speed breeding of trees

[gilbert]

Does anyone have thoughts on how to speed up tree breeding cycles by hastening seed bearing of young trees? I've heard about grafting techniques, cultural conditions, and growth regulator treatments, but I'm just embarking on my research and haven't found any hard information yet. If anyone has any ideas or links, let me know!

If I find anything, I'll post it here.

If tree generations could be reliably shortened to a couple of years seed to seed, I think a lot of progress could be made. Maybe we could get the resilience of long lived perennials with the adaptability of annuals.  

[reed]

What a goofy, very interesting, idea. I have recently collected and planted some huge hickory nuts. Much larger than any others I'v ever seen, larger than most walnuts even. One of the only two of these trees fell in a storm this spring so now that one tree and the nuts it makes may be all there is left. Worse is they are apparently favorites of squirrels so very few are left to be found. And it is growing in a narrow strip between a mowed park and a plowed field so any extras the squirrels bury don't have a chance.

I never would have though it might be possible to speed up how long it takes them to produce, not necessarily for production but just to increase the number of trees that can make them. Assuming those I planed grow, let them do so for two or three years and then graft onto a branch of an older tree? Yep, very interesting idea!

[imgrimmer]

I was told by an german peach/plum/apricot breeder that young trees become faster in maturity when growing in a greenhouse. He managed to grow trees with more than 3 feet within the first year from germination. First flower was in 2nd or 3rd year.
If I remember right walt posted here about peaches that where selected for early maturity. Within 3 generation seedlings became very precocious. Is this right @walt ?
There is a precocious Poncirus which is able to flower and fruit within 1 year.
Chemicals like Paclobutrazol are able to induce flowering in some plant species. I applied it to several plants in my garden to test it. Very few Citrus seedlings flowered in their 2 or 3 year. but at least some did. All other plants showed more or less negative response to it. I am sure it all depends on the right application but results are species related too.

[walt]

I remember that peach breeders in California, where the growing season is long, developed a breeding population that started production very early. I think it was in their second year. That might be as little as 24 months if they used embryo culture to avoid the mid-summer embryo dormancy that some species of the Prunus genus have.
For plums and apricots, I have bought a Prunus maritimus selection that Oikostreecrops.com say blooms in 1 year from seed. The seedling I bought didn't bloom in one year, but maybe next year. Oikos says that 5 seedlings out of thousands bloomed in one year. So they saved and isolated those 5 and they bred true. That sounds like a single gene mutation to me. So I want to breed it into apricots to speed up generation time in breeding apricots for later bloom. P. maritimus blooms as much as 6 weeks later than most apricots, so the seedlings from Oikos seem like the perfect match.
I have read some papers online about growing seedling apples in greenhouses with optimum temperature and daylight hours to get them to bloom in as little as 2 years. That seems wrong, since it is easy to find online how many hours a given apple variety needs to break dormancy. That has been well studied. But it appears that if apple seedlings are given the best temperature and daylength, they don't go dormant in the first place, and go ahead and bloom.

[walt]

Found it.

www.actahort.org/books/56/56_21.htm

It took a while.  All the new research on precoccious bloom in apples deals with hormones and gene control.  I'm too old to start learning that.  And/or too poor to afford those methods.  Not that greenhouses are really cheap.

[jocelyn]

A well grown seedling chestnut, castanea, can have a scion taken just before its second leaf and grafted to a mature, blooming age
second tree. Many (some) will bloom the year placed, male flowers only. My personal experience is the other way around, placing a scion from a mature tree onto a well grown established tree too young to bloom, and having the scion bloom. Others have told me about the seedling blooming as a scion placed on a mature tree. It sure would speed up the generation interval, grin.  There was quite a discussion on the American Chestnut list the other week.

[walt]

When looking for the link I posted, I came across a paper that said there are 3 stages, juvenal, transitional, and mature.
Mature, of course, is when they have started production, and will continue to produce as long as conditions are right.
Juvenal is where they won't bloom no matter what is done.
Transitional is when treatments like Jocelyn mentioned, as well as hormone treatments, girdling, etc., can trigger bloom a year, maybe two, sooner than they would have anyway.