Abstract
Anthracnose leaf blight (ALB) and Zebra Chip disease (ZC) represent serious threats to maize and Solanaceous crop production respectively. ALB control relies on resistant lines, but high genetic plasticity in the fungal causative agent, Colletotrichum graminicola, resulting in the evolution of new pathotypes makes it challenging to breed for durable genetic resistance. ZC control is based on antibiotic treatment against the causative agent ‘Candidatus Liberibacter solanacearum’ (CLso) and insecticide applications to control the psyllid vector, Bactericera cockerelli. However, this will lead to resistance emergence in the psyllids and CLso. A potential alternative is to boost host resistance by employing Plant Growth-Promoting Rhizobacteria (PGPR) and Arbuscular Mycorrhizal Fungi (AMF). I found in vitro that the PGPR Pseudomonas chlororaphis 30-84 inhibited the growth of C. graminicola M1.001 via phenazine production. In vivo, the AMF Rhizophagus irregularis and P. chlororaphis 30-84 triggered effective systemic resistance to C. graminicola-induced foliar lesions on the susceptible B73 maize line. The level of disease control was similar to that of the resistant line W438. Both biocontrol agents (BCAs) reduced foliar fungal biomass. Coinoculation mirrored R. irregularis effect and revealed different and competitive mechanisms triggered by each BCA. Mutation of the ZMLOX12 gene enhanced disease severity on bacterized plants, whereas mycorrhized plants were still resistant. When introduced sequentially, I found no effect on the rate of root colonization by either organism on the other. To investigate the role of mycorrhizae on Zebra Chip disease development and psyllid survival, I used a ‘no-choice’ assay, in which three couples of male and female B. cockerelli harboring either CLso haplotype A or B (LsoA and LsoB respectively) were placed on a single leaf. Despite reports suggesting mycorrhization facilitates feeding by phloem-feeding insects, R. irregularis substantially delayed and reduced symptoms of ZC diseases on ‘Moneymaker’ tomato as compared to non-mycorrhized plants treated with psyllids. Mycorrhization also impaired the survival of psyllid larvae from parents harboring LsoA but increased slightly the survival of those from parents harboring LsoB. PCR with specific CLso primers revealed that mycorrhization did not prevent CLso transmission by the insect or translocation to newly formed leaves.
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Claims 14
Claim · model-written summary
P. chlororaphis inhibited C. graminicola growth in vitro via phenazine production.
- Interactor
- C. graminicola M1.001
_G.W._Wilson_1235209.jpg?width=60)
Colletotrichum graminicolae0pathogen - Second interactor
- Pseudomonas chlororaphis 30-84Pseudomonas chlororaphis subsp. aureofaciens 30-84e0biocontrol_agent
- Compound
- phenazinee0
- Outcome
- growth of C. graminicola M1.001e0
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
_G.W._Wilson_1235209.jpg?width=500)
Verbatim
e0“the PGPR Pseudomonas chlororaphis 30-84 inhibited the growth of C. graminicola M1.001 via phenazine production”
t0“Maize Anthracnose Leaf Blight”
Claim · model-written summary
R. irregularis triggered systemic resistance to C. graminicola lesions in susceptible B73 maize.
- Material
- B73e0
- Treatment
- Rhizophagus irregularise0
- Interactor
- C. graminicolaColletotrichum graminicolae0pathogen
- Second interactor
- Rhizophagus irregularis
Rhizophagus irregularise0symbiont - Outcome
- C. graminicola-induced foliar lesionse0
- Direction
- effectivee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the AMF Rhizophagus irregularis and P. chlororaphis 30-84 triggered effective systemic resistance to C. graminicola-induced foliar lesions on the susceptible B73 maize line”
Claim · model-written summary
P. chlororaphis triggered systemic resistance to C. graminicola lesions in susceptible B73 maize.
- Material
- B73e0
- Treatment
- P. chlororaphis 30-84e0
- Interactor
- C. graminicolaColletotrichum graminicolae0pathogen
- Second interactor
- P. chlororaphis 30-84Pseudomonas chlororaphise0biocontrol_agent
- Outcome
- C. graminicola-induced foliar lesionse0
- Direction
- effectivee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the AMF Rhizophagus irregularis and P. chlororaphis 30-84 triggered effective systemic resistance to C. graminicola-induced foliar lesions on the susceptible B73 maize line”
Claim · model-written summary
Disease control in inoculated maize was similar to resistant W438.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The level of disease control was similar to that of the resistant line W438.”
