Breeding for Late Blight Resistant Tomatoes

[Justin Jardinier]

I have no idea why I have so many with open flowers.

Wow, lots of exsertion and openness, they look great!

I agree, but I do not consider utilizing a handful of PH genes to be "multiple methods."

1) PH-2 + 3 homozygous populations/lines
2) PH-5 populations/lines
3) Interbred largely or wholly outcrossing populations with various resistant sources not from PH genes.

For me, these 3 methods = multiple methods.

While it's more work to stack the 100 genes up front, given a growing area with a steady background of disease pressure and minimal selection, I wouldn't expect it to be difficult to maintain once created.

If someone created it and it was delicious and grew here well, I would happily grow it! If I created it, I would probably never know, referring to my point about that above. Either way, I have nothing against the idea in principle - I support it.

Stacking a handful of carefully-selected genes may be less work up front, but you will never truly be caught up, because a single new disease mutation can nullify one or even all of these genes.

Judging by the quote I gave above about the PH genes, it seems PH-2 has been identified since at least 1955 and PH-3 since 1994 - not sure how long they have been in use in commercial tomatoes but combined they seem plenty to provide excellent resistance. Would you think that they would not be useful by the time we are able to breed some nice tomatoes with them? And I'm not aware of PH-5 being used yet in commercial tomatoes, so it would surprise me if both of these would no longer be sufficiently advantageous by the end of this decade. But I do not know - do you think so?

And you could lose most or all of the crop the first year the new disease mutation reaches your garden.

That is basically the situation for non-PH tomatoes right now, so far as I understand, in such areas with sufficiently heavy LB - total loss once LB comes.

Then it will take multiple years to find a new single-gene with resistance and cross it into your existing varieties.

For me, I am not searching for any new single genes. I'm breeding with the known genes because they are the only tomatoes known to work in the conditions I am breeding for, to my knowledge. As for the unidentified forms of resistance, I have no idea how many genes are involved and I am attempting to employ them in mostly or wholly outcrossing populations. And I feel like I don't mind if I loose most of the crop of those, so long as there is enough left to give sufficient diversity, including enough SI alleles in the purely outcrossing populations, for the populations to be sustainable. I would rather expect there to be heavy losses for a while.

And yes, we are on the same page with SI tomatoes!

I think a 50 percent SI tomato population would also be intensely interesting. I may have a mixed SI and SC system in my garden just by virtue of my interest in the wild SI species

I'd be really curious how that works. Especially whether any of the SI can be pollinated by the SC, and vice versa.

[reed]

That is some decent exsertion of the style and stigma. Might be worth assaying some of your saved potato leaf seed for existing outcrossing rate.

I don't remember what you said about potato leaf. Wasn't it that it's recessive, so any regular leaf that shows up is a cross?

[reed]

Got a little poll for you all.
In the pictures of the open flowers, what are the chances that they were already self-pollinated when the photo was taken?

[William Schlegel]

I would expect that the SI and SC mix from habrochaites that it mostly has pollination from SI to SC with rare exceptions. The LA2329 accession while I think listed as SI is really mixed itself and at least capable of some selfing. I think all these things are liable to have rare exceptions. Like Andrew's thread from several years ago about how to overcome some of the crossing barriers. There are always exceptions. If we wanted to be extremely accurate we should probably say something like 99.999% obligate outcrossing rather than 100%. Note that those numbers aren't based on research just a wild guess. So I entirely do expect some SC pollination of SI plants especially given your recent observations. However I have noticed another barrier. The hybrids can be quite small initial seedlings.

[Justin Jardinier]

Got a little poll for you all.
In the pictures of the open flowers, what are the chances that they were already self-pollinated when the photo was taken?

I guess that might depend on the orientation of the flowers, whether pointing up or down, towards or away from the wind?

I would expect that the SI and SC mix from habrochaites that it mostly has pollination from SI to SC with rare exceptions.

I'd be curious how the SC wouldn't be bred out of a natural population that way, if the [SC x homozygous SI]'s SC pollen could not pollinate the SI members of the population, and if heterozygous SI are SI. Would that not decrease the number of SC plants each generation? Though there might be a part of this story that I'm missing.

Unless perhaps it's not as simple as SC vs SI, rather that perhaps the SI barriers are somewhat broken down in that population?

I agree about exceptions. For my own project, I figure I don't mind if there is sporadic non-SI behaviour so long as they are all homzygous SI and the pollinations occuring from SC or self pollen doesn;t disrupt the sustainability of the population, for example giving only very few seeds and so those fruits can be selected against for seed saving.

However I have noticed another barrier. The hybrids can be quite small initial seedlings.

