PL and disease tolerance

[snugglekitten]

I have read lots of contradictory comments on potato leaves and their alledged qualities related to foliar disease resistence.

Last week, late blight set in here and my PL crop is SPOTLESS.

granted, they are at a f3 stage now, the PL gene has been isolated, but it could also be something else in the plant's genotype, so I just can't know....

If anyone has any hard data on this it would be highly appreciated.

My biggest hurdle in accepting this idea without peer reviewed trial data is the simple idea that a recessive gene, generally rare could NOT have taken over the general phenotype of the species if it were so superior to disease resistence - that being said, I also read that wild tomatoes are promisciously pollinated, and therefore human breeders who created all the inbred cultivars today may have had arbitrary reasons for keeping RL in so many of the popular cultivars in circulation.



Thanks in advance,

SK

[snugglekitten]

I have no scientific basis to assume this - but it does appear to be that PL has a decrease in the quantity of trichomes compared to RL, and perhaps there is a tradeoff here of protection vs insects and bacteria, but this is just amateur speculation.

The PL dominates in nature when bacteria is prevelent, the RL when insects are prevelent.

[carolyn137]

I have long said that PL varieties have greater tolerances to foliage diseases at many sites and for many years.

Not everyone would agree with me,which is fine.

But late in the season my RL plants could be down while most of the PL's are still doing OK. And of course that's a seasonal issue since spores and bacteria are not always present in any one season

What I have proposed is that the epidermis of the upper leaf surface of PL leaves is thicker than RL leaves so it makes it harder for the foliage pathogens to attach and infect.

I have not researched epidermis thickness for RL vs PL, so have no answers as to whether or not that's true.

So I don't see it as a genetic issue per se as related to a specific gene/alleles, I see it as a possible difference in the entire epidermal structures of RL and PL.

Carolyn

[snugglekitten]

Originally Posted by carolyn137

I have long said that PL varieties have greater tolerances to foliage diseases at many sites and for many years.

Not everyone would agree with me,which is fine.

But late in the season my RL plants could be down while most of the PL's are still doing OK. And of course that's a seasonal issue since spores and bacteria are not always present in any one season

What I have proposed is that the epidermis of the upper leaf surface of PL leaves is thicker than RL leaves so it makes it harder for the foliage pathogens to attach and infect.

I have not researched epidermis thickness for RL vs PL, so have no answers as to whether or not that's true.

So I don't see it as a genetic issue per se as related to a specific gene/alleles, I see it as a possible difference in the entire epidermal structures of RL and PL.

Carolyn

Thats a very fascinating hypothesis, Carolyn. I had no idea that the epidermal thickness was different.

That being said, have you noticed as well that PL tend to have less trichomes??

I could be totally wrong, but this is my overall observation.

[maf]

Here, the only variety that has been infected with late blight so far is a potato leaved cultivar. I think the disease tolerance genes are leaf agnostic.

[Fusion_power]

There is no association of leaf type with disease tolerance. There is an effect where potato leaf plants grow a bit faster and can to an extent keep ahead of septoria a bit longer than RL plants. It is only a temporary effect. I've searched diligently among the wild relatives of tomato and found that S. Habrochaites has foliage disease tolerance beyond anything we see in domestic tomato.

[carolyn137]

Originally Posted by Fusion_power

There is no association of leaf type with disease tolerance. There is an effect where potato leaf plants grow a bit faster and can to an extent keep ahead of septoria a bit longer than RL plants. It is only a temporary effect. I've searched diligently among the wild relatives of tomato and found that S. Habrochaites has foliage disease tolerance beyond anything we see in domestic tomato.

Darrel, that's a pretty strong statement you made when you said that there is NO association with leaf type and disease.

And one with which I don't agree for the reason you gave.

I have no idea what "effect" you refer to when saying that PL plants grow faster.

I've grown one heck of a lot of PL varieties as well, of course also RL varieties, and regardless of leaf type they can grow at different rates in any one season b/c of all the variables we know of.

You posted:

(I've searched diligently among the wild relatives of tomato and found that S. Habrochaites has foliage disease tolerance beyond anything we see in domestic tomato.)

Fair enough, you've posted about this before, but the question the OP posted was about PL vs RL and disease.

Carolyn

[carolyn137]

Originally Posted by snugglekitten

Thats a very fascinating hypothesis, Carolyn. I had no idea that the epidermal thickness was different.

