Hybridizing stone fruits

[Auburn]

I'm excited as I will be getting fruit off a raspberry hybrid of mine this year

Looking forward to seeing pictures when it fruits

[Auburn]

I only stored my pollen last year just long enough to pollinate my immediate needs. I'm going to store some this season so it will be available on demand.

[bradkairdolf]

@Drew51, what do you use for brushes? I've used regular paint brushes for hand pollination (not caring about specific crosses) and that works very well. Too well I think for planned crosses because the pollen is extremely difficult to remove. I'd think you want something clean for each cross so there is no cross contamination (no pun intended!).

[Drew51]

I talked to Pete Tallmen the breeder of Niwot Black raspberry. He sent me instructions from a horticulture professor on how to grow seeds. With brambles getting the seeds to grow is one of the hardest parts! Both Tallmen and the professor said that first year plants need to be protected for the first winter. Most of mine did, but one did not, it grew 3 feet from seed. I ended up losing the others when I had to go away for a couple weeks, but this fast grower was fine. It is unheard of that from seed a plant would be big enough to plant out, but mine was. Why I'm excited about it. I looked at it and buds are swelling. It made it through the winter planted out the first year. The canes are not impressive, but the fact it has 3 foot canes is amazing in itself. Chills (Scott) was over here the other day and noticed a new cane emerging from the plant. The first of all my raspberries this year to already have canes starting.

[Drew51]

what do you use for brushes? I've used regular paint brushes for hand pollination (not caring about specific crosses) and that works very well.

Yes, that is all I use too, I use a thick blunt camel hair paint brush. About the size of your thumb, the brush part. It's a little big, but seems to really grab the pollen. Yes, you need a brush for each pollen if you are trying to do a specific cross. What I do is use a brush for brambles, then use it for stone fruit next, as the raspberry pollen is not going to do anything, so I can use them more than once. If you soak the brushes and scrub them with a dish washing brush you can clean them. You hit on something important about contamination of the brushes.
I too do mostly hand pollination for fruit, not crossing with stone fruit. Reminds me though I could use a few more brushes to make sure I have all I need.

Also when collecting the pollen if a few flower parts get in there, I just leave them, it doesn't hurt anything.

I use a utility blade to emasculate flowers, not in the holder, but use the razor blade by itself. If you cut a little deep, it's usually ok as the calyx protects the ovaries.. After a while you get a feel of how far in to cut the pedals and male parts off. One girdling cut usually does the job. It's fairly easy to do with practice.

[bradkairdolf]

I use a thick blunt camel hair paint brush. About the size of your thumb, the brush part. It's a little big, but seems to really grab the pollen

I use basically the same thing and agree. It grabs pollen really well. I'm slowly expanding my stone fruit collection so I might try to do some specific crosses in the next year or so, especially if the new varieties I got this year take and grow well. I may start looking around the house to see what might be suitable as a pollination tool. I'd prefer something that is disposable to remove the chances of contamination. Maybe short pieces of clean, nylon twine or something similar that I just throw out after each use.

[Drew51]

. I'd prefer something that is disposable to remove the chances of contamination.

That is a good idea for sure.

When collecting I cut off the filaments with the pollen into a jar, the clumps disperse into grains once dry. Just thought I would mention that. So easy to collect the pollen. Just hold the jar under them and cut.

[bradkairdolf]

Yes, definitely a good idea. Another thought I've had would be to cut a small piece of fruiting wood from the pollen source before bloom begins and bring indoors and stick in a cup of water to force blooms early (I believe Olpea has shown some really nice photos of peach blossoms indoors that he forced early to test flower bud viability while everything outdoors was still dormant). You'd further limit contamination issues and would be able to collect pollen for crosses even if the pollen source is a late bloomer (assuming enough chilling has occurred). It would also give you a chance to dry the pollen and be ready to go for the first tree blooms.

[Drew51]

Wow, you're full of good ideas!

[TheLoud]

I'm excited to see the results of everyone's projects!

A few thoughts: There already is a peach cultivar with an edible kernel, like an almond. I think it's grown in India.

Different ploidy levels are a barrier between Prunus species, but blueberry breeders have similar ploidy issues that they've overcome in various interesting ways. There are many different species of blueberries at various ploidy levels, diploid (various wild species), tetraploid (northern and southern highbush), and hexaploid (rabbiteye.) People have crossed diploid x tetraploid to get a sterile triploid, which they then doubled with colchicine to get a hexaploid to cross with rabbiteyes. They've also crossed diploid x hexaploid to get a tetraploid to cross with highbush.

It would be cool if it were possible to cross some of the really sugary Prunus species, like European plum (hexaploid) with peach, sweet cherry, or apricot (diploid) to get some sort of sugary tetraploid, which could be crossed with tetraploids like the Romance series cherries to get something both sugary and cold-hardy. This wouldn't require any colchicine. Of course, there may be barriers besides ploidy between these species.

