Author Topic: Blight Resistance in Potatoes and Tomatoes  (Read 949 times)

William S.

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Blight Resistance in Potatoes and Tomatoes
« on: 2018-11-04, 09:45:44 AM »
This is more of a question to start a thread.

Late blight is relatively rare here though there was an outbreak some years back.

I noticed yesterday that potatoes were one of Carol Deppes five recommended crops on the cover of her "resilient gardener" book which I still haven't read, despite starting it back in 2012 with a library copy.

I then looked up some info about historic potato growing in Ireland and apparently just half an acre of potatoes could support a family along with some dairy.

Then of course along came the potato blight.

I haven't gotten very far with TPS I have a couple packets of it and started a plant that still survives in 2017.

Curious what is necessary for blight resistance.
Western Montana garden, glacial lake Missoula sediment lacustrian clay mollisoil sometimes with added sand in places. Zone 6A

bill

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Re: Blight Resistance in Potatoes and Tomatoes
« Reply #1 on: 2018-11-04, 12:11:31 PM »
Blight resistance is a complex topic for potatoes; I don't know much about tomatoes.

In the US, it is a bigger problem in the east and the south than the north and west.  I see blight some years, but it usually isn't a big deal.

Most commercial breeding work focuses on about a dozen R genes that primarily come from wild relatives.  Mexico has the greatest diversity of Phytophthora races and, consequently, the greatest diversity of resistance genes in wild relatives, but there are also resistance genes in South American potatoes.  Those R genes are effective against different races of Phytophthora and some are now pretty useless in parts of the east and in Europe.  Some varieties manage to stack three or four resistance genes.  The Sarpo line of potatoes developed in Europe has been very resistant, although LB continues to evolve in response.

Breeding for horizontal resistance is also possible and likely more effective in the long run, at least for smaller scale agriculture.  Late maturity is strongly correlated with several traits that provide incomplete resistance.  Early varieties tend to mature before blight becomes a problem.  Mid season varieties are the trickiest.

Diane Whitehead

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Re: Blight Resistance in Potatoes and Tomatoes
« Reply #2 on: 2018-11-04, 01:21:46 PM »
I haven't seen blight in potatoes, though frequently in tomatoes.

Perhaps it is because of our dry summers.  If our tomatoes are going to get blight, it happens
when the rains start in the fall, and by then the potatoes have been dug.
Victoria, British Columbia, Canada
cool mediterranean climate  warm dry summers, mild wet winters,  70 cm rain,   sandy soil

reed

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Re: Blight Resistance in Potatoes and Tomatoes
« Reply #3 on: 2018-11-04, 03:19:27 PM »
I haven't seen blight in potatoes, though frequently in tomatoes.

Perhaps it is because of our dry summers.  If our tomatoes are going to get blight, it happens
when the rains start in the fall, and by then the potatoes have been dug.

I also don't have much blight on potatoes but lots on tomatoes, perhaps for the same reason. Potatoes however are becoming more and more difficult to grow in my garden, I think because of more frequent hot dry spells rather than disease.  Unless I can make better arrangements for irrigation than I ever used to need and maybe use shade cloth, I may have to give them up entirely. Last year was a 100% failure of potatoes.

I have an ample supply of TPS and have found them easy to sprout and transplant, Next year I'm going to try a lot of plants, maybe something will come through and make both edible sized tubers and seeds.

nathanp

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Re: Blight Resistance in Potatoes and Tomatoes
« Reply #4 on: 2018-11-04, 06:31:44 PM »
This thread on Tom Wagner's Tatermater forum has a lot of information.

http://tatermater.proboards.com/thread/790/late-blight-breeding-info

Regarding Sarpo Mira, it has 4 known R genes, but possibly more that are not identified.  R8, R9, 3 others in one reference, R3a,R3b,R4,Rpi-Smira1,Rpi-Smira2 in a 2nd reference.  I think Rpi-Smira1 and 2 may be analogues for R8 and R9.

True durable field resistance (essentially a similar, but more current term used in place of horizontal resistance), is really only found in a handful of potatoes that have been bred in central Mexico near the center of origin of Late Blight.