That being said, have you noticed as well that PL tend to have less trichomes??

I could be totally wrong, but this is my overall observation.

No, I have never looked at trichome densities and couldn't anyway since one needs a microscope to see them, see link below.

Here is a link Iknow you'll find interesting.

http://www.growingformarket.com/arti...-tomato-plants

Ihadn't reliazed that trichomes are also found on stems and fruits, not just on the upper leaf surface.

And yes, it is thought......that they might be more studied in terms of disease tolerances.

An additional suggestion.

There are specific know attachment sites on the upper leaf surface for the more common fungal foliar pathogens. Molecules of chlorothalinol ( Daconil, Bravo and friends) cover those attachment sites helping to prevent pathogen attachment and infection.

I don't know the structure of those attachement sites, no one does as far as I know, so might one suggest that there could be a whole family of structurally different trichomes, and also present on the leaf surface with different areal densities.

I'm not sure I'm explaining this well, but could try again later if it's not making sense.

Carolyn

[carolyn137]

Originally Posted by maf

Here, the only variety that has been infected with late blight so far is a potato leaved cultivar. I think the disease tolerance genes are leaf agnostic.

So you are growing one plant of a variety that supposedly has one or more ph genes for Late Blight and still that one plant got LB?

So you've decided that those LB tolerance genes are, shall we say "unknowing", aka agnostic?

Not a problem at all. Just notify the breeder of the the PL plant you have, no doubt a PL plant and a hybrid, and tell the breeder that he/she needs to devlop some gnostic genes for those toelrances.

Sorry, I just couldn't help myself.

Carolyn, and if I've misinterprted what you said, please correct me.

[snugglekitten]

Originally Posted by carolyn137

No, I have never looked at trichome densities and couldn't anyway since one needs a microscope to see them, see link below.

Here is a link Iknow you'll find interesting.

http://www.growingformarket.com/arti...-tomato-plants

Ihadn't reliazed that trichomes are also found on stems and fruits, not just on the upper leaf surface.

And yes, it is thought......that they might be more studied in terms of disease tolerances.

An additional suggestion.

There are specific know attachment sites on the upper leaf surface for the more common fungal foliar pathogens. Molecules of chlorothalinol ( Daconil, Bravo and friends) cover those attachment sites helping to prevent pathogen attachment and infection.

I don't know the structure of those attachement sites, no one does as far as I know, so might one suggest that there could be a whole family of structurally different trichomes, and also present on the leaf surface with different areal densities.

I'm not sure I'm explaining this well, but could try again later if it's not making sense.

Carolyn

Thanks for the link, Carolyn. Bookmarked for weekend reading.

[snugglekitten]

Well, I don't want to get into an argument about this, certainly I would assume that if such an obvious indicator held an advantage it would be documented by now, that being said, if I were to see two identical plants, one with PL the other RL, I'd take the PL, call me superstitious, but it is just anecdotal that my PLs outlast my RLs this time of year.

[maf]

Originally Posted by carolyn137

So you are growing one plant of a variety that supposedly has one or more ph genes for Late Blight and still that one plant got LB?

So you've decided that those LB tolerance genes are, shall we say "unknowing", aka agnostic?

Not a problem at all. Just notify the breeder of the the PL plant you have, no doubt a PL plant and a hybrid, and tell the breeder that he/she needs to devlop some gnostic genes for those toelrances.

Sorry, I just couldn't help myself.

Carolyn, and if I've misinterprted what you said, please correct me.

Sorry for the confusion, not the best choice of word. I meant it like the tech term "platform agnostic", in that specific disease tolerance genes are likely "leaf-form agnostic", i.e. they are compatible with various leaf forms. Just anecdotally pointing out that the only plants I have had to pull for disease this year have been PL, while the RL are fine. For the diseases I see over here (late blight outside, grey mould inside)I don't see a difference based on leaf form. Doesn't mean anything in the grand scheme of things, small sample size and all that.

I wasn't growing plants with any ph resistance genes this year, it just happens that, for whatever reason, the ones that caught LB were PL, while the RL are (so far) unaffected.

