Selecting Tomatoes for Disease Resistance

This year I planted 8 different varieties of tomatoes. 4 out of the 8 have been affected by early blight. The first to be affected (and separated by a house and two outbuildings from the rest of the garden and other affected tomatoes) is a variety known as "Galina". "Galina" is growing beside "Black Plum" which has a known resistance to early blight, and "Gardener's Sweetheart" which was introduced by Will Bonsall. For my own seed saving purposes I'm going to assume that it is at least somewhat resistant. Out of the 5 Galina plants, 1 has not had any signs of early blight!!! I want to select this variety for disease resistance, and so I would assume I would naturally collect seed from this resistant plant, and then in subsequent years save seed from many of the disease resistant offspring to reduce inbreeding. (Correct me if I'm wrong or share your experience!)

But for my remaining varieties affected by early blight: Mortgage Lifter, Cup of Moldova, and Kalinka... all have shown at least some sign of the disease. How should I select for disease resistance? Should I select plants that hold up the best? Should I instead select for something else like early production and yield?

What would you do in this situation?

That's what I'd do too.

Dolly Bigelow wrote:What would you do in this situation?

Bwah, ha ha!

I think it's a loosing battle to try to select standard commercial or heirloom tomato varieties for disease resistance. I can't select for traits that don't already exist in the population.

If it were me, I would stop growing named varieties of tomatoes. Every seed in a stable tomato variety is basically a clone of every other seed of that variety. They have been inbred for many generations, and suffered 3 genetic bottlenecks during domestication, and thus lack the genetic variability to be able to do much adapting to diseases, pests, farmers, soils, climates, etc...

What I am doing on my farm, to select tomatoes for disease resistance, is that I crossed my tomatoes with wild tomatoes to introduce lots of genetic diversity. Then from the offspring of those plants, I am selecting for open flowers that are highly promiscuous. Then once I have a population of tomatoes that is reliably and consistently promiscuous, I'll be able to easily trial hundreds or thousands of genetically diverse plants for disease resistance.

I have a lot of experience with late blight on tomatoes. I plant almost exclusively beefsteak tomatoes, with a Kelloggs Breakfast yellow and a Yellow Pear thrown in amongst them.

Several years ago I quit growing tomatoes in my usual small garden and made a test plot several hundred feet west of the old garden. I planted Celebrity and an unknown beefsteak there. No Blight! So the next year I made another new "field" (12"x16') between a peach and the Honeycrisp apple tree. Viola! Late blight. The two new patches were about 30 or 40 feet apart. Meanwhile I grew Caliente Mustard in the old field (11x14' for two years. You'll notice these gardens are rather small, the reason for doing what I've been calling rotating gardens as opposed to rotating crops.

So it's now three years since I first grew in the test plot and haven't had late blight in any of the 3 years. This year after 2 years of dormancy the old plot looks fairly promising. I noticed today two leafs looking yellowed, and that's the first. Meanwhile the 12x16 plot has many of the tomatoes blighted for about the last month. I trimmed the bottom of all the plants and the few times I've had to water I let the hose run at the base of the plant, so as not to wet the leafs. My problem there is I can't control the frequent rain which insists on wetting the entire plant.

So my take on all this is that my best approach would be to plant tomato plants in various places throughout the lawn to find those places that are immune to late blight. That would mean I'd need a 3 foot diameter 5 foot tall deer fence for each. I've planted at most 4 tomatoes in the test plot, reducing to 3 plants as the peach roots grew. I'd also say not planting tomatoes in my old garden was good for  that garden, except that It's clouded by also planting the Caliente 199 Mustard there.

I should add that my neighbor next door has some problems with late blight and her garden is closer to the two new plots than to my old plot. They say the blight (spores?) can travel miles but it hasn't traveled the 40 feet between the two new gardens.

My beefsteaks this year:

Rozovyi Giant pink
Mortgage lifter
Janes Big Red
Red Brandywine (bought as Pink)
Pink Ponderosa
Marrianna's Peace
Giant Belgium
Tennessee Heirloom
Crnkovic
Dester

I'd say that after 35 years of gardening and what I learned from my mother and my grandmother that there is some variability in beefsteak tomatoes. If you save seeds for traits that you find you can improve your tomatoes in future years. If you don't save thick skinned tomatoes you'll see an improvement. And the shape of the tomato. And I save seeds from my first beefsteak of the year, however I can't really see a difference from one year to a year a couple decades ago. Let me tell a story about someone in my family who liked the giant beefsteaks with multiple lobes. This person saved seeds from beefsteaks that looked like butts. Every year more butt looking tomatoes were grown. And they seemed to get bigger. They tasted luscious and they went into the sauce so the shape didn't matter.

