Abstract
As a prerequisite to infection of flowers, Erwinia amylovora grows epiphytically on stigmas, which provide a conducive habitat for bacterial growth. Stigmas also support growth of several other bacterial genera, which allows for biological control of fire blight; although, in practice, it is very difficult to exclude E. amylovora completely from this habitat. We investigated the dynamics of growth suppression of E. amylovora by comparing the ability of virulent and avirulent strains of E. amylovora to compete with each other on stigmas of pear, apple, and blackberry, and to compete with a co-inoculated mixture of effective bacterial antagonists. When strains were inoculated individually, virulent E. amylovora strain Ea153N attained the highest population size on stigmas, with population sizes that were approximately double those of an avirulent hrpL mutant of Ea153 or the bacterial antagonists. In competition experiments, growth of the avirulent derivative was suppressed by the antagonist mixture to a greater extent than the virulent strain. Unexpectedly, the virulent strain enhanced the population size of the antagonist mixture. Similarly, a small dose of virulent Ea153N added to inoculum of an avirulent hrpL mutant of Ea153 significantly increased the population size of the avirulent strain. A pathogenesis-gene reporter strain, Ea153 dspE