This link has a lot of information about vertical vs horizontal resistance.
http://tatermater.proboards.com/thread/314/horizontal-vertical-resistance

I've grown a fair amount of late blight potatoes and have a few late blight tomato lines, though I don't get late blight every year, so that makes it difficult to evaluate. 
There are two main resistance genes, Ph2 and Ph3.  With tomatoes, having plants that are homozygous for each gene is much better than being heterozygous for the gene. And both Ph2 + Ph3 is better than each alone. 

[EDIT]  I found the list:
Homozygous for Ph2 and Ph3
Iron Lady
Lizzano
Skykomish (from Tom Wagner)
Crimson Crush

Heterozygous for Ph2 and Ph3
Mountain Magic
Mountain Merit
Defiant
Jasper (probably has both - not confirmed, unsure if heterozygous or homozygous)

Homozygous for Ph3
Plum Regal

Homozygous for Ph2
Legend (OP)

Possibles/Probables
Matt's Wild Cherry - probably Ph3
JTO-545 - probably Ph2
Sun Gold   Some resistance anecdotally, but I am not sure what it is from.

These are the ones I have grown. I am currently working on growing out several of the F1 hybrids to stabilize the lines. Skykomish is F8/F9 so that is stable already, though a little too long season for my climate. 

Homozygous for Ph2 and Ph3
Iron Lady
Skykomish (from Tom Wagner)

Heterozygous for Ph2 and Ph3
Defiant
Jasper (probably has both - not confirmed, unsure if heterozygous or homozygous)

Homozygous for Ph3
Plum Regal

I had seen some literature a few years ago mentioning a Ph5 gene which had been identified, but I am unsure if anyone is working with it.  Ph1 is basically useless, so it isn't used.  The NC State program is one of those breeding for LB resistant tomatoes in the US.

[EDIT] This web page has a more complete list than my list and some detail on effectiveness.
https://articles.extension.org/pages/72678/late-blight-management-in-tomato-with-resistant-varieties
« Last Edit: 2018-11-05, 04:44:30 AM by nathanp »

reed

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Re: Blight Resistance in Potatoes and Tomatoes
« Reply #5 on: 2018-11-05, 05:02:45 AM »
I'v grown Mountain Magic, Mountain Merit and Defiant and saw no apparent  difference at all in how badly they were with blight compared to any other tomatoes that I grow.  Plum Regal is a little better but still the difference isn't all that significant. They are all good, not great as far as flavor except for defiant which is pretty bad.

I kept Plum Regal to dehybridize and in F4 or 5, not sure what it is now, it is pretty much the same as the F1, never segregated much at all. My other tomatoes, later in the season, too varying degrees get disease on the skin of the fruits not just the leaves. If it is the same organism then Plum Regal is way more tolerant of that. The fruits have a tendency to dry easily instead of rotting and I think they might be good for sun drying.

As far as vines staying healthy all season the accidental pimpinellifolium crosses are by far the best. Unfortunately the largest of those is about the size of a ping pong ball and they are too sweet for canning juice or sauce.

Oxbow Farm

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Re: Blight Resistance in Potatoes and Tomatoes
« Reply #6 on: 2018-11-05, 07:36:40 AM »
In my experience, in the eastern US, late blight has become adapted to be much more virulent on tomatoes than potatoes. After the great blight outbreak of 2012, my answer to late blight in tomatoes is to never grow them outdoors ever.  This has completely solved blight for me with tomatoes, which is a major income generating crop for me.  For potatoes, which I grow primarily for my own consumption, I have almost never seen severe late blight, I'm surprised by bill's comment saying late blight is not a big issue in the PNW.  I thought it was.

Here on the east coast, they grow tomatoes year round in Florida and on the Gulf Coast, which provides a year round habitat for late blight, and provides a selection pressure towards increased adaptation for virulence in tomatoes.  At least it seems so to me.  AFAIK, we don't have both breeding types of late blight in the US, which is baffling since it is endemic in Mexico, but they do in Europe and is capable of forming oospores/recombining etc in Europe but must persist in live tissue here in the US? 

reed, have you considered changing your timing or cultural practices to avoid the hottest part of the year?  It seems crazy that you can't grow potatoes along the Ohio river.



nathanp

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Re: Blight Resistance in Potatoes and Tomatoes
« Reply #7 on: 2018-11-05, 05:42:24 PM »
I've grown Mountain Magic, Mountain Merit and Defiant and saw no apparent  difference at all in how badly they were with blight compared to any other tomatoes that I grow.  Plum Regal is a little better but still the difference isn't all that significant. They are all good, not great as far as flavor except for defiant which is pretty bad.

