Breeding for Late Blight Resistant Tomatoes

[Roland]

Abigail F1 is heterozygous for both ph2 and ph3.

[William Schlegel]

The European open source seed organization now has five tomatoes with some late blight resistance.
Sunviva, Vivagrande, Marchenwald, Marchenglanz, Marchenengel, very interesting looking work!

https://www.opensourceseeds.org/en/seed/tomato-%E2%80%9Esunviva%E2%80%9C
https://www.opensourceseeds.org/en/seed/tomato-vivagrande
https://www.opensourceseeds.org/en/seed/tomato-m%C3%A4rchenwald
https://www.opensourceseeds.org/en/seed/tomato-m%C3%A4rchenglanz
https://www.opensourceseeds.org/en/seed/tomato-m%C3%A4rchenengel

[AndrewB]

The European open source seed organization now has five tomatoes with some late blight resistance.
Sunviva, Vivagrande, Marchenwald, Marchenglanz, Marchenengel, very interesting looking work!

https://www.opensourceseeds.org/en/seed/tomato-%E2%80%9Esunviva%E2%80%9C
https://www.opensourceseeds.org/en/seed/tomato-vivagrande
https://www.opensourceseeds.org/en/seed/tomato-m%C3%A4rchenwald
https://www.opensourceseeds.org/en/seed/tomato-m%C3%A4rchenglanz
https://www.opensourceseeds.org/en/seed/tomato-m%C3%A4rchenengel

Very cool! I imagine if one were to make a cross with these and something OSSI Pledged you would need to adopt the European Open Source German Court protection rather than the simple OSSI Pledge. Something I think would be wonderful!

[Nicolas]

I grew most of those last year, and even if LB pressure was light, they showed more health at the end the season than the standards cultivars.

I confirm that sunviva taste is a little more fruity.

[William Schlegel]

I think it is very interesting that our European members and then our European sister organization are working very hard on this problem out of necessity! Some of those tomatoes look fantastic and would be very useful for further breeding!

[Justin Jardinier]

There I asked him a question about how he does it and he uses agbiotech in California. https://agbiotech.net/dna-markers/?fbclid=IwAR2tgIaL-QuhNzxn_q2z_IaLTJYB9gFrzlZLK4TzlbhITOVUXxxQ2XydEDA you can click on the tomatoes there and see that they offer PH2 and PH3 testing a long with a lot of other tomato genes.

They can just test for PH2 and PH3 for us. Which probably wouldn't be too expensive for one set of tests. It would be pretty expensive though for a whole segregating F2 I am guessing.

I'm a little afraid to email them and ask what it costs

Did anyone find out the costs yet? I think it could be great to test. Maybe growing out F2 (e.g. from a homozygous ph-2 and ph-3 crossed with something early and tasty and preferably with some hab. LB resistance if possible) and even deliberately infecting all the seedlings with blight, or taking cuttings from each and infecting the cuttings, then maybe send off to test the ones that pass that test but also have other desirable traits by the end of the season?

LA1033 has a multi gene resistance to late blight that briefly got the PH4 designation before it was reassigned to a single gene trait in a pimpinillifolium accession or some such. Mainstream breeders have little use for this because using it would be difficult.

In the paper 'Identification and mapping of quantitative resistance to late blight (Phytophthora infestans) in Solanum habrochaites LA1777' - Junming Li - 2009, it seems LA1777 is significalty superior against LB than LA1033. Why would you use the latter rather than the former?

[William Schlegel]

That is a good question. First I heard of that paper. I believe I have LA1033 but do not have LA1777. Haven't made much progress with LA1033. Might have saved a small amount of uncrossed seed.

Another thought though is: for diversity. LA1777 is quite famous. It might be good to go with obscure on occasion.

[Justin Jardinier]

Another thought though is: for diversity. LA1777 is quite famous. It might be good to go with obscure on occasion.

Maybe a way around that without having to reduce LB resistance, would be to cross LA1777 with those lesser resistance strains like LA1033 and LA2099, grow them for a few years in an area with heavy blight (or better still, deliberately expose them to various different strains of blight like in that paper), and then use the offspring for crossing with domestics?

I have 4 types of hab growing. 1 has some blight, one more maybe not or maybe a little, and 2 have none, LA1777 and one other that is earlier but likely not as good against LB in general. I have made cross attempts but rather late, though might get fruit. With the intention of using for crosses in future generations to combine LB resistance and more early. But I had only 1 LA1777 and 2 of the other, so, not ideal. Well, not for making a good sustainable population, but even their F1 could be useful for using in crossing maybe. Probably more useful than just the pure earlier 1 and would fit the diversity criterion! And next year if I want to work towards a sustainable population of habs I could just grow them among more of each of those 2 accessions.

