Heirloom tomatos tested for disease resistance

plantslayer(8)October 29, 2010

Can anyone point me to resources on studies heirloom types that have been tested for disease resistances for various kinds of disease? Next year I will be gardening in a community garden which apparently had bad problems with late blight this year, and at least one person told me that they think people should only grow plants bred with specific disease resistances, i.e. hybrids. Personally, the reason I like to garden vegetables is to grow interesting varieties that I would otherwise not get to see or taste, so not growing heirlooms is not an acceptable option for me. Also plenty of heirlooms most likely have good disease resistance (isn't that where the people who develop hybrids get the genetics they want anyway?), but there has been only limited testing for them.

I'd like to know more about this so I can tell people I tried in good faith to grow robust varieties.

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carolyn137(z4/5 NY)

A few points.

When you speak of being tested for disease tolerances to me that means the challenge tests that hybrids have to meet before they can be said to be tolerant/resistant to those tested diseases and the abbreviations for those tolerances as letters, follows the name of the hybrid when listed.

Those challenge tests are done in approved labs and are not cheap, far from it. Since heirloom varieties are orphans, no one is going to pony up the money to pay for such tests, so no, I don't know of even one heirloom variety that has undergone those controlled tests.

This or that person will say that this or that disease is found more or less in this or that variety or in this or that geographic location in a given year but those are anecdotal comments and aren't really that helpful b/c one year yes, my tomatoes had X, and the next year, no, that variety didn't have X.

And diagnosis of diseases is often a huge problem. Often someone will say that their tomatoes have "blight" which is a general word that many use to indicate a sick tomato plant but don't know the exact disease and didn't show pictures or go to a disease site to make a diagnosis.

Most of the diseases of tomatoes are the foliage diseases, not the systemic ones, and there's no variety, OP or hybrid, that has any strong tolerance to the foliage diseases with a couple of exceptions re Early Blight ( A. solani), which is of use only to large scale commercial farmers where they can spray every 7 to 8 days rather than every 4 to 5 days.

Actually I don't think there's a variety out there, hybrid or not that's always tolerant/resistant, to ANY tomato diseases.

So while I can see the concern opf others in that comunity garden I also don't think they're aware of the fact that hybrids can acquire foliage diseases as easily as hybrids b/c foliage diseases are spread by air and embedded in rain droplets.

Even those hybrids that are said to be resistent/tolerant to this or that systemic disease are not 100 % tolerant or resistant. Maybe a week or so more of growth. but that is an advantage to those commercial farmers who decide when to harvest by doing Brix tests for soluble sugars.

Finally, while foliage diseases are found in almost all parts of the US, the distribution of systemic diseases such as Fusarium and Root Knot Nematodes and Verticillium and Alternaria Stem Rot and so many others, are geographically found in only limited places in the US.

I don't know what diseases you have in your 8b area b'c you didn't indicate that, which would give us a better idea of the concerns of those in the Community garden.

I hope that helps with your discussions with the others in the Community Garden. ( smile)


    Bookmark   October 29, 2010 at 1:14PM
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Once upon a time there was very little, if any, use of chemicals for farming or gardening. And because of this, Extensions began developing tomatoes which showed resistance to their local disease pressures. Contact your local extension or grange and ask what tomato varieties they developed 70, 80+ years ago and hopefully some of these varieties will still be around in catalogues so you can get those varieties. (There's no way to tell from your member page where you live so I can't suggest which extension for you to contact. Give it a try and see what you can find out.)

Your local extension may also have input on which OPs do better in your area and can suggest some varieties which are popular. You did not mention if your community garden is or is not undergoing the certification process to become an organic CSA. If they are aiming towards organic growing you will be surprised to see that they will grow selected hybrids because they are disease resistant. The word hybrid doesn't mean "without taste", there are many hybrids with great taste and conversely, there are many OPs which fall flat on the palate.

I'll paste in below a catalogue link--take a close look at it and see how many OPs are listed as disease-resistant. Of course, won't help you until you know your local disease pressures--so, you need to find out what the local tomato diseases are--aks that garden what they have seen in their plots. Once you know what diseases are in your area you can then start reading catalogues to narrow down your selection list.

