The Tropical Fruit Forum

The origional Kishu, before the mutation to seedless, had mostly nucellar seeds.  So if you use Kishu to get seedless gene into a breeding population, at least 2 crosses back to the population would be a good idea before letting it cross at random with the population.  I plan to keep it seperate and continue backcrossing to my population, never putting the gene(s) into my breeding population.

Kishu Seedless mandarin has a dominant gene for seedless.  There are many seedy citrus that people would like seedless versions of.  Tree breeding takes time of course, but when dealing with a single dominant gene, like the seedless gene in Kishu Seedless, it needn't take much space.
My Kishu Seedless has bloomed in a 5 gallon pot, so it isn't taking up much space.  And I have a Rubidoux Ponciris in a 5 gallon pot, which doesn't have to bloom for this project.  And I have a finger lime in a 5 gallon pot.  So the 3 trees don't take up a lot of space.
So I plane to pollinate the finger lime with pollen from Kishu.  Half of the resulting seedlings will have the recessive seedy gene from Kishu and will be of no value in this breeding program.  But I won't know which seedlings have the seedless gene and which have the seedy gene until the fruit resulting from this pollination is mature.  So to take up as little space as possible, the seedlings will be grafted onto the Rubidoux. 
When the F1 seedlings on the Rubidoux mature fruit, a fruit from each graft will be checked for seeds.  Those with seedy fruit will pruned off.  One or more of the seedless seedling grafts will be left on the tree.  Pollen from them will be used again on the finger lime.  Again, the seedlings will be grafted onto the Rubidoux.  Again, the seedling graft will be kept until fruit mature, and seedy grafts will be pruned off.  The seedless grafts will be be checked for quality, because, unlike the F1 fruits which should be rather uniform, the backcross fruits will not be uniform. 
Depending on how good the backcross fruits are, the above can be repeated over and over. 
I also plan to do the same with my cold hardy citrus population.  In each generation, the best quality tree with zygotic seeds will be used as the seed parent.  Pollen from the best seedless seedling will be used as pollen parent.  This addition to the breeding population of cold hard citrus will only take one or two extra trees.  And after after two or three generations, the seedless line will be quite like the cold hardy population.

I bought 4 Pt plants for grafting.  They arrived in good shape, but just after they got here the temperature outside went up to 107F, I think that is about 45C.  So it is very hot.  I have little experience grafting citrus, but I would never graft apples or plums in this heat.
I have 2 broken branches on good citrus that are still attached to the trees they were on and they still look healthy after a few weeks so I think they could be grafted onto 2 of the rootstocks using approach grafts.  I don't usually like approach grafts but it looks like they might work in this heat. 
The rootstocks came in 4 inch pots and I've transplanted them into 5 gallon pots.  I haven't seen any new growth yet and I think grafts might better wait for active growth.  I need advice.

Sorry to hear about the harsh weather and thermostat malfunctioning. Hopefully you have good success going forward. Do you have any specific breeding plans for the citrus stock that you replaced? Also, it might be valuable information to see how long it takes for the Ponciris trifoliata to start fruiting from the growth from the roots.

I am going to concentrate on finger lime x Pt+, and bring in the seedless gene from Kishu.  But while working on these, I'll be growing citandarins, citromelos, and Kumin's F3 C-35 seedlings for working on these later when some winter hardy citrus caviar trees come out of my short-term work,
Also I'll make crosses to comirm or prove wrong that Laaz" FFP is a single recessive gene trait.

In central USA it has been a hard winter.  Local statistics show it was the worst since 1975.  I remember 1975.  In that spring, Dad sold his dairy.  He said it had been the worst winter in his life.
January had record low temperatures week after week.  Then February, usually our worst month, was warmer than usual, fooling some species of trees into starting to leaf out.  Then March was colder than usual.
So my 7 or 8 year old Ponciris trifoliata from second generation Korean P. t didn't leaf out this spring.  They were all dead to the ground.  So after checking on them a few times, they are 6 miles from my home, I gave up on them.  But yesterday I looked again.  All but one of the have come up from the roots.
So It has been 50 years between two Ponciris-killer winters.  And the new growth from roots shows that trees as hardy as pure Ponciris could produce fruit for several years before their tops are killed.  And if on their own roots, they  will come back.
Of course, this assumes weather will continue like the past, which is not a sure thing

As for my breeding stock.  My thermostat got stuck on while I was at work.  I came home to a house that was over 120 F.  All my indoor plants died except a couple of cactus and a snake plant.  All my citrus breeding stock were dead.  They have been replaced.  It wasn't cheap, though members of this forum were generous , charging less than I expected.  And other plants were bought from dealers.  These were more expensive, but a breeder has to have the right plants.

So I will continue trying to breed hardy edible citrus.  Its what I do.  I've lost a few years work, but that's life.

If you don't want to cut off the top, you can induce branching by slicing into the tree just into the cambium with a razor or very sharp knife.  That can cut off the link between the apical dominate bud and the bud just below the cut.  Cut just above the bud you want to make a branch.
I have not tried this with citrus, but it works with various fruits like apples, pears, peached, etc.  I have also done it with a wisteria seedling making EVERY leaf bud branch while other seedlings made NO  branches.
Cut just past the bark barely into the wood.
And get back to us on how well it works,  Just because it works on 99 species doesn't mean  it will work on the one hundreth species.  But I don't see how it would hurt to try.

Turunji x kumquat might give big kumquat.  Maybe a backcross to kumquat. 3/4 kumquat 1/4 Turunji would be more moderate in size.

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.

Does anyone have fruit or seedlings from Laaz's fast flowering Ponciris?   Or scions available next spring?

Welcome to our rabbit hole.  It is  a deep one.

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!

There are enough branches I can try several ways.  So I'll try rooting cuttings too.

There is already a couple of threads on grafting additional rootstocks on a tree to help it grow faster and/or better.  One is "Multiple rootstock grafting" on a non-citrus.  I think there was one on citrus but I couldn't find it.  So I'm starting a new thread because I need advice.
A year ago I bought an Etrog from Logees and got a nice healthy tree but in a tiny pot.  I potted it up but it quickly declined and died.  I think it didn't have enough roots to absorb enough water in the hot dry windy climate here in central Kansas.
So I decided to buy another and graft on 2 more rootstocks.
The Etrog is about 35 cm tall and in a pot about 5 cm square and 5 cm deep.  The rootstocks I have are Citrus x Ponciris but I don't know which variety.  They are a little smaller than the Etrog.
My plan is to plant all 3 in a 3 gallon pot and use approach grafts to join them and cut off the tops of the 2 new rootstocks after the grafts have taken. 
One problem I see is keeping the Etrog alive until until the grafts take.  Another problem is that it is up to 100 F just now and this is a bad time to do all this.
Any advice is welcome.