Author Topic: Breeding for Late Blight Resistant Tomatoes  (Read 8950 times)

Roland

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Re: Breeding for Late Blight Resistant Tomatoes
« Reply #60 on: 2021-12-27, 06:35:01 AM »
There are not many homozygous ph2 and ph3 tomatoes:
Galahad F1 ph2 and ph3 homozygous
Mountaineer Pride OP ph2 and ph3 homozygous
Iron Lady F1 ph2 and ph3 homozygous

Purple Zebra F1 ph2 and ph3 heterozygous
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William S.

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Re: Breeding for Late Blight Resistant Tomatoes
« Reply #61 on: 2021-12-27, 09:09:25 AM »
https://eorganic.org/node/10822 clear reference for Carol Deppe's published PH2 PH3 homozygous assertion for Iron Lady F1.

Galahad F1 is very new so there isn't much information. However found an announcement by the breeder recently on facebook. It asserted PH3 homozygosity not both. That is not necessarily bad though PH3 homozygosity may be very useful. https://m.facebook.com/groups/479332809623391/permalink/522096665347005/?m_entstream_source=group

Mountaineer Pride was released in 2017. https://wvliving.com/a-better-tomato/amp/
Can't find a ph2 and ph3 reference. This linked article does confirm Iron Lady in the back ground in their search for septoria resistance so it is possible but I would like to see it in a reference.

Have been down this path before and I need a reference to believe.

With the purple zebra the heterozygous condition suggests that in the subsequent generations you might be able to simply stabilize it and it must get stripes from both parents. Which means a lot of the work towards a striped open pollinated late blight resistant has already been done.
« Last Edit: 2021-12-27, 09:23:18 AM by William S. »
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Tim DH

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Re: Breeding for Late Blight Resistant Tomatoes
« Reply #62 on: 2021-12-27, 01:44:16 PM »
Trawling through old Tomatoville posts. I discover that back in 2010 Tom Wagner thought Skykomish was homozygous for ph2 & ph3.

He also mentioned a variety called ‘Make My Day’ which is also homozygous ph2 & ph3.
The post is dated 14th Sept 2010, but I can’t find any more recent references to this variety. Curious.

Apart from that there is another AAS variety which mentions blight resistance, Jasper F1. My interest in this is that it is listed as 60 days (Purple Zebra F1 is 80/85 days) Does anyone happen to know what sort of blight resistance Jasper has?

Tim DH

nathanp

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Re: Breeding for Late Blight Resistant Tomatoes
« Reply #63 on: 2021-12-27, 02:16:54 PM »
Trawling through old Tomatoville posts. I discover that back in 2010 Tom Wagner thought Skykomish was homozygous for ph2 & ph3.

He also mentioned a variety called ‘Make My Day’ which is also homozygous ph2 & ph3.
The post is dated 14th Sept 2010, but I can’t find any more recent references to this variety. Curious.

Apart from that there is another AAS variety which mentions blight resistance, Jasper F1. My interest in this is that it is listed as 60 days (Purple Zebra F1 is 80/85 days) Does anyone happen to know what sort of blight resistance Jasper has?

Tim DH

See this topic for link to an article that tested Skykomish.  Skykomish as tested is heterozygous for Ph2 and lacks Ph3.  But it was listed amount the most resistant tomatoes in the 2011 trial.  Make My Day also tested similarly.  I would guess they have some other resistance that has not yet been quantified.  Matt's Wild Cherry is similar with acknowledged resistance, but not Ph2 or Ph3.

http://opensourceplantbreeding.org/forum/index.php?topic=58.75

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjh96--vrDtAhVfFVkFHRUmBzUQFjAFegQIBxAC&url=https%3A%2F%2Fresearch.bangor.ac.uk%2Fportal%2Ffiles%2F20580359%2Fnull&usg=AOvVaw1Z33V1p5OPTTn63oQLYgHIaaa

I should mention that there are four other tomatoes that tested homozygous for both Ph2 and Ph3
« Last Edit: 2021-12-27, 02:18:25 PM by nathanp »

William S.

