Citrus > Cold Hardy Citrus

Graft chimeras and hardy citrus

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SoCal2warm:
How much do we know about graft chimeras and hardy citrus?

Graft chimeras are a sort of hybrid, but not a genetic one, between two different species that resulted through grafting, typically from growth offshoot coming out of a graft union area and then separately propagated. The graft chimera is comprised of a mixture of cells between the two citrus types.

There are different types of graft chimeras. The most homogeneous ones, and the ones of most interest are periclinal chimeras, which typically involve a single layer of cells distributed throughout the growth of the plant.

I'm also experimenting with joining together different seedlings together at the earliest stage of their development, so that the seedling sprout consists of a mix of cells from two sources. (This takes some very fine precision and a good eye)

How much hardiness can a cold hardy variety confer to another normal citrus variety when they are part of a chimera together?
Could this be a viable strategy for developing new cold hardy citrus?

From what I've seen, many obscure citrus varieties that are believed to have originated as a graft chimera have not actually been confirmed as being so, so it's not truly known with certainty.
The only way to be sure is if there's obvious phenotypical differences in different parts of the tree, or on different parts of the fruit, but in that case its not a very homogenous chimera, and not a periclinal type of one, which would be expected to give the best hardiness because the cells are more evenly distributed throughout the plant.

Say for instance we had a Satsuma graft chimera together with a Satsuma-trifoliate (citrandarin) hybrid.
The Satsuma-trifoliate hybrid within the chimera system could be a triploid with only one of its three sets of chromosomes coming from trifoliate.*
That could potentially make the resulting chimera nearly indistinguishable from normal Satsuma.


* (This could come about through hybridizing a tetraploid Satsuma with a normal diploid trifoliate, or the pollen may have been unreduced coming from the Satsuma, or the female parent being used could have been a "seedless" triploid, and so any rare seeds that did manage to form would be much more likely to have originated from an unreduced female gamete, since triploid cells that undergo meiosis have a fairly high chance of turning out aneuploid and won't develop. Also, you have to have a non-nucellar citrus variety for the triploid to turn out seedless, otherwise the seeds are still going to form from nucellar tissue even though the zygote failed to develop.)


Prague Citsuma is believed to be a graft hybrid, but it has not yet been positively confirmed with certainty. (A few basic tests were done but were inconclusive)

Vlad:
Is cold hardiness a characteristic of the cells or of the entire organism? If it is a characteristic of the cells, then your idea will not work because the cold susceptible cells will die UNLESS the cold hardy cells can somehow make the cold susceptible cells cold hardy.
I love your idea and wish you great success.

SoCal2warm:

--- Quote from: Vlad on January 16, 2019, 11:21:00 AM ---Is cold hardiness a characteristic of the cells or of the entire organism?
--- End quote ---
Probably a little bit of both. When cells are so mixed like that, many times messenger chemicals from one cell will affect surrounding cells and tissue, and lots of chemical substances are floating around in the plant's phloem, which is the cause of much freeze damage as the phloem freezes and expands leading to side cracks.

I don't think this particular area is really well studied.

Zitrusgaertner:
I can't say if Prag is a chimera or not, but I can say, that it is very cold harda as a whole plant, but leaves are damaged at rather low temperatures. A closer look shows also, that parts of a leave's tissue die earlier than others. The second thig I can say for sure is, that it sometimes produces offshoots that are pure Poncirus. And -last but not least- Prag produces Satsuma-like fruit with no poncirin aftertaste and no bitterness at all.

lavender87:
I just figured it out that there were many other excellent fruits trees can be grown in zone 5-9. Why must it be citrus?

- Persimmon (there are so many types of persimmons fruits, both crunchy and soft also known as astringent and non astringent)

- Jujube (there are so many types as well, good for fresh eating or dried eating)

- Apple (many types, different flavors)

- Pear (many types, different flavors)

- Russian Pomegranate

- Cherry

- plum

- Apricot

- Berries... etc

  I initially plan to grow citrus just to collect leaves for cooking. I found citrangequat grafted on FD Poncitrus rootstock. Leaf does not smell as good as lemon but rather than nothing. I don't care about fruits, horrible taste.

 No more cold hardy citrus. It is just a waste of time, money, effort, soil, space for something inferior. Why could we spend 20-30 years for something taste like sh... Sometimes we tried to self-enourage by considering ourselves researchers, scientists???

Instead I will enjoy other fruit trees in coming years and later when having a chance I will move on my life to elsewhere with warmer weather to grow best type of citrus. Goodbye citrus in the up coming years.

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