The Tropical Fruit Forum

A few days ago I made the 100 mile trip to Hong's Landscaping in Wichita, KS.  It was raining hard but I picked up 1000 fruit of Ponciris from the ground under the 35 year old tree.
Last night I opened 3 fruit and got 109 seeds.  I washed them in two changes of distilled water, then put the seed in hydrogen peroxide where they stayed the night and these I will start to practice micrografting.  The rest I'd like to store until spring or late winter as my space inside is limited. 
So how is it best to store the seeds over the winter.  How do I do it?

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.

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.

Today Citrus Industry news says 50 to 100 ppm improves citrus health including disease resistance and cold tolerance.
It also said several products have come out with silicon at those strengths.  Also said several products already had silicon in them but lumped silicon in "inert ingredients".  Names of such products weren't mentioned,

As a child and young man I kept bees.  I like them and I like honey.  But my citrus "orchard" is on the edge of town ad bees close to a population of humans seems a bad idea.  I know at least one neighbor who is allergic.  So I'm thinking of buying a start of  native stingerless bees.  I know that some temperate zone fruit orchards are using them with good results.  Are they being used successfully with citrus and other fruits?
And as a breeder who wants masses of crosses, I'd like bees to do some of my work for me.

II have read that lemons and limes in general have only nucellar seeds.  Are there exceptions? 
I understand that Meyer and  Ponderosa are zygotic but not true lemons,

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.

I have over 100 Poncirus seedling from 7 years old to new seedlings started last fall.  None have been pruned as I wanted all possible growth to go toward making a big healthy root.  But really, 7 years is a bit much.
I don't think pruning now would be good.  I think it would stimulate new growth that wouldn't be well established for winter.  Winters here get down to 0 F, or about -18 C.
But come spring, what would be a good plan for pruning?  Cut back lower branches, I would guess, as the lowest branches are 1 cm or 2 cm above ground on some of them.  Some have been pruned by deer, which I'll be dealing with.  And should I not take off too much in one year.

And should I prune those special ones I got for breeding differently than those to be root stocks?  The breeders I want to bloom as soon as possible, the root stocks may never bloom, as far as I care.

I'm asking here because it seems Poncirus pruning in zone 6 isn't a hot research topic.  If anyone on Earth knows how to do this, here is the best place to look.

As it says in Game of Thrones, "Winter is coming."
Actually, winter weather is already here, and it will stay a while.
So, how do more experienced people care for their citranges, citandarins, and citstuff that you are overwintering.
I know some of you live where they won't even drop their leaves and require no care over the winter.
Some of you live where they do drop their leaves, but require no special care over the winter.
But mine must come inside or they will never make it to spring.
I left mine outside until they dropped their leaves, then brought them into a cold basement.  I have lights on them, but not enough to do any good.
In the past I kept them in an unheated greenhouse, where the got some light freezes, but never lost their leaves,  But the greenhouse burned.  California isn't the only place with wildfires, through my fire was nothing like theirs.
I had hoped to have a new greenhouse by now, but it will be another couple of months at least.

It is frustrating, though sometimes necessary, for breeders to grow breeding stock for years before actually making a cross.  So how about including pollen here?  I might start by suggesting that same rules should apply as for seeds, as I'm not absolutely sure that pollen can't spread virus.  I'm sure they don't spread insects, at least.
I can see that sometimes an inexperienced person might harvest unripe pollen, or not keep it dry enough.  And how to quantify the amount of pollen.
Comments?

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.