My mother and grandmother had a pink beefsteak that was always perfect. There was never any cracks around the top. The stem just went neatly in and there was never all that white pulp inside the tomato top. The seed cavities were small so the tomato was very meaty. There was never a mark on the bottom. I would call this the "family name Perfect Pink". We lost this tomato the year before my mother died. Every tomato was a cherry tomato that year. Up to a hundred years of development, positive and negative were lost. I bring this up because every once in a while one of these tomatoes was red. If you saved the red perfect you'd get another round of perfect pinks.

One more story. This year one of my yellow pears has a cluster of pear tomatoes and next to it a large tomato on the same plant. It's still green so I don't what color it'll be, nor what size.

I particularly like joseph's method as that is where modern tomatoes got their disease resistance from originally, from wild tomatoes. You could try saving seed from varieties that show no damage but on the whole most domestic tomatoes are not going to adapt very quickly as they have been bred for homozygosity and stability for generations.

I dont get late blight because i don't plant standard varieties. So, if it were me i would venture out from the norm. Try something new or unusual and unexpected, or contact your local university to see if you can get new varieties being developed.

I think the OP is talking about early blight, not late blight.

This winter I heard that sprinkling corn meal around your tomatoes will help with early blight.  I tried it and I think it helped.  But it was very unscientific so I can't stand behind my findings at all.  But it's cheap to try.  Next year if I'm ambitious I'll do it again with a control.

Oh. Well i don't get any blight.  Early, late,  or any in between. I'm not bragging,  i just don't have to deal with it because i decided to stop fighting nature and instead work with what works for me genetically.  It's a genetics problem, not a soil problem,  or a pest or disease problem even from my point of view. You can either plant host susceptible plants that will harbor and spread it or you can not.

My two cents whether they are helpful or useless either way.

Andrew Barney wrote:i decided to stop fighting nature and instead work with what works for me genetically.  It's a genetics problem, not a soil problem,  or a pest or disease problem

I tend to agree with this sentiment. It's much easier for me to choose plants with different genetics than it is to change the soil, the humidity, the insects, the blights, the sunlight, the farmer's habits, etc...

Dolly Bigelow wrote:What would you do in this situation?

Some plants grow well in a true permaculture environment while others just survive. The needs of tomatoes warrant separate treatment - traditional garden bed and crop rotation to avoid disease.

Soil moisture is critical - only moist, use a finger stuck in the soil, it should be cool and not stick too much.

Soil prep with lots of compost. Full sun aspect.

A few pinches of potash at planting and again at flowering time will strengthen the cells and reduce disease.

Trim off the bottom leaves close to the soil, mulch but away from stem. NEVER wet the leaves when watering.

A tip for improving growth is to strip the lower leaves off an advanced seeding and plant it deep - tomatoes will produce roots from the stem, improving nutrient/water uptake and plant stability.

All tomatoes benefit from staking, even the bush varieties - stops them leaning onto the ground = disease issues.

If all this fails (!), the cherry/pear varieties tend to have fewer disease issues - thicker skins

Have fun!

Good discussion on the sources of resistance/protection to crop plants.  Just two additions that I hope don't confuse the issue.

1)  If I had a variety of something that I really liked--AND I wanted it to have greater pest/disease resistance, I probably would save seed from the most naturally resistant in the garden along with one or two seed lots that maybe didn't represent the best resistance, but nevertheless had the best productivity traits (size, flavor, storability, etc.).  While it is likely that many wild disease resistance traits may have been bred out of some of the commercial offerings and even some of the heirlooms, it should be remembered that disease resistance is not a 'static' trait:  The genes underlying resistance can arise de novo on account of natural mutation that is ongoing.  Something as simple as a chitinase gene (encoding an enzyme that can break down the cell wall of attacking fungi) can undergo the smallest mutations that might increase the effectiveness of the gene and result in that one plant in the garden that appears to be performing better than one next to it.

