Breeding with wild tomato species

[William S.]

I feel like we need a thread for breeding with wild tomato species in general.

I started with wild tomatoes two garden years ago when Joseph sent me some seeds of Solanum habrochaites, Solanum peruvianum and Solanum pimpinillifolium.

There are 14 or so species of wild tomato all from south america. I currently have seed for I think nine of these mostly from Joseph and Andrew with a couple packets from other sources such as the TGRC.

Personally I am currently most invested in trying to cross and or bridge with Solanum peruvianum a project for which I have already started a thread.

There are a number of traits available in wild tomatoes that have historically and currently led both amateur and professional breeders down some fantastical paths. Some realized, some realizable, and some which so far have been just out of reach.

So some examples of projects with wild tomatoes each of which eventually will need it's own thread as may each tomato species:

Transferance of entirely different breeding system (Joseph)

Transferance of promiscuous pollination features (Joseph)

Salt Tolerance (lots of mainstream interest)

Cold Tolerance (Dar Jones, Joseph, and J and L gardens are all active in this)

Frost Tolerance

Perennial Rhizomes (Tim Peters worked on this)

Insect Tolerance

Disease Tolerance (lots of mainstream interest)

Domestication of different tomato species with or without introgression from the domestic species (Josephs BC1 and S. peruvianum selection are examples)


The difficulty of working with wild species ranges from easy for closely related species like Solanum pimpinillifolium to extremely difficult for Solanum lycopersicoides. One work around for difficult species is the afformentioned potential to just start a domestication project for the wild species of your dreams. Especially if a portion of your garden is appropriate habitat for that species. 

In my garden I've devoted one garden bed to wild tomatoes and hybrids and it is the bed which gives me the most joy and interest. So one reason to grow and work with the wild tomato species is very intrinsic. That is that they are a source of wonder and may make the curious gardener happier!

[Joseph Lofthouse]

One thing that has really pleased me about the wild tomato species, is how tremendously adaptable they are....

When I work with domestic species, every plant is pretty much the same as any other plant, with minor differences in fruit color/size, or leaf shape. They don't adapt much to my garden, they are just tomatoes, and grow about the same as any other tomatoes...  However, the self-incompatible wild species rapidly adjust from being barely able to survive in my garden to thriving for me.

So I have great hope for plain old domestication projects with the wild species. The fruity flavors make that very desirable to me. 

[William S.]

Joseph, what all species do you consider to have made progress towards adaptation in your garden?

You've sent me seed for Solanum Peruvianum(volunteers for me), Solanum habrochaites (does OK for me), Solanum penellii (I killed my only seedling so far), Solanum pimpinillifolium (your strain volunteered for me). Then Hab x domestic (got seed back from one plant), BC1 (didn't save seed, trying to test for volunteerism), and Andrew was the ultimate source within our group for Penellii x domestic (got seed back from one plant) though you both sent me seed for that one it was all grown by Andrew. I've heard you write about growing some additional species- any adaptation happening there? So far it seems to me that pimpinillifolium, domestic, and Peruvianum are adapted enough to volunteer in my garden. I suspect that the segregating interspecies hybrids where only one individual produced seed will have a tremendous genetic shift towards adaptation to my garden.

I'm nervous about some of the new species Andrew and TGRC have sent me for 2019, some have reputations as difficult. I'm curious about the potential for adaptation within species. In reading about the habitat differentiation of the species in their native range it seems like there is tremendous variation, reminds me of mountain ranges I've known in California. It also seems like my garden is similar to yours enough (a slightly milder version with longer days) that I can grow most things you can grow- so any species that adapts to your garden can probably adapt to mine.

[Joseph Lofthouse]

Joseph, what all species do you consider to have made progress towards adaptation in your garden?

Solanum peruvianum and S pimpinellifolium volunteer reliably in my garden. My population of S pimpinellifolium came from a local garden where they had been volunteering for a decade before I got them, so I was expecting pimpinellifolium to be well adapted. 

I'm growing two populations of S peruvianum complex. The first has grown only as volunteers for 2 growing seasons now. This year, they were small plants, only growing about 18" long vines. The other population I have grown by traditional means (saving seeds, and growing transplants). The vines might be 6 to 8 feet long. They produce a huge abundance of fruits with lots of diversity in size, color, texture, and flavor.

