Breeding for Late Blight Resistant Tomatoes

[Tim DH]

Sorry to hear about your lack of fruit. My Uluru Ochre has been quite productive. ....

[Justin Jardinier]

But if you can get Uluru Ochre to fruit at your growing location, it may have some excellent genes for surviving late blight

What makes you think this? Also, is it possible that it requires short days to flower? Mine is now flowering under short day conditions.

[Cathy A]

What makes you think this?

The fact that mine was tall (for a dwarf), with a thick, healthy stem and healthy green leaves, at a time when nearly every tomato plant surrounding it had turned brown and died.

[Cathy A]

Is it possible that it requires short days to flower? Mine is now flowering under short day conditions.

I doubt it, because mine flowered all summer. But the flowers never yielded fruit, while all the tomato plants surrounding it produced a steady supply of fruit.

[Justin Jardinier]

Ah, I had one of Joseph's 'elites' like that, did well while others were dying from blight around it, set plenty of flowers, but almost no fruit. Probably due to the inserted stigmas and being self incompatible, I'd guess (this one I mean, not Uluru Ochre). I'm still really curious what's going on there, since of the 8 fruits it did make, 5 of them were ones I had hand pollinated. I clearly accepts SC pollen. I've seen that with BH-NT as well, which seems to be derived from Joseph's BH line but crossed with something with late blight resistance, and has open anthers and very accessible stigma. I'd love to know what's making that happen, what mechanism! Seems so strange to be able to receive SC pollen from others but not their own pollen. And I have tested them the other way around - SC plants can be pollinated by their pollen. So it seems quite different from the usual SI system.

Anyway that's nice news about Uluru Ochre disease resistance at least, perhaps it will give value in crosses.

[Cathy A]

Yes, it was very odd. I've never heard that Uluru Ochre could be self-incompatible, but even if it were, it was surrounded by other tomato varieties producing pollen and a healthy bee population.

My guess is that something was causing early blossom drop, but that's just a guess, and even if true I have no idea of the root cause.

[Justin Jardinier]

Oh yeah I'm not at all suggesting Uluru Ochre could be SI. Just that what you said related to my experience, for different reasons. My talking about those 'promiscuous tomatoes' not being able to pollinate themselves but readily receiving SC pollen, was pretty off topic really, it's just something that's been on my mind and I seem to be the only one talking about it, so I'm still trying to work that out.

[William Schlegel]

You may be the only one who has observed it! Very interesting observation though!

[Justin Jardinier]

Intriguing. I wonder if I am the only one who has observed it because I am the only one who has tried and recorded results, or if it is merely due to outliers making up my very small sample size?

[William Schlegel]

Oddly on the back porch at the work week apartment I planted three R18 and one The One in pots. They got extremely tall, showing that tbey are not dwarf, and dropped flowers. I tried pollinating them, without emasculation, with some pollen from Brad Gate's Amethyst Cream and they finally have set very green fruit. I may clip off a bouquet of them, if frost is predicted, and I am there. Grow them next year and see if there are any crosses. Hmm I should separate a thread here.

Oh also my hoped for crossing block to get MMM x The One didn't work last year but The One x MMM may just have. 2023 Third generation the one plants seem to be ~5 varieties and it is very unclear if it is segregation and or hybridization that is the culprit.

[William Schlegel]

https://landracegardening.discourse.group/t/blight-trials-for-williams-tomatoes/1638/5

Julia Dakin posted some very interesting results for some of my accumulated late blight breeding material and some of my other material in her late blight prone Coastal California garden. Long cool growing season down there.

[William Schlegel]

I've pretty much cleared out the tomato plants for the year. But to my surprise, while almost everything planted at the start of the season is throughly dead and turned into a brown mush (without a frost, so probably late blight)...

...the Uluru Ochre plants are still tall, firm, and green.

Unfortunately, they still haven't produced any fruit, and apparently won't here.

But if you can get Uluru Ochre to fruit at your growing location, it may have some excellent genes for surviving late blight that could be crossed into any projects you have.

I got one very late tomato from Uluru Ochre but didn't manage a cross. I ended up cutting into it too early for good flavor so just saved the seed.

[Justin Jardinier]

Oh wow that's great news about Uluru Ochre! I was just crossing to it today in fact, and have numerous crossed fruits in both directions forming. The pollen I was using on it today was a few kinds of domestic x chm. F1s. I heard chm. can give earliness, apparently, if I understood this correctly:

Finally, an F 2 population derived from S. lycopersicum and its late-flowering wild relative S. chmielewskii (line CH6047) was used to study the genetic mechanisms underlying flowering time in tomato (Table 9.7; Jime´nez-Go´mez et al. 2007). This work allowed the identification of two QTLs affecting days to flowering and six QTLs for leaf number (the number of leaves under the first inflorescence). Interestingly, some of the early flowering QTL alleles were contributed by the S. chmielewskii parent, highlighting the usefulness of this wild species for the improvement of flowering time, and in general the importance of exploiting the genetic variation existing among all wild relatives of tomato.

Source: Wild Crop Relatives- Genomic and Breeding Resources - Vegetables - Chapter-9.-Solanum-sect.-Lycopersicon.

Julia Dakin posted some very interesting results for some of my accumulated late blight breeding material

I'm surprised Iron Lady suffered from late blight! It's homozygous Ph2 + Ph3, which I thought was basically the gold standard fro LB resistance. That's kind of worrying. Are we sure it's LB they were suffering from?

[William Schlegel]

Nothing is certain. Also, in the accompanying imagery- it looks like the Iron Lady vines did survive. Where some of the strains like my Mission Mountain Sunrise of which we didn't really expect any resistance to anything- they just died very nice and cleanly dead.

Also: it could be a vigor thing. Last year I noticed that the F2 Iron Lady parents of the F3 Julia grew out were kind of low vigor meh. Someone suggested that could be outbreeding depression and might improve in the F3 and subsequent. I think Julia's results seem consistent with that hypothesis.

[Nicolas]

Iron Lady F1 is determinate, so even if it takes LB well, it looks less healthy at the end of the season because of the lack of continuous growth.