Abstract
Quantitative disease resistance (QDR) is the most common form of disease resistance in crops, but it is challenging to understand at the cellular level due to the involvement of many genes and biological processes. Ralstonia solanacearum, the causal agent of bacterial wilt disease, is a destructive plant pathogen of Solanaceous species that is best controlled by quantitatively resistant varieties, but few QDR genes are known. We previously found that a tomato auxin pathway mutant known as diageotropica ( dgt) has enhanced resistance to R. solanacearum. Here, we show that, as with wild-type quantitatively resistant tomato plants, resistance in dgt is the result of multiple mechanisms. Mock-inoculated dgt roots have endogenously higher levels of the plant defense hormone salicylic acid (SA). However, the SA-deficient double mutant dgtNahG is still resistant to R. solanacearum, indicating that SA-independent pathways are also required for resistance. Scanning electron microscopy revealed that R. solanacearum colonization of the root xylem is delayed in dgt. We found an increased number of lignified xylem cells and altered root vasculature anatomy in dgt, and dgt root length was not impacted by R. solanacearum treatment. Similar to the wilt-resistant wild-type tomato Hawaii7996, RNA sequencing results suggested that dgt may tolerate R. solanacearum-induced water stress better than the wilt-susceptible parent. Thus, resistance in dgt is due to several pathways, including preactivated SA defenses, physical barriers in the xylem, and an ability to tolerate water stress. The pleiotropic nature of this single mutation appears to mimic quantitative resistance. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .
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Claims 7
Claim · model-written summary
Mock-inoculated dgt roots had higher salicylic acid levels.
- Taxon
- tomato
Solanum lycopersicumt0 - Material
- dgte0
- Organ / stage
- rootse0
- Outcome
- levels of the plant defense hormone salicylic acid (SA)e0
- Direction
- highere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Mock-inoculated dgt roots have endogenously higher levels of the plant defense hormone salicylic acid (SA)”
t0“Tomato”
Claim · model-written summary
SA-deficient dgtNahG retained resistance to R. solanacearum.
- Taxon
- tomatoSolanum lycopersicumt0
- Material
- dgtNahGe0
- Interactor
- R. solanacearum
Ralstonia solanacearume0pathogen - Outcome
- resistant to R. solanacearume0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the SA-deficient double mutant dgtNahG is still resistant to R. solanacearum”
t0“Tomato”
Claim · model-written summary
R. solanacearum colonization of root xylem was delayed in dgt.
- Taxon
- tomatoSolanum lycopersicumt0
- Material
- dgte0
- Interactor
- R. solanacearumRalstonia solanacearume0pathogen
- Outcome
- R. solanacearum colonization of the root xyleme0
- Direction
- delayede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“R. solanacearum colonization of the root xylem is delayed in dgt”
t0“Tomato”
Claim · model-written summary
dgt had more lignified xylem cells.
- Taxon
- tomatoSolanum lycopersicumt0
- Material
- dgte0
- Outcome
- number of lignified xylem cellse0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased number of lignified xylem cells and altered root vasculature anatomy in dgt”
t0“Tomato”
Claim · model-written summary
dgt root vasculature anatomy was altered.
- Taxon
- tomatoSolanum lycopersicumt0
- Material
- dgte0
- Outcome
- root vasculature anatomye0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased number of lignified xylem cells and altered root vasculature anatomy in dgt”
t0“Tomato”
Claim · model-written summary
R. solanacearum treatment did not affect dgt root length.
- Taxon
- tomatoSolanum lycopersicumt0
- Material
- dgte0
- Treatment
- R. solanacearum treatmente0
- Interactor
- R. solanacearumRalstonia solanacearume0pathogen
- Outcome
- root lengthe0
- Direction
- not impactede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“dgt root length was not impacted by R. solanacearum treatment”
t0“Tomato”
Claim · model-written summary
RNA sequencing suggested dgt better tolerates pathogen-induced water stress than its susceptible parent.
- Taxon
- tomatoSolanum lycopersicumt0
- Material
- dgte0
- Interactor
- R. solanacearumRalstonia solanacearume0pathogen
- Outcome
- R. solanacearum-induced water stresse0
- Direction
- bettere0
- Comparator
- wilt-susceptible parente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“RNA sequencing results suggested that dgt may tolerate R. solanacearum-induced water stress better than the wilt-susceptible parent”
t0“Tomato”
The same questions in other papers
Ralstonia solanacearum · growth · Solanum lycopersicum (tomato)Positive and negative results
1 paper in the same direction as this paper · 4 in the opposite direction
- negative
- negative
- negative
2 papers more in this group
See all 6 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.