Crossing with Solanum Habrochaites

[Frosti]

Start of part 1

For better readability, I'll split this post into multiple parts.

As part of my little breeding project, I experimented with some wild tomato cousins.
In particular:

• Solanum pimpinellifolium
• Solanum peruvianum
• Solanum sisymbriifolium
• Solanum habrochaites

The goal of these experiments was to produce a hybrid with Solanum lycopersicum (the tomato we all love), that would be resistant to some of the diseases that plague the tomato.

• S. pimpinellifolium was easy, since it's entirely compatible with Solanum lycopersicum (the tomato we all love). This cross has been done before 1000 times.
• S. peruvianum was a complete failure. The plant dropped all of its really beautiful flowers and didn't produce a single fruit (S. peruvianum seems to be incompatible to S. lycopersicum as well as itself. I did not plant a second plant, but I should have). In hindsight, I should have tried to use the pollen of S. peruvianum on a normal tomato instead of the other way around. On top of that, the plant died of what looked like late blight really early in the season, while all of the other plants were doing just fine. So much for disease resistance I guess.
• S. sisymbriifolium was another disappointment. For this one I had two plants, so self-incompatibility was no problem. In a nutshell, the cross did not work, which already dawned on me, once I saw the potato-like flowers of the plants. The germination time for these plants was insane btw. upward of 4-6 weeks. I almost started to believe that ALL of the seeds I bought were duds. The fruits ripened so late in the season, that the yield was pretty low. Oh and having to pick fruit with gloves on is no fun, let me tell you.
• The last one on the list is S. habrochaites. This one was an interesting beast. The plant I grew, was of the version that is self-compatible (apparently there are multple versions). With this one I used the pollen of the wild tomato on the stigma of a small yellow dwarf from my own breeding project. The cross worked. The following sections will go into further detail on this cross.

Parental fruit
The 2021 season was horrible for growing tomatoes, it was far too cold and far too wet for far too long. So I didn't think much of it, when the resulting fruits (2) from the cross with S. habrochaites stayed rather small. I was just glad, that the damn flowers did not drop this time . However, once it was time to harvest those fruits and cut them open, I realised that the weather might not have been the only factor affecting the fruit size. I'm sure many of you have noticed that poor pollination leads to small fruit with few seeds. Well, after cutting both fruits open, I wasn't sure if there was ANY viable seed in there at all. One, maybe two looked kind of big enough to be viable, but the rest were basically empty husks. I'm assuming those husks resulted from seed abortions caused by incompatibility between S. lycopericum and S. habrochaites, but I can't be sure without a reproduction of this cross. Obviously, this incompatibility has to be incomplete, otherwise none of the seeds would have been viable. What's rather intriguing is that one can already see at this stage that the viable seeds in the fruits were not from some stray pollen of an ordinary tomato, but from S. habrochaites. The seeds were smaller, darker, and had a different shape than normal tomato seeds. However they did not look exactly like either of the parent seeds. If I had to descirbe them, I would say that they looked like a bigger version of S. habrochaites seeds.

These are the parental seeds:

parental_seeds.png

And these are the seeds from the cross

seeds_from_cross.png

This is what the fruit of 4-21 (the female parent) looked like (the depicted fruit was properly pollinated)

4-21-female-parent-fruit.JPG

Unfortunately I did not document everything as thoroughly last season, so I do not have a closeup of S. habrochaites from that season, let alone the fruit. But here is a picture from the internet that shows what the fruits look like:


End of part 1

[Frosti]

Start of part 2.

The seedling

To give myself the best chance of success, I decided to plant ALL of the seeds from both fruits. I didn't give myself more than a 20% chance that anything would sprout. So it was with great delight, that I noticed a single teeny tiny sprout emerging from the soil. Later, another seed also germinated, but it died before it could emerge from the soil. Anyway, that successful sprout was the most fragile and tiniest tomato seedling I had ever seen. And it stayed that way (compared to the normal tomato seedlings) for a long time.

Here is the seedling just after sprouting. I was crossing my fingers that I would not have to remove the seed coat manually. At this point I did not so much as breathe on it :

10-22_just_after_sprouting.png

Luckily six hours later, the seedling was free of the seed coat. Notice the discrepancy in size compared to the other seedlings:

10-22_free_of_the_seed.png

12 days later, the seedling was out of the woods:

first_true_leaf.png

One can see that the 17 days old seedling is a bit hairier than an ordinary tomato, which is a trait that it shares with its male parent S. habrochaites aka "the hairy wild tomato":

hairy_seedling.png

Still tiny compared to the other seedlings:

17d_still_tiny.png

At 4 weeks old, one of the interesting characteristics of this cross is nicely visible. The leaves have a very nice glossy sheen to them. The plant is starting to establish itself nicely and is rapidly catching up to the other seedlings:

shiny_leaves.png

At 6 weeks old the plant started to develop edema, which was a problem that I also had the season before with S. habrochaites. It seems that the cross inherited the drought tolerance of its male parent, which probably means a susceptibility to overwatering. That, combined with not enough light indoors, led to edema:

6w_edema.png

Time to plant outside!