It's a bunch of simple steps to get you in the right direction for finding the right varieties which suit both you and the community garden.

Find out what tomato diseases your community garden has encountered.

Contact your extension or grange and ask for recommendations.

Read seed catalogues to find varieties you can grow with an expectation of disease tolerance.

Good luck,


Here is a link that might be useful: Victory Seeds

    Bookmark   October 29, 2010 at 2:21PM
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THanks for your help, Carolyn and Trudi. I live in the Seattle area, for what that is worth. Anyway, I believe the gardeners are most concerned about late blight, but assuming they are not experts on plant disease it could just as easily be septoria leaf spot, early blight, some kind of mold etc. etc. I saw what their garden looked like in late October (lots of sickly/moldy tomato plants and rotting fruit) so I guess it's one of these problems or another.

After looking around on the web it seems that the best way to avoid these disease (for a small cottage gardener like me who grows 8 plants or less) is simply to trellis and prune diligently (especially near the bottom) and don't plant too close together (I am guilty of this in the past I'm afraid...)in order to ensure good air circulation for taller plants, maybe use plastic mulch or a thick layer of conventional mulch to keep soil borne fungus or disease away from the foliage. I don't know if growing a resistant variety will keep it out of my plot, but I'd hate to limit myself to boring workhorse hybrid varieties just to be blameless.

I think that if I am diligent about these things no one should find fault with my choice of variety... In any case, my favorite right now is Anna Russian, which has sparse and thin foliage, so it should probably be safer due to better circulation.

    Bookmark   October 29, 2010 at 3:14PM
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carolyn137(z4/5 NY)

Late Blight is a real problem in the PNW and it isn't a foliage disease, it can kill a plant within a week of infection and all you'd see would be a stinking mass of black tissue.

The most up to date varieties with LB resistance are two hybrids developed by Dr. Randy Gardner, formerly of NCSU. I've been distributing seeds for the two hybrids Mountain Magic F1 and Plum Regal F1, seeds from him and with his permission, which have the latest genes for LB incorporated and are better than the genes used for Legend which was bred by Dr. James Baggett at OSU, now retired, but I have no more seeds to give away. And many have reported that Legend isn't all that good in terms of preventing Late Blight (P. infestans)

So where does one buy seeds for the two above hybrids? Bejo seeds in the Netherlands is doing the placement and so far Mountain Magic F1 has been placed with Seedway, about $32 for 100 seeds. There's an outside possibility that Johnny's may carry it and while several of us are in contact with Bejo reps no final decisions have been made and we're led to belive that it depends on how much seed production there was to go around.

The best way I think to help prevent LB is to spray on a regular basis with Daconil. LB can be lethal and there are many many threads here about it if you search, with links to especially the Cornell FAQ links and more.

Of the common foliage diseases the two fungal ones, Early Blight ( A. solani) and Septoria Leaf Spot can nicely be prevented with Daconil but you'd have to use something different for the two common bacterial foliage diseases which are Bacterial Spot and Bacterial Speck.

LB and the two fungal foliage diseases are spread by air as well as in rain, so ensuring good air circulation and composting is not going to help that much as I see it.

YOu certainly can prune off any affected LB leaves ASAP but that isn't a sure fire way to prevent the disease IMO.

YOu can also do as Trudi suggested and contact your local Coop Ext for recs for older varieties, but there wouldn't be any info about LB b'c the major problem with LB started back in about 1990 and 91 with the disease, a new serotype, being imported into the US, not that it hadn't been here before, but it never was the problem it is today.

As to older varieties and disease, I'm an old lady, was raised on a farm where we grew acres of tomatoes and back then there was little to no disease, honestly. And none of the varieties we grew back then in the 40's had any known tolerance/resistance to any foliage diseases and where I live and garden there are no really prevalent systemic diseases , or weren't then, and aren't now, with just some local limited outbreaks.

