Breeding for Late Blight Resistant Tomatoes

[Nicolas]

Not sure that Ph2 and Ph3 will last long to new mutations or sexual reproduction of late blight

[Adrian]

Dangerous for me to play all on ph2 and ph3.
A variery tolerant today is may sensitive tomorow and a variety sensitive today is may tolerant tomorow if the blight has a so fast evolution.

However selected f2 between ph2 and ph3 is a better idea for get a better adaptation.
How much tolerancy combinaisons are possibles with f2 between ph2 and ph3?
And between ph1; ph2 and ph3.

The better idea is to get the maximum combinaisons possibles.

[William Schlegel]

That is why I added in PI 270443 Solanum pimpinellifolium which may be the PH5 source material. I did manage to make a cross with it in 2022 and my Mission Mountain Sunrise.

I also am very curious about LA 1033 Solanum habrochaites which I grew this year as it is supposed to have a resistance that is multi gene. Though this would be hard to work with, but I don't think it is impossible. I did not manage to make a cross with it, but I did finally get some seed back.

The biggest problem for me is finding someone with late blight problems to send the seed to for testing who will send seed back in a geographic region where we can freely send seed back and forth legally.

Then I could grow out the F1's of my crosses and send F2 seed to that person and they could send me back promising F3 seed which I could do half sibling crosses with. We could use such a process end up with a PH2, PH3, PH5 homozygous tomato eventually which might be pretty resilient to late blight.

If we could work with the habrochaites LA 1033 we might make a resilient strain, there as well. I think we would just need to keep it very high percentage habrochaites. Which is also a work flow I'm interested in with LA2329 for arthropod resistance. Just keep back crossing with the habrochaites like Joseph has been doing to get a tomato that is essentially habrochaites and has this multi gene resistance intact. Also, this could potentially work with the multi gene salt tolerance from Solanum galapagense. Sort of an open-source organic version of the gene editing de-novae domestication article we discussed some time ago. 

[Nicolas]

I also think horizontal resistance is the way even if it is much more difficult than Ph2+Ph3 to select for.

It is ok for us amateurs to have plants that are resistant to LB but produces small fruits, fruits that does not keep, odd colored or shaped fruits, indeterminate, etc. so what is non viable for big breeding folks (corporate or univ) is achievable for us frequenting this forum.

[UnicornEmily]

It is ok for us amateurs to have plants that are resistant to LB but produces small fruits, fruits that does not keep, odd colored or shaped fruits, indeterminate, etc. so what is non viable for big breeding folks (corporate or univ) is achievable for us frequenting this forum.

And in fact, some of those traits are even more desirable for a home gardener.  Many people would rather get a little fruit every day over a long period of time than all the fruit at once, for instance.

[Adrian]

A tomato with 99% of ph3 and 1% of ph2 is different than a tomato with 100% ph3 and she has a diffent tolerancy for exemple and different than a tomato with 50% ph2 and 50% ph3.
With the f2 between ph2 and ph3 we can have a different % of ph2 and ph3 on each plant.
A infinity of combinaisons are possibles.

Imagine a tomato with  π% of ph3 and (100-π)% of ph2 this combinaison is also possible

[Nicolas]

Adrian, Ph2 and Ph3 are simple genes, not QTL.

So there are only 16 combinations for the two genes taken together,

from

ph2/ph2 ph3/ph3 (no resistance)
...
Ph3/Ph3 ph2/ph2 (homozygous just for Ph3)
...
Ph2/ph2 Ph3/ph3 (heterozygous for both - usually the LB resistant hybrids)
...
Ph2/Ph2 Ph3/Ph3 (homozigous for both resistances - Iron Lady F1 ... Fn)

[Adrian]

Thank you Nicolas!
Ok the possibilitys with ph2 and ph3 are
1.(ph2/.ph3/).(ph2/.ph3/)

2.(ph2/.ph3/).(ph2/.ph3) = ph2/(ph3/.ph3)

3.(ph2/.ph3/).(ph2.ph3/)=ph3/(ph2/.ph2)

4.(ph2/.ph3/).(ph2.ph3)

5.(ph2/.ph3).(ph2/.ph3/)= ph2/(ph3.ph3/)

