted OK. Not really great, but OK. I have only tasted regular P.t, a citandarin, a citandarin x mandarin, and and a Taiwan lemon x Pt
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Have you ever thought of Ichang Papeda? Is it suitable for your climate zone?
Ichang Papeda grows much better than Poncirus and some flower after 3 years, but not all.
Poncirus grows so unspeakably slowly that I am already wondering whether it is at all suitable for my climate.
This autumn I also got a (mostly) seedless Ichang Papeda. When pollinated, it sometimes does make seeds.
(https://live.staticflickr.com/65535/51606064332_a31d9ab8bb_z.jpg) (https://flic.kr/p/2mCfyZS)
(https://live.staticflickr.com/65535/51607773265_7daa38e163_z.jpg) (https://flic.kr/p/2mCpk1e)
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I also thought about creating a hybrid swarm first, consisting of many different early bloomers.
As I understand it, early flowering in hybrids is often not heritable, probably it is a form of recessivity of one or more genes. So that the trait is quickly lost in the next generations.
Backcrossing could help, but that poses other practical problems, or perhaps a hybrid swarm of early-flowering varieties. Maybe different genes that produce early flowering can be combined with each other (provided it is not the same genes in all early flowering varieties) or, if it is the same genes, one can breed for better fruit quality within this swarm.
Later, an early bloomer with better fruit quality could be used for crossing with "normal" citrus.
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Ichang Papeda is not as readily available in the US as in europe. And most of the time when it is offered it is a hybrid seedling so it has other ancestry other than ichang papeda.
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Ichang Papeda isn't hardy enough for my location. I thought about using both it and Pt. But that would dilute the percentage of mandarin genes in my population. That's a judgement call that others might disagree with. But I take my best guess and go with it.
I wonder what a hybrid swarm from Ichang Papeda x Pt would be like. But I must limit my efforts if I am to get anything done.
I do like it when other people give comments, offer additional ideas. Its not like I know all about this. I just make my best guesses and act on them. And as I said before, Kumin showed that I was wrong about how quickly one can get hardier citrus. Others may show that I could have gotten better or quicker results going a different way. Good. As long as there is progress, I'm happy.
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I'm in agreement, Walt. Poncirus being the hardiest known Citrus relative and being hardy in zone 6, except in extreme Winters, all of it's hardiness is required for a reasonable chance at success. The first hardy hybrid selections will likely have their hardiness challenged during severe Winters. Deciduousness, true dormancy, and actual Winter bud scales are all important attributes that contribute to Winter survival. It's almost a requisite to conserve these traits in any new cultivars for zone 6.
There are obviously a number of hurdles to overcome, such as early ripening to beat Autumn freezes. There's a sense of needing all of the tree traits Poncirus brings to the table, plus all of the fruit traits Citrus brings to the table. A tall order, but also a great challenge!
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Ichang Papeda isn't hardy enough for my location.
My information tells me it is only hardy down to zone 8a, or possibly even 7b in parts of the deep South (in the US).
I am growing two Ichang papeda plants in the Pacific Northwest, zone 8a, and they do not seem to be doing too well, although they appear to be surviving, in contrast to several Yuzu plants that seem to be doing well. This despite every source I've ever come across saying that Ichang papeda should be able to survive significantly more cold than Yuzu. My Ichang papeda plants have leaves that do not develop a dark green color, and I think it is because they do not like the cool to cold temperatures when they first begin leafing out in the late Spring. I have considered the possibility that the strain of Ichang papeda I have may not be the same variety that exists in other parts of the country, so I can not necessarily be certain of extending my observations to the Ichang papeda species in general. Maybe they just do not like the cooler weather and shorter growing season in this climate. But the Ichang papeda plants in Europe seem to be growing quite well, so maybe this is not true.
On the other hand, Ichang papeda doesn't have any of the awful flavor of poncirus, and I could even manage to eat the entire fruits, with the peel and all (though of course not the seeds). It seemed to be sour, not fully ripe, low flesh ratio, not much juice, flavor like citron or lemon with some lime, specifically kaffir lime flavor, but also a little reminiscent of Yuzu in a strange sort of way with some deepness, but not that little bit of spiciness that Yuzu has. Not really the best fruit quality but definitely edible. It reminded me very much of a citron, with its softer semi-edible peel and yellow lemon flavor. By comparison, Yuzu has a much more fragrant orange or mandarin orange like flavor.
