Manually crossing tomatoes

Last year I did a manual cross of a ‘golden currant’ (which looked like a yellow cherry tomato, size of berry and leaf shape, wasn’t phenotypically a pimpinellifolium), and a brandywine pollen donor. A few weeks ago I planted the seeds. At first I thought it didn’t work, but now the crossed tray looks different than the uncrossed offspring. My question is when crossing a regular leaf with a potato leaf plant, should I expect this much consistency? I suppose that makes sense because it was an F1, but I had the impression I should look for some potato leaf seedlings. Does that come in the next generation?

GC x Brandywine

Uncrosses golden current (likely an unintended hybrid I got from HR Seeds)

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Regular leaf is dominant.
Potato leaf is recessive.

So your first cross if you use the potato leaf as the mother any regular leaf seedlings are definitely crosses. They have one regular leaf gene and one Potato leaf gene.

If you used the regular leaf as the mother you will have all regular leaf plants. If the cross was successful then the offspring will carry one recessive gene for potato leaf but you can’t see it. Only the next generation do they sort out into: 25% regular leaf, 50% regular leaf (and carrying Potato leaf), 25% Potato leaf.

As Joseph has said in the various places… when you get into mixing the wilds in the leaf shapes show plenty of variation and it’s not all simple dominant and recessive genes.

Kadence is correct, 25% will segregate back to potato leaf in the F2. F1’s can be extremely uniform unless they are between two unstable lines.

I just up-potted about 13 of those Golden Currant x you sent me last year. (was it?). I’m excited to play around with those over time. Thanks again for the seeds!

Thank you!

When you make all these F1 Hybrids, how many do you like to keep for growing out for the future generations? Are seeds from a couple representative of the entire batch? Assuming space and time are limiting factors, of course.

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I’m just getting into plant breeding this year so… this is all based on reading and not experience yet. But I am familiar with livestock, which has similarities.

The F1 is going to be most similar across the offspring. Assuming the parents were each a set variety that had been selected for set traits. The more different the parents, the more differences you’ll see in the offspring of further generations.

For example (as best I recall from the dwarf tomato project video) a currant tomato crossed to a 1# beefsteak. Small fruit is dominant. The F1 offspring plants had cherry sized fruits.
Currant parent genes dominant, assuming SS.
Beefsteak parent genes recessive, ss.
So the F1 plants are all cherry size fruits, got one gene from each parent. All are Ss. This goes for all genes so the first group tend to be the most similar.
When these self or cross they are getting one gene from each Ss parent. Which gives the breakdown as I said before. Punnett square that most are probably familiar with.
Ss x Ss =
25% SS, homogeneous dominant, small fruit.
50% Ss, heterozygous, small fruit.
25% ss, homozygous recessive, large fruit.
So the F2 and beyond will be a random amalgamation of trait combinations from currant to beefsteak fruits plus all other traits from both parents.

As many as you can manage is best. It’s a numbers game, looking for the plant with the right combination of traits you are looking for.
For dwarfs at the F2 and after you can start lots of seeds and thin out to just the dwarfs. So keep lots knowing you’ll end up with 25% dwarf in the F2. So keep at least 75% more than you want in that case because the 25% is what you’ll actually be working with that are dwarf.

I like having extras and back ups so I tend to keep more than strictly needed.

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I’m really interested in hearing answers to this too. I’d guess the common answer would be ‘they’re all the same’ when it comes to crossing 2 stable varieties but I’m interested to hear for example when crossing a stable variety with a wild species, which might have a lot of diversity in the pollen of even one flower (which I guess might apply not only to SI species but also facultative SC?).

Also when I’m crossing with wild species, I’m taking pollen from as many plants as I have from that accession, mixing it, and using that, to get as much diversity as I can. I’m doing that partly to increase the chances of a successful cross. But also to potentially increase the number of crosses. I don’t even know if it would be at all easy to tell whether the different F1 offspring from such as cross fertilised fruit are genetically different from each other, or if they would all still have very similar appearance - it seems perhaps wilds can have big genetic but small/no phenotypic differences, in contrast to domestics with very low genetic but large phenotypic differences. So, I’m also curious how to approach the stage of growing the F1s out. Though I guess in this context, one would be please to get any that survive and produce viable offspring, so… perhaps plant as many as one has space for, and carefully ave or share the rest of the seeds?