6.(ph2/.ph3).(ph2/.ph3)

7.(ph2/.ph3).(ph2.ph3/)

8.(ph2/.ph3).(ph2.ph3)=ph3(ph2.ph2/)

9.(ph2.ph3/).(ph2/.ph3/)=ph3/(ph2.ph2/)

10.(ph2.ph3/).(ph2/.ph3)

11.(ph2.ph3/).(ph2.ph3/)

12.(ph2.ph3/).(ph2.ph3)=ph2(ph3/.ph3)

13.(ph2.ph3).(ph2/.ph3/)

14.(ph2.ph3).(ph2/.ph3)=ph3(ph2.ph2/)

15.(ph2.ph3).(ph2.ph3/)=ph2(ph3.ph3/)

16.(ph2.ph3).(ph2.ph3)

We can now note the mosts tolerants combinaisons among the 16

[Tim DH]

Hi Adrian,
     I'm not understanding you there.

     In Nicolas's post he has ph to show the gene is inactive and Ph to show the gene is active.

     In your post you have no 'Ph's only 'ph's. So I'm unclear about what you mean.


     I reckon there are nine combinations, using Nicolas's format:

ph2/ph2 ph3/ph3   No resistance
ph2/ph2 Ph3/ph3   heterozygous for Ph3
ph2/ph2 Ph3/Ph3   homozygous for Ph3

ph2/Ph2 ph3/ph3   heterozygous for Ph2
ph2/Ph2 ph3/Ph3   heterozygous for both
ph2/Ph2 Ph3/Ph3   heterozygous for Ph2 homozygous for Ph3

Ph2/Ph2 ph3/ph3   homozygous for Ph2
Ph2/Ph2 ph3/Ph3   homozygous for Ph2 heterozygous for Ph3
Ph2/Ph2 Ph3/Ph3   homozygous for both

 


Tim DH

[Adrian]

 ----- Allele 1  / Allele 2
-----2³-----2²------2¹---2⁰----↓(binary)
1-16.(ph2.ph3).(ph2.ph3) 0
2-5.(ph2.ph3).(ph2.Ph3) 1 (2⁰)
3-9.(ph2.ph3).(Ph2.ph3) 2 (2¹)
4-13.(ph2.ph3).(Ph2.Ph3) 3 (2⁰+2¹)
5-2.(ph2.Ph3).(ph2.ph3) 4 (2²)
6-11.(ph2.Ph3).(ph2.Ph3) 5 (2⁰+2²)
7-10.(ph2.Ph3).(Ph2.ph3) 6 (2¹+2²)
8-14.(ph2.Ph3).(Ph2.Ph3) 7 (2⁰+2¹+2²)
9-3.(Ph2.ph3).(ph2.ph3) 8 (2³)
10-7.(Ph2.ph3).(ph2.Ph3)9 (2⁰+2³)
11-6.(Ph2.ph3).(Ph2.ph3) 10 (2¹+2³)
12-15.(Ph2.ph3).(Ph2.Ph3) 11 (2⁰+2¹+2³)
13-4.(Ph2.Ph3).(ph2.ph3) 12 (2²+2³)
14-8.(Ph2.Ph3).(ph2.Ph3) 13 (2⁰+2²+2³)
15-12.(Ph2.Ph3).(Ph2.ph3) 14  (2¹+2²+2³)
16-1.(Ph2.Ph3).(Ph2.Ph3) 15   (2⁰+2¹+2²+2³)

Sorry Nicolas In programmation we like use "/" for show a condition not present.
It may more easy now!

[Nicolas]

Adrian,

I get your idea, you just need to keep the ph2 together and ph3 together

We are talking about two genes (ph2 and ph3). Has the tomato is diploid, you can see each gene has a pair variable (x,y) so for example ph2 = (x1, y1) and ph3 = (x2, y2). Alleles are what value can take a gene. for ph2 it is [Ph2, ph2], for ph3 it is [Ph3, ph3] (some genes can have more than two alleles available (e.g. B gene)). So here x1 or y1 can take either Ph2 or ph2.