I'd say that compared to Yuzu, Ichang papeda has a little bit of an overall inferior flavor and fruit quality, but the peel of a fresh Ichang papeda is also very slightly softer and more tender than a fresh Yuzu, although if you eat too much of the peel it can have a little bit of a skunky after-flavor.
It seems to me very few people have ever got the opportunity to actually taste Ichang papeda, so I hope these insights are valuable to some of you.
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Ichang Papeda is not as readily available in the US as in europe. And most of the time when it is offered it is a hybrid seedling so it has other ancestry other than ichang papeda.
I wouldn`t care. as long as these are vigorous plants and still quite cold hardy.
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Ichang Papeda is not as readily available in the US as in europe. And most of the time when it is offered it is a hybrid seedling so it has other ancestry other than ichang papeda.
I wouldn`t care. as long as these are vigorous plants and still quite cold hardy.
Yeah they'll be vigorous till you get the seeds and found out that it has lemon as the pollen donor... how hardy is that?
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I don't understand what you're trying to say?
I didn't mean anything by my last post.
Of course, it doesn't make sense to cross Ichang Papeda with something that is sensitive to cold. One of my goals is to cross with Ichang Papeda to transfer vigorousity to hybrids.
Hybrids of "F1 Poncirus hybrids" with Ichang Papeda grow much better than pure Poncirush hybrids for me. But that is just my observation and only refers to my climate. It may not be helpful elsewhere....
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"Hybrids of "F1 Poncirus hybrids" with Ichang Papeda grow much better than pure Poncirush hybrids for me. But that is just my observation and only refers to my climate. It may not be helpful elsewhere...."
I'll have to check this out. Hybrid vigor can be a very useful tool.
I now have P. trifoliata from 5 sources. I'll be comparing them for vigor, winter dieback, brix, acidity, and every other trait I can think of. An important part of plant breeding is exploring your options.
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Yeah you're right mikkel, ichang papeda hybrids are vigorous. One of my N1Tri/Ichangstar F2 grew about a foot since planting them in February of this year.
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Only problem is finding an pure ichang papeda to be the female parent...
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Only problem is finding an pure ichang papeda to be the female parent...
There's a very big bush-tree in the Hoyt Arboretum in Portland, OR, right up against the side of the visitor center.
I can tell you it grows very easily from cuttings.
For those in SC, Woodlanders sometimes has some, although they're prohibited from selling to you if you're in GA.
Keraji seems pretty promising too. Maybe you could try using Keraji to pollinate a zygotic selection of poncirus hybrid and hope for the best.
Loch Laurel sells Keraji but they do not do mail order.
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Woodlanders ichang papeda is seed-grown, would be a gamble but I guess that's a way.
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Woodlanders ichang papeda is seed-grown, would be a gamble but I guess that's a way.
If the Ichang papeda crossed with something else, I think it would be obvious from the leaves and fruits that it was not Ichang papeda. Ichang papeda has very symmetrically sized leaves when it comes to the winged petioles.
I believe Ichang papeda is very zygotic (seeds resulting from sexual recombination), but assuming the plant crossed with itself, I would expect it to come out mostly true to seed.
Of course my personal experience of Ichang papeda plants not seeming to be very cold tolerant might counter that theory.
If this species was as cold tolerant as everyone else seems to observe, then I think it would have a lot of potential for breeding, judging by the quality of what I've tasted from the fruits. Especially anyone specifically trying to breed something with more of a lemon or lime flavor rather than "orange" flavor. Ichang papeda only takes one cross with something else to get something edible. Poncirus trifoliata, on the other hand, takes two or three. I'm going to say Ichang papeda is probably on about the same level of edibility as a Thomasville citrangequat, the best poncirus hybrid I've tasted. Just my personal opinion. (I'd imagine many would say the Thomasville citrangequat is a little bit better)
It's extremely rare for poncirus to cross just one time and result in something that is possible for anyone to eat. US-852 citrandarin and Dunstan citrumelo might be the best two. Still some bad poncirus flavor but some people can manage to eat them without too much problem. (I personally have not had an opportunity to taste either yet, but am going by the reports of others)
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Have you ever thought of Ichang Papeda? Is it suitable for your climate zone?