My arc crosses did well in F1, and most of the sibling crosses that germinated are so far doing well in the F2. But those crossed to other tomato species and hybrids, the seeds are being tricky. Of those I have tried germinating, some have done well, at germination and now with several leaves; but some not, whether that be not germinating at all, or having issues directly afterwards before making any true leaves. Also the F2 seeds themselves mostly look great, but crossing them with other species or hybrids, the seeds mostly look in some way or another potentially problematic. I don't mind pampering them so long as they go well not too many generations down the line.

In comparison, the chmielewskii crosses crossed to other species and hybrids, seem to be giving fine looking seeds. Not germinating them yet actually because of that reason - am germinating the dodgy looking seeds because I figure they have a higher chance at germinating while fresh. But have started just a few chm cross x other hybrid out of curiosity, and one is just germinating now, looks good so far but early days yet.

The arc crosses x peruvianum seeds look very poor, but several have germinated now and I am in full pampering mode for them. I have some confidence that they will do well in some future generations but that is a purely faith based position of joyful naïvety and optimism

I have noticed some hybrids, I forget now which species - maybe a hab cross - have given the first leaves before a root, which seems a bit odd and impractical! I'm hoping this will remedy in the F2.

On the topic of small seedlings, eating one tasty cheesmaniae, which I expect is in fact a hybrid with pimp, I found the small seed size rather pleasant and interesting in the eating experience. And wondered, perhaps it could be nice to breed a small seeded line. It would have the disadvantage of giving a slow starting small initial seedling, but I wonder, might be worth it for the pleasant novelty of that different texture when eaten. I think the main reason why I have never been into cherry tomatoes is because of the high ration of seeds and skin to the part I actually want to enjoy. This could address that somewhat perhaps.

[William Schlegel]

I don't remember what you said about potato leaf. Wasn't it that it's recessive, so any regular leaf that shows up is a cross?

Yes, potato leaf is recessive, so any regular leaf that shows up in your potato leaf seed is a cross!

Another similar recessive is the rugose dwarf trait or traits that the dwarf tomato project used. They also can be selected as young seedlings in the F2, but any non-dwarf seedling from a dwarf mother is also a cross. I've hypothesized the ultimate mother would be potato leaf, dwarf, and exserted.

To address your poll Reed: Alot depends on the actual rate of outcrossing. In 2022 I set up crossing blocks with my potato leaf mother lines Mission Mountain Sunrise and Mission Mountain Morning. Then I planted a bunch of those potato leaf seeds. Mostly no crosses. The year before I got plenty of crosses. One of the big differences was in 2021 I had essentially free choice fathers- lots of available fathers. One exception in 2022 was the MMM F2 with the best exsertion in an extremely densely planted row of lots and lots of varieties. Plenty of crosses from that one plant- more than one cross I reckon based on the regular leaf seedlings I found. So it is not enough to have a good mother- you have to have a good father too, one that produces plentiful pollen. In some cases I think the crossing blocks when the other way than I intended. Judging from the degree of exsertion on those flowers in your pictures, I would still expect pretty rare cross seedlings. Doesn't take much to plant 1000 potato leaf seeds and see if any come out regular leaf though. Then transplant that one regular leaf seedling and baby it a little because it will produce plentiful F2 seed! Also you can transfer pollen to stigmas like that without emasculation. Emasculation sometimes leads to the flower just drying up on me. So if you have a potato leaf tell- you can grab pollen with a pollen spoon and pollinator tool and just dip all those exserted stigmas in them, especially when the flower is young- it won't even have released its own pollen yet, and you'll give that foreign pollen a head start. Tie a little paper price tag too it and you won't forget which one it was either.

Justin I am inspired by your successes with Solanum arcanum to grow it again. Gotta add it to my 2024 list- once I get that list started.

[Joseph Lofthouse]

In helianthus tuberosus, the self-incompatibility rate is known.

With a self-incompatibility rate of 99.2% I'd expect about 1 seed per 3 flower heads. If there are around 200 flower heads per plant I'd expect a single self-incompatible plant to produce about 70 seeds. Sure it'd be a pain to thresh a gallon of seed heads for a quarter teaspoon of seeds. It's not like my labor has a price attached.

[reed]

I think the natural crossing in my tomatoes is probably higher than what might be considered normal. Problem is I grow very small populations; I rarely plant more than twenty or so plants and nearly all of the fruit is eaten fresh or canned and I haven't really tired very hard to purposely discover the likely crosses, yet.

Assuming though that the flowers are not already completely self-pollinated before they even open it will be easy to just pick out a few to apply other pollen and then keep track of them. Then the next year plant ALL of the seeds from those fruits. I always keep lots of back up seed so no worries about messing up my favorites.

