F2 citrange winter hardiness trial

[Ilya11]

For me the main problem is very mild winters that we experience recently. I am overwhelmed with hybrid seedlings so this season decided to experience with artificial freezing. For the moment have some encouraging results of freezing two month old hardened seedlings at -8C for two hours, approximately 20% of them survive, some without any damage.

[kumin]

Excellent point, Ilya. I'm probably overthinking this. The idea of cold testing seedlings at an early stage would certainly screen out excessive numbers of tender seedlings. I was thinking of testing chambers for large seedlings, which seems impractical in my situation.

However, pre-screening small seedlings would be a quick, contained process. A freezer with a thermostat and timer sounds easily doable. (The timer would be for me, so I don't get distracted)!

Most years we will have opposite challenges, in your case, eliminating marginal plants. In my case, not having the exposure so severe as to eliminate all seedlings.

[kumin]

The month of May is proving to be payback for the winter we escaped. Southeastern Pennsylvania hasn't been spared in the present Arctic cold wave. Saturday had light snow flurries during the afternoon.

I don't usually make much distinction between frosts and freezes. Subfreezing winds, however, can't be ignored. There was ice in unprotected shallow water and even a crust of frozen soil in freshly disturbed, exposed surfaces.

There is more Spring cold damage on Poncirus, than I have ever seen previously. The outdoor Conestoga # 011 damage paralelled that of Poncirus, but was not more severe.

[Millet]

From what you wrote, it seems that the previous warm weather brought the trees out of dormancy, and then the cold snap was able to do the damage.

[kumin]

Yes, they're in active growth as are many other trees. Peaches appear to be a total loss for the year. Strawberries at an 80% loss with two more nights of low temperatures, tonight and tomorrow night.

[SoCal2warm]

Yes, they're in active growth as are many other trees. Peaches appear to be a total loss for the year.

Well, there is a reason peaches were considered a Southern crop and not something for Pennsylvania.

[kumin]

Growth habits of several Poncirus/Poncirus hybrid seedlings:

Poncirus +: nothing remarkable noticed in plant habit


5* Citrumelo: densely branched, strong tendency toward being  evergreen,  stocky plant, sturdy trunk develops early, height shorter for age





TaiTri: slender wispy branches, tendency for branches to droop over. vigorous, but not stocky






Conestoga plant awaiting a number, dense branching, a bit like TaiTri in growth habit



Conestoga 006 



Conestoga 058: monofoliate plant, the most Citrus-like in appearance, a bit less hardy, a few bifoliate leaves, slugs favor this clone. Very strongly evergreen.


Original 058 plant, good vigorous growth, upright growth habit.


Conestoga 010: deciduous, hardy plant, small  leaves.



Conestoga 011: deciduous, very hardy plant, strong, open branches. Twin thorns frequent, small-medium leaves with wavy edges.

[kumin]

400 of 800 Poncirus seedlings to be budded/grafted as soon as the caliper increases a bit. At this stem diameter any budding/grafting would take very steady hands and very good vision! Fortunately I'm near sighted, removing my glasses will put these right in my focal range.

The bark may be a bit too fragile to allow much manipulation, however. The buds/scions would also need to be of a similar tiny diameter.

[Ilya11]

Around 500 seedlings to be grafted?

[kumin]

There are more than 800 ready this summer and next summer. I will have a bit of a challenge to get them all completed. I hope to do serious outdoor trials of all the clones I presently have. I have a nephew located 320 kilometers (200 miles) south of my location in zone 7b. He's agreed to trial some of my grafted clones at his location.

 In addition, there are several hundred original seedlings that were neglected, but survived in the original field trial beds. These had little to no damage during the past mild winter. I've weeded these beds and will give these plants an additional winter trial to test their hardiness. Some of these are starting growth in the last few days, about 10-14 days later than Poncirus. They are a mixture of evergreen and deciduous plants. Finding these plants, some of which had no dieback was a pleasant surprise. The low temperature during the winter was +10 deg. F (-12.2 C).

[Millet]

Quite some trialing.  Wishing you and all of your seedlings  the very best.

[mikkel]

I like your work!
+10°F was the average low for my area some years ago. In the last winters it is around +21°F (-6°C).
These second survivors might be already hard enough for my climate.
How many survivors are there now in total?

[kumin]

Mikkel, I don't have a count, I will probably wait until all of them leaf out. There may be some that will fail to do so. I think there should be a minimum of 100. In about 2 weeks I should have a better idea of the numbers. It is quite possible that many of them will fail in a severe winter in this area. That's the reason a test in zone 7b is being planned.