2)  For the seed saver/home body---you are adapting your varieties to **your** homestead.  Observed improvement in your crop (via deliberate and careful seed keeping from previous generations) will likely end up being as much about selecting for genes that condition "receptivity" to beneficial microbes unique to your garden/soil as it is about new disease-resistance genes.  Although I need to track down the actual study and data, I was at a recent conference where it was presented that a 'legendary' (for lack of a better term) disease resistance gene cluster against a soil root rot pathogen was actually NOT genes for pathogen resistance at all, but rather genes that conditioned a novel cohort of biocontrol microbes to accumulate around the root zone of that genotype and provide protection from disease.  I'm hoping to obtain the data from the author since this would be a pretty monumental shift in generalized thinking of how disease-resistance is being selected and what that resistance is due to.

Such a good time of year (northern hemisphere) to be talking tomatoes!....

The genes underlying resistance can arise de novo on account of natural mutation that is ongoing.  

John, I have read enough of your posts to know you have a good grasp of biology, but this seems unlikely from my understanding. The level of mutations are pretty low in eukaryotic transcription, and assuming you will get one that is beneficial seems remote. There was some hope that afterprocesing would be an alternate pathway for change but my reading of the literature in higher organisms seems disappointing, at least in terms of a dramatic increase in de novo beneficial expression, although better than direct protein encoded mutation. I fell down the CRISPR rabbit hole a while back but I'm out now. But there may be some stuff that has passed me by for sure. So despite the fact that Joseph is in a very different climate, he has way more genetic variance than the whole seed catalog from Southern Exposure in one row, just some genes are not expressed. I could grow stuff for 100 years and not develop that diversity, because a big landrace will hold more variation already than I could develop in a handful of plants' mutations from the current genomes. Those plants are the survivors of hundreds of years of mutations in vaster areas.

Observed improvement in your crop (via deliberate and careful seed keeping from previous generations) will likely end up being as much about selecting for genes that condition "receptivity" to beneficial microbes unique to your garden/soil as it is about new disease-resistance genes

^Yes x 10! This is the cool thing. I wasted a couple years trying to find someone who had the right varieties for "my climate" but there is so much more! And my local soil is hopefully changing annually anyhow, and I need the genetics to adapt to it.  I would likely do better with a local landrace but I haven't found one, and he has stuff from all over the place. It's a good starting point. I won't be out there pulling stuff with inverted stamens, because I barely get out there to pull tomatoes! I want indeterminant plants and I select for them by forgetting to put up cages and stepping on the trailing vines primarily. The seed saving to me is really most beneficial when some really good genes are kicking around already and I can just be lazy and let the selection occur by the bees and soil microbes and bugs. Just not deer selection, those guys suck at beneficial selection pressure. They have eaten some of my favorites. Payback this fall is going to be a B*TCH Bambi.

I agree with John Weiland. Since this thread is titled " Selecting Tomatoes for Disease Resistance" I'm going to express my viewpoint on Late Blight; even though it's actually a fungus.

I'm going  to continue to grow the varieties that I always have. Mainly beefsteaks; with a couple yellow varieties thrown in for variety and as a last resort in case my heart burn problems get so bad I can't eat the beefsteaks. I grow the tomatoes that I enjoy eating. I wait all year to get those delicious tomatoes that you don't get at the grocery or at a restaurant. If I had to grow the varieties that they present there then I'd just quit growing tomatoes. The tomato is not the most grown plant grown by gardeners to get a cherry tomato or some tomato with a number instead of a name. Gardeners grow tomatoes to get those delicious, high acid, vine ripened tomatoes.

If gardeners insist on growing the tomatoes they've always grown then some attention might be focused on the problem. If everyone just gives up and grows the resistant varieties to what ever it is ails tomatoes, then it will just be accepted that the problems solved.

I can take this position as the blight I get is troublesome, but doesn't prevent me from getting tomatoes that we can enjoy. Seems to me that what I've lost over the years is the ability to harvest the big beefsteaks in October like we used to. I've never seen a tomato damaged by these problems. My mother always tried to save a nice tomato to serve at Thanksgiving dinner, what I get trying to preserve that tradition is a small beefsteak about the size of a cherry tomato.

I gave a few beefsteak seedlings last year to my neighbor who in the fall commented that the only tomatoes she's getting were from the beefsteaks that I'd given her. Yesterday her son told me that she planted beefsteaks again this year. She buys seedlings from Burpee, but I think I made a convert from my little gift. She's been struggling with late blight for years, but she went back to growing the good tomatoes.