But do see if your Coop ext suggests anything that they KNOW is tolerant of LB, which is the biggie concern here, and ask them for data. ( smile)



    Bookmark   October 29, 2010 at 5:23PM
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Thanks again Carolyn. I only browsed their websites, but the local extensions (Washington State U. and Oregon State) seem to indicate that good spacing and improving air circulation does help prevent late blight somewhat, though really it's just common sense for anyone growing around here; they also both mention that even varieties bred to resist it such as Legend don't really resist reliably in high "disease pressure" situations, which might describe this garden, considering how many plots seemed to have LB when I saw it a few weeks ago. I think the best I can do is to prune carefully, space them out, stake them out flat on a trellis rather than a cage, and hope for the best. I'd be perfectly happy with fungicides like daconil, but we're supposed to grow "organically" in these community gardens, so I believe I would be breaking the rules if I used it. The extension info says copper-based sprays might help, but can cause metal buildup in the soil... which begs the question, why is this method acceptable for organic growers but not Daconil? Anyway, I'm not here to stir up a hornets nest online or in my community garden. I'll just do what I can and hope for the best.

    Bookmark   October 29, 2010 at 6:04PM
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I use an organic fungicide called Serenade--it's not a cure or even a great preventative, but it does do a good job holding off the inevitable. On the plus side, if you spray in the morning you're safe to pick and eat later that same day.

Community gardens can have their little "overlords" so it's certainly a good idea to do everything by the book for the first year or two until you see who does what and how they do it--basically, find out who the experienced folks are, who the blow-hards are, and who to avoid ;-O With time and experience you fall into a wonderful routine and meet some great folks to share experiences as well as the fruits of your labors.


    Bookmark   October 29, 2010 at 6:26PM
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One more thing to keep in mind--as Carolyn said, there are very, very few tomatoes, hybrid or not, with resistance to late blight. It's highly unlikely that many, if ANY, people are growing those selected varieties. So hybrid or heirloom, you're going to have a hard time avoiding it... so what that person said to you is basically irrelevant as far as late blight is concerned.

    Bookmark   October 29, 2010 at 6:34PM
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Heirlooms have been included in replicated field tests for disease resistance.

the April 2010 issue of Tomato Magazine on page 8 begins an article about a group looking at heirlooms for the Great Lakes region. It's an odd viewer to look at the magazine in pdf. it does allow linking of specific pages to be accessed via social networking sites.

So I posted a direct link to that page at my twitter account (should be able to see without "joining"). That is http://twitter.com/kctomato if you are interested in seeing that report.

The general link to the April issue of the magazine is below

Here is a link that might be useful: April issue

    Bookmark   October 29, 2010 at 8:59PM
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carolyn137(z4/5 NY)

Keith, would you or someone else please help me here?

I'm trying my best to read the article, which is difficult b/c I just had two cataract surgeries and am OK with seeing distance but not reading up close despite the fact that my surgeon told me to get these cheap reading glasses until he does the refraction for glasses in November.

I saw where it was done by Dr. David Francis at OSU and even recognized some of the varieties listed that I can see b'c I know David and sent him a slew of heirloom varieties at his request for a different project.

And then I could see poundage for some of the varieties, but not which diseases were being monitored and what the results were for for those diseases, by variety.

And I did see that it was done once, I think in the summer of 2009.

So Keith or anyone else, could you please help me out here on this b'c despite the fact it was a one time event it's always good to know the results when someone savvy about diseases is doing something.

It just occurred to me, also, that this was an open field study, and not a challenge study, but if all were grown rather close together it should be OK.

So......Keith, anyone else here, how about some results from that article.

Carolyn, whose far seeing vision is now almost 20/20, well it is in the left eye, and thus qualifies for spear hunting Mastodons and Mammoths. LOL And that comes from an interesing chat that my eye surgeon and I had about the evolution of sight in humans, as in way back when you had to see dinner in order to kill it to survive. ( smile)

    Bookmark   October 30, 2010 at 7:34AM
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Trudi, I noticed you say that you use Serenade as a fungicide. The Cornell Late Blight FAQ mentions a product called Sonata, a biofungicide made by the same company, which is shown to be somewhat effective against LB. It's made by the same company (AgraQuest) that makes Serenade. But according to the company's literature, Serenade is only meant to control bacterial spot, mildew, etc. while Sonata is supposed to prevent LB. The problem is, the only way to buy Sonata apparently is in 2.5 gallon drums of concentrate that cost $100. This is a bit more than I need for my 200 sqft garden with 8-10 tomato plants. :)

There is one article here that claims Serenade is good at LB control:


but that's just a newspaper columnist, and I wonder if they did more than superficial research when they wrote that.


