You should search for good cold hardiness among the trees that survive as high up the mountains as possible

I would imagine that it would take several thousand seedlings for just one tto show up with the genes to survive cold temperatures.

And then the time to grow them to maturity and find viable seed or asexual propagation tolerance and then caffeine retention.

To get an idea of what it takes, read about the rhodie breeders of ~a century ago and what they did simply for color variation in a polyploid plant.

Totally possible! Caveats though...
The biggest gains in cold hardiness are going to originate from existing genetic material. Basically, your initial breeding stock needs to be pre-selected for cold hardiness. Your job will be to reduce cold hardiness variability in the species through selective crosses. The biggest gains will be in the first few generations. Further crosses will have diminishing returns because you will be increasingly dependent on random mutations which happen around evolutionary time frames.

So...biggest gains will be within the existing variability of the species.

To answer your question: yes, I think of the camellia and gardenia (as well as other plants) breeding that has been going on. Upon introduction into this country, only the semi-tropic regions and warmer could cultivate these two shrubs. Now both have cultivars that are able to resist colder temps (below freezing) pushing the growing zone limitations.

While I am not aware of the amount of r & d that breeders are putting into coffee trees, I suspect if enough work is applied, a more cold resistant plant may be developed.

As as a side: coffee trees make easy houseplants. I have an arabica that I purchased from a box store for a conversation piece and I have had to cut on it 3 times to keep in the room! Given enough sunlight and it will grow at least 8 feet tall and produce coffee beans! So if you a spot in the house, give it a try.

Breeding is tricky business & has consequences. All the "new" butterfly bushes -- white, red, deep purple, look different. But they all seem to lack or have less of the wonderful smell, and don't attract as many insects.

I think that with most trees, the time span of the experiment would by well over a 100 years as you would not know if the tree was truly change or not until it had become mature. Mature is more than a sprig 3 or 4 inches in diameter in your front yard.

To know if you really changed the tree you would need to grow a couple of generations of the tree to maturity, in several areas, That could be as long as a couple of hundred years for most trees.

I think beng brings up a good point....even If I do find a coffee plant with hardiness it might not have all of the traits I was looking for..like the ability to produce coffee beans.

I am wondering if splicing some genes into a coffee embryo would be easier? Not sure what kind of equipment I would need or how to even find genes that contribute to cold hardiness in some other plant like a sugar maple for example.

I read that with the american chestnuts some embryos were spliced with wheat genes that provide resistance against fungi. Those chestnuts are currently planted near the bronx zoo in New York and are free of blight. So if that can be done I don't see why I can't do something similar with coffee and cold hardiness.

I am wondering if splicing some genes into a coffee embryo would be easier? Not sure what kind of equipment I would need or how to even find genes that contribute to cold hardiness in some other plant like a sugar maple for example.

If you were a billionaire you could do that at your house. Otherwise not gonna happen.

Yeah, you are looking at an incredibly long period of time to selectively breed anything into coffee. It takes 4-6 years for the new plant to get big enough to bear more seed. So lets say average of 5 generations.

For pepper plants, it takes a minimum of 8 generations just to stabilize a new strain after you get it set the way you want it before its recognized as being a legit new strain.

For a coffee tree, thats 45 years of work *AFTER* you get the plant you want. It could easily take another 50-100 years' worth of breeding to even reach that point.

Even ignoring the timescale, the only way you could really do it is to plant out huge amounts of the plants, and completely control the temperatures they are exposed to (unless you just feel like moving your entire operation a hundred miles north every 5 years or so), because you have to have it cold enough to kill the less hardy ones, but not cold enough to kill the more hardy.

As far as gene splicing goes, that simply is not something an individual can do at this point. You would need millions of dollars for the equipment alone, not to mention the time and money required to get the doctorate degrees required to run the things properly.

If you want to breed a new strain of something, pick a plant that has a generation measured in months, not years.

Ive read of someone doing this by slowly (over 20 years) exposing the plant to colder temps, forcing the pups to climatize. This was done with an aloe,which profusely produces pups rather than seeds which would take longer to produce adaptation.

This coupled with the selection of hardy plants in general MIGHT eventually produce something, but the way I mentioned was again used to produce vegitative adaptation, not seedling hardiness which is done by crossing hardy cultivars as well as adaptation to slightly colder areas over a long period of time (decades or a century who knows).

Not only is this issue similar to what the rhodie breeders did a century ago - it is different from the rhodie problems in that the light quality and duration in the tropics is different than at higher latitudes.

So not only do you have to breed a polyploid for one trait that lasts and can be selected across a generation of 4-8 years, now you likely have to select for a second trait for light quality and still have these two traits produce a bean that has the same compounds as in a completely different environment.

I'm sure someone at Kew or some such place thought of this 100 years ago and there is still a small program soldiering on somewhere.

Yeah. Coffee is a *HUGE* cash crop world wide. I think its safe to assume that the big international companies have been looking into ways of growing it in colder climates already. Fact that its still limited to equatorial regions even after a couple centuries of cultivation for Europeans probably does not bode well.

Yeah I thought about those international companies already....I am sure this idea has crossed their minds.

Getting back to coffee I read that its native to the highlands of Ethiopia so would elevation be a draw back. I mean if I planted the coffee at a lower elevation would it still be able to function?

At present it probably does not make economic sense, but theoretically at least, gene splicing could be used to create greater hardiness in just about any plant. No need to wait decades for results like the early rhododendron breeders or years more to build up stock via seeds or asexual reproduction. Gene splicing plus tissue culture would mean tens of thousands of new super hardy plants available very quickly in our brave no-longer-quite-so-new world.

