Breeding for Late Blight Resistant Tomatoes

[William Schlegel]

https://www.discovermagazine.com/the-sciences/the-source-of-the-irish-potato-famine-pathogen-is-finally-identified?fbclid=IwY2xjawIMzg5leHRuA2FlbQIxMAABHcp-UizMWdyfJEt_13fLN0tXiKjAy6qknsVkulAYmHAfY3F6j7uCSTcOMg_aem_DGQQMT5Wknz1vAHMJR0ynw

[Roland]

Almost all varieties of Gana Seeds have the ph3 gene:
https://ganeseed-en.imweb.me/33

I know F1 Appleberry yellow is ph3 homozygous.

[Nicolas]

Interesting, small sizes though

[ThomatoGarden]

Question:

MM F4 Salat No 2(very very resistant ,hard , slow ripening)   
    Resistance better Primabella, nearly immune to any disease outside,
    but hard slow ripening fruit, Like "Supermarket" Tomatoes
    only few brown leaf at the bottom, at the end of the year. (160% rain than normal)
    half under a small tree. worst place of all. Healthiest plant last year.

what to do? is there any use for this "Supermarket" Tomatoes?
I don't want to throw them away, cause they are so resistant, but the fruit were so weird!?
 


   

[Roland]

Does it maybe have the Rin gene for never full ripe and long shelflife in heterozygous form?

[ThomatoGarden]

It seems so.

Oh found a video, my memory was not 100% correct.
there were a little bit disease on 20.9.2024, but not that much.
It was still the healthiest plant at the end of the year. Although it had really the worst place.

https://youtu.be/Kz5oj2ReAnw Time: 0.10-0.40

I think i will grow 2 plants, just out of curiosity, but have no really use for it.

Will it ripe better in polytunnel, with more heat ?

[Roland]

The Rin gene is great for making your own hybrids. Once you have stabilized it I would love to buy some seeds from you.

[ThomatoGarden]

Maybe i can grow a few more (plant closer) and select early to make space.

But I only give away seeds for free. :-)

[Cathy A]

Galahad is an interesting variety, i think Roland knows more about it, but its determinant.

I'm growing Galahad F1 for the first time this year, mainly to see if it is more resistant to the diseases in my garden than other varieties. I hope to attempt some crosses with it, but I am still trying to successfully cross tomatoes!

[ThomatoGarden]

Hello to all,

here's just a little Report on how it is going in my Outdoor Tomato Trial. (started writing maybe 1.
I have not seen any Late Blight, but Early Blight (EB) is present in different degrees.

9.8.2025 in the span of two days LB has shown up heavily, just as the Temperatures got 24°C and above.
   So now it gets interesting. Today removed 11 Plants cause of LB and 1 EB.
   Total of 15 removed.



- Primabella x Bulgaria Giant Tomato F2       29 Plants
  One Plant was weak and seemed to have some root disease, removed it.
  From the others there are many Salad Size Tomatoes (5-6 cm) and some Cocktail size ones (3-4 cm)
  The Salat Size Tomatoes often look like tiny Beefsteak tomatoes !?
  3 Plants are Beefsteak Tomatoes (9-10 cm) with the size like Damsel F1.
  (One of these Plants is really small ? maybe it has also some root Problems but i keep it for now
  cause if i theoretically upscale this Plant it would have the biggest Tomateos)
  The Resistance to EB is overall ok, some show no signs of disease like Primabella 2024, some have a few
  leaves infected.
  The problem with the huge amount of seeds persists sadly.
  9.8.2025 in two days a whole Plant got heavily infected, even fruit, by late blight ! removed immediately
           a few more removed , sadly one beefsteak.

- MM F4 Cocktail                                7 Plants
  Overall good Selection, the plants and Fruit Sice are similar to each other. Nice good growing vital
  Plants.
  EB infection differs a little from very little to some leaves infected but not dramatic.
  Hope one plant will have good LB resistant this year , that would be great.


- Primabella x Sunniva F2                      21 Plants
  Many big Plants (2 m), from dense to loose foliage. EB is present from 0 to concerning like Sunviva.
  So as to expect from a F2 Generation. What is unusual is that some Fruit are bigger than both Parents!?
  Overall there are some really nice vital strong growing Plants.
  4 are yellow and 1 yellow is crack resistant and a bit like Sunviva, also good taste , this was the goal.
  The other 3 have only little horizontal cracks which seem to heal, they have also bigger fruits.
 

- Hot Streak F3 No 5                             10  Plants
  Small Plants until now, 1m +- , good Fruit setting. some are heavily infected with EB and i will remove
  them soon.
  But there are also some with only a few infected Leaves, so hopefully some will survive also LB.
  The Fruits are smaller then expected but the Advantage is they have no cracking! which nearly all Plants
  had last year.
  Another Advantage of the smaller Fruit is that they ripen faster here.
  9.8 removed one cause EB destroyed all leaves.