Out of the ones I've grown, I do see some differences, but it mainly seems to just be delaying actions.  All the plants eventually get LB, some just sooner and others more delayed. 
Quote
I kept Plum Regal to dehybridize and in F4 or 5, not sure what it is now, it is pretty much the same as the F1, never segregated much at all. My other tomatoes, later in the season, too varying degrees get disease on the skin of the fruits not just the leaves. If it is the same organism then Plum Regal is way more tolerant of that. The fruits have a tendency to dry easily instead of rotting and I think they might be good for sun drying.

Plum Regal should segregate and maintain the Ph3 as a homozygous trait unless it gets crossed.  I was not much impressed with the yield on it though, so I stopped dehybridizing it after the F3.

My general impression of LB varieties that I have grown is that they are sorely lacking in flavor.  Defiant might be the best of the commercial ones, but I didn't find it great.  Tom Wagner's Skykomish has great flavor, but it's just a bit too long season for my garden.  I've slowly been trying to work on shortening that, but I basically get tomatoes on it only during the last wee or two of my growing season before temperatures drop enough to impact flavor.  I have a few lines out of some Brandywine x Ph2 +Ph3 crosses that were gifted to me a few years ago that I am selecting from.  Those crosses are more satisfying for taste, but I may lose the resistance genes eventually as it segregates.

Quote
For potatoes, which I grow primarily for my own consumption, I have almost never seen severe late blight, I'm surprised by bill's comment saying late blight is not a big issue in the PNW.  I thought it was.

I agree with you overall.  My tomatoes get affected much more than tomatoes. For some reason I get surprised by that seemingly every year.  Oxbow Farm, both mating types of LB are in the US, but some strains do not really appear to change much.  That probably means it is just a matter of time before they mix and new strains co-evolve to beat the resistance.  The link I posted above actually details which LB strains are mating type 1 or 2 close to the bottom of the web page.

Quote
I'm surprised by bill's comment saying late blight is not a big issue in the PNW.  I thought it was.
I think it varies.  Some parts of the NW are reported to have it endemically, but I think Bill's location is either more isolated or some other factor is involved in sparing him  ;)
« Last Edit: 2018-11-05, 05:45:22 PM by nathanp »

reed

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Re: Blight Resistance in Potatoes and Tomatoes
« Reply #8 on: 2018-11-05, 06:40:19 PM »
Plum Regal should segregate and maintain the Ph3 as a homozygous trait unless it gets crossed.  I was not much impressed with the yield on it though, so I stopped dehybridizing it after the F3.

Plum Regal is very nicely productive for me, starts ripening a little later than most of my tomatoes but then comes on and keeps up till frost kills it.

I don't really have any idea what kind of blight is in my garden but it's there in abundance. It must be in the wind and rain,  I can plant tomatoes right in the previous year's old composted vines and others in a new spot where they were never grown before and there is no difference in when and how badly they get it.

Even so, I usually still get a good harvest to process our juice and sauces before the vines completely croak, so I'v made my peace with the vines dying. If I do notice a plant that seems a little less effected I save more of those seeds of course. I don't save any seeds from plants where the skins of the fruits are effected and that seems to have helped in eliminating that for the most part.

Other than Plum regal and the pimpinellifolium crosses my most disease resistant are two that both came from a Brandywine/Rutgers hybrid called Red Rose. They are very similar to each other except one is more lobed and green on top, we like them both a lot fresh and for canning juice. I don't think the F1 was advertised as blight resistant and I don't really remember if it was but it's descendants are more so than those advertised for it.

 

William S.

