Breeding new genetic dwarf stonefruit

General Fruit Growing
#1

I’ve been growing a Sunset series nectarine (a genetic “super dwarf”) for about 4 years, it’s low chill (good for my area), has beautiful dark purple foliage, grows only to a top height of about 80cm, flowers heavily with rich pink flowers, and sets a lot of good tasting fruit (though it must be said, not that much better than a good store bought nectarine).

I figured it’d be a perfect candidate for breeding some new genetic dwarf stone-fruit, and so set about testing it by crossing it with my White Opal peach to see how well the dwarfing trait carried forwards, as I couldn’t find any data of people breeding with this specific line…

I chose the W.O. Peach for two reasons, one: it grows some of the best peaches I’ve ever tasted, and two: peaches and nectarines are basically the same species (only a few genes of difference), and so would cut down on pollination incompatibility in my tests (I didn’t have another nectarine at the time).
A note: All crosses were Sunset Nectarine x W.O. Peach

I made the first crosses about 2 years ago, with the seedlings now being about a year old here are my current observations:

  • All seedlings carried the purple leaf genes to some extent, with some being a little darker, some being a little lighter
  • All seedlings carried forwards the dwarfing genes, as evidence by their small first year size, and noticeably tighter inter-bud distance
  • High precociousness observed, as some are flowering in their first year (I’ve labelled these for further development).

Here’s a (blurry, sorry) photo of one of the flowering ones:

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Note the red/purple leaves just shooting, and the two flower buds swelling, as well as that super high bud density.

I also created a second set with the same parents last year, with those having sprouted in June I have noticed what appears to be the same traits in about the same mix - always nice to be able to reproduce results!

This year I’m hoping to aim high, and attempt to pollinate with Fireball Apricot.
Both species are typically diploid with 16 chromosomes, and are both self-fertile, so it should be possible, if difficult for an amateur to get the cross to take.

I’d love a little sunset nectacot, and will update folks as it progresses.

edit: I’ve just received a papershell almond and will be adding it to the dwarfing trials too!

Anyone else doing any breeding with genetic dwarf/super dwarf stonefruit varieties?

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#2

I looked into genetic dwarf peaches a few years back. I had a few threads on them back in 2020 I believe. Issues I found was the genetic dwarf peaches/nectarines are not hardy to lower zones regular peaches are hardy to. A regular peach will often times be hardy to zone 5 with some exceptions but a genetic dwarf peach will be hardy to zone 6 and up. Nectarines are a little less hardy than a peach with many going zone 6 and up but a few ending in zone 5. This actually translates into many genetic dwarf nectarine only being hardy to zone 7 and up though. Those are the main stone fruit without a dwarfing rootstock. Cherries I know have dwarfing rootstocks. I have not looked into apricots too much to see if they have a dwarfing rootstock or not.

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#3

Thankfully I’m a Zone 9a equivalent, so I’m actually hoping for lower chill requirements!
Apricots do have some dwarfing rootstocks available but from what I can gather they’re both not very common, at least here in Australia (dwarfing cherry rootstocks are also scarce around these parts), and quite large still (~3-4 meters + 3.5m wide) compared to the genetic dwarfs (1.5m x1.5m max).

There’s definitely a lot of work to be done to improved the genetic dwarfs, but that’s exactly what I’m hoping to do, haha

#4

in case you missed it, here’s some history of genetic dwarf peach breeding:

I think the genes responsible are well understood, for example “dw” (recessive), and shown in mapping studies like this one:
https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.13772

so someday it should be possible to turn on dw in existing peaches, once someone figures out peach transformation (editing and regrowing a peach with the edits preserved - not yet demonstrated for peaches, but demonstrated for many other plants). in the meantime your breeding efforts are cool. are you doing anything to help germination, like extracting the seeds from the pits?

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#5

Those are great resources that I’ll definitely be reading through a few times!

My germination process has been pretty standard really, remove the seed from the pit, stratify in a resealable sandwich bag filled with vermiculite (and a sprinkle of water) for ~3 months (or until I see it sprout).

My germination rate has been nearly 100%, but my post-germination success (continued healthy growth after planting) is more like 50/50.
I’m using a high vermiculite, real soil potting mix that works wonders on apple seeds, but I’m starting to suspect isn’t great for stone fruit- happy to take advice what to improve there!

#6

Schme16,

Interesting plans. But I wonder about the logic of dwarfed peach trees. I fertilize my trees to get a lot of new growth.

Peaches need vigorous growth to replenish fruit wood each year. I have 3 red haven’s, standard size. I keep them at 8 feet but I could have kept them at 6 feet.

Last years fruit wood is loaded with peaches and hanging down. They will be removed next spring. This years new growth, next years fruit wood and there are many hundreds of them, are standing straight up. The new fruitwood number will be reduced and the remaining will be shortened. The cycle goes on if you have rapid growth.

The issue with old peach trees is they lose the vigor.

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#7

As a backyard home grower of fruit I dislike prunning and trying to protect large trees from birds and squirrels. Small trees can be bagged. Dwarf trees also allow for more variety in a small area. Once a tree is established I want slow growth.

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#8

do you have any practical tips on removing the seed? I’m trying to improve my rootstock germination and was going to start but haven’t tried yet

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#9

These natural super dwarf varieties are a little different from standards/semi-dwarfs, in that they are specifically best left unpruned, and still bear prolifically, something to do with the ultra low inter-bud distance I’ve been told, so even a few centimetres of growth per year gives a huge amount of new buds, and old buds flower with nearly the same regularity as new ones; and because of the high bud density the branches are much thicker than normal, and so keep their shape with ease.

Their real issue is that the total lifespan isn’t as long, I’m told that it’s around half as long as it’s parent varieties (15-20 years is the best I can find on my sunset series, but so much is hidden behind pay-walled journals, and trade secrets).
But as @danzeb said, the dwarfing is less for long term planters, and more for space conscious, or high variety conscious folks, or (as is increasingly becoming the norm) renters, who cannot make permanent changes to the house/unit/etc, and must pot their trees- super dwarf varieties excel even in small pots, whereas dwarfing rootstocks like large pots, or to be planted.

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#10

You’ll laugh at me, but my method for extracting the seed from the pit is:

  1. Remove any pulp/flesh from the pity, and scrub it with a hard plastic-bristle brush
  2. Place it on paper towels in a dry shaded spot for a few days to fully dry out
  3. Take the pits down to my shed and place them into my vice with the seam touching the jaws (this is important!)
  4. Place my fingers top and bottom and start to tighten the jaws until I hear it crack (fingers help stop the jaws crushing the seed when the crash happens all at once)
  5. Done.

It’s pretty caveman style, but has worked very well for me over the last couple years.

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#11

I use the same procedure. It gives good control of the splitting process.

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#12

Technically the pit is the seed. What you are doing is a partial embryo extraction. I am guessing that you routinely just plant the partially extracted embryo as you would a seed, maybe with some refrigerated stratification, then water it and hope for the best.

You could bypass stratification and cause the embryo to germinate in a few days by further removing the testa, the brown paper-like coating around the embryo. I’ll send you some instructions if you pm me with your email address.

my method for extracting the seed from the pit is

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#13

Sounds great!