Author Topic: Breeding with wild tomato species  (Read 196 times)

Andrew Barney

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Re: Breeding with wild tomato species
« Reply #15 on: 2018-10-25, 09:06:11 PM »
Though there is a non-introgression route it would probably lead to a cherry tomato only species for some time.

That is a good point. However from the podcast he says fruit size is the result of one point deletion or mutation. Another idea is to use mutation breeding. If we had lots of seeds to sacrifice there was a free seed radiation service that was mentioned on the old forum. Mutation breeding is not a bad idea if we are having trouble crossing and are trying to domesticate from scratch.

William S.

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Re: Breeding with wild tomato species
« Reply #16 on: 2018-10-25, 10:25:26 PM »
That is a good point. However from the podcast he says fruit size is the result of one point deletion or mutation. Another idea is to use mutation breeding. If we had lots of seeds to sacrifice there was a free seed radiation service that was mentioned on the old forum. Mutation breeding is not a bad idea if we are having trouble crossing and are trying to domesticate from scratch.

Just finished listening to the podcast. His approach is interesting with using only genome editing. It raises the possibility of having 14 domestic tomato species if desirable. I agree about the radiation breeding. There are three approaches here: introgression, radiation breeding, and genome editing. The third may be genetic engineering depending on the legal definition. However, the first two are commonly fair game for organic and open source breeding. If we had the ability of big labs to do genetic testing of seedlings it would be pretty easy to select seedlings that had the desired traits.

However, there is one trait that really stands out and that is large fruit size. So a radiation bred galapagense or Peruvianum would be pretty simple. Create lots of mutants until you find one with big fruits.

For our rocky Mountain purposes working with pure galapagense might be difficult. Pure pimpinillifolium seems to much like domestic tomato. However to me Peruvianum seems like a likely target for us because it seems pretty straightforward to raise large amounts of seed. We could potentially send in a pound of seed, get it irradiated, and select out a large fruited mutant from resulting seedlings in short order. Which seems like a good alternative if introgression fails to work to bring in desired genes.

It seems like the species we can't grow very well wouldn't work with mutation breeding just because we can't produce enough seed. It would make sense to work with some species in places where they already grow well such as their native range or its equivalent in another part if the world if it exists. Which it may not- for instance how many high elevation salt deserts are there with short day lengths?

I wonder if mutation breeding could create knock out mutants that would actually be easier for us to work with of some of the species? For instance a high elevation Chilense that isn't day length sensitive and blooms continuously?

I've thought that introgression is the key to making some species easier to work with, however it's possible that all the really cool hard to obtain traits we dream of in wild tomatoes are polygenic as discussed in the podcast. By introgressing we would break these traits at least temporarily. The trick would be to keep back crossing to the wild parent until the desired suite of polgenic traits is functional again, but the simple domestic trait like large fruit is transferred. One way to do this might be to be to do the introgression in an environment similar to the native habitat, with galapagense and salt tolerance that could just be seawater. My uncle has a small salt water fish aquarium and salt water for aquaria is readily available. Seedling trays in saltwater anyone? Trichomes, cold tolerance, and others could be a little trickier.

I wonder which of the three techniques is fastest? The example that comes to mind is GMO transgenic blue tomatoes. They are still not readily available a long time after development. Conventionally bred blue skinned introgression  tomatoes are tremendously widespread. So using introgression has potential from that recent historic analogue.

Radiation breeding has some enhanced patentability and has been used to obtain non-GMO herbicide resistances in small grains like wheat that are patented. In this case it's the precise description at the genetic level of the induced mutation that is patentable. Mutation breeding can also be done open source- you just select the big tomato.

GMO technology like transgenes and perhaps gene editing is highly patentable and controlled, we have yet to see much of any GMO tech become available in an open source manner. Though the simple fact that patents do eventually expire suggests that it will eventually all be common use material. When I took a plant genetics course at OSU in Oregon in 2012 gene editing was still a bit of a regulatory unknown. Not sure where it stands legally in 2018. I could see a case for it being as benign as radiation breeding. Even done by universities patentable tech tends to get patented. So I suspect patentability might be part of the draw there. Still for us two open source routes to domestication for additional tomato species are possible.
« Last Edit: 2018-10-26, 04:41:00 AM by William S. »
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Joseph Lofthouse

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Re: Breeding with wild tomato species
« Reply #17 on: 2018-10-26, 09:54:25 AM »
Here's a photo of a tomato that showed up among the progeny of [domestic X habrochaites]. I think it is self-compatible. It had closed flowers, so it doesn't match the project goals. It is a tasty fruit. The largest so far from the cross. And the most productive. It was early. The most unusual trait was that it is hollow, sorta resembling a pepper inside. 

Because it produced so much seed, I gave it a name, and intend to include it in my seed catalog this winter.

Fairy Hollow Tomato


A couple days ago, I sent a bunch of the interspecies tomato seeds to a collaborator in a warmer climate. They are making crosses and  F1 hybrids for me during the winter. I'm hyped about that.

I have been pleased with the progress that we have made towards domesticating wild species. I was working with a population that I was calling corneliomulleri. Originally, the fruits were the size of peas. This year, one plant had fruits the size of a grape. Woot! And there were plants that produced tasty fruits, and plants that produced yucky fruits. So yup, I think there is a lot that can be done with plain old selection. So next year, I'm intending to plant a lot of seeds from the grape-sized fruits, and from the lovely tasting fruits.

I still find myself struggling sometimes with the meme of "gotta keep things pure". For example, I've been growing a population that I suspect was 75% habrochaites, and 25% domestic. I call it BC1. This year, I found some fruits with 3 locules in the population, which is  more of a domestic trait than an habrochaites trait.  It took me a good hour of thought to finally merge BC1 into the general habrochaites population. But now, it is done, and cannot be undone. And I grew the [domestic X habrochaites] and [domestic X pennellii] progeny only 20 feet away from the habrochaites patch, hoping that they will cross-contaminate each other. However, I just couldn't bring myself to screen the habrochaites fruits for taste!!!!!!!!!!!!!!!!! Bleck! I'll do that when some non-habrochaites fruit types start showing up.

 
« Last Edit: 2018-10-26, 10:01:56 AM by Joseph Lofthouse »

William S.

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Re: Breeding with wild tomato species
« Reply #18 on: 2018-10-26, 10:39:46 AM »
Neat tomato!

Interesting that you call the hollow interior unusual Joseph. I've been researching tomato history and a lot of the original domestic tomatoes bred by native Americans were yellow, hollow, ribbed big heirlooms- and reportedly they had some different flavors.

Kind of like this 80 DTM yellow stuffer from victory seeds.

https://www.victoryseeds.com/mobile/tomato_yellow-stuffer.html

One such effort to create the modern tomato was that of A.W. Livingston of the book which I haven't read "Livingston and the Tomato"

http://blog.seedsavers.org/blog/livingston-tomatoes
« Last Edit: 2018-10-26, 01:37:12 PM by William S. »
Western Montana garden, glacial lake Missoula sediment lacustrian clay mollisoil sometimes with added sand in places. Zone 6A