Ichang Papeda grows much better than Poncirus and some flower after 3 years, but not all.
Poncirus grows so unspeakably slowly that I am already wondering whether it is at all suitable for my climate.
Mikkel,
there is quite a lot of variety with PT seedlings. Some are vigorous others not at all. You have to select the vigorous ones.
(https://live.staticflickr.com/65535/51607773265_7daa38e163_z.jpg) (https://flic.kr/p/2mCpk1e)
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Keraji, Changsha, Kishu...
Anybody consider hybridising PT with mangshanensis mandarins, and other pure lineages (not necessarily just pure mandarins, but with any pure citrus?) Maybe utilizing pure genes would be helpful in some respect, like less ambiguity related to the prediction and expression of gene sets? Whereas the expression of genes of the progeny from say, a 'complex-hybrid x PT-hybrid' would be quite a lot less predictable?
At least, perhaps 'pure x PT' hybrids could be used as F1 parents for further hybridising.. Anybody catch that drift or am I delusional?
Also, saw a video where citrus breeders grow their hybrid seedlings pretty much as straight sticks to induce the earliest possible flowering (as opposed to bushy w/ side branches). In case you may have not known.. cuts down time.. although I don't know if this applies to all citrus types..
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I know nothing about mangshanensis mandarins. I'll have to do some searches on those.
Its true that some of the pedigrees of what I think of as F1s include Changsha which is not pure mandarin. I don't see this as a problem. I know of someone who is breeding for zone 7 kumquats. He is using Meiwa kumquat, which I thought was pure kumquat. But a few days ago I was reading a publication that quoted Swingle saying he didn't believe Meiwa is pure kumquat. I certainly wouldn't know the difference.
Kumin has had amazing success using C-35 seedlings, C-35 is Rusk orange x Pt. All oranges are from interspecific hybrids.
I'm sure many, most, domestic citrus have been crossed around. An exceptipn is finger lime. And it seems some plants in the USA sold as finger lime are an F1 hybrid.
I don't see a problem with using impure citrus in breeding. My issue is where can I find useful genes.
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The mangchanensis are from the zone 9 mountains close to zone 8. I think the Changsha are probably from right around there too. They are obscure wild mandarins but look cold hardy like Changsha. You could use a 'mang x PT' and breed that rudimentary with something sweet like perhaps navel orange or hybrid something and it would definitely be cold hardy (maybe not quite to z6.. but perhaps some seedlings?) and have pure tangerine genetics involved. Mangschanansis apparently contain the same amount of sugars but more citric acid than most domestic mandarins, according to this article - https://www.sciencedirect.com/science/article/pii/S1674205218301874
- and also contain 'abundant healthy phenolic compounds and antioxidants'. I personally like zangy mandarins and mandarin hybrids. They are actually by far my favorite citrus. I don't like just sweet and bland like some satsumas are, at least the ones grown around here. The tommy Atkins trees of citrus. Almost like wasted space and effort with some of them. The intense tangy mandarins are a lot more nutritious. Clementine is great but even more tang would be better. Just not so sour as say a Calamondin or lime so it's still enjoyable. It would be cool to even have purple flesh with anthocyanin benefits, so blood oranges could replace navel with that theoretical hybrid. I think Moro is the sweetest? I do enjoy sweet but accompanied by a lot of tang. Y'all's ponciris+ could be the PT in that hybrid to get rid of the nasty. So I stand by
['ponciris+ x (good mang selection)' x 'Moro x minneola' ]
Or replace minneola with navel or something sweet. Even satsuma. I just like tangelos.
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Crossing Satsuma with Poncirus yields a sour fruit. Based on the link above, domesticated Satsumas have less sourness, so would be the preferred choice as the sourness is not coming from both parents.