This article from Oregon State Extension says that Serenade can suppress LB, so maybe it's the best bet. I'm just a little confused, because the product sheet on the company's site doesn't claim it suppresses LB. Perhaps they haven't jumped through the legal loopholes necessary to make this claim, but Oregon State's info is backed by independent research data or something?

I suppose if I wanted I could go all out and do copper-based fungicide, even together with the biofungicide, but to be honest it seems like a bit much for just a few plants.

    Bookmark   October 30, 2010 at 8:19PM
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I don't think the study Mulio linked to gives very detailed info on LB; they just mention that crops at one or two areas were destroyed by LB, but do not break that down by variety. It does however mention total marketable yield (I think Opalka scored highest).

    Bookmark   October 30, 2010 at 8:26PM
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10 quarts for a hundred bucks. Wow. I paid almost that for six pounds of serenade powder. I'll stick with the serenade ;-)

    Bookmark   October 30, 2010 at 9:36PM
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I just found your forum and might be able to offer some help.I have been working with late blight for the last 40 years and have some relevant observations. Here in Wales, we have wet summers and lots of blight in our potatoes every year. In our Sarvari Research Trust we are selecting new varieties of potatoes for sustainable and low input growing, the Sarpo varieties.

Tomatoes are grown commercially in UK within glasshouses mainly by big multinational companies supplying the supermarkets. Only gardeners and smallholders try to grow tomatoes outside and many lose their entire crop most years. There is clearly a need for varieties that can ripen fruit in years when blight pressures are heavy. Seedsmen in UK offer several blight tolerant varieties and these can be useful in delaying the onset of blight by a few days or even weeks, depending on the season. We have varieties like Ferline and Fantasio from a French breeding programme and Jim Baggett’s Oregon cv Legend.

The thing to remember about the pathogen (Phytophthora infestans) is that many strains exist and these will come and go over the years and what looks like a resistant variety one year can be almost totally susceptible the next year. The blight that hit the eastern states so badly last year was caused by new strains of blight that had not been seen previously. Also the blight strains that you have across the pond are quite different from the ones we have here. This means that a variety that is resistant in one region or country may be susceptible in another. So it is necessary to be vigilant and keep sceening potentially resistant material with the newest strains of blight for the region you want to grow in. The breeder’s work is never done.

And heirloom varieties? These are old favourites which have survived because they have a great flavour or are good do-ers. You often find that some of the old varieties are a bit more tolerant of disease as these are the ones that are easiest to keep going over the years. But it is rare to find any that are highly resistant.

And what other methods can help to control the disease? Glasshouse growers don’t get blight because the plants are kept dry to prevent the “fungus” forming swimming spores on the leaf surface just before infection. This means that if we keep our plants dry by growing them under an umbrella, they will escape infection. I did some trails some years ago to test out the use of polythene cloche “umbrellas”. The results were spectacular. Protected plants remained healthy and gave a massive crop whereas the unprotected ones yielded no healthy fruit.

Another way is to avoid the blight by raising the tomato seedlings early and planting out, initially under cloches to hasten maturity. Many gardeners here use the variety Red Alert because it ripens many weeks before the others, and usually before blight arrives, usually in late July here. Also Red Alert is a fairly weedy looking plant and its sparse foliage means that the fruits are exposed to the air and dry off quickly after rain. Varieties like Legend do far better if plants are severely pruned to keep a minimum of foliage around the fruits.

Another trick is to use a high temperature treatment to cure fruit that are still green but will not ripen as the blight takes over before the fruit is red. In an article I wrote for The Organic Grower (vol. 11) earlier this year “No more green tomato chutney” I describe experiments with fruits that have a latent infection that is not yet visible. These are kept at 40C (104F) for at least 12 hours and then keep in a dry warm spot indoors to ripen completely. Untreated batches of green fruit rapidly developed nearly 100% blight. So if your plants become infected with late blight, it is often best to pick all the fruit and heat treat in an egg incubator or similar before ripening indoors.