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Re: Breeding for Late Blight Resistant Tomatoes
« Reply #64 on: 2021-12-27, 02:24:42 PM »
I think we have ruled out good resistance in Skykomish. It worked in Washington state for Tom but hasn't been widely useful elsewhere and reports from our fellow board members suggest it isn't so. I think I looked and tried but could not locate Make My Day, it may still be in someone's collection so try asking around. No reason to be absolutely certain it is if Skykomish isn't. Tom has written about having a large number of introgression lines ready to be tested against late blight on the shelf, but he has hopes of making some money from some of his extensive work so isn't releasing some of what he considers to be his best stuff. I hope it works out somehow, but I am concerned it may just be really hard to make money at this sort of tomato breeding!

That same eorganic article https://eorganic.org/node/10822 references Jasper F1 but not Lizzano F1. Jasper has very good resistance to the US-23 strain of late blight and the source of that is unknown- Edit from Nathan's link above it is heterozygous for PH3. Lizzano F1 at 63 days may only have PH2 according to the article Nathan just linked. We thought for a time it was homozygous for both on this forum. I would suggest Lizzano F1 as well as Jasper F1 for a short season possibility as 60 vs 63 days is not really much difference. Though Lizzano is a basket type. I got some F2 Lizzano seed but I am not certain it was Lizzano as what I ended up with was a microdwarf and grown near Pinnochio microdwarf this summer I couldn't really see any difference between the two. I kind of want to get new Lizzano seed and see if it segregates out microdwarfs. I actually got a packet from Amazon last year and I suspect it was a fraud as the seeds don't look like tomato seeds and did not germinate. So a packet from a reputable source and see if it does indeed so segregate in the F2!

Sounds to me like most late blight resistant varieties might be best used as a parent to cross to Iron Lady F1. Which would mean an Iron Lady F1 x Lizzano F1 or alternatively x Jasper F1 would be a good route to go to try to find segregants that are short season and highly resistant to late blight. Same with Purple Zebra- Iron Lady x Purple Zebra would give you a higher chance of getting a homozygous PH2/PH3 striped tomato in the F2 segregants though the F1 would not be striped if my experienced with Exserted Tiger is any indication. If Late Blight becomes a huge problem in short season gardens or already is that doesn't leave many short season let alone colorful options.

Personally, I still think it would be most interesting to cross Iron Lady with my own varieties to try to spread those exserted stigma genetics to places where they otherwise wouldn't be able to grow because of Late Blight pressure.
« Last Edit: 2021-12-27, 06:14:52 PM by William S. »
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William S.

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Re: Breeding for Late Blight Resistant Tomatoes
« Reply #65 on: 2021-12-27, 05:35:17 PM »
Table 2.6 and 2.7 in that PhD thesis do list some more varieties as PH2/PH2 and PH3/PH3 however when I searched the document for "Table 2.6" I found an explanation that both Table 2.6 and Table 2.7 should be utilized with caution because the testing method was a little hard to interpret for a couple reasons so might have thrown some false positives.

Table 2.6 lists Ailsa Craig but Table 2.7 lists Ailsa Craig as not resistant. The others are Amai, Bella Rosa, and Matina in Table 2.6. None of which appear to be known for blight resistance when I searched for seed sources.

Now Table 2.7 lists quite a few more including Iron Lady F1 but everything but Iron Lady F1 seems to be a breeding line number shared with the researcher. Meaning that we have just Iron Lady F1 to work with.
« Last Edit: 2021-12-27, 06:54:34 PM by William S. »
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Tim DH

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Re: Breeding for Late Blight Resistant Tomatoes
« Reply #66 on: 2021-12-28, 01:57:40 PM »
Hi Nathanp
   Thanks for re-posting the link to that article. …. Only 214 pages long, so its taking a little while to digest!
   It does mention BOTH varieties I was asking about. (Jasper is heterozygous ph3)

   Interestingly the PhD was part of the development program for ‘Crimson Crush F1’ which no one on here is talking about. It would be reasonable to assume that CC is one of the three experimental varieties which showed promise. It pretty much says so on page 13.

   Incidentally the article also mentions grafting conferring Blight resistance, irrespective of whether the rootstock has Blight resistance!! (p29)

   I’ve been thinking further about William’s concerns regarding breeders being able to turn a profit. On one level it wouldn’t make sense for a commercial outfit to release a homozygous ph2&ph3 because we’d treat it like an open pollinated variety! We wouldn’t have to go back every year for fresh seed.

