Somatic Hybrids

General Fruit Growing
#1

[I wasn’t sure about the forum category for this one, but since it’s applicable, I thought it was as good a choice as any.]

Somatic hybrids! Strip the cell wall with an enzyme, fuse the cells with an electric current, and culture a sort-of hybrid plant, with both sets of chromosomes in each cell. (It’s closer to hybrids than to chimeras).

I’ve read here on the forum and elsewhere that somatic hybrids aren’t always stable, and I’ve read somewhere that they’re particularly unstable at the diploid level… But I haven’t seen any source elaborating on the concept. What’s the mechanism? Why are they supposedly unstable? What’s the end result? Does it count as a failure?

I was very interested in somatic hybrids, and they seemed rather promising to breed some interesting new plants, but I don’t quite understand the matter of instability. I would’ve thought it’d be similar to natural allopolyploids.

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Secondly… Is it possible to commission a laboratory to make a particular SH? I’ve had some ideas bouncing around my head for a long time, but I don’t have the kind of resources to make such experiments myself. Given the potential issues with reproductive sterility in wider crosses, I think it’d be particularly useful for developing vegetatively propagated plants.

At the top of my list, I’d like to see a SH of Ulluco and Madeira Vine. Ulluco is an established edible, with beet-y or starchy tubers (depending on the variety) and apparently top tier greens; it’s also rather susceptible to hot and cold climates, and a somewhat delicate plant. Most people don’t seem to recognize Madeira Vine as an edible, but I grow it and eat it, and it’s quite nice; tender greens, starchy roots, even the bulbils are edible, and it’s one of the toughest, most neglect-resistant plants you can grow. A tough, vigorous, climbing, vining, bulbil-bearing Ulluco is quite a compelling image, in my opinion.

Here in PR, we eat a lot of Cocoyams, both Yautía (Xanthosoma spp.) and Malanga (Taro, Colocasia esculenta). A SH between these two might produce a worthwhile new crop. Interestingly, while all the corms are edible, the two species have opposite harvesting patterns: with Taro, we harvest the mother corm for eating and plant the little cormels; with Yautía, we eat the cormels and cut up the mother corm for planting. Elephant-foot Yam (Amorphophallus paeoniifolius) might make for an interesting SH with either of the others, but it’s unknown in my neck of the woods, and its growth pattern is a bit different.

Any of the Gingers (Common, Turmeric, Galangal, etc) together might make interesting new flavor combinations. Garlic and Onion seem an intuitive combination (they’ve been traditionally hybridized with the help of embryo rescue, but as far as I’m aware, it’s never been released to the public). Arracaca, Celeriac, Skirret and Yampah are all related, and Yacón and Dahlia are related to each other as well.

On the fruiting side of things, the rose family is full of plants that might bear interesting fruits if hybridized somatically (if reproductive sterility were not a barrier).

Where would one go to try to get these things made?

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#2

The only way I can think of to end up with a diploid after fusing two cells like this is if you were fusing two haploid cells together.

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#3

My mistake, I didn’t phrase it right. What I meant to say… I’ve read that diploid to diploid somatic fusions (with tetraploid results) are apparently particularly unstable compared to higher ploidy fusions.

Why this is so (allegedly) was not satisfactorily elaborated upon. It still doesn’t make sense to me why somatic hybrids would be any less stable than natural allopolyploids.

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#4

I would simply doubt the claim that they’re inherently unstable as someone’s opinion rather than fact unless there was solid evidence to back it up. Frankly, even if there was good evidence it would be unlikely to apply equally to all species.

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#5

I read a blog? somewhere a fellow going to college in Florida was looking to fuse passiflora incarnata with edulis by doing an electro-slide. His female professor has a citrus combo of ‘Dancy’ tangerine and poncirus she made 20 years earlier by same method; it never bloomed in all those years… :pensive:

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#6

Last time I did that was at a wedding reception :wink:

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#7

Contrary to JohannsGarden, somatic fusion does produce genetically unstable plants. I’m aware of hybrids of tomato and potato that demonstrate it. Cells fused via somatic fusion tend to lose entire chromosomes when going through meiosis. (quick refresher, mitosis is vegetative growth, meiosis is production of germ cells to make seed) Loss of chromosomes is random but generally favors removal of chromosomes from one parent species and retention of chromosomes from the other parent. I’ve read of hybrids between Zea Maize (corn) and tripsacum Dactyloides that lost up to 50% of the tripsacum chromosomes within 2 generations.

