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Topics - Walt

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https://pubmed.ncbi.nlm.nih.gov/26920394/

The above link takes you to a research report on a viral vector that contains a gene that can make a seedling bloom in less than a year.  The virus is transmitted by grafting a seedling onto a stock that has been lnfected with it. 
This is then not transmitted via pollen, and rarely via seed.

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Cold Hardy Citrus / new thoughts on breeding hardier citrus
« on: November 04, 2021, 04:56:23 PM »
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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Cold Hardy Citrus / information on Taitri and (Clem x Tri) x Clem
« on: November 08, 2019, 04:21:07 PM »
I have several seedlings of Taitri and (Clem x Tri) x Clem.  I'd like to know more about them. 
Are they the only seedlings from the crosses that were made?  Or were many seedlings grown from the crosses and these plants, Taitri and (Clem x Tri) x Clem, and the plants that now exist under those names selected for hardiness and/or quality.
Should I remake those crosses hoping for variation to select from, or did the origional breeders of these plants already do that?

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Cold Hardy Citrus / Pruning Poncirus for root stocks
« on: July 26, 2019, 04:03:41 PM »
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.

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Cold Hardy Citrus / Winter twig die back.
« on: July 26, 2019, 03:40:05 PM »
I am growing many Poncirus seedling, some for pollen or seeds for breeding.  Most are for rootstocks for grafting.  When they were leafing out this spring, I noticed that many had twigs that had died back some, mostly 15 cm. to 30 cm.  That is just the amount of die back, not size of the seedlings.  Some of the seedlings have been through 7 winters here, and more have been added every year, in hope that I'll some winter hardy seedling to graft onto them.
Several of the seedling had no die back, but nearly half did.
Its not a big deal if a seedling for grafting has die back before grafting.  But when I do graft onto them, 30 cm die back means the scion is dead. 
So what is causing this die back and what can I do to prevent it?
I have seldom lost a whole tree to winter kill.  It seems to me it is only one summers growth I am loosing, maybe less.

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Cold Hardy Citrus / Winter care of citranges, etc.
« on: November 16, 2018, 12:32:31 PM »
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.

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Citrus Buy, Sell, & Trade / citquats
« on: September 30, 2018, 03:31:49 PM »
Does anyone have, or will have later in the fall, seeds from citquats?

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Citrus Buy, Sell, & Trade / Buy, sell, or trade pollen here?
« on: May 07, 2018, 03:18:03 PM »
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?

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Well, the title says it all.  I'm looking for Laaz's precocious P. trifoliata to in hopes of speeding up my citrus breeding.  PM me with price etc.

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Cold Hardy Citrus / 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.

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