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Re: Blight Resistance in Potatoes and Tomatoes
« Reply #9 on: 2018-11-09, 09:49:32 PM »
Currently reading Carol Deppe's book "The Tao of Gardening"- started it today, read the section about Josephs squash and then made a beeline straight for the tomato chapter.

I didn't from the previews note that the tomato chapter would have such an emphasis on this very topic. Also in the seed chapter there is an additional section on dehybridizing the resistant varieties- I will read that bit tomorrow.

I remember reading something Tom Wagner posted somewhere. I think the gist of it was that he had been quietly doing a lot of work to introgress genes like this into some of his lines for a long time.

My main source of any potential resistance is direct from the wild species I'm growing, but currently late blight is not common here, so no way to know if any particular plant has or does not have resistance.

I think it would actually be better if the population of tomatoes in any given garden had a lot of variable resistances really.

I wonder what tomatoes are like in the parts of Mexico where late blight comes from? It seems to me that any heirloom tomatoes found there would probably also be resistant?
Western Montana garden, glacial lake Missoula sediment lacustrian clay mollisoil sometimes with added sand in places. Zone 6A

Diane Whitehead

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Re: Blight Resistance in Potatoes and Tomatoes
« Reply #10 on: 2018-11-09, 11:52:45 PM »
The tomato that has proved itself blight resistant for me is Cuatomate, an orange currant.
I planted it once and it then carried on sowing itself year after year.

I remember one year when all the tomato plants in the several acres of our allotment gardens
were brown with late blight - all except for the patch of Cuatomate in my plot.
Victoria, British Columbia, Canada
cool mediterranean climate  warm dry summers, mild wet winters,  70 cm rain,   sandy soil

Dominic J

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Re: Blight Resistance in Potatoes and Tomatoes
« Reply #11 on: 2018-11-12, 07:38:05 PM »
I'v grown Mountain Magic, Mountain Merit and Defiant and saw no apparent  difference at all in how badly they were with blight compared to any other tomatoes that I grow.  Plum Regal is a little better but still the difference isn't all that significant. They are all good, not great as far as flavor except for defiant which is pretty bad.

I kept Plum Regal to dehybridize and in F4 or 5, not sure what it is now, it is pretty much the same as the F1, never segregated much at all. My other tomatoes, later in the season, too varying degrees get disease on the skin of the fruits not just the leaves. If it is the same organism then Plum Regal is way more tolerant of that. The fruits have a tendency to dry easily instead of rotting and I think they might be good for sun drying.

As far as vines staying healthy all season the accidental pimpinellifolium crosses are by far the best. Unfortunately the largest of those is about the size of a ping pong ball and they are too sweet for canning juice or sauce.

My limited trials have shown that Mountain Magic did far better for me than most other tomato varieties.

Carol Deppe

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Re: Blight Resistance in Potatoes and Tomatoes
« Reply #12 on: 2018-11-22, 09:45:05 PM »
Late blight usually doesn't inconvenience us much in the maritime NW because  it tends to come only after the beginning of the rainy season, at which point the cold rain and cold weather tend to make the tomatoes split as well as not be very flavorful. After we're tired if tomatoes and quit picking them. But because of the existence of both mating types, I'm expecting this to change dramatically, and for it to become impossible to grow heirloom tomatoes outdoors at all in the NW and most of the rest of the country within the next 5 to 10 years. (As is now the case already in most of Europe.) The problem is not just that the two mating types will allow sexual reproduction, thus faster evolution. It's that the propagules resulting from sexual reproduction persist in the soil for years. Up until now, we have been dealing with only the vegetative spores, and those survive only in living plants. So we could avoid infection simply by starting our transplants from seed or buying from local farmers. (Not from big box stores, which often import infected transplants from Florida where the pathogen can survive year round on live wild solanums or tomato or potato volunteers.) It takes enough time for wind to spread the disease that in most areas the disease doesn't reach you till late in the season. But once the blight starts propagating sexually, it will be everywhere right at the start of the season.

If we want to have wonderful heirloom quality flavors in op tomatoes in the future, we freelance plant breeders are going to need to breed them. Hence the emphasis in breeding tomatoes, especially, in The Tao of Vegetable Gardening, including sections on known LB resistance genes, and the big section on tomato gene nomenclature and the genes and inheritance of all the characteristics  heirloom tomato lovers care most about.