- Honey Moon F2                                  4 Plants
  Sadly 3 Plants are determinant, so only one indeterminant. EB is a big Problem, and contrary to last
  year fruits are cracking. The healthy Fruit were the only Reason to test again, so Plants will be removed
  soon. 
  9.8 Removed.


- MM F4 Salat                                     7 Plants
  Sadly this selection is not so uniform than the Cocktail Selection, cant really judge this atm.
  But most are resistant to EB

- Galahad x Ph5        F3                         7 Plants
  Very wide Variety of Plants. Maybe there is something interesting.
  Unfortunately The Fruits are all a bit soft and mushy.
  9.8 Removed some cause of LB

 
- Damsel F1                                       4 Plants
  Nice Plants with Beefsteak Size (10cm) Tomatoes. At first there were some yellow leaves from EB but the
  plants fought it off and the areas are now dried off and the leaves are still alive .
  Some Fruits have Cracks at the top that for now heal, but it worries me a bit.


- Rondobella                                      3 Plants
  Very unique Plant. Loose foliage, tall 1.7m , light green leaves. EB is present over 1/3 of the plant,
  but only on very small spots, maybe some kind of defense. Unique fruity taste.


- Giant of Siebenbuergen                          5 Plants
  Typical hanging thin Foliage, Plant around 1.5m , a little bit of EB but ok. Cause its not a known
  resistant Variety we have to wait how its doing Outdoors. Big Fruit even outdoor here.
  Some fruit had LB, have to monitor that. The Plants look ok. I give this variety a little more time
  to see what happens, otherwise fruit LB would be an no go.


- MM F4 Salad (very resistant ,hard slow ripe)      9 Plants
  Most are Medium size compact strong Plants, little to no EB. Only one Plant has small thin leaves. 


- Purple Zebra F2                                3 Plants
  Pretty healthy Plants, EB was defeated by drying of the infected spots. no yellow leaves anymore.
  The size of the fruit differs a little. One is smaller and has a pointy little tip.
  9.8 a little LB now but lets see how the Plants handle it.


- Lemon Drop                                      2 Plants
  Cherry size Tomatoes, taste ok, first a bit EB but it didn't spread further to the upper leaves.
  Sadly Fruits are cracking much.
  9.8 removed.


- Primabella 2024                                 4 Plants
  First they start slow but then they keep going and grow steadily
  Few Signs of EB one some. Despite selecting the strong Resistant Plants in 2024 there is the same
  variation in Plants again, 2 with dense,strong a bit hanging leaves which are more healthy and 2
  with thinner horizontal leaves with a bit more EB. ??

- Gourmansun F2                                   3  Plants
  not much EB so they can stay a bit longer :-) One has very little EB and the Fruits are more like
  Beefsteak. also this Plant is a bit more vital.
  9.8 removed the first cause LB.

- VG x Sunviva F3 yellow                            2   Plants
  one already removed cause to much EB (one half of a 1.4 m plant) the other one is a little bit better
  but also smaller, they are still cracking fast outdoors and also indoor.
  In the Greenhouse they are the biggest Plants and i couldn't stop the growth by letting two stems grow.
  Maybe good crossing Partner for old yellow heirloom Tomatoes like Old German, Pineapple.... .


Crosses i managed this Summer:
  Wasipicon Peach x Primabella
  Cerise Red  x Primabella
  Dancing with Smurfs x Primabella
  Giant of Siebenburgen x Primabella
  Primabella x Giant of Siebenburgen

[Tim DH]

Late Blight hasn't arrived here yet.
This is Potemkin F1 (Imur Prior Beta x Latah) which has performed well in the last two seasons. That is, of course, no guarantee that it will stand up against 2025's strain of blight. But at the very least I'm going to get some fruit before it goes down!

Tim DH

[ThomatoGarden]

Results October 2025

Primabella x Sunviva F2
      luckily found a yellow, crack resistant, small, shiny Tomatoe.
      It won the annual taste Testing! realy delicous. very aromatic and sweet.
      The resistance is like Sunviva, which should be ok.
      Hope to stabilize this next seasons.
     
      Another red one is more vital, resistant, crack resistant but not
      as tasty as the yellow one. but still good tasting.

MM F4 Cocktail
      suprisingly all plants have the same fruit size and
      2 have good resistance (like primabella)and are also crack resistant.
      Didn't expect this cause last year this was not the most resistant plant !
      hope this will continue next year.
      The plants are very similar to Primabella but faster growing in the first weeks.

Primabella x Bulgarian Giant tomato F2
      No.17 is a very healty and very vigouros Salad size tomato, but low production
      still i will grow this one next year.
 

[Tim DH]

Hi TG,
    Blight never really became a problem here last season, so my blight trials are all void! Still, can't complain, I got loads of tomatoes!!
    Do you hope your Primabella/Sunviva yellow will be more blight resistant than its parents?

Tim DH

[ThomatoGarden]

Hello Tim

No, the goal was to get a crack resistant Sunviva. Everything else is a bonus.
Didn't expect that the taste was so exceptional for the small yellow one.

Greetings Thomas