There are lots of angles to the blight problem. One is that one person is troubled by early blight, another person gets the late blight. I have a plot that hasn't fallen to the blight and 40 feet away another plot gets the problem. This indicates to me that this isn't an airborne spore problem. Something else is at play here. We need to know more about this than what we learned in the 1840's. They say that growing potatoes from seed will prevent the problem. They say that frost will kill the problem over the winter. But if I get blight when I plant my tomatoes from seed, then why is that a cure for potatoes.

Tj Jefferson wrote:

The genes underlying resistance can arise de novo on account of natural mutation that is ongoing.  

John, I have read enough of your posts to know you have a good grasp of biology, but this seems unlikely from my understanding. The level of mutations are pretty low in eukaryotic transcription, and assuming you will get one that is beneficial seems remote........ despite the fact that Joseph is in a very different climate, he has way more genetic variance than the whole seed catalog from Southern Exposure in one row, just some genes are not expressed. I could grow stuff for 100 years and not develop that diversity, because a big landrace will hold more variation already than I could develop in a handful of plants' mutations from the current genomes. Those plants are the survivors of hundreds of years of mutations in vaster areas.

The tomato genome is about 1 giga basepairs in size with a standard replication error rate, even after accounting for DNA repair,  of around 1 in 10 million.  Granted most of the genetic variation produced via random mutation will either be 'silent', as you noted, or even possibly 'culled' via death of those individual cells that inherit deleterious mutations.  But note the abstract shown below regarding the 'lab rat' of plants, Arabidopsis thaliana, which has a genome size about 1/10 the size of that of tomato.  They clearly find genetic "sectors" of the plant.....not visual sectors, but harvested bits of tissue from around the same plant....that possess genetic changes between the different sectors.  Since floral tissue might become initiated from one of these sectors, that variation wholly or in part, will end up in the seed in some form.  So yes, while I agree that selection within more homogeneous genetics is rather a needle-in-a-haystack approach, and predicated not just a little on "luck", de novo genetic variation is not trivial and selection within one's current seed/germplasm pool might be considered in parallel with the acquisition of greater diversity from elsewhere.

To be sure, Joseph and others using wide hybrids with subsequent select for both interesting and useful traits....ALONG with the preservation of diversity remains the 'gold standard' of plant breeding.  But it's worth looking at it from two angles:  Wide hybrids present one with diversity,....and a great deal of that diversity may or may not be useful towards immediate needs (although I'm certainly a proponent of never throwing out the baby with the bathwater.....that diversity may come in useful at some point in the future).  Selection within an heirloom or more uniform germplasm, however, likely will come with fewer surprises in the next generation....*IF* that is what one values in their homestead/operation.....and can still produce variation from which useful selections may be made.  The nasty surprise from the latter approach which would be much less likely in the former is complete collapse of your (more genetically homogeneous) generation due to high disease pressure.  So trade-offs all around it seems, but both providing results in their own way.

More of a technicality, but each time a cell divides in a plant in your garden, the DNA must be 'replicated' so that each new cell gets one copy of the genome.  Essentially like pop-beads on a string, for tomato that means 1 billion base-pairs of DNA being duplicated each time one.....just ONE....cell divides (and just talking the nuclear genome here, not the chloroplast or mitochondrial genomes).  The act of DNA replication is where mutations occur due to errors in this monumental process.  Errors *can* occur in transcription as well---the act of converting the genes in the DNA into 'functional units'.  [DNA is like the blue-print.....transcription converts the blue-print into 'RNA' which carries the message to the machinery that makes proteins.  The latter, protein, is the entity of myriad forms....enzymes, structural building units (think Legos), etc.....and great nutrition for those who consume it.]  But for each gene, transcription occurs many thousands of time at a minimum.....thus, there may be an error in the first or the 1000th molecule of RNA that is made, but the remainder of those that were made might be just fine.  It's a pretty astounding process in all that never ceases to amaze!

Ultimately, what I really find inspiring in this issue is (hopefully!) the increasing number of independent growers of all stripes, combined with the increasing education on the sheer value of any given person's seed stocks and selections, and combined again with the spirit of open distribution of seeds (and this includes those who sell seeds as long as they don't have draconian patent protection on those seeds).  The end result, with greater communication between local growers, is that you might find that Ed or Edna down the road from you has pretty much the same tomato variety as you....but by chance selected a mutant a few weeks ago, or even a few years ago....and they are willing to give you some of that variety to introduce into your own germplasm.

....that idea X millions of growers!

John Duda wrote:I agree with John Weiland. Since this thread is titled " Selecting Tomatoes for Disease Resistance" I'm going to express my viewpoint on Late Blight; even though it's actually a fungus.