You could look at something co operative based too...like many tree breeders do. You start your project, and then give away seeds for a small donation. The new growers sign a growers' agreement to do whatever is needed...you need to think about it before drawing one up. They grow your plant a few miles more to the north/at the edge of hardiness. You have access to their seeds from survivors. If many people do this, there will be a LOT of selection going on and much seed swapping. The limits will be the variation that occurs to select on. This is already happening with sweet chestnut/american chestnut and white elms. If you don't need the controll of a growers' agreement, you just do it informally on the honour system....all to share seeds.

Jocelyn

You have two issues: You want to keep genetic variability. You want to increase cold hardiness.

I suspect you want to start like this:

1. What is the variabiliy in cold hardiness at present? Suppose that it ranges over 3 zones. Take plants from the coldest zone. Sprout lots of them, and expose them to 1 zone colder You will have a lot of die off, but you will probably have 5% or so that survive. Breed these. Repeat.

2. At the same time find other plants in the the genus that arabica can cross with. Treat these the same way. Breed back for flavour once you have a hardy bean.

This is how we have prairie hardy apples. M. domestica varieties here have a fair amount of M. baccata (siberian crabapple) in them.

Cold hardiness is probably more than a single gene, but is rather a whole complex of genes. Some involving timing, some involving chemicals, some involving dormancy triggers. This is one reason you want to maintain a substantial population in your research.

But it is working. American Chestnut used to be a zone 6 plant. Now there are zone 5 varieties, and some chinese hybrids that can do zone 4.

I am bored so I am gonna take an amatuer crack at an answer. They grow these plants in some really remote places with very specific conditions. I think that it would take alot of work to produce the right conditions, soil, weather and some artificial means of altering the light amount and a lot of time trying to alter hardiness, but may be possible. I would think that with increased hardiness, flavor would suffer. Some millionaire may be able to fund this type of thing, I'm thinking large greenhouse, special soil blend, air circulation adding humidity, false rain, extra false daylight. Likely too expensive to make a profit for many years, until someone finally may get things right. Poaky1 with nothing else to do tonight.

Since then I've been reading about cold hardiness. It's not simple:

1. Trigger the dormancy process. Some plants do this on temperature, some on daylight. Both have slop, and are themselves multigene operations. A plant in Virginia may have 2 months more nice weather at the fall equinox, where here in Alberta, the first killing frost has probably already happened.
   
2. Water removal from tissues. While you want the plant as a whole to go into winter well hydrated, many plants winterize by pulling water from their cells. This leaves a stronger solution in the protoplasm that has a lower freezing point. This confers 10-20 degrees of frost protection.
   
3. Antifreeze in the tissues. Some plants mak alcohols and glycols. These further lower the freezing point, and interfere with the creation of ice crystals.
   
4. Protection of buds. Not only is winter cold, but long. Buds can dehydrate to the point of being non-viable. Sunny days just below freezing are the worst for this. The roots can't supply water that warmer temps pull out. This does in cedars, particularly ones on the south side of the hosue.
   
   My feel is that you can probably breed 2-3 zones colder with patience and interspecies cross breeds. But if you can find a member of the genus that has the trait you want, and will produce a non-sterile hybrid you have cut a job of centuries down to mere decades.
   
   The creation of northern apples is one such story. U Saskatchewan's work with hardy sour cherry is another. The cold tolerance comes from a mongolian pea cherry with tiny fruit that taste awful. Cross it with a decent cherry. Cross the off spring. Select for cold hardiness and taste. Repeat.

A cold hardy coconut tree would be great!

I know, and a cold hardy Mandarin orange tree too. I have a Dwarf one in my greenhouse, but, the fruits can only get a certain size or the fruits will be too heavy for the small sized tree/shrub to hold. There's a tree that I saw in Florida that makes small slightly fuzzy fruits that look like apricots but aren't apricots, they have the canned version of them on Chinese buffets usually. I'd love to grow that tree the fruit is great. The leaves are about 6-7 inches long and lancelate shaped. Or a simple leaf shape, no lobes or fancy shapes. The pit is pretty big and easy to remove. Maybe Lychee or Longon, I'm guessing.

if you cross a mandarin with trifoliate orange you might end up with a zone 6 ish edible orange after awhile

if you cross a mandarin with trifoliate orange you might end up with a zone 6 ish edible orange after awhile

No you won't. it's safe to say after over 100 years of people trying, you don't end up with anything that most people would call edible with a primary trifoliate orange hybrid.

There was a company in the DC area that was trying to do this about 15 years ago (genetic engineering of plant hardiness). It folded, although the good news is (according to the founder who I used to know) is the mechanism of plant hardiness and the genes involved is, to some degree, quantified. I guess with CRISPR it might be more feasible these days. Even with CRISPR it will be very expensive in terms of human capital costs, and for the foreseeable future it will be a handful of crops that would get any cold hardiness research, if any do. There would seem to be far more pressing problems in agriculture RN to address with gene editing, like the on-going collapse of the Florida citrus industry due to huanglongbing disease.

If anybody cares, it was a Loquat tree that I wish I could find a hardy version of, and that I picked fruit off of in Florida. Not likely I'm sure. If they had a dwarf variety I could pot up and keep in my greenhouse, I'd try it.

wonder what the name of the company was called?...just curious....anyhow with Loquats it seems they flower in winter so that may be a problem in a colder climate. You would probably not get any fruit.

It turns out it isn't a Loquat tree that I wanted the fruit of, but, a non citrus fruit. I got my Dwarf owari mandarin from Citrus.com though. My greenhouse has been warm enough for my Dwarf Calamondin orange to fruit though. Good for squeezing the juice into tea, too tart to eat. I hadn't known that before I bought it, but, still now I know that citrus will be fine in my Gh in winter.