The time it takes to grow seeds might be a barrier. Considering that sweet cherry or apricot seeds develop very fast in those early-ripening fruit, and other fruits like late peaches or plums have slower-developing seeds, I don't know if hybridized seeds would develop properly in the time it takes for a fruit to ripen. Zaiger genetics sometimes uses techniques like embryo rescue to overcome this incompatibility, but this is probably beyond the reach of the typical hobbyist.

[Drew51]

I face similar problems with brambles. I found a place that sells colchocine. I may try using it in the future. Seems easy enough to use. I am a professional lab tech, so for most I would not suggest using this chemical.

[bradkairdolf]

Anyone here have luck crossing a plum with peach/nectarine? I have an isolated area that had a single peach and plum right next to each other. Both had nice blooms with a fairly good overlap. There was a lot of activity from pollinators and the peach always had a good fruit set but the plum didn't set a single fruit. After grafting a few pluots onto the plum, it then set well. Maybe it was just those particular varieties. If crossing these species is that difficult though, does anyone here doing interspecific crosses use some sort of negative control to test whether there might be pollen contamination? For example, in the case of a self-infertile variety, maybe using the variety's own pollen on a few of its flowers, where the formation of a fruit would indicate there is contamination from another pollen source getting in somehow.

[Antmary]

I have seen video where they used dark glass from sunglasses. Put the pollen on the dark glass surface and touched pistils to glass. The downside is that there should not be any wind to blow it off.

[itheweatherman]

A member from Dave Wilson Nursery has. He crossed a peach with a plum. He called it Wellmans Delight. The fruit and seed resembles exactly like a plum, except for the foliage. It resembles like that of Citation rootstock.

[bradkairdolf]

I think I found the post you are referring to. Is there another post with more details about the fruit and its parentage? The one I read just said it was a peach/plum hybrid without any other details. The picture and fruit description sound like a plum. I couldn't really see the leaves all that well. I certainly don't mean this as a criticism of his fruit but am wondering what makes him think it's a peach hybrid. Was the peach the seed parent? I guess that gets back to my question. Does anyone use negative controls as a verification that the seeds from the actual crosses are a result of the interspecific cross and not open pollination or contamination?

[Drew51]

Does anyone use negative controls

I'm not sure what you mean, but no. Soon it will be easy enough to DNA test. Many figs have been tested to see how different they are, as many varieties appear to be the same.
Some of the Dave Wilson fruits were tested and I heard some of the pluots were not showing any apricot DNA.

[bradkairdolf]

@Drew51, If doing specific crosses with a plum seed parent, I'd want to control for the possibility of a different plum in the area pollinating it. My "negative control" would be flowers that are treated the same way but instead of using pollen from the pollen parent, I'd brush on either no pollen (a blank) or maybe pollen from the seed parent, assuming it's self infertile. Then bag the flowers like the others. If everything went well, I'd expect those controls not to be pollinated and then I'd have more confidence that the crosses I made weren't from contamination. If some of the negative controls did get pollinated, I'd know something went wrong and the other crosses could be from something else.

[Drew51]

OK, that is a good idea if you want to see if your technique is working.
I never really isolated any of my stone fruit crosses as my goals didn't require it. I have with brambles, and I noticed that not all the drupes were pollinated. A sign no other pollen got in. Also a sign I need to do a better job of pollinating the flower.
A negative control would be useful to see if your technique works, it is well known these methods (bagging and emasculating) do work though. So not sure you really need a negative control?.
I feel interspecific crosses are a rare thing, and if one of us makes one, I doubt I'll see another. I'm not talking Almond-peach, they are very closely related, one should be a sub-species of the other IMHO. I would rather work on making a plum more hardy, and also breed for unusual flavors. Just growing out any pluot seed might result in a fantastic pluot. Every one is a hybrid. No worries of self pollination, and any possible contamination may make a better fruit than what you were thinking. Don't mess with Mother Nature.

I'm still working on having enough stock to work with.

[itheweatherman]

Last week I pollinated my Mariposa plum x Myrobalan Plum hybrid with peacharine pollen, after pollination was complete. Then I covered the pollinated flowers with newspaper and I colored coded each flower, depending its pollen source, with yarn. Since this hybrid needs a pollinator, I'll give it two weeks to see if the pollination was successful or not.

[bradkairdolf]

I feel interspecific crosses are a rare thing, and if one of us makes one, I doubt I'll see another. I'm not talking Almond-peach, they are very closely related, one should be a sub-species of the other IMHO. I would rather work on making a plum more hardy, and also breed for unusual flavors.

You and I are on the same wavelength Drew. I meant that the controls would be useful for these complex interspecific crosses like the peach x plum, which do seem to be rare (although it could have been cultivar specific in my case, I just don't know). Like you, I'd be less interested in complex, interspecific parentage and more interested in the result, mainly excellent flavor with good (or tolerable) adaptability to my specific climate.

Have you done emasculation on self fertile varieties like peaches? I have no doubt it works but I have never tried it so have less confidence in my own implementation. I have some peaches that haven't bloomed yet so maybe I'll try a few and bag them just to see how successful I am at preventing self pollination.