If these wild species were available, it would be good to try for hardiness.
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I think z6 would be almost unfeasible (not impossible) to breed for something really good but could end up with some good selections for z 7 and 8 with y'all's efforts if they live.
I still stand by my above theory with some modifications
['Ponciris+ x mangschanensis' x mangschanensis'] x ['Moro x navel']
With this, there would be beneficial genes floating around for cold hardiness, anthocyanins, low seediness, low bitter, quality fruit, easy peel, tang (hopefully not excessive). Although, other genes for seediness, small fruit, excess sour also present.
You could substitute mangschanensis with another tangerine that is hardy in the teens F I suppose. I guess 'pure' might not matter too much here but don't discredit that purity could have it's place in some aspects of breeding.
Then navel could perhaps be replaced with something else sweet. I would like to be able to replace navel with minneola, sunburst, cara cara, clementine, Kishu, satsumas, if any of those would even work out nicely. Who is to say the relative sweetness in any of those domestics would even be accurately expressed? anyway I think this general set of genetics could create something really good and still quite cold hardy, but I wouldn't count on z6 exactly.. I would predict the F5 or F6 (basically the end product seedlings of all that hybridization) to probably generally withstand zone 7..
Ponciris+ I assume can withstand somewhere around -15 - -20 F
Satsumas low teens F
Minneola mid teens F
Wash navel & cara cara high teens F
Clementine mid teens F
Sunburst 20F
Mangschanensis probably mid to low teens F
Can one predict general cold hardiness for a batch of hybrid seedlings accurately? For example, could 'PT x wash navel' seedlings be predicted to withstand around 0F since average cold hardiness -20+19/2= -2? I realize cold hardiness traits are inherited not averaged but can it generally be predicted to work out like this with most cold hardy citrus hybrids?
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Roughly speaking, the greater the number of seedlings, the greater the chance of finding one or a few that are more cold tolerant.
Hybrids do not have uniform characteristics, but a variance of traits (similiar to gaussian normal distribution). F1 hybrids are usually still quite uniform (if the parents are not already hybrids), F2 are then very broadly spread in their characteristics.
Obtaining sweet fruits I think, is more about "less sour" genetics than "higher sugar level "genetics. It seems sourless is often recessive inherited and needs therefor backcrossing.
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F1 hybrids are usually still quite uniform (if the parents are not already hybrids), F2 are then very broadly spread in their characteristics.
That's what I was pretty much getting at with using pure ones.
Obtaining sweet fruits I think, is more about "less sour" genetics than "higher sugar level "genetics. It seems sourless is often recessive inherited and needs therefor backcrossing
That's useful!
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What Mikkel said about value of population size was demonstrated by Kumin's 20,000 C-35 seedlings.,
Only 3,000 of them counted as the rest were nucellar. It gave 12 that have 3 zone 6 winters survived in good health. Several others survived with damage, some died to the ground but came back, Given that so many survived, I now think this is going to be easier than I thought. But I said that above, didn't I?
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F1 hybrids are usually still quite uniform (if the parents are not already hybrids), F2 are then very broadly spread in their characteristics.
That's what I was pretty much getting at with using pure ones.
For me, the F2 is the interesting one, because that is where the really interesting things happen. In pure parental lines, the F1 generation consists of uniform types with mainly intermediate traits. But if you want to transfer a trait (e.g. cold tolerance) to another variety with good traits, it happens in the F2.
The F1 will be intermediate between the parents in fruit quality and cold tolerance, the bad of both worlds, so to speak.
In the F2 and the following generations the traits split and new trait combinations appear (e.g. ideally good fruit and cold tolerance) these have to be selected, therefore mass is needed. Since recessive and dominant as well as other genetic factors play a role, it varies from species to species which hybridisation is used in the following generations.
Of course, this is idealised theory and varies in reality. Especially when the parent varieties are not homozygous or / and already have hybrid traits.
Kumin's trial is, in the sense of this consideration, to interpret an F2 mass selection, the generation in which the splitting and recombination occurs for the first time.
For this reason I also try to work with F1 hybrids as crossing partners, this saves a lot of time.
