Abstract
A disarmed Tn5 vector (pUT::Ptac-phzABCDEFG) was used to introduce a single copy of the genes responsible for phenazine-1-carboxylic acid (PCA) biosynthesis into the chromosome of a plant-growth-promoting rhizobacterium Pseudomonas fluorescens. The PCA gene cluster was modified for expression under a constitutive Ptac promoter and lacked the phzIR regulators. PCA-producing variants significantly improved the ability of the wild-type P. fluorescens to reduce damping-off disease of pea seedlings caused by Pythium ultimum, even under conditions of heavy soil infestation. Under conditions of oxygen limitation that are typical of the rhizosphere, PCA production per cell in vitro was greater than that recorded in fast-growing, nutrient-rich cultures. Similarly, when the in vitro nutrient supply was limited, P fluorescens::phz variants that produced the most PCA effectively competed against P. ultimum by suppressing mycelial development. Soil-based bioassays confirmed that the level of PCA biosynthesis correlated directly with the efficacy of biological control and the persistence of inocula in soil microcosms. They also showed that soil pretreatment with bacteria provides a suitable method for plant protection by reducing infection, effectively decontaminating the soil. These data demonstrate that the insertion of a single chromosomal copy of the genes for a novel antifungal compound, PCA, enhances the ecological fitness of a natural isolate already adapted to the rhizosphere and capable of suppressing fungal disease.
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Claims 6
Claim · model-written summary
PCA-producing Pseudomonas variants improved damping-off suppression of pea seedlings relative to wild type.
- Taxon
- pea seedlings
Lathyrus oleraceuse0 - Treatment
- PCA-producing variantse0
- Interactor
- Pythium ultimumGlobisporangium ultimume0pathogen
- Second interactor
- P. fluorescens
.JPG?width=60)
Pseudomonas fluorescense0biocontrol_agent - Outcome
- damping-off disease of pea seedlingse0
- Direction
- improvede0
- Qualifier
- heavy soil infestatione0
- Comparator
- wild-type P. fluorescense0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.JPG?width=500)
Verbatim
e0“PCA-producing variants significantly improved the ability of the wild-type P. fluorescens to reduce damping-off disease of pea seedlings caused by Pythium ultimum, even under conditions of heavy soil infestation”
Claim · model-written summary
Under oxygen limitation, PCA production per cell in vitro exceeded that in nutrient-rich cultures.
- Taxon
- pea seedlingsLathyrus oleraceuse0
- Interactor
- P. fluorescensPseudomonas fluorescense2biocontrol_agent
- Outcome
- PCA production per cell in vitroe1
- Direction
- greatere1
- Qualifier
- oxygen limitatione1
- Comparator
- fast-growing, nutrient-rich culturese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“pea seedlings”
e1“Under conditions of oxygen limitation that are typical of the rhizosphere, PCA production per cell in vitro was greater than that recorded in fast-growing, nutrient-rich cultures”
e2“P. fluorescens”
Claim · model-written summary
With limited nutrients, the highest PCA-producing variants suppressed Pythium mycelial development.
- Taxon
- pea seedlingsLathyrus oleraceuse0
- Interactor
- P. ultimumGlobisporangium ultimume1pathogen
- Second interactor
- P fluorescens::phzPseudomonas fluorescense1biocontrol_agent
- Outcome
- mycelial developmente1
- Direction
- suppressinge1
- Qualifier
- in vitro nutrient supply was limitede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“pea seedlings”
e1“when the in vitro nutrient supply was limited, P fluorescens::phz variants that produced the most PCA effectively competed against P. ultimum by suppressing mycelial development”
Claim · model-written summary
PCA biosynthesis level correlated directly with biocontrol efficacy.
- Taxon
- pea seedlingsLathyrus oleraceuse0
- Interactor
- P. fluorescensPseudomonas fluorescense2biocontrol_agent
- Compound
- PCAe1
- Outcome
- efficacy of biological controle1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“pea seedlings”
e1“the level of PCA biosynthesis correlated directly with the efficacy of biological control and the persistence of inocula in soil microcosms”
e2“P. fluorescens”
Claim · model-written summary
PCA biosynthesis level correlated directly with inoculum persistence in soil microcosms.
- Taxon
- pea seedlingsLathyrus oleraceuse0
- Interactor
- P. fluorescensPseudomonas fluorescense2biocontrol_agent
- Compound
- PCAe1
- Outcome
- persistence of inocula in soil microcosmse1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“pea seedlings”
e1“the level of PCA biosynthesis correlated directly with the efficacy of biological control and the persistence of inocula in soil microcosms”
e2“P. fluorescens”
Claim · model-written summary
Soil pretreatment with bacteria reduced infection.
- Taxon
- pea seedlingsLathyrus oleraceuse0
- Treatment
- soil pretreatment with bacteriae1
- Interactor
- P. fluorescensPseudomonas fluorescense2biocontrol_agent
- Outcome
- infectione1
- Direction
- reducinge1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“pea seedlings”
e1“soil pretreatment with bacteria provides a suitable method for plant protection by reducing infection”
e2“P. fluorescens”
The same questions in other papers
inoculation · Pseudomonas fluorescens · Lathyrus oleraceus (pea)Results agree
3 papers in the same direction as this paper
- positive
- positive
- positive
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.