[Roland]

Late blight test:

As a test, I infected a number of deliberately selected seedlings with Phytophthota.
I sowed the following varieties:
Black cherry (no resistance genes)
Koralik (ph2 homozygous)
Sungreenf1 x Vivagrande (ph3 heterozygous)
Sungreenf1 x Mountaineer pride (ph2 and ph3 heterozygous)
Primabella (ph2 and ph3 homozygous)

Leaves collected from varieties that do not possess resistance genes. The leaves or stems were affected by approximately 50%.
Place the leaves in a container with water.

The test was 30 days after sowing. The seedlings just had the 3rd true leaf in the head of the plant

The next day, mist this water over the seedlings so that the leaves and stems were thoroughly wet.
After this, place the tray with seedlings under plastic and spray water into the plastic on the bottom so that the humidity remains 90%. It was 15 to 25*C.

24 hours later the humidity appeared to drop and the seedlings were therefore sprayed again with contaminated water.
12 hours later, remove the plastic and let the seedlings continue to grow dry.

The first attack was visible 72 hours after the first spraying. Some leaves seemed to dry up.

The status was drawn up 5 days after the 2nd infection:
90% affected on leaves and stem: (no resistance genes)
75% affected on leaves and stem: (ph2 homozygous)
75% infected on leaves, stems are free of infection: (ph3 heterozygous)
50% infected on leaves, stems are free of infection: (ph2 and ph3 heterozygous)
<10% affected on leaf: (ph2 and ph3 homozygous)


For pictures check here:
https://www.facebook.com/permalink.php?story_fbid=pfbid02ARvTSK8GhHgzADrKFXqNZcBgvsvvAkFRj32mgbN7HXeFppFRy8QJrggp4WwmS95Kl&id=100024953531011

[Tim DH]

Nice work Roland.

How did you make your innoculum (contaminated water)?

Have you any idea which strain or strains of blight it was?

My reading of this paper:

https://research.bangor.ac.uk/portal/files/7454967/PDB4626-00.pdf

Is that the researchers found eleven different strains of Late Blight in samples collected from amateur growers.

Because of poor germination (Tut tut, expensive commercial seed as well) I only got one plant of Crimson Cherry F1 this year. It's supposed to have two blight resistant genes (ph2 & ph3?) but it got completely wiped out by Blight.

Somewhat surprisingly, my own F1s with Latah as pollen parent are still producing. Everything else is long dead.

[Cathy A]

Everything I planted this year is long dead except the Sungold F1s. Brown shriveled stalks, with leaves eaten by tomato hornworms. I've pulled all of them and tossed them in the woods (not compost).

I don't think the Sungold F1 have any resistance. I just planted those later in the season, and that let them escape the worst of the infection.

It was an extremely hot, wet year, and I had planted my tomatoes very densely for the trial, so they may have been weaker with less room to root.

[Steph S]

That is nice work, Roland.  Definitely looks like homozygous is the way to go.

It's interesting that late blight has such a similar resistance profile to early blight (Alternaria), with resistance being specific to leafs vs stems.
For Alternaria blight the stage of maturity of the plant, whether fruiting, ripening, heavy fruit load etc makes a big difference to resistance as well.   Indeterminate plants are more resistant than determinates, perhaps because of this.  The ethylene given off at ripening and the hormonal pathways involved in ripening really drop the plant's resistance and makes for a worst case exactly when you want to keep your leaves and stems in place. 

I recently read a covid study, that was in a CT correctional center, and their work showed that high virus load caused resistance from prior vaccine and/or prior infection to collapse, with much lower rates of protection than you would expect.
I think with these plant diseases it is the same, resistance only holds to a certain point after which the overwhelming spore load (produced by non resistant plants as hosts) makes complete resistance impossible. 

[William Schlegel]

My Crosses with some hope for Late Blight Breeding
MMM x LB PH5 Pimp PI 270443
MMM x Purple Zebra F1
MMM x (MMM x LB Pimp PI 270443) which may make recovering potato leaf blue exserted bicolor and size easier.
(MMM F2 x Purple Zebra F1) x (MMM F2 x PH5 PI 270443 pimpinillifolium)
(MMM x Purple Zebra F1) x (MMM x LA1375)
(MMM x PH5 LB pimp PI 270443 ) x (MMM x LA1375)
Sunviva x MMMF3
(MMM X Purple Zebra) X (MMM x Brad's Atomic Grape)
MMR Dwarf No Blue x (MMM X PH5 LB Pimp PI 270443)
Amethyst Cream x (MMM X Purple Zebra F1)
Galahad F1 x (MMM X Purple Zebra F1)
Utah Heart x (MMM x Sweet Cherriette) - collaboration with Reed whose varieties survive diseases.
Utah Heart x (MMR Dwarf) - collaboration with Reed whose varieties survive diseases.
(MMM x Purple zebra) x (mmm x galapagense x)

[Nicolas]

Homozygous for Ph3
Plum Regal

Plum Regal F1 is heterozygous for Ph3

From this document, parents are NC 25P and NC 30P

From this page, NC 25P has Ph3, but not NC 30P

[Cathy A]

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.