Of course, this does not mean that hybridising pure species is not also useful. I also find mangshanensis very interesting.
Obtaining sweet fruits I think, is more about "less sour" genetics than "higher sugar level "genetics. It seems sourless is often recessive inherited and needs therefor backcrossing
That's useful!
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there is a thread about it:
https://citrusgrowersv2.proboards.com/thread/728/inheritance-low-acidity
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Large populations increase the number of throws of the genetic dice. Heavy selection pressure and elimination of plants expressing undesirable traits should skew the results in a favorable direction, provided those genes are present within the population.
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This morning I saw the first flower about to open on US 1279. That's a mandarin x Pt that is more than 95%zygotic. I don't have anything here to cross it with.
Kumin's C 35 citrange F2 s haven't put out any new growth this spring, though they are looking good.
But US 1279 can be selfed and give F2 seedlings provided the fruit don't drop as some do.
So I'm excited.
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My first F2 C-35 citrange seedling to fruit appears to produce nucellar seeds. The pollen should be viable, however. The tree is full of flower buds and should bloom as soon as temperatures rise.
I'm impressed that your 1279 is flowering, there's obviously little wait from rootstock to mature phase.
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3 weeks ago my pure P. trifoliata that I've had in the ground for several years first broke domorancy
US 852, 1279, 1281, and 1282, Ponciris+ seedlings Laaz Fast Flowering, Ponciris and 3 seedlings from Kumin, and a couple of citromelos and Bishop citandarin were all protected but went dormant due to quite cool conditions. But now all are growing, except Laaz FFP It looks healthy so I think it will start next week.
Changsha and a kumquat stayed in leaf but with little or no growth until last week.
I lost Kishu Seedless and Etrog I think.
I'll be grafting Kumin's seedlings onto in ground Pt, but continue to protect the main plants just in case. Kumin and I are in the same zone but our weather isn't the same.
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Re: sweetness vs sourness in crosses:
Wikipedia's page on mandarins notes that the wild mandarins that gave rise to the domesticated varieties have similar levels of sugar when compared to wild sour mandarins - but up to 90-fold less citric acid than them.
Lemons famously have more sugar than strawberries, but it's their acid that makes people perceive them as sour. I agree that the key to producing 'sweet' fruit would be to concentrate on eliminating the biochemical pathways responsible for acid production - although given that acidless citrus strains are often perceived as 'insipid' and 'not-citruslike' I'm not sure a complete elimination would really be ideal.
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There is a discussion about that on CitrusGrowersForum
https://citrusgrowersv2.proboards.com/thread/728/inheritance-low-acidity
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Add Yuzu to the list. In zone 7 mine (in the ground) died back after 6-7f but is now coming back from the base.
I'm not too worried about citrus for eating fresh out of hand since many can be cooked into marmalades or used as lemon substitutes, yuzu x poncirus+ is definitely a goal. My potted yuzu is about to flower but I don't have any type of poncirus flower or pollen yet so that will have to wait.
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Your yuzu is on its own roots or grafted?
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own roots against a brick wall
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Finally the Fast Flowering Ponciris I got from Laaz last summer is showing new growth. There are 5 tiny new branches with leaves. The longest is about one cm., which is really small, but it the start of new growth, It is over a month behind my older established trees. I believe this is due to transplant shock, not that these trees will always be late starting growth in the spring.Actually I'd be glad if it was late leafing in the spring. I think that would make it less likely to be hurt be late frost. But I think it is just due to transplant.
I don't know whether it will bloom this year. I know it is old enough because it had 3 fruit on it when it arrived last summer.
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Pollinated 2 castrated yuzu and meyer lemon flowers with dried poncirus+ pollen. Stored the rest in an airtight container in a small fridge. Waiting for kumquats to flower. Don't know if the pollen is viable but will report if anything happens.
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Meyer dropped the fruit. Yuzu might have a take
(https://i.postimg.cc/GHCxxWGZ/IMG-20220611-WA0001.jpg) (https://postimg.cc/GHCxxWGZ)
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Walt, any updates on the US 1279? Did any fruit set?