I’d be really interested to hear how others handle this will domestic-wild crossing. As well as other unstable crosses, such as crossing two F1s even if domestics. I guess in that latter case, again one wants as much space as possible to grow as many as possible since the F1 gen of such a cross would immediately be highly varied.

If the two parents of the F1 are themselves stable you wouldn’t need many! The trick is just to have plenty of seed for the F2 where all the fun happens. I reckon 10 would give you seed to share widely in many instances.

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If parents are stable then it’s not that important to have many. One breeding lecture showed a chart which said that by 8th generation there are 2 million possible compinations. Can’t remember what it was in F2 or F3, but the point is that you are going to get overwhelmed by possibilities before they are stable. Only slightly limiting factor might be how seedy your F1 is. Most of the time there will be enough seeds even from one plant for several people, but atleast some beefstakes have very little seeds and in that case more would be better for F2 growout. Even then at some point numbers will multibly by each generation and very fast you will have more combinations than even lots of people can grow. So I wouldn’t worry too much about growing enough. Having some extras might still be good as there might be number of factors that get plants killed before they produce.

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F2 generation seeds of such a cross would be a lovely addition to a cherry tomato grex…

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Hmm, why would that be? Is it that the potato leaf trait goes along with a bunch of other genetics, such that having potato leaf on both chromosomes would mean lower diversity because a whole bunch of genetics would also be the same on both chromosomes? I’m trying to cross Black Sean Man (BSM), a potato leafed sturdy fat stemmed fat fruited tomato, with various wilds. I was thinking in future generations, if my crosses are successful, to try to breed them as potato leafed varieties if I can, since you mentioned that possibility of advantages. But if that goes along with a bunch of other stuff that might be undesirable, maybe it’s not worth trying that… My idea was to try to cross the various crosses I hopefully get, like BSM x chmelewskii, BSM x peruvianum, BSM x cheesmaniae, BMS x galapagense, and some various BSM x (domestic x wilds). Like a new multispecies population. I’m also trying some other short fat big fruited early producing domestics with all these wild crosses. And, I want to try also crossing with chilense, but that should be hard. I have some BSM seedlings right now that I want to try making mentor grafts with to chilense, then use the BSM ‘pupil’ (or is it called ‘disciple’? I forget) as female to chilense pollen - a bit of a long shot but decades ago some Russians claimed to do this using peruvianum disciples with mentor grafts to domestic mentors, so I figure it’s worth trying, could be nice to have those chilense roots so don’t need to water them in long dry spells!

I’m glad to see some of my galapagnse and cheesmaniae starting to flower with exserted stigmas. I really look forward to seeing how crosses turn out with them! One galapagense has really nice flowers too, quite big!

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Yep, Hoosier Rose is the only potato leaf I have. I got it several years ago and believe it was called Red Rose or maybe Rose Red. I found conflicting info on if Red Rose was an F1 or not but the seeds I saved segregated into a regular and a potato leaf. Fruits were very similar and the red one was maybe prettier, no deep lobes or green shoulders but didn’t taste quite as good so I named this one Hoosier Rose and kept growing it.

How do people feel about the different tomato leaves? Is there a specific benefit of potato leaf tomatoes? I have a bias towards them but don’t know why. Maybe it’s the Black Sea Man I have, which just looks so sturdy and the leaves look really strong and solar-efficient. I have a feeling I may also have read some benefit of the potato leaf types, but I can’t remember what.

I’m trying to cross Black Sea Man with wilds, because it seems so sturdy and such big and relatively early tomatoes, that people say have great flavour - I am yet to taste them. It seems like a great candidate to cross with wilds.