I wish I had more potato leaf varieties. Right now, the only one is the Hoosier Rose and it isn't the one I most want crosses from. But on that point, if potato leaf is recessive then pretty much any normal leaf could be carrying it. So, If I use Hoosier Rose as the pollen parent, and Mr. Stripy as the mother, there is some chance that some offspring will be potato leaf?

And I can use any pollen on the Hoosier Rose and look for normal leaf in the offspring. Except if the pollen parent happened to not be homozygous for normal leaf, then potato leaf could still show up too? I have a lot of back up seed, so next year I could plant a few hundred Hoosier Rose and see if I may already have some crosses.

Are there any other real obvious traits in tomatoes that signal a cross has occurred?   

[William Schlegel]

Mr. Stripey shouldn't throw any potato leaf in the F1 but 25% would show in the F2. Non-zero though but extremely unlikely. If you had potato leaf in recession on your strain of Mr. Stripey you would probably have seen it by now as it would segregate our at 25%.

Obvious traits to me are any segregation. Sometimes this would show in the F2. Anything that is different from the mother could be a sign of a cross. Different fruit size, leaves different, different colors, and anything else different. That does get tricky in similar varieties but if you are familiar with them you might notice.

[ThomatoGarden]

Primabella is currently the most resistant variety available in Europe. It is an inbred line of Philovita F1 but has been crossed in the field by an insect of an unknown variety.

Philovita F1 is heterozygous for ph-3 and Primabella is homozygous for ph-2 and ph-3.

Mountain Magic F1 comes from a cross between a resistant beef variety (NC 2 CELBR) x a sweet cherry tomato (NC 2 grape). And is heterozygous for ph-2 and ph-3 genes. He is also heterozygous for the rin gene for extra long fruitlive and not ripening fruit. And there is the br gene (brachytic) what means the fruit clusters are closer and need les internodes.

How many F2 plants have you grown?
It is certainly possible that you have found some very resistant selections in F2 that are equivalent to Primabella's resistance.
In many tests, the resistance of Mountain Magic F1 appears to be very high.

Have you also noticed differences in taste in your F2 plants and perhaps you have found the rin gene that do not ripen?
Or did you find the br gene that made the plants more compact and the fruit clusters were every 2 leaves instead of 3 leaves?

ps. you can also find determinate plants in the F2.

I think Mountain Magic have a lot of potential to create nice OP varieties.

Hello Roland,

i grew only 16 Plants and was lucky to get some good ones. One the other Hand no luck with Crimson Crush.

dont know if ther are some other genes involved,i only selected for health and fruit quality.
Have to look for the br gene next year sounds interesting.

The plants were big and healthy. The taste was the same as the original. no cracking.
Sunviva for example was healthy but all fruits cracked (too much rain here).

https://www.youtube.com/watch?v=F_fAB7S3rX4 the fist plant in front of the green pole (2 stems)
is the MM F2 with bigger fruits

Does someone have expierience with Honey Moon F1 ?

[reed]

If you had potato leaf in recession on your strain of Mr. Stripey you would probably have seen it by now as it would segregate our at 25%.

Ah, so none of my other NL varieties are likely to be carrying recessive PL because it would show up once in a while anyway. I'm not a 100% sure they haven't from time to time over the years, but I never used to pay good attention and probably would have just thought I got my seeds mixed up.

Hoosier Rose did segregate and the strain I ended up keeping is potato leaf and now I understand that it stays that way, because it's recessive. Hoosier Rose came from a commercial variety called Red Rose which I thought was an F1. But looking it up now it does not call it and F1, just that it came from a cross between Brandywine and Rutgers. Regardless the seeds I saved the first year I grew it segregated into NL and PL varieties.

OH! I just thought, that explains why it still has slight variations, especially in the fruits. Some plants have more deeper lobes on top, some have more green shoulders. And since I have never really chosen just one to type to favor {add} other than going on with the PL, it just stays that way. It' might still be segregating too, and maybe even recrossing, I'd guess I'd have to deliberately work at if I wanted it completely stable, but I don't.

I think the volunteers in these same pictures that I posted before came from it. And one from the purchased seeds, which like I said I thought was an F1 at the time.

[ThomatoGarden]

Nicolas reported in another thread that "Tim's taste of paradise" had good resistance in France.

Tomatenflüsterer reported that "Black Centiflor" was the last Tomato in his Garden until snow.
 https://www.youtube.com/watch?v=rWj2yM3Q3rY the ones on the table.

Has anyone else experience with this varieties?

[William Schlegel]

Nicolas reported in another thread that "Tim's taste of paradise" had good resistance in France.