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No. A few days after I posted, there was wind that broke tree branches all over town. No damage to my citrus except the (very few) flowers were gone. I had good bloom later on Laaz Fast Flowering Ponciris but nothing to use the pollen on.
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Last year about this time, a farm supply store was selling citrus marked way down because it was late in the season. The trees looked healthy, so I bought a kumquat tree.
A couple days ago I was there again and there was a kumquat with many flower buds and it was only $7 so I bought it. II took it home and put it by last years kumquat. I then saw that my "kumquat" from last year has trifoliate leaves! I have read many times on this forum that any trifoliate leaves mean it is P. trifoliata or its hybrid. So I googled kumquat leaves pictures. My new blooming tree is really a kumquat. My old tree must be a rootstock whose scion didn't take and no one at the nursery noticed.
So it has been a few days and I'm about over feeling stupid.
I have nothing else in bloom or buds. I'd really like to pollinate these flowers with Hong Kong, Kishu seedless mandarin, or Ponciris trifoliata. I doubt such pollen is being produced this time of year but I thought I'd ask.
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Poncirus as well as some Poncirus hybrids, in addition to blooming on the previous season's twigs in very early Spring, are capable of reblooming on the newly formed buds intended for next Spring's bloom. These fruits usually fail to mature properly by Fall, but should certainly have viable pollen. I don't have any such flowers at present. but might within the coming month. Your present chances may be better with members farther to the South.
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Precocious trifoliate in my experience can be able to bloom 3 times a year, and right now I see another flower bud preparing to open probably next week. Not able to hold any fruit because of its size but still has viable pollen in spring, summer, and early fall.
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Perplexed, my standard Poncirus has 3 stages of bloom this year also. In the past, the initial Spring flowers set fruit that ripened in October. The second set of fruit didn't achieve full size, but produced viable seeds. The group flowering at present is a lost cause in regards to mature fruit.
This photo shows large fruit, which will mature, smaller fruit which should provide seeds. The flowers are out of luck, although, as you mentioned, all 3 sets should have fertile pollen.
(https://i.postimg.cc/JtPT3Ff2/PXL-20220809-131348977.jpg) (https://postimg.cc/JtPT3Ff2)
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My thoughts on breeding hardy citrus is it might make sense to try to cross Changsha mandarin with Dunstan citrumelo.
I'm in the PNW, climate zone 8a, and these two varieties have been the ones that have seemed to survive the best in this climate. The others got almost completely wiped out after temperatures went down a little colder than usual. I have trialed a lot of different hardy varieties.
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A friend got two Satsuma mandarin from Home Depot like a decade ago. They are really really great and definitely cold hardy. He's in Lafayette, Louisiana and gets at least one freeze a year and they still do well. The best dang oranges I've ever had too. I asked him to air layer some for me, but he said it's too much work. I may try getting some scions and graft, then air layer the graft. There are so many Satsuma and no info on how they compare, so I'd prefer to. Grow one I already know is amazing.
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Get 1 from onegreenworld.com. It will come on the most cold hardy rootstock. You will either have to keep it in a pot or adjust the soil for that rootstock's needs if needed.
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My thoughts on breeding hardy citrus is it might make sense to try to cross Changsha mandarin with Dunstan citrumelo.
I'm in the PNW, climate zone 8a, and these two varieties have been the ones that have seemed to survive the best in this climate. The others got almost completely wiped out after temperatures went down a little colder than usual. I have trialed a lot of different hardy varieties.
Neither are hardy in my climate. But if both are hardy in your climate, try it. I'll be trying cirtrumelos x Kumin's hardy selections from C35 F2 selections. And Changsha is a parent of 3 of my citandarins in my breeding stock.
I have freezing temperatures 24 hours a day for as much as a week at a time most winters. Yjough yje last two winters have been milder, getting abve freezing most days.
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Changsha certainly looks like it might be a worthy contributor to a cold hardy breeding plan. Decent hardiness for a true Citrus, reasonable palatability, early maturity, plus mandarins reduce the trifoliata off-flavors. May also transmit more precocity than sweet orange and grapefruit.
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Changsha certainly looks like it might be a worthy contributor to a cold hardy breeding plan.