Good luck with your growing.

    Bookmark   October 31, 2010 at 2:05PM
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That's great advice Corby, I'm glad to have your expert opinion. Luckily I have in the past put the seedlings out early under a tent cloche, and it does seem to get good results. One issue I have had, however, that the plants will grow fast, but pollination is often poor inside the cloche (possibly due to too much humidity). Regardless, the plants do seem to be much hardier overall. They do seem to succumb to fungal disease before the people who plant theirs out later, but I think that is simply because they have been alive longer, and have had more time for the diseases to develop. The cloches do have to come off eventually, however, since they are small crude jobs made with PVC pipe and sheet plastic, and the plants out-grow them. :)

    Bookmark   October 31, 2010 at 3:23PM
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When I lived in Seattle the only thing that worked SOMEWHAT was to grow my tomatoes under plastic, as stated above, and keep them dry. I used the same plastic hoops I used for frost, with the thickest clear plastic sheeting I could afford (6 mil if possible) draped over the hoops and clipped on. You have to keep the ends open to keep them from becoming saunas.
Here is a link to the frame sold at Territorial Seeds.

Carla in Sac

Here is a link that might be useful: Tufflight cold frame

    Bookmark   October 31, 2010 at 11:08PM
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That looks like nicer plastic than what I used, but it's pretty much the same thing. When we made the frame, we pounded 2ft rebar into the soil and simply slipped the .5" PVC pipes on top of it... luckily it just happens to be a perfect fit. Also, instead of garden clips, we use jumbo binder clips which can snap onto the .5" pvc easily.

Like you said Carla, the tent gets really humid inside and I think that's what causes poor pollination at first. We cut slits in the tent this year and found that the plants seemed to be much better off than the previous year when we didn't. However, according to the stuff I read about late blight, it seems that leaving open apertures can allow spores to get in, so it's not a 100% blight proof measure in that case. Anyway, I'm sure it is better to leave the tent open than not, because it is way too humid otherwise.

I am wondering if I should make "windows" and staple fabric on top of them or something, but of course the more holes you make the weaker the plastic is.

    Bookmark   November 1, 2010 at 12:56AM
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Carla, Plantslayer,
The tents or minitunnels we used successfully were open at the ends and lower sides so that air circulated very freely. See photos at the URL below. The link also has lots more information on how blight works.

It really does not matter if spores land on the leaves and fruits as they will die if deprived of free water. Smallholders here often use walkin tunnels but even with open ends, these encourage condensation on the foliage as the air cools in the evening. If blight spores get in, expect trouble. Commercial growers with glasshouses apply a little heat in late afternoon or evening to prevent condensation.

Here is a link that might be useful: Sarvari Research Trust

    Bookmark   November 1, 2010 at 5:39AM
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Excellent, I was more worried about keeping the plants warm than dry, now I know better. If I keep them under a tent but with the ends open, how much warmer would you think it makes them? I just need to know what outdoor temperatures they can withstand when under one of those.

    Bookmark   November 1, 2010 at 12:48PM
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I think that there will not be much temperature gain under an open tent or tunnel.

You may have noticed in the photo that the plants were planted through a woven plastic mulch. I find that this too, helps to keep the plants dry as otherwise weeds can grow up and harbour moisture.

    Bookmark   November 1, 2010 at 3:34PM
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simply click on the page (just once) you cant read and it will become larger. Also a small toolbar will appear at the bottom which will help you scale the file. It's actually a pdf and before you click on it, in the upper right, there is a navigation toolbar which one options allows you to save that page as a pdf to your computer. Which could then be opened in Acrobat and viewed and scaled however you want.

    Bookmark   November 1, 2010 at 4:29PM
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There were people looking at various lines in their tests when I was doing research for all kinds of disease. So some lines have been field tested but don't always get written up or evaluated further if they don't show something worth noting.

    Bookmark   November 1, 2010 at 4:34PM
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