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There are lots of angles to the blight problem. One is that one person is troubled by early blight, another person gets the late blight. I have a plot that hasn't fallen to the blight and 40 feet away another plot gets the problem. This indicates to me that this isn't an airborne spore problem. Something else is at play here. We need to know more about this than what we learned in the 1840's. They say that growing potatoes from seed will prevent the problem. They say that frost will kill the problem over the winter. But if I get blight when I plant my tomatoes from seed, then why is that a cure for potatoes.

I'm a laaaaaazy gardener......if you looked at my garden you would think I was growing weeds for herbicide trials!  ;-P    But lazy is where I get my problems with potatoes.  I stupidly ate the best potatoes out of the root cellar each year and planted the smallest and probably most disease-ridden stock.  No brainer that I slowly shifted my potato stocks to low grade.  And this year they are getting clobbered by potato beetles.....needless to say Frito Lay isn't coming 'round to offer me a grower's contract any time soon! ;-)

You are right that we still have a lot to learn about what goes into diseases.  The classic diagram taught about plant diseases is "the disease triangle"---one point being the genetics of the plant, one point being the genetics of the disease pathogen, and the third point being "the environment".  The idea is that all three need to be right for disease to really take hold.  What is lacking from that model for historical reasons is soil biology.  Crop rotation, soil amendments, fertilization, etc. were all 'nods' to the fact that soil was important in some way, but the dynamic nature of the biology was just too difficult in days past to really examine in a useful way.  There is still a long ways to go, but some advances are slowly being made and may explain your "plot effect" that is in the same general growing area.

For the record and for use at your next cocktail party, late blight technically is caused by an oomycete, Phytophthora infestans...more related to algae than the true fungi, whereas early blight really is fungal in nature, caused by Alternaria solani.  But Phytophthora can often be confused since it grows like a fungus and many of the same chemicals used to control fungi will control late blight as well.

I'm no expert of the genes of a tomato, when I ponder genes I'm also thinking the color blue.

But I would say that the heirloom tomato, and especially the beefsteak tomato has possibly evolved the most of any tomato. Let's think about this. It has size going for it. Fill a quart jar from one tomato. The acid makes it easy to can. It's got taste, arguably the best. And think about the range changes the beefsteak tomato has made. From a tropical origin, near the equator,  it was transplanted to southern Europe. And then over centuries it was moved north. And as it moved north it seems to have improved impressively. Myself I have tomatoes growing in my garden this year from several eastern European  countries.

I've talked to two people who tried to grow tomatoes from Pittsburgh. One in the South West. One in Texas. One of those people carried seedlings from Pittsburgh and had problems getting the good tomato they expected.

I don't know if tomatoes are like potatoes, but potato flavor-quality is location-sensitive, probably mostly a matter of overall climate.

I'd long ago noticed that regardless of variety, California-grown potatoes are bland, and Idaho-grown potatoes are better but not great, while North Dakota-grown potatoes are especially flavorful. So whilst living in CA, I planted potatoes from some extra-good ND starts. And they tasted exactly like the usual CA potato -- bland and bleh.

For what it's worth, when I am contemplating adding a new field to my farm, I eat some dirt... Because my experience is that root crops end up tasting like the dirt that they are grown in... Idaho potatoes taste like Idaho dirt... I suspect that something similar happens with above ground portions of the plant. They end up tasting different due to the farmer's habits and ecosystem.

Joseph Lofthouse wrote:Because my experience is that root crops end up tasting like the dirt that they are grown in... Idaho potatoes taste like Idaho dirt... I suspect that something similar happens with above ground portions of the plant. They end up tasting different due to the farmer's habits and ecosystem.

The dirt-to-flavor thing is probably a matter of micronutrients. CA dirt is relatively devoid of same. Occurs to me to wonder what adding a broad-spectrum mineral source (eg bone meal) would do there. How you fertilize, how you cultivate (how deep the roots can go without struggling), water hardness, etc. -- makes sense this affects the plant and therefore the taste.

To the nominal topic, no disease seen as yet on my random assortment of tomatoes. But they've got it good -- rich soil, lots of water, and good drainage.

Also so far nothing chewing on 'em, tho the abundant grasshoppers have been chowing down on the potato vines (which were already yellowing and about done for the year) and holing leaves on the turnips and radishes (both big and crispy). Still green enough here that they're not so hungry as to try less-tasty stuff.