There are, by the way, a number of University breeders, working on LB resistant tomatoes.  (I participate in NOVIC, an organics oriented organization that trials and tastes released  and unreleased vegetable varieties from participating  breeders and farmers.) But as far as I know, with one exception, the university breeders are breeding inbred lines for seed companies to use to make proprietary hybrids, and their inbreds would not be available to us to breed from without a contract giving the university partial ownership or royalties on anything developed. The anathema of open source.

 In addition, there are two other problems with the university-bred varieties. First, they seem to all be bred so heavily for crack resistance that the skins are so tough I spit them out. That is, these are all commercial tomatoes. I would rather deal with a certain amount of cracking and have a tomato with an edible skin. I can't use the tomatoes in a salad unless I  peel the skins off. Second, they don't taste very good. The USA University and commercial breeders have been incorporating uu, the gene for uniform shoulders, in all their varieties. This recessive gene is necessary if you want the perfectly uniform color instead of green or off color shoulders. That gene has now been positively proved to also invariable lower the sugar content and the amount of aromatics, that is, flavor, in the fruits. So if it has seemed to you that the most beautiful uniformly colored tomatoes never taste very good, it's because they don't.

Presumably the poor flavor of the current LB resistant tomatoes is because they are bred to look completely uniform, ie carry uu, and possibly other genes such as for slow ripening, not because of the genes for LB resistance. I picked a batch of one such hybrid and tasted one every few days. They kept about three weeks, looking totally glorious, but at no point actually tasting like food. Inspired by blight resistant tomatoes, my flavor scale now includes two additional classes. 4 is "I might sometimes grow and eat this, but only if it was the only tomato variety on the planet." 5 is "I would not ever grow and eat this, even if it was the only tomato variety on the planet." Arise fellow freelancer breeders! Surely we can do better than this!

The one University breeder I know of who has developed a relevant open pollinated LB resistant variety is Jim Myers at OSU. He's developed a medium size op tomato that carries Ph2 and Ph5. Alas, it also carries uu, and doesn't taste very good. However, when it is released it will give us a good source of Ph5 to play with. And the lack of flavor should vanish if you cross to something tasty and then resist the temptation to select for uniform color. I expect that OSU will put a PVP on the new variety, but it is legal to breed from a PVP.

« Last Edit: 2018-11-22, 11:54:23 PM by Carol Deppe »

Carol Deppe

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Re: Blight Resistance in Potatoes and Tomatoes
« Reply #13 on: 2018-11-23, 12:53:45 AM »
Yes, I've tasted all the unreleased OSU tomatoes. No. No seed snitching.

I have a simple rule. I do not take or save seed of or breed with any unreleased germplasm without the explicit written consent of the breeder, with or without an MTA.

I know you're just kidding, but it would actually be a lot nastier thing to do than many realize. There is always some poor grad student working on that project whose entire career might be sabotaged if the variety was stolen and introduced as if someone else's. Even if no real harm was done, it would sure be paranoia inducing and demoralizing. The sort of thing grad students have nightmares about.




William S.

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Re: Blight Resistance in Potatoes and Tomatoes
« Reply #14 on: 2018-11-23, 02:09:30 AM »
Carol, your comment on the blight getting much worse in the next five to ten years is important.

This suggests I should make immediate alterations to my tomato breeding plans.

I guess I have several tomato goals but for my area this hasn't been one. I live in a mountain valley where seed potato bproduction is a major industry. There was a blight outbreak- perhaps ten years ago and it was big news. We even bought some potatoes from the local farm that didn't keep well- from blight.

I don't think my tomatoes have ever died of blight. Frost has always been my tomato killer.

So if blight becomes much worse in the time frame you suggest it will be a huge change.

It would also be just about enough time to get some dehybridization started or a few crosses made to short season varieties I've just gotten interested in. I don't think there is any such thing as a super short season blight resistant variety of tomato- though I could be wrong.
Western Montana garden, glacial lake Missoula sediment lacustrian clay mollisoil sometimes with added sand in places. Zone 6A