Tomatenflüsterer reported that "Black Centiflor" was the last Tomato in his Garden until snow.
 https://www.youtube.com/watch?v=rWj2yM3Q3rY the ones on the table.

Has anyone else experience with this varieties?

Interesting! this summer of 2023 I grew and made a couple of crosses with Fruity which is what "Tim's Taste of Paradise" was selected from, Tim Peter's work. I had to Google Black Centiflor but it looks to me from what I read that it appeared amongst some Red Centiflor one of Alan Kapuler's tomatoes. It looks like a cross with one of the blue skinned tomatoes to me. Alan's Centiflor tomatoes are amongst his occasionally outcrossing tomatoes, so a new variety springing up from that makes sense.

I am currently trying to reread Carol Deppe's "Breed Your Own Vegetable Varieties" and just finished chapter five though it is the second edition and I originally read the first edition though have had and read portions of the second which I first got a decade ago. I have really been enjoying reading again about Tim Peters and Alan Kapuler's work. It's amazing to me that they were doing the same work with tomatoes we are attempting to expand on now when Carol's first books were written. Carol writes about how they both would dehybridize hybrids, but also make new crosses with tomatoes including wild tomato species. It doesn't surprise me that some disease resistance would show up in their work or its descendants as their work likely contains an interesting amalgam of genes and at least in Alan's case the ability to occasionally produce a spontaneous cross.

I had long tress, blue skinned, cherry tomatoes show up in three places direct seeded in 2023- my The One direct seeding isolation garden, one of my two Mission Mountain and The One reseedings of the 2022 crossing block, and my direct seeding of Lofthouse promiscuous. This was a bit unexpected of a result, they don't match anything I have a memory of. I did some recombining of The One seed after growing them out in numerous gardens in 2022. In 2022 I did grow out some blue skinned descendants of Alan Kapuler's Golden Tressette that just showed up amongst the original seed from him and Yellow Centiflor Hypertress Cherry in 2022 and there was one patch of The One in that same garden.

[Steph S]

Hello Roland,

i grew only 16 Plants and was lucky to get some good ones. One the other Hand no luck with Crimson Crush.

dont know if ther are some other genes involved,i only selected for health and fruit quality.
Have to look for the br gene next year sounds interesting.

The plants were big and healthy. The taste was the same as the original. no cracking.
Sunviva for example was healthy but all fruits cracked (too much rain here).

https://www.youtube.com/watch?v=F_fAB7S3rX4 the fist plant in front of the green pole (2 stems)
is the MM F2 with bigger fruits

Does someone have expierience with Honey Moon F1 ?

On the subject of Mountain Magic, I received some seeds from a friend in Ontario.  The area was devastated with LB this season, and the only one who had a crop was this farmer with Mountain Magic, which she bought and saved seeds.  She described the tomatoes as "huge" ie bigger than cherry size - so it may be this is already an F2 or F3 with significant resistance to the LB that affected Ontario this year.
I also got some seeds of the original F1, along with Mountain Gem and Plum Regal, in a package deal from Veseys.
I'm actually looking for Alternaria alternata/stem canker resistance which is part of the package, but it would be an asset to conserve LB resistance when working with these lines.  We don't commonly have late blight on tomatoes, but I have seen it on potatoes years ago, and also on potatoes of commerce.  So if there's blight in potato growing areas it is also finding its way here and could turn up any time.

[Justin Jardinier]

Has anyone tried Austrian Mountain Cherry? I've heard it has great blight resistance. Here's a link to it, terribly long URL!:
https://tatgut.de/public/product-view/eyJpdiI6IjlkbjZJWENxT3MrWHdzRVRpZEZ5dGc9PSIsInZhbHVlIjoiWmxEL0s2Wm14SWhwKzlRQ3VRSXVyZz09IiwibWFjIjoiM2RlMzgwMjdhNTZkMzAyYjgyZjEyNjcyZTdhNTMyYzZjOTI4NTg2MWRhZDM2NDU1ZTkzZTA0ZjRkYjA3YWQyYSJ9

Using automatoed translatoin it says:

Variety discovery from Austria, where this red cocktail tomato has been grown at an altitude of 1,650 m since 1920.

The AMC tomato, short for Austrian mountain cherry, tastes sweet and tomatoey. The plants have strong foliage and grow to around 1.80 m high. They can also be pulled with two drives. It's nice that this variety has been preserved thanks to Lukas Wallmann, who is also committed to its further development (open breeding).

No mention of late blight but this is what I hear from someone who is doing late blight breeding, so I am curious if anyone with late blight pressure has tried it here, or heard about it.