   SO there possibly is merit in trying to grow out F1 heterozygous ph2&ph3s, because in the homozygous state we might end up with a better variety.

   I wonder if CC is an F1, but homozygous for ph2&ph3! My reading of the article would suggest it is!! Possibly its just ‘called’ an F1 to dissuade seed saving? ((Now I’m wondering what the actual status of Purple Zebra is.))

   Lastly (for now) This article was inconclusive about the nature of Blight resistance in Koralik. I’ve come across a later paper from the same stables suggesting that Koralik has a differently mediated Blight resistance.

https://research.bangor.ac.uk/portal/en/researchoutputs/qtl-mapping-in-salad-tomatoes(db230825-92e0-4c75-892b-b295f0201c7c).html

   Some seed sellers call Koralik a heritage variety, some call it an F1. To add to the confusion some list it as ultra early and some list it as late! Perhaps there are two Koraliks??

Tim DH

William S.

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Re: Breeding for Late Blight Resistant Tomatoes
« Reply #67 on: 2021-12-28, 03:06:31 PM »
Some fraction of the F2 and subsequent generations of the heterozygous F1s should turn up homozygous for PH2 and PH3.

In Galahad F1's breeder Jason Cavatorta's Facebook post about Galahad F1 he said something about a linked resistance on the same chromosome on PH3 that was hard to recombine because he wanted both resistances. That sort of difficult breeding might be harder than the PH2 and PH3 breeding for late blight  that Carol Deppe proposed.

I think the professional breeders know that a small fraction of us will dehybridize any F1 they release to us. Particularly relatively independent small breeders probably have little interest in making it impossible for us to do that effectively.

However, there might still be some hybrid situations we cannot easily replicate.

We could make some open source hybrids though with open source recipes.

One way to start that could be to desegregate name and ossi pledge a descendant of Iron Lady F1 so we have a named replicable PH2/PH3 homozygous parent line. Then keep a running list of good open source combinations. One way to do that might be to  test cross it with every registered OSSI tomato. Just throwing that out there since it represents a lot of work...
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Diane Whitehead

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Re: Breeding for Late Blight Resistant Tomatoes
« Reply #68 on: 2021-12-28, 03:30:44 PM »
Is there an easy way to test for resistance to late blight, or do we just have to grow out a lot of plants and wait for some spores to blow into the neighbourhood so we can see which ones remain healthy?
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nathanp

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Re: Breeding for Late Blight Resistant Tomatoes
« Reply #69 on: 2021-12-28, 04:23:29 PM »
do we just have to grow out a lot of plants and wait for some spores to blow into the neighbourhood so we can see which ones remain healthy?

This is why I got precisely nowhere with anything I have done with LB lines.  No noticeable LB has shown up since about 2013 or 2014.

William S.

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Re: Breeding for Late Blight Resistant Tomatoes
« Reply #70 on: 2021-12-28, 04:29:17 PM »
Is there an easy way to test for resistance to late blight, or do we just have to grow out a lot of plants and wait for some spores to blow into the neighborhood so we can see which ones remain healthy?

Depends on your funding! Marker assisted selection is available. Jason Cavatorta posted this recently: https://www.facebook.com/groups/479332809623391/posts/911998313023503 to the "Tomato Breeders" group on Facebook.

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 because so far, my tomato varieties are worth about $50 a year if I grow them out myself and sell the seed which I have decided not to do for 2022. (I just sent them a question about the cost of the testing).

So let's say I wanted to make Exserted Orange into a PH2 PH3 homozygous line. I would cross it to Iron Lady and get a PH2 PH3 Heterozygous F1 every time. Then I could grow out the F2 and have every plant tested for PH2 and PH3. Any that tested as homozygous (if that is possible) could then be continued with.

Alternatively, we rely on those group members who have bad and fairly regular late blight to narrow things down a bit. If we had a really good performing say F6 we could just test it. Or just rely on its performance.