t0“Maize Anthracnose Leaf Blight”
Claim · model-written summary
R. irregularis reduced foliar fungal biomass.
- Treatment
- Rhizophagus irregularise1
- Interactor
- Rhizophagus irregularisRhizophagus irregularise1symbiont
- Outcome
- foliar fungal biomasse0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Both biocontrol agents (BCAs) reduced foliar fungal biomass.”
t0“Maize Anthracnose Leaf Blight”
e1“the AMF Rhizophagus irregularis and P. chlororaphis 30-84”
Claim · model-written summary
P. chlororaphis reduced foliar fungal biomass.
- Treatment
- P. chlororaphis 30-84e1
- Interactor
- P. chlororaphis 30-84Pseudomonas chlororaphise1biocontrol_agent
- Outcome
- foliar fungal biomasse0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Both biocontrol agents (BCAs) reduced foliar fungal biomass.”
t0“Maize Anthracnose Leaf Blight”
e1“the AMF Rhizophagus irregularis and P. chlororaphis 30-84”
Claim · model-written summary
Coinoculation mirrored the R. irregularis effect and revealed competitive mechanisms.
- Interactor
- R. irregularisRhizophagus irregularise0symbiont
- Outcome
- different and competitive mechanismse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Coinoculation mirrored R. irregularis effect and revealed different and competitive mechanisms triggered by each BCA.”
t0“Maize Anthracnose Leaf Blight”
Claim · model-written summary
ZMLOX12 mutation enhanced disease severity on bacterized maize.
- Treatment
- Mutation of the ZMLOX12 genee0
- Gene
- ZMLOX12e0
- Outcome
- disease severitye0
- Direction
- enhancede0
- Qualifier
- bacterized plantse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Mutation of the ZMLOX12 gene enhanced disease severity on bacterized plants”
t0“Maize Anthracnose Leaf Blight”
Claim · model-written summary
Mycorrhized ZMLOX12 mutant plants remained resistant.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“whereas mycorrhized plants were still resistant”
e1“Mutation of the ZMLOX12 gene enhanced disease severity on bacterized plants”
t0“Maize Anthracnose Leaf Blight”
Claim · model-written summary
Sequential introduction did not affect either organism’s root colonization rate.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When introduced sequentially, I found no effect on the rate of root colonization by either organism on the other.”
t0“Maize Anthracnose Leaf Blight”
Claim · model-written summary
Mycorrhization delayed and reduced Zebra Chip symptoms in Moneymaker tomato relative to non-mycorrhized plants treated with psyllids.
- Taxon
- tomato
Solanum lycopersicume0 - Material
- Moneymakere0
- Treatment
- R. irregularise0
- Interactor
- psyllidsPsylloideae0pest
- Second interactor
- R. irregularisRhizophagus irregularise0symbiont
- Outcome
- symptoms of ZC diseasese0
- Direction
- delayed and reducede0
- Comparator
- non-mycorrhized plants treated with psyllidse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“R. irregularis substantially delayed and reduced symptoms of ZC diseases on ‘Moneymaker’ tomato as compared to non-mycorrhized plants treated with psyllids.”
Claim · model-written summary
Mycorrhization impaired survival of psyllid larvae from LsoA-harboring parents.
- Taxon
- TomatoSolanum lycopersicumt0
- Treatment
- Mycorrhizatione0
- Interactor
- psyllide0pest
- Outcome
- survival of psyllid larvae from parents harboring LsoAe0
- Direction
- impairede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Mycorrhization also impaired the survival of psyllid larvae from parents harboring LsoA”
t0“Tomato Zebra Chip Disease”
Claim · model-written summary
Mycorrhization slightly increased survival of psyllid larvae from LsoB-harboring parents.
- Taxon
- TomatoSolanum lycopersicumt0
- Interactor
- psyllide1pest
- Outcome
- survival of psyllid larvaee1
- Direction
- increasede0
- Qualifier
- parents harboring LsoBe0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased slightly the survival of those from parents harboring LsoB”
e1“survival of psyllid larvae”
t0“Tomato Zebra Chip Disease”
Claim · model-written summary
Mycorrhization did not prevent CLso transmission or movement to new tomato leaves.
- Taxon
- TomatoSolanum lycopersicumt0
- Treatment
- mycorrhizatione0
- Interactor
- CLsoe0pathogen
- Outcome
- CLso transmission by the insect or translocation to newly formed leavese0
- Direction
- did not prevente0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“mycorrhization did not prevent CLso transmission by the insect or translocation to newly formed leaves.”
t0“Tomato Zebra Chip Disease”
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