[Jibro]

Growth habits of several Poncirus/Poncirus hybrid seedlings:

Conestoga 010: deciduous, hardy plant, small  leaves.



Conestoga 011: deciduous, very hardy plant, strong, open branches. Twin thorns frequent, small-medium leaves with wavy edges.

These two looks almost like pure poncirus to me, the leaf in the middle is shorter than usual F1 hybrid with trifoliate, the same cold hardiness as poncirus is another sign, that these are much more close to poncirus than orange...
Conestoga 011 reminds me one of my Tetraploid poncirus, shorter  petiole, wider leaves with wavy edges are one of the sign of tetraploid.

a| Tetraploid poncirus, b| regular diploid poncirus

[kumin]

Jibro, since the F2 generation is genetically still quite close to the original parents, it stands to reason that the progeny most closely resembling either parent, will likewise have hardiness and fruiting characteristics similar to that particular parent. An honest assessment would likely conclude, that the most likely use and value of these plants is as parents, on the way to further refined and improved selections.

[kumin]

Around 500 seedlings to be grafted?

Actually more than 800 (rootstocks, not scions). There will be multiples of the more promising scions.

[Ilya11]

You will do it alone?

[kumin]

Yes, I'm semi-retired and this is my only real interest. I've done many grafts and buddings since I was a teenager. So I'm actually looking forward to this. Some people gamble, some travel, some follow sports, I immerse myself in horticulture.

[kumin]

 Two additional monofoliate plants.

Conestoga 064 rather large leafed, sparsely branched. There's an occasional bifoliate, or trifoliata leaf.


A different plant having slender, dense branches and small leaves. This plant was initially trifoliate.

[mikkel]

beautiful! I like the narrow leaved types the most. Interesting to see that you have exactly the same herbs around like I have in my garden half way round the world

[kumin]

Yes mikkel, many, but not all of our weeds have European origins. The early settler's plants didn't arrive with phytosanitary certificates.

[kumin]

Growth habits of several Poncirus/Poncirus hybrid seedlings:

Conestoga 010: deciduous, hardy plant, small  leaves.



Conestoga 011: deciduous, very hardy plant, strong, open branches. Twin thorns frequent, small-medium leaves with wavy edges.

These two looks almost like pure poncirus to me, the leaf in the middle is shorter than usual F1 hybrid with trifoliate, the same cold hardiness as poncirus is another sign, that these are much more close to poncirus than orange...
Conestoga 011 reminds me one of my Tetraploid poncirus, shorter  petiole, wider leaves with wavy edges are one of the sign of tetraploid.

a| Tetraploid poncirus, b| regular diploid poncirus

Jibro, I took a few minutes to examine Conestoga 011 in some detail and must agree that the petiole is shorter than the other plants. It appears to be only +/-  30% of the length of Poncirus petioles. I'm not certain this is a positive for my purposes, although if it's truly a tetraploid, I suppose triploids could be created at will. I will need to research how to get the ploidy tested at some point.

[Jibro]

You can read about Tetraploid plant identification here: http://tropicalfruitforum.com/index.php?topic=24488.0

Chromosome counting can not be done easily without special fixings, stains and rather powerful microscopes.
The easiest "kitchen" methods for ploidy determination is comparative measuring of leaf stomata replicas
with the help of nail polish (colorless) and a microscope (x40 - x100 will do). You apply the nail polish on a clean dry leaf, wait for it to dry and the peel it off. Afterwards you mount the peeled nail polish on a slide and cover with glass slip.

I've been thinking about crossing Tetraploid poncirus with regullar poncirus, both with better taste and select triploid seedless more edible poncirus, but I am not sure if it's possible without in vitro technic Embryo rescue and how to idntify triploid one...
Your Conestoga 011 may be good seed parent for similar purpose...

I may have several tetraploid poncirus seedlings and two poncirus clones with better taste have also short, wide petiole: " Sladka" and "Poncirus Plus"






"Sladka" also have very thick and bumpy rind, this should by another sign of tetraploid:

[kumin]

Very interesting post, jibro. Do you do Citrus breeding? If so, have you developed any selections?

[SoCal2warm]

I've been thinking about crossing Tetraploid poncirus with regullar poncirus, both with better taste and select triploid seedless more edible poncirus, but I am not sure if it's possible without in vitro technic Embryo rescue and how to idntify triploid one...

It's both easily possible to make a cross, and easy to identify the triploid by its fruits. Triploids will be relatively seedless (or at least obviously far fewer seeds, sometimes tiny shriveled up seeds).

(Of course, you will actually have to grow the seedling until it becomes big enough to fruit, to determine that)