A mentor at a local greenhouse back in 2017 thought their were distinct benefits and healthier plants with potato leaf. I stayed skeptical, but I work with them heavily because as a recessive trait it is a really simple and easy genetic marker to make sure my crosses with regular leaves took. Though I saw on Facebook somewhere where an experienced breeder said you would eventually just have confidence in your crosses. Though I also am kind of fond of the idea of helping out other beginning breeders by stabilizing traits that may make it easier for them to make their own first crosses.

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It seems to me that potato leaf is a bit more prone to leaf diseases, but I am not a large-scale breeder or overly conscientious observer of tomatoes so I can’t say that for sure and the one I call Hoosier Rose seems to be an exception. Some other heirloom, potato leaf types, certainly did suffer more than average but all of my tomatoes suffer at least to some degree from disease, depending largely on weather conditions. I don’t worry much about it as I still generally get more tomatoes than we need.

I won’t say I’m skeptical, maybe agnostic, about endophytes and epigenetics, but something is at play that allows my tomatoes to produce despite the presence of diseases. I’ve had most of them for twenty years or more, so maybe they really have adapted by some non-traditional genetic means to my soil and all the mico-critters that live there. I’ve said before that I’m a bit concerned about it because I only have a few kinds and most new ones I’ve tried in recent years barley grow regardless of how many letters they have behind their name. Hoosier Rose is an exception to that as well, as I’ve only had it for maybe ten years at most.

When I first got Hoosier Rose, by its other name it segregated in the first year into a potato leaf and a regular leaf. The potato leaf was maybe a bit more productive but distinctly better tasting than the regular leaf, so it is the one I kept. Or maybe it didn’t segregate, maybe the seed company got their seeds mixed up??

Now though, once in a while when I plant my Hoosier Rose seeds a regular leaf shows up. Are those random crosses with a regular leaf and have I made a mistake by not paying much attention to them? It’s really only happened a couple of times but I only plant 10 - 15 seeds per year, if they are a cross maybe there are lots of them in my archived seeds.

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I think it is simply that a lot of potato leaf varieties are close relatives. So by crossing them with wild species you could potentially really help yo diversify them!

Ah, I see what you mean now I think. So nothing inherently depressed about potato leaf but just that most tend to be - cool, sounds easy enough to fix! Let’s see if I have this right:
tasty potato leaf x tasty wild-domestic hybrid

no potato leaf

25% potato leaf, so cross the potato leafs

100% tasty genetically healthy potato leafs

Is that right? And even more genetically healthy if using crosses from different parentage in F0 and F1, and even more stably healthy if choosing exserted stigmas to make a higher natural crossing rate in the population. And then even more genetically diverse though taking more time to get tasty, if using wild or not yet stably tasty wild-domestic hybrids, as F0 parents.

Yep that is kind of my standard potato leaf breeding scheme! I just keep picking out the F2 potato leafs. One caveat sometimes that 25% seemingly skips a generation. So my Mission Mountain Morning x Aztek seems to have no F2 potato leafs. However my F2 Mission Mountain Morning x Sweet Cherriette does. In the F2 I will probably cross the two lines a dwarf MMM x Aztek F2 x a potato leaf MMM x Sweet cherriette. Then try to get a dwarf potato leaf in the F2 of that. Then probably cross that F2 with something else! Also I figure if I make some F1 x F1 crosses I should still preserve the chances of getting a potato leaf in the new F1. So (MMM x pimpinillifolium F1) x (MMM x galapagense hybrid F1) may happen this year. I have four different F1s in one of my manual crossing block gardens and am just waiting for blooms. Then a few more inside the nearby greenhouse.

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Cool. What spacing do you do between plants and between rows William? And do you use stakes or strings or, nothing? And aside from edibles, how about supports for wild species? Thanks!

Generally anywhere from six inches apart to ten feet for transplants and possibly just a few inches or less for direct seeded. Though there is a lot of variation. No supports generally. Maybe the occasional tomato cage just because I have a few available. The vast majority get nothing. Then with no support, shallow topsoil, and thousands of tomato plants reproductive output per plant is not impressive. However, even one tomato is often enough for seed saving. I go a very different route than those who maximize the potential of individual plants. Still kind of overwhelming at peak production.

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