But! When it works, the results can be amazing. I would love a tomato/potato hybrid that makes fruit above ground and tubers below ground.

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#8

It seems that the diploid to tetraploid (and back again) dance happens a fair bit. its sort of the “standard route” of polyploidy if you consider the haploid set the building blocks and diploid as the “original” state of reproductive life. Why exactly a set of chromosomes would spontaneously double or undouble themselves is hard to wrap your head around any way you shake it.

Interesting propositions on the whole, @Caesar. Id like to know more about techniques for wide crosses in general. So much unexplored potential! Technology is only as good as its users intentions. Surely there might be unintended consequences to playing Dr. Moreau, but so much of the pitfalls of biotech rests on the fact that its used for crappy purposes. What we could use, Ive long thought, is some cleverness around genuine crop improvement. Im not sure the sum total of 21st century plant science holds a candle to the development of corn or any number of other novel crops. Funny how easily people have come to see these things as ‘normal’ crops, forgetting entirely the elaborate and exotic origins of most of what we grow.

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#9

I suppose that would probably be due to the syntax of the chromosomes being a little off such that they are less able to form homologous pairs at a locus, similar to what happens during recombination.
There seems to be something almost entropic about that kind of mutation, like a change of harmonic or energetic state.

On a related note, arent there crops for which somatic mutation figures heavily into their improvement and cultivation? Garlic and sweet potato are two that spring to mind. What do we really know about it? Ive hunted around a bit trying to understand it more, but information is sparse.

#10

The loss of chromosomes is also known to happen in some offspring of plants with uneven ploidy (pentaploid for example) because there are so many options for uneven splitting during meiosis. Regarding me being wrong about somatic hybrids being stable. I think there’s a miscommunication happening. I’m just trying to avoid blanket statements. Some fusions producing unstable plants should not be translated to ALL fusions make unstable plants.

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#11

100% agree. As I stated, when it works, the results can be amazing.

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#12

Fritz Kohlein - iris breeder/expert agreed with you. He remarked an unusual hybrid he made was claimed apopmictic. It was missing a characteristic loop of chromosomes from one parent. He then explained the parent with the loop was the female pod-parent. The hybrid was then accepted as genuine with chunks of chromosomes lost in the natural process.

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#13

Randyks, Somatic hybrids are not the same as reproductive hybrids. I don’t know the hybrid you describe but it sounds like a reproductive hybrid, meaning pollen on stigma to produce a seed. I’ve seen research documenting reproductive hybrids that lost DNA though the process is different than when a somatic fusion embryo loses chromosomes.

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#14

Yes, I quite understand, the iris hybrid was by manipulating natural methods. I was just bringing up sexual fertilization can lose chromosome pieces also.

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#15

I would like to clarify one thing mentioned above. When a somatic fusion cell is produced from two different species, it is not tetraploid. These are said to be allotetraploid (containing four genomes from two or more different species); or if appropriate, amphidiploid (with two genomes each from two diploid species)

A true tetraploid contains 4 sets of chromosomes originating from the same species. As an example, a somatic fusion of a tomato with another tomato would be a true tetraploid. A somatic fusion of a diploid tomato with a diploid potato would be an amphidiploid.

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#16

That’s why most of my prospective choices are clonally propagated crops. It gets around any meiotic, fertility and productivity issues.

Really? I had never heard of that. Are such somatic hybrids available in the public sphere? I was very frustrated to learn that one scientist managed to classically crossbreed garlic and onion with the help of embryo rescue, but that the hybrid was never released as far as I could tell. Such wasted potential!

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