Another strategy to minimize testing costs might be to cut down on the likelihood to need as many repeat tests by back crossing to Iron Lady or by making an initial cross to a variety that would cut down on the chances of the offspring not being homozygous. For instance, if we wanted to cross Iron Lady F1 which is PH2/PH2 and PH3/PH3 with Galahad F1 which we know is at least PH3/PH3 we would only need to test the offspring for PH2 which means half the testing. Or if we wanted to cross Purple Zebra F1 which we currently think is heterozygous for both PH2 and PH3 with Iron Lady F1 it would be like backcrossing once to Iron Lady F1. Significantly more likely to have homozygous outcomes and should cut down the number of generations you would need to test.

Could also just do a lot of stabilizing and back crossing to Iron Lady F1 until you got a plant that was very likely to prove homozygous PH2 and PH3 before testing- basically introgression of whatever important traits you wanted into Iron Lady. 

My thought to avoid testing costs is to just never personally create a finished variety for Late Blight Resistance but instead make crosses and then freeze some F2 seed and send some off to collaborators.

I started a thread for this, but I am curious basically about how much variation there is in Iron Lady. There has to be some to get hybrid vigor. It is possible that we could dehybridize multiple lines from Iron Lady for different trait variations. Like how short season could we get a dehybridized Iron Lady if we selected strongly for that desired outcome? I suspect the answer lies mostly in how much difference there is in days to maturity on the two breeding lines they use to make Iron Lady each year. Same with fruit size. I would expect both parents to be boring red tomatoes so it would be relatively minor differences. 
« Last Edit: 2021-12-28, 11:42:52 PM by William S. »
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William S.

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Re: Breeding for Late Blight Resistant Tomatoes
« Reply #71 on: 2021-12-28, 11:04:45 PM »
https://territorialseed.com/collections/new-products/products/purple-zebra

Territorial's description for Purple Zebra F1 is very good sounding. Much closer to Carol Deppe's vision of creating heirloom quality late blight resistant tomatoes than Iron Lady. If it were possible to desegregate Purple Zebra F1 into a homozygous PH2 and PH3 line it would be far better than Iron Lady F1. As a desegregation project it strikes me that the color and striping should be stable- that they must have used two purple striped parent lines to produce Purple Zebra F1.

I was looking at Carol's old posts on here and she actually suggested backcrossing to the heirloom not Iron Lady F1. She thought it would be hard to get rid of the Iron Lady F1 flavor. So particularly for that first improved variety the introgression of PH2 and PH3 into an heirloom quality tomato would be hard.

So it looks like Mark Mccaslin and Frogsleap Farms have created a very interesting tomato with this one. Essentially accomplishing that first step of getting PH2 and PH3 into a tasty tomato. Which means desegregating it maybe should be a priority.

https://all-americaselections.org/product/tomato-purple-zebra/
https://frogsleapfarm.blogspot.com/?fbclid=IwAR3OhNctblhUNV0LulZr9_RvJkhV-PmUQOGsBph5Lkq0qUWNbgXXiO74oMs

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William S.

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Re: Breeding for Late Blight Resistant Tomatoes
« Reply #72 on: 2021-12-28, 11:24:59 PM »
Its not clear for me if we have spores that overwinter. Most people say the phytophthora start in potatoes and later it get to tomatoes.

In Netherlands is working:
Homozygous ph2 is not working
Heterozygous ph3 is giving a bit resistance but not enough
Homozygous ph3 is working very well
Heterozygous ph2 and ph3 is working very well
Homozygous ph2 and ph3 are best but there is still some infection.

Hence Purple zebra F1 heterozygous for ph2 and ph3 have very good potential for Netherlands.

ps Skykomish seems to be homozygous for ph2 and do not show resistance in Netherlands.
The cross of Skykomish x Primabella  is working very well because this cross is heterozygous for ph2 and ph3.

Seems like Skykomish x Galahad F1 would work well also. I don't think we can get Primabella easily in the United States.
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Roland

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Re: Breeding for Late Blight Resistant Tomatoes
« Reply #73 on: 2021-12-29, 05:49:28 AM »
Do u guys know the late blight genes from tomato Darkstar F1?

https://territorialseed.com/collections/tomato/products/darkstar?variant=41647595880622
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William S.

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Re: Breeding for Late Blight Resistant Tomatoes
« Reply #74 on: 2021-12-30, 01:03:25 AM »
I tried searching for dark star. Didn't find anything notable. Funny how some breeders seem to give out more info than others. Though we may be in a small minority who get really excited to see details on exactly what kind of late blight resistance a variety has.
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