It's important to point out that your profile says you are in zone 6b. (Changsha has a limit of 8a, maybe the border of 8a and 7b but it might struggle)
For you in particular it may be more practical to just stick to US-835 (Changha x poncirus hybrid).
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Changsha certainly looks like it might be a worthy contributor to a cold hardy breeding plan.
It's important to point out that your profile says you are in zone 6b. (Changsha has a limit of 8a, maybe the border of 8a and 7b but it might struggle)
For you in particular it may be more practical to just stick to US-835 (Changha x poncirus hybrid).
Changsha is unlikely to be sufficiently cold hardy to contribute directly as an F1 parent. My interest in Changsha is in using it's hybrids with PT in further crosses. Without exception, all of my breeding stock relies on PT as it's hardy genetic contributor.
I consider Changsha hybrids as worthy of consideration as a source of Citrus parentage in advanced cold hardy hybrids. Satsuma has great attributes, except for it's sterility.
(https://i.postimg.cc/qNKmgsYX/PXL-20220618-163056255-MP.jpg) (https://postimg.cc/qNKmgsYX)
F1 Changsha X Poncirus hybrid
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Dunstan was a great breeder. I have crosses with his d370 grape. His citrus hybrid isn't good to eat but close enough for a cross. I would be interested in crosses with it. Maybe cross sugar bell with it would be best due to greening resistance. Honey bell or Meyer lemon crossed with it would be good
Sour orange or lemon is about the same. Orange or lemon flavor who cares
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I googled Inheritance of sweetness in citrus. Got this along with much other information.
https://phys.org/news/2019-02-identification-genes-responsible-sour-citrus.html
It seems that much of the sweetness is due to 2 genes. nd the differences in amount of sweetness is due differences in gene mutations in the genes that turn on and off those 2 genes. If I read this right, it will be easier to get sweet hardy citrus than I could have dreamed of.
Did I read this right??
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No because people have been trying this for over 100 years without success. The crosses have lousy fruit. You can start with someone else's work like Dunstan which is almost there.starting from scratch probably not in your lifetime.
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CRISPR/Cas will help ;D
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Crisper(https://i.postimg.cc/zLk5fCtf/IMG-0360.jpg) (https://postimg.cc/zLk5fCtf)
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Growing plants in containers or constructing some type of greenhouse would make more sense than trying to breed a cold hardy citrus. Though I would be interest in slight improvements in cold hardiness.
If you take a place like Florida- we haven't had a hard freeze down here in ten years. Seems like it is getting warmer. Though maybe 12 years ago we had record breaking cold and it was snowing in North Florida, got prolonged hard freezes that killed everything.
There's always that one really cold winter that wipes everything out. When this happens the Florida citrus industry is scrambling to protect their trees anyway they can. It's just a lot easier to have a dwarf tree you can drag inside for a few days or couple weeks when you get hit with an artic blast.
My main problem was the "dwarf" trees were too large. By the time you add a couple feet for the pot and then a six feet tall plant, the only plant small enough was the dwarf meyer lemon, which is only about five or six feet maximum height, though stays smaller in smaller containers. So I would be more interested in breeding dwarf trees or something that would grow well in containers. My dwarf tangerine was just slightly too big. If it was just a hair smaller I could have managed it.
Things like the meyer lemon I could grow outside all the way to the point of a freeze. I mean if it was a low of 35 and a high of 45 it would grow fine outside. A lot of citrus won't grow well in chilly weather like that. Then when I brought it indoors it seemed to do ok. Again, a lot of plants not doing well indoors. Just crossbreed the dwarf meyer lemon with a dwarf tangerine or something.
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For years, while I was a professional plant breeder, I had a list of ideas I wanted to work on, but my employers didn't see any money in them. One of them was winter hardy citrus for the zone I was in. Zone 6.
Now "retired", I'm working on that list of things I wanted to breed. Especially the hardy citrus. Especially mandarins. Yes, I want them for myself. But also there is the challenge.
When I first posted about it here, Kumin posted about his 20,000 seedlings from C-35 citrange. Out of 3,000 zygotic seedlings he got 12 that have come through 3 winters now in Pennsylvania. Same zone as I'm in. I had not believed it could happen in the F2. I had expected to have to backcross to P. trifoliata to recover winter hardiness. So Kumin showed it was much easier than I thought possible.