End of part 2.

[Frosti]

Start of part 3.

Growing like a weed

I gave the plant the sunniest spot that's still roofed over. The pot size is 20L but it was only filled up to about 12-13 liters (~3.3 gallons). I know, I know that's not ideal, but that's around the pot size I also used for almost all of the other tomatoes. The plant did not have drooping leaves even once, which I suppose is due to the inherited drought tolerance (the tomato next to it does have issues with the pot size and sometimes has drooping leaves). The composition of the soil is as follows:

• 3 parts used potting soil (containing peat moss) from last season
• 2 parts home made compost for the nutrients
• 1 part native soil for the contained minerals

The following pictures show the vigor of the plant from the day it was planted outside to now. Flowers and fruits will get a seperate post, so from here on there will be a slight asynchronicity.

The plant was planted outside exactly 2 months after germination:

2m_just_planted_outside.png

A week later. It's growing rapidly:

rapid_growth.png

Fast forward to 3.5 months old and the plant has managed to outgrow every single other tomato. Very impressive, given how slowly it grew in the beginning:

16w_outgrown_everything_else.png

Another interesting characteristic is that the plant has some small leaves surrounding the base of almost every sucker node and almost every flower cluster:

leaves_at_every_node.png

While we're on the topic of growing like a weed ... look what I found litereally growing as a weed in between paving stones:

literally_a_weed.png

I believe that to be an offspring of last year's S. habrochaites. It does have the correct growth habit and that nice sheen. I cannot say if it's an unintentional cross with a normal tomato or a true S. habrochaites. Either way, I painstakingly dug it out and transplanted it into a pot. Maybe I'll be able to provide comparision pictures after all, who knows.

End of part 3.

[bower]

What a beautiful plant!

[Frosti]

What a beautiful plant!

Indeed, and the most healthy of them all - which is the reason for this line after all .

[bower]

I like the truss architecture too... reminds me of those long, long Sungold trusses.
Editing for lack of coffee!!
The dwarf parent fruit is really pretty.

[DriftlessRoots]

What an interesting project! I wish you lots of luck in it. I've got a mystery(ish) solanum I may try crossing with a tomato just for fun now. (As soon as I work up the nerve to test it for toxicity the old-fashioned way.)

[Frosti]

What an interesting project! I wish you lots of luck in it. I've got a mystery(ish) solanum I may try crossing with a tomato just for fun now. (As soon as I work up the nerve to test it for toxicity the old-fashioned way.)

Thanks! What Solanum do you think your mystery plant is? Please be careful with unknown Solanum plants, some of them are highly poisonous ... if you're going down the old fashioned way of toxicity testing then go very slowly (spread the test of a single fruit over multiple days, maybe try if skin reacts to the fluids?). I'd never swallow a fruit from an unknown solanum plant if it tastes bitter. Just my thoughts, please be careful!

[Frosti]

Start of part 4.

Parental plants

I managed to dig out some old photos from last season after all!

This is the female parent 4-21 at the end of June 21, which was in dire need of bottom pruning at this point :

4-21.JPG

This is the male parent solanum habrochaites in the middle of June 21. One can see that it also has that nice sheen on the leaves:

solanum_habrochaites_21.png

End of part 4.

[Frosti]

Start of part 5.

Flowers

8 weeks after germination the first flower clusters started to form, this is what they looked like:

8w_first_flower_clusters.png

12 days later (I believe that's the same flower cluster). As you can see, the plant had me worried there for a few days, since the first two flowers dropped :

12d_later.png

This is what an open flower looks like:
Frontal view. Notice the width of the petals:

flower_front.png

View from the side:

flower_side.png

View from behind:

flower_back.png

What's also noticeable is the frequency of stigma exsertion (pretty much all of the flowers have it to some degree):

flower_stigma_exsertion.png

End of part 5.

[Frosti]

Start of part 6.

New growth

Like S. habrochaites the plant has a strong tendency to develop a lot of suckers. What's also noticeable is the change in color that the stem goes through. Initially it is very purple and slowly turns a normal tomato green once it matures enough. The purple is the most intense on the parts of the stem that are exposed to the sun. This is very similar to how anthocyanin tomatoes behave, so I guess S. habrochaites has some anthocyanins as well:

lots_of_suckers_plus_anthocyanin.png

End of part 6.