[Tim DH]

Hi Adrian,
       I coloured your Phs on my word processor to be able to see them more clearly!! Sadly, when I cut and paste that text into this forum the colour disappears! I've tried to re-create it here:

1.(ph2.ph3).(ph2.ph3)
2.(ph2.ph3).(ph2.Ph3) 
3.(ph2.ph3).(Ph2.ph3) 
4.(ph2.ph3).(Ph2.Ph3) 
5.(ph2.Ph3).(ph2.ph3) 
6.(ph2.Ph3).(ph2.Ph3) 
7.(ph2.Ph3).(ph2.ph3) 
8.(ph2.Ph3).(Ph2.Ph3) 
9.(Ph2.ph3).(ph2.ph3) 
10.(Ph2.ph3).(ph2.Ph3)
11.(Ph2.ph3).(Ph2.ph3) 
12.(Ph2.ph3).(Ph2.Ph3) 
13.(Ph2.Ph3).(ph2.ph3) 
14.(Ph2.Ph3).(ph2.Ph3) 
15.(Ph2.Ph3).(Ph2.ph3) 
16.(Ph2.Ph3).(Ph2.Ph3) 

From this I separated the list into the nine phenotypes:

1.(ph2.ph3).(ph2.ph3)

3.(ph2.ph3).(Ph2.ph3)
9.(Ph2.ph3).(ph2.ph3)

2.(ph2.ph3).(ph2.Ph3) 
5.(ph2.Ph3).(ph2.ph3)
7.(ph2.Ph3).(ph2.ph3) I think this one should have been 7.(ph2.Ph3).(Ph2.ph3) since this combination is missing from the next set.
 
4.(ph2.ph3).(Ph2.Ph3) 
10.(Ph2.ph3).(ph2.Ph3) 
13.(Ph2.Ph3).(ph2.ph3) 

6.(ph2.Ph3).(ph2.Ph3) 

11.(Ph2.ph3).(Ph2.ph3)

8.(ph2.Ph3).(Ph2.Ph3) 
14.(Ph2.Ph3).(ph2.Ph3)   
 
 12.(Ph2.ph3).(Ph2.Ph3) 
15.(Ph2.Ph3).(Ph2.ph3) 

16.(Ph2.Ph3).(Ph2.Ph3)

Hope that's helpful.

Tim DH 

[Adrian]

The line 7 is well that
(ph2. Ph3 ).(Ph2.ph3)

Good idea Tim Dh to colored Ph2 and Ph3 in red!

[Adrian]

1-16.(ph2.ph3).(ph2.ph3) 0 nr
16-1.(Ph2.Ph3).(Ph2.Ph3) (2⁰+2¹+2²+2³)

2-5.(ph2.ph3).(ph2.Ph3) 1 (2⁰) Ph3
5-2.(ph2.Ph3).(ph2.ph3) 4 (2²) Ph3

3-9.(ph2.ph3).(Ph2.ph3) 2 (2¹)  Ph2
9-3.(Ph2.ph3).(ph2.ph3) 8 (2³) Ph2

4-13.(ph2.ph3).(Ph2.Ph3) 3 (2⁰+2¹)
13-4.(Ph2.Ph3).(ph2.ph3) 12 (2²+2³)

6-11.(ph2.Ph3).(ph2.Ph3) 5 (2⁰+2²) Ph3
11-6.(Ph2.ph3). (Ph2.ph3) 10 (2¹+2³) Ph2

7-10.(ph2.Ph3).(Ph2.ph3) 6 (2¹+2²)
10-7.(Ph2.ph3).(ph2.Ph3)9 (2⁰+2³)

8-14.(ph2.Ph3).(Ph2.Ph3) 7 (2⁰+2¹+2²)
14-8.(Ph2.Ph3).(ph2.Ph3) 13 (2⁰+2²+2³)

12-15.(Ph2.ph3).(Ph2.Ph3) 11 (2⁰+2¹+2³)
15-12.(Ph2.Ph3).(Ph2.ph3) 14 (2¹+2²+2³)

Nr or ph2.ph3 = line 1
Ph2= line 3-9-11
Ph3= line 2-5-6
Ph2.Ph3=line 4-13-7-10-8-14-12-15-16

I think really that it will usefull!

[Roland]