I haven't found a volunteer of Solanum habrochaites. The plants grow rambunctiously in my garden. They seem a bit long season, but are producing plenty of fruits. They have grown in my garden for as much as 4 generations. This year, I planted S habrochaites about 20 feet away from the interspecies (domestic  X habrochaites) hybrids, so I'm hoping that S habrochaites has been contaminated. I tried that contamination manually, in the population that I'm calling BC1. At harvest this year, I rolled the bulk of the BC1 seed into the general population of S habrochaites. I kept some of the most promising of the BC1 fruits separate, just to play with them further.

This fall, I abandoned the name of S corneliomulleri, and combined that into what I am calling peruvianum complex. Corneliomulleri is the population that has adapted the most dramatically to my garden. It was so iffy the first few years, and so robust this year. This was the third generation, which I think of as the magical generation in my landrace breeding projects, when things often come together for great productivity in adapting new varieties to my garden.

S chilense didn't do well for me.

S cheesmanae does OK, but since it's an inbreeder, I'm not all that interested.

S galapagense eeks out a meager existence in my garden. Another inbreeder, so whatever.

This is the first year that S pennellii has done decent for me. I don't know if that is due to the plant adapting, or if it's cause the farmer adapted to the plant.

I have been trying for years to get a domestic tomato to volunteer in my garden. I suspect that the seedlings get munched by flea beetles.

Yup. It would be interesting to have an understanding of what each species native habitat is, so that we could try to mimic it. I think the only reason I can grow S pennellii, is because my watering system for it resembles dew... .

[Andrew Barney]

Yup. It would be interesting to have an understanding of what each species native habitat is.

I had sort of started that with my plant breeding website with maps and stuff. But i got spam on my mediawiki and tried to delete it and restore a backup but had major problems. Mostly with a MySQL database which i don't understand. I have the backup with all the photos and information,  but i don't know how to restore the wiki.

I could work on extracting the map information. But i miss the nice pages with flowering information and compatibility. Oh Well. Im not good with maintaining a website. Maybe I'll mail you a CD with my backup and see if you can do anything with it.

[reed]

Solanum pimpinillifolium  has been a well established weed in my garden for a long time. I rarely even save seeds cause there are always so many, I just transplant a few to the edge each year and let them lean against the fence.

Few seasons ago apparent crosses with domestic showed up. They look and grow like my old  pimpinillifolium strain but fruits are larger, up to the size of quarters and most are very sweet but a couple have tasted awful. They vary in shape with most being round and some pear shape. They range from yellow to red in color.

I have some wild flowers that each year when they bloom, I cull out those I don't like. I'm doing similar with these tomatoes. Once I know what the fruits taste like all but one or two of the best get culled so most of next year's volunteers are from the best ones.  I did save some seed from a particularly nice one this year but doubt I'll mess with planting any cause hundreds will probably come up on their own.

[William S.]

Andrew recently encouraged me to Google Earth my accessions of Solanum arcanum I plan to work with. What I found was very interesting. They seemed to be from a dry coastal desert, not far from large olive groves.

I used to work as a botany tech in a southern California mountain range where you could go from West side coastal sage scrub communities, riparian areas, all the way up to subaline zones, and then down to the Colorado portion of the Sonoran desert on the other side with huge botanical diversity. It was easy there to pick out the habitats closest to My Montana homeland. For one thing the species were the same! I suspect that the wild tomato species have diverged in similar ecological gradients and I wonder sometimes which species grows in the habitats closest to our own. Obviously so far we've found Solanum pimpinillifolium and Solanum peruvianum to be good volunteers. Logically high elevation accessions would make sense to do well here. Though it's very possible that only very specific accessions would a's within species variation as to climatic adaptation may be enormous. It would be interesting to have a lot of cooperators to do a large scale common garden experiment with all the species.

[Andrew Barney]

I'm not sure if this is helpful information or not, but here are some maps of where each wild tomato species is from and can highlight when some outlier accessions come from other areas. It does not give the whole idea of what climate or elevation or full habitat of each wild species is adapted to, but it's a start. I may need to do this in multiple posts since i can't upload more than 5 photos at a time. Here's hoping this works and helpful in some way.

EDIT: These maps were generated via Google Maps and the accession data provided by the TGRC (Tomato Genetics Resource Center). For those who would like to interact with the maps directly and explore them further.

Link: https://tgrc.ucdavis.edu/Data/Acc/Wildspecies.aspx

[Andrew Barney]

Juglandifolium sure looks interesting in it's habitat range compared to the others...

[Andrew Barney]

more photos.

[Andrew Barney]

oh, and a picture of the Galapagos Islands with S. galapagense, cheesmaniae, and pimpinellifolium. The interactive version of this may help identify likely hybrids between these groups as accessions as well as some DNA stuff i found in a paper once. I think i blogged about it maybe.