[Frosti]

Start of part 7.

Unripe fruits

This is what a fully developed fruit cluster looks like:

fully_developed_cluster.png

Here is a view from below. Notice the green line at the bottom of every fruit? You'll find the same line on every single S. habrochaites fruit. So this seems to be a dominant trait:

fruits_from_below.png

A closeup from the side. As you can see the fruit is not round like its male parent (S. habrochaites). Instead it has a similar shape to the female parent. The fruit does have a tip like the female parent, another dominant trait. I believe the fruit is also a lot less hairy than S. habrochaites:

fruit_from_the_side.png

The size of the fruits is pretty small, which was to be expected, since I crossed two plants with rather small fruits. I did however expect the resulting fruits to be a bit larger. Nothing that can't be fixed down the line, so no problem.

None of the fruits are ripe yet, so I can only show them in the ripening stage. I'll post some pictures of the ripe fruits at a later date of course.
However, just this week I stumbled upon a video of another cross between Solanum lycopersicum and Solanum habrochaites. This is what the result looked like:

ripe_fruits_external.png

I suppose mine will turn yellow. Hopefully the green line on the bottom stays visible .

What I'm really interested in is the seeds. Will I once again be able to SEE a difference between the seeds? I think it's possible that a certain percentage of the seeds will look like regular tomato seeds, while the majority will look like S. habrochaites seeds. What do you think?

End of part 7.

[DriftlessRoots]

Thanks! What Solanum do you think your mystery plant is? Please be careful with unknown Solanum plants, some of them are highly poisonous ... if you're going down the old fashioned way of toxicity testing then go very slowly (spread the test of a single fruit over multiple days, maybe try if skin reacts to the fluids?). I'd never swallow a fruit from an unknown solanum plant if it tastes bitter. Just my thoughts, please be careful!

Consulting with a solanum friend (actually a potato PhD so...) he supported my belief that it's a thornless variety of S. quitoense. I found it in the weed pile where people discard garden debris at our community gardens. The gardens are at a major university with hundreds of gardeners from around the world. That makes me think it's something edible. I don't want to hijack your thread, but I can PM you pictures if you'd like, although the flower ones aren't very good.

[Frosti]

Thanks! What Solanum do you think your mystery plant is? Please be careful with unknown Solanum plants, some of them are highly poisonous ... if you're going down the old fashioned way of toxicity testing then go very slowly (spread the test of a single fruit over multiple days, maybe try if skin reacts to the fluids?). I'd never swallow a fruit from an unknown solanum plant if it tastes bitter. Just my thoughts, please be careful!

Consulting with a solanum friend (actually a potato PhD so...) he supported my belief that it's a thornless variety of S. quitoense. I found it in the weed pile where people discard garden debris at our community gardens. The gardens are at a major university with hundreds of gardeners from around the world. That makes me think it's something edible. I don't want to hijack your thread, but I can PM you pictures if you'd like, although the flower ones aren't very good.

I'd love to see some pictures! I say go for it, try the cross! I'd be very surprised if S. quitoense were to be compatible with S. lycopersicum though. If there's any chance, then I'd say it's using S. lycopersicum as the female parent.

[Pippin]

Really interesting project you have here, hope you will keep us updated!

Wild tomato species are little unknown territory to me, I have only one pimp cross that I have been following up. It is extra sweet but also has this strange off flavor, especially early in the season, which reminds me of Asian Fish sauce. I actually like it as long as the tomatoes are mixed with normal tomatoes. Could be that it is just full of umami flavor which might be off putting if there was too much of it, IDK really, just guessing.

I remember reading that both the Delta (reddish orang) and Beta (orange) tomato colour genes in cultivated tomato originates from a cross with green fruited wild species, not sure which. Both are dominant genes but express only in the presence of lycopene. You might want to cross your tomato line back to a red tomato to see if you had Delta or Beta in your line. They won’t be visible in a cross with yellow (r) or tangerine orange (t) tomatoes.

What comes to the seeds of F1 plant, I believe the genes of F2 generation can be expressed already in the seeds of an F1 plant. Interesting to see if you will observe different seed colours in F1. In my breeding project, I am selecting a phenotype that might be related to a smaller seed size. When sowing F2 seeds, I try to sow all sizes of seeds to avoid eliminating any trait. My gut feeling is that I have been more successful in finding my wanted phenotype when sowing smaller, weak looking F2 seeds.