[Fusion_power]

Strong statements because they are needed Carolyn. I went through my garden with a notepad this year to see which were and which were not disease tolerant to any extent. Both potato leaf and regular leaf plants were equally affected by septoria and early blight. In other words, there was no association between tolerance and leaf form. There were individual varieties that handled disease better on average and kept producing longer. Eva Purple Ball is a very good example. Note that it is regular leaf. Bloody Butcher is a potato leaf example. In the end, all of them went down to disease. The only exceptions in my garden were the two S. Pimpinellifoliums that I kept seed from last year and the S. Habrochaites that I saved seed from last year. The Pimpinellifoliums eventually go down to septoria, but they keep producing a few fruit and they stay alive by producing new foliage at the growing tips of the vines.

LA2175 (S. Habrochaites) is the most unbelievable plant in my garden. It has minimal affected senescent leaves at the bottom of the plant with a huge fruit load and plentiful healthy foliage. It is a regular leaf plant. I've been stomping on them trying to keep them from taking over that area of the garden, but I think I may be doing the wrong thing, the stems are rooting.

[RayR]

Originally Posted by Fusion_power

Strong statements because they are needed Carolyn. I went through my garden with a notepad this year to see which were and which were not disease tolerant to any extent. Both potato leaf and regular leaf plants were equally affected by septoria and early blight. In other words, there was no association between tolerance and leaf form. There were individual varieties that handled disease better on average and kept producing longer. Eva Purple Ball is a very good example. Note that it is regular leaf. Bloody Butcher is a potato leaf example. In the end, all of them went down to disease. The only exceptions in my garden were the two S. Pimpinellifoliums that I kept seed from last year and the S. Habrochaites that I saved seed from last year. The Pimpinellifoliums eventually go down to septoria, but they keep producing a few fruit and they stay alive by producing new foliage at the growing tips of the vines.

I agree completely. Whatever the reason some gardeners have anecdotal evidence that one leaf type is more resistant to certain fungal pathogens than others certainty can't be duplicated in every garden. On another thread I said that Sungold had the worst resistance to Septoria than other varieties in my garden. Some agreed and some had the opposite opinion. I expected as much. Just like other fungi and oomycete out there in the wild there are different strains of Septoria. some more virulent than others. I think that all of us that are confronted with Septoria every year in our gardens probably don't have the same strains present every year.

I think pathogen resistance all comes down to chemistry. All plants produce chemicals that protect it from certain diseases. On top of that beneficial bacteria and fungi that colonize plants add to that resistance by their own chemical means. Whether a pathogen is successful or not at infecting a plant depends on it's ability to defeat enough of those chemical barriers.
For example, one mechanism that tomato plants have is production of alpha-tomatine, a saponin that is very toxic to fungal pathogens, but tomato pathogens like Septoria, Early Blight, Late Blight and Fusarium all have something in common, they defeat this one barrier by producing tomatinase, an enzyme that detoxifies alpha-tomatine. Even non-pathogenic fungi produce it which allows them to colonize tomato plants.

[carolyn137]

Strong statements because they are needed Carolyn. I went through my garden with a notepad this year to see which were and which were not disease tolerant to any extent. Both potato leaf and regular leaf plants were equally affected by septoria and early blight. In other words, there was no association between tolerance and leaf form. There were individual varieties that handled disease better on average and kept producing longer.

&&&&&

Darrel, above I said that not everyone would agree with me and you don't and that's OK.

You recorded data for one season whereas I did the same for several decades.

All the years I had hundreds of plants out I would take my data notebook and walk down the rows, recording first blossoms, first fruit set, plant habit, color and size and shape of fruit for each variety/

And of course which varieties had foliage diseases, no important systemic diseases where I grew and I knew those diseases very well since the head of the Cornell Cooperative extension for the 5 county regiona around Albany had been taught by , sheesh, I can't remember his name now, but the head infectious disease person at Cornell. Ja, I remember his name startedwith a Z.

Then they wanted to do a disease survey one summer in my tomato patch and I was asked to grow some hybrids for comparison, and they had interns coming a few times a week to double record what I had recorded, but independently, and the head of the project then came once a week to review all the data.

Aha, his name is Dr. Zitter, I knew it would come to me.

For all those years there was no Tania website, just in the early 80's Glecklers and Seeds Blum and in the SSE Yearbooks some listers never gave the kind of data I needed and wanted.

So you recorded for one season and me for several decades.

Whether it's a difference in susceptibility due to leaf form, I can't prove my theory as to leaf thickness, and no doubt there might well be other factors involved as well.

Did you read the link I gave above about trichomes? That's another variable.


Carolyn