[William S.]

https://davisla.files.wordpress.com/2013/10/south-america-plant-hardiness-zone-map.jpg

https://davisla.wordpress.com/plant-zones/south-america-plant-hardiness-zone-map/

This map shows usda zones in south america. It would be interesting to superimpose these with the tomato range maps.

Old school way to do that was with simple transparencies. I usually use ArcGIS but don't have access to a license right now.

Interesting in and of itself, as my USDA zone is currently 6a, prior to the 2012 revision it was 5b, is that zone 6a according to this map, barely exists in South America. I somehow thought the south American climate had much larger cold areas than it does apparently.

[William S.]

https://www.researchgate.net/publication/225583610_Distribution_ecology_and_reproductive_biology_of_wild_tomatoes_and_related_nightshades_from_the_Atacama_Desert_region_of_northern_Chile

This article talks in one section that stood out to me about a few accessions of high elevation chilense. Comparing this article, the maps you just posted Andrew, and the map I found it seems like Northern Chile high elevation accessions of any species might be interesting because that's where the mountains may start to climb through familiar climate zones to gardeners of the rocky Mountain west.

However, the article specifically mentions unusual chilense populations around San Pedro De Atacama and Sale de Ata Cana calling out

LA 4117A (3540 meters) and B

LA 4329
LA 4330
LA 4332

As distinctive morphological populations. Also mentioning that they have even more extreme daylength sensitivity than is normal for this species and flower only at short day lengths. A trait which is very frustrating for a northern grower! So while high elevation these are not going to be easy to work with!

Other high elevation accessions of chilense are available in the TGRC database I found five others between 3250 meters and 3530 meters. Though LA 4117A mentioned in the article seems to be the highest by ten meters.

This is interesting to consider and could inform future requests for material if I am successful working with the chilense accession from sacred succulents and the accession I requested for its known ability to cross with other species.

However its very interesting to me that some of the highest elevation species of tomato are still hard to work with! They might be climatically close in terms of temperature, but it sounds like these are short day length, high elevation deserts with perhaps salty soils. High Desert gardeners further south in North America might be excellent collaborators for working with some of these accessions.

Interestingly at my latitude I garden at about 3000 feet, the accession I am working with comes from 1100 meters which is 3600 feet and the 3540 meter accession would be an astounding 11600 feet elevation.

Edit: So while I think I should continue with the Chilense material I have for this coming year, I think if that works, in subsequent years if we could get a cross between LA 4117A and our existing Solanum peruvianum grex to the F2 we might be able to affect an interesting increase in the adaptability of the grex to our climates.

An even easier to work with alternative might be to cross in the highest elevation accessions of S. Arcanum, S. Huaylense, and S. Cornelio-Muelleri

Though perhaps not. The two species S. Pimpinillifolium and S. Peruvianum that have done the best in our northern gardens by virtue of volunteering ability are rather low elevation in their native range. It could be that adaptation to ruderal habitats and fast opportunistic growth is far more important to garden adaptation regardless of latitude than is cold and possibly even frost tolerance.

[Andrew Barney]

William and others like Joseph,

I am starting to warm up to this domestication idea, why not just domesticate the wild species? I think domestication along with natural outcrossing and breeding simple domestic traits into the wild forms rather than trying to repeatedly backcross the wild traits into domestic forms is a winning idea.

Something that is domestic-like will be far more interesting than a domestic with one wild trait. If you listen to the podcast, many of the wild forms have multi-allele traits like for salt tolerance or pest repelling trichomes, therefore preserving as much of the wild genomes is good i think. Some may have some genetic drag that may need to be selected out, but for the most part i don't think they have as much genetic drag as most people might think.

https://www.talkingbiotechpodcast.com/089-de-novo-domestication/

[William S.]

Interesting. I will listen to the podcast after my little toddler guy goes to bed.

I've been thinking more about the domestication route since Joseph found those large fruits in the BC1.

The simple idea that we could have four species of domestic tomatoes just with the three wild species we are working with now is an compelling one.

I think interspecies breeding has a relatively few potential fates. Most of those ultimately lead towards the result being an population with some introgressed genes from another species. So switching the paradigm to the wild species being the gene recipient is an elegant solution to this.

Yes it might be possible to construct a new species from two or more species, break down a species barrier and create a single species from two or more, or some other outcomes, but these may be more difficult to achieve than the rather elegant solution of domesticating one particular new species by introgressing a few domestic genes. Though there is a non-introgression route it would probably lead to a cherry tomato only species for some time.