And here I learned about Ponciris+ which lacks the resin flavor. So what I had thought would take at least a couple of generations had been done for me.
Now the paper I linked to above says, if I understand correctly, that sweetness won't be as hard to get as I had thought.
Nothing against breeding and growing dwarf citrus. That has brought joy to generations of people. But it is not what I'm about. Likewise, Kumin, Ilya, Mikkel, and other who I know less about. I'm sorry to the ones that didn't come to mind just now.
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Walt, I also concede that breeding in the pursuit of zone 6 hardy Citrus is a major challenge. About 20 years ago I planted 5 - 6 "cold hardy" Citrus trees from Stan. Unfortunately, they didn't survive to midwinter. At that point I temporarily discontinued the pursuit.
A few years later I continued to be impressed by Poncirus' reliable and steadfast ability to thrive and consistently fruit each year. I re-entered the pursuit by intentionally tying the effort very closely to Poncirus. Since only a small fraction could be expected to survive, there needed to be a large population from which to select. My number 1 criteria has been and remains to be, extreme cold hardiness. I would rather select for palatability among hardy trees, than hardiness among palatable trees.
I expect that once an initial cultivar is developed, it may provide a gateway to additional improved cultivars.
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I agree that once a good tasting winter hardy citrus is developed, others will soon follow. And we may not be the first to do it. There is a man in Tennessee working on winter hardy kumquats. Given that kumquats are generally more cold hardy than most citrus, and that he is in zone 7 I think, he could be the first. And there may be others out there working on bringing citrus north. In fact, I mentioned earlier in this thread that finger lime x Ponciris+ F1 might be liked by some people with a taste for sour bits in their salads or whatever.
And the list of results from your work that came much quicker than I thought possible is precocity. I bought an Etrog to use as a source of genes for precocity. Then you report that some of your F2 plants are precocious.
I aim to get the seedless gene from Kishu into my breeding. That is all the outcrossing that might be needed other than what we already have on hand.
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Marumi kumquats on Poncirus trifoliata and Flying dragon are said to be safe to 0F with leaf loss and down to 10F with no damage. I am in Zone 6 (-10F) which is to cold. The length of winter cold is also to long causing desiccation death in citrus. In zone 8 a polar vortex will drop to 0F and the Marumi losses leaves and the winter cold is 2 months shorter so the tree doesn't desiccate before growing in spring.
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My potted kumquats take around ~8-9 months to ripen fruit, turns orange around winter but still needs time to sweeten up into the spring once I bring them in my grow room, except the hindsii which turns orange in half the time? Point being what good is a hardy tree if the fruit will freeze to mush before it's ripe.
For a fully outdoor (unprotected) cold hardy citrus in zone 6 & 7 especially, fruit will need to ripen before hard freezing otherwise if you're going to go through the trouble to protect the fruit while it ripens you might as well grow the non-hardy types with delicious fruit hehe.
Marumi kumquats on Poncirus trifoliata and Flying dragon are said to be safe to 0F with leaf loss and down to 10F with no damage. I am in Zone 6 (-10F) which is to cold. The length of winter cold is also to long causing desiccation death in citrus. In zone 8 a polar vortex will drop to 0F and the Marumi losses leaves and the winter cold is 2 months shorter so the tree doesn't desiccate before growing in spring.
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Ponciris does ripen fruit here in zone 6. OK, what good is a ripe fruit that tastes awful? But the genes are there for ripening before hard freeze. I think that there will be those trees that can ripen better tasting fruit before freezing. Then keep selecting for sweeter less acid fruit.
When I was just starting out. I slowly ate 4 P. trifoliata fruits, trying to ignore the resin and acid flavors and concentrate on the other flavors. The orange flavors are there. We just need to select for more sugar and less acid. The resinous flavor is said to be lacking in Ponciris+.
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Clem-yuzu 2-2 goes down to 10F and ripens in September and October. More cold hardiness needed. Grafting onto PT of FD should help.