Information and discussion regarding garden diseases, insects and other unwelcome critters.
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July 15, 2019 | #1 |
Tomatovillian™
Join Date: May 2016
Location: sw ohio
Posts: 153
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Disease resistance and what that means
I googled this, and mostly found people suggesting which varieties are most resistant.
But what I'm curious about, is what exactly does that mean? Are the leaves of the plant less likely to have the fungal disease spread on it somehow? Or, are they developed so that they have quickly growing new growth, so that they "outrun" the disease but having plenty of growth as the grower prunes away diseased leaves? Thanks if anyone happens to know about this. Jan H. |
July 15, 2019 | #2 |
Tomatovillian™
Join Date: May 2016
Location: Williamsburg VA Zone 7b
Posts: 1,110
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Jan:
The mechanism of resistance is often very complicated and hard to explain. Here’s a “non-technical” explanation of bacterial speck resistance: Non Technical Summary In tomato, resistance to bacterial speck disease is determined by the resistance protein Prf, a host resistance protein with a nucleotide-binding site (NBS) and a region of leucine-rich repeats (LRR). Prf indirectly recognizes either of two effector proteins, AvrPto or AvrPtoB, delivered by the Pseudomonas syringae pathovar tomato (Pst). Sometimes the resistance results in less disease growth or the resistance allows high pathogen growth with little damage. |
July 15, 2019 | #3 |
Tomatovillian™
Join Date: Feb 2012
Location: Newfoundland, Canada
Posts: 6,794
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Afaik, I think "tolerance" is when the disease is present but the plant outgrows it or is not affected ie continues to grow, fruit, etc.
Resistance is when the plant is slower to be affected and show symptoms of the disease.. |
July 15, 2019 | #4 |
Tomatovillian™
Join Date: Feb 2016
Location: Southeastern PA
Posts: 1,420
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For example, I grow County Fair cucumbers which are bacterial wilt resistant. They eventually get wilt but not until late in the season when I have harvested plenty of cucumbers.
Non resistant varieties die before I get anything. The cucumber beetles transmit this disease. |
July 16, 2019 | #5 | |
Tomatovillian™
Join Date: May 2016
Location: Williamsburg VA Zone 7b
Posts: 1,110
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Quote:
I graft on to resistant rootstock - most of these tomatoes will last until the first frost with vines well over 20 feet long. Jeff |
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July 16, 2019 | #6 |
Tomatoville® Moderator
Join Date: Jan 2006
Location: Hendersonville, NC zone 7
Posts: 10,385
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So the best way to consider this is the absolute definition of resistance and tolerance.
Resistance means that the mechanism of the plant resists attack of the agent - in the case of Fusarium, a fungus that moves into the roots from the soil, a F resistant variety means that the roots resist movement of the agent into the roots. Tolerance means that even though the agent moves into the plants, the plant can tolerate the attack and do reasonably well for a spell after attack. But here's the thing - the terms are really relative and misinterpreted. In high disease pressure areas, plants won't resist or tolerate the disease indefinitely. For example, let's say you have a Fusarium resistant plant. The plant will resist the disease a bit longer than a non resistant plant, but if the disease pressure is high, it will go down a few weeks later (or some time frame). So with grafts, if rootstock is highly resistant to this or that disease, in principal it will from some to alot more time. The key then is to use good garden hygiene, keep soil from splashing onto foliage above the graft line, etc - that plant top will be just as susceptible to the disease as an ungrafted plant - the protection is whatever the roots can provide.
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Craig |
July 16, 2019 | #7 |
Tomatovillian™
Join Date: May 2016
Location: Williamsburg VA Zone 7b
Posts: 1,110
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You got me interested so I just read a paper on BW in tomatoes from 2014.
Looks like the resistant root stock keeps the bacteria out somehow - the plants were negative for the bacteria. Other facts about BW: Around 2012, over 80% of the tomato plants in Japan were grafted. A resistant rootstock that works in China might not be effective in the US - the strains of Ralstonia solanacearum can vary. RS can persist in soil up to 10 years - even with nothing planted! |
July 16, 2019 | #8 | |
Tomatovillian™
Join Date: May 2016
Location: Williamsburg VA Zone 7b
Posts: 1,110
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Quote:
My next move - if grafting ever becomes ineffective - would be to move to grow bags with a sterile medium. Do you replace your medium? Do disease build in it year to year? |
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July 16, 2019 | #9 |
Tomatovillian™
Join Date: Jan 2006
Location: Brownville, Ne
Posts: 3,294
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Resistance or tolerance, either way the most resistant or tolerant gives the home gardener an extra week or so of healthy plant. I find cultural practices do more than worrying about varieties with tolerance or resistance; soil health, mulching program, proper watering, staking or caging being disinfected yearly...just plain sensible gardening practices.
If I were a market tomato farmer the extra week may mean making a profit or losing the farm. As for me, a few extra tomatoes or cleaning out the garden early by a week is mostly inconsequential. Here we have less problematic disease than many other areas of the country so I worry less than other growers. Still all reasonable precautions are taken other than base my varieties grown on tolerance or resistance.
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there's two things money can't buy; true love and home grown tomatoes. |
July 16, 2019 | #10 |
Tomatovillian™
Join Date: May 2016
Location: Williamsburg VA Zone 7b
Posts: 1,110
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With grafting in my area it's extra months - not just weeks. I would be growing out of bags if grafting only gave me a week or two.
Jeff |
July 16, 2019 | #11 |
Tomatoville® Moderator
Join Date: Jan 2006
Location: Hendersonville, NC zone 7
Posts: 10,385
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If your grafts are working that well, bravo - you have a great match between what is in the soil as a disease agent, and the particular graft used. Good to know, and great news.
Using bags or bales (both sterile) are great for things like Fusarium and Bacterial wilt, but the air-spread fungi like septoria and early blight are still an issue. Foliage removal and good spacing and keeping foliage dry work well.
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Craig |
July 16, 2019 | #12 |
Tomatovillian™
Join Date: Feb 2012
Location: Newfoundland, Canada
Posts: 6,794
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So true that it is all about buying some time... Every plant goes down with some funk or other at the end of the season.
Resistance can make a huge difference in a commercial greenhouse. We had a row one summer of plants that were very susceptible to ?? don't even know what it was. They went down more than a month before the others, although they did produce some fruit. Sick tomato plant mess is pretty gross... I'm always steering toward resistance and away from the dreaded high maintenance varieties. |
July 18, 2019 | #13 | |
Tomatovillian™
Join Date: Sep 2009
Location: Alabama
Posts: 7,068
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Quote:
Bill |
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July 18, 2019 | #14 | |
Tomatovillian™
Join Date: Sep 2009
Location: Alabama
Posts: 7,068
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Quote:
Bill |
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July 18, 2019 | #15 |
Tomatovillian™
Join Date: May 2016
Location: sw ohio
Posts: 153
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Boy I have to learn the disease language. I'm assuming the foliar disease I've had is always early blight -- it's possible there have been other issues and not known it. I've not yet had plants die, they do produce while struggling with foliar issues. (none so far this year).
This year I'm just learning a lot -- seeing what works and what doesn't. Learned in a article that some seeds may be disease resistant but just haven't been tested for it, so they can't list them that way. Sounds like some of the disease resistance is more aimed at bacterial rather than fungal maybe? I'll find a thread about grafting, sounds interesting! |
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