[DriftlessRoots]

I'd love to see some pictures!

PM sent

[Frosti]

Really interesting project you have here, hope you will keep us updated!

Wild tomato species are little unknown territory to me, I have only one pimp cross that I have been following up. It is extra sweet but also has this strange off flavor, especially early in the season, which reminds me of Asian Fish sauce. I actually like it as long as the tomatoes are mixed with normal tomatoes. Could be that it is just full of umami flavor which might be off putting if there was too much of it, IDK really, just guessing.

I remember reading that both the Delta (reddish orang) and Beta (orange) tomato colour genes in cultivated tomato originates from a cross with green fruited wild species, not sure which. Both are dominant genes but express only in the presence of lycopene. You might want to cross your tomato line back to a red tomato to see if you had Delta or Beta in your line. They won’t be visible in a cross with yellow (r) or tangerine orange (t) tomatoes.

What comes to the seeds of F1 plant, I believe the genes of F2 generation can be expressed already in the seeds of an F1 plant. Interesting to see if you will observe different seed colours in F1. In my breeding project, I am selecting a phenotype that might be related to a smaller seed size. When sowing F2 seeds, I try to sow all sizes of seeds to avoid eliminating any trait. My gut feeling is that I have been more successful in finding my wanted phenotype when sowing smaller, weak looking F2 seeds.

Sure, I'll keep you guys updated, as soon as there is anything noteworthy .

I have a few pimp crosses as well. All of them exhibit that nice pimp flavor (which I like, but some don't) to some extent. Naturally, since all of them are F1, the pimp flavor is not as strong as with the wild parent. That's what I will work on in those lines.

Regarding the tomato color genes, I do plan on crossing a tomato with that mystery plant I recently discovered (this time using the wild plant as the female parent). I'd bet that that's a pure S. habrochaites. I might just cross it with a red tomato (this time a huge one), to see if there's anything one can learn from that cross. @Shule, maybe I'll try to create a cybrid line .

I sure do look forward to cutting one of those fruits open! Interesting observation that seed size might be linked to other traits.

[bower]

I really love your attention to the details and great photos showing what you observed. This is the best description I've seen of growing wild relatives and it's a great learning experience to read about. Thank you!

[Frosti]

I really love your attention to the details and great photos showing what you observed. This is the best description I've seen of growing wild relatives and it's a great learning experience to read about. Thank you!

Thanks! I figured there must be other people out there who would find this fascinating. Glad I was right .

[Frosti]

Start of part 8.

Ripe fruits

There has been a surprising development.
Today I went outside and saw that most of the tomatoes of the first fruit cluster had fallen to the ground. A few hours later the same happend to the second fruit cluster.

tomatoes_falling.png

The fact that the tomatoes fell to the ground is not that surprising, given the fact that the very same thing happend to S. habrochaites last year. That's normal.
The reason I was surprised is the timing. After seeing the picture of other S. lycopersicum x S. habrochaites crosses (red), I fully expected the fruit to be yellow like the female parent's. Afaik, the fruit color dominance hierarchy roughly goes like this:

red > orange > yellow > green

What's the explanation for this then?

ripe_color.png

The color is NOT yellow. Instead it is a sort of ivory with a green hue. I believe that is about the same color that the fruits of S. habrochaites had last year, but I'm not sure. If the mystery plant I found is indeed S. habrochaites I will of course be able update you on this question.
The fruits definitely change color when ripe, but it is a very subtle change. I believe the easiest way to tell the ripeness of the fruits is to look at the green line, which gets a lot more yellow when the fruit is ripe. Oh, and they also lose their green shoulders completely.

Regarding the question of the seeds:

very_few_seeds_on_first_cluster.png

Keep in mind that these are fruits from the very first fruit cluster, which has fruits that are a lot smaller than the later ones. There seem to have been some pollination issues as well (or genetic incompatibility), since there are only very few mature seeds per fruit. I'm currently fermenting this very first batch of seeds, so I'll provide a closeup of the seeds in a few days.
The taste is definitely reminiscent of S. habrochaites, but it is not as strong. The fruit is also a lot sweeter. I think I read somewhere, that one should let S. habrochaites fruits ripen off the vine for a few more days before consumption, so the jury is still out on the final taste verdict.

My current best guess as to the color of the fruit is that the green of S. habrochaites comes from an allele that is different from the normal green alleles found in GWR S. lycopersicum varieties. That theory presumes that the dominance hierarchy above is correct and that a cross between yellow and ivory (very faint yellow) results in yellow.

What do you make of this?
Can someone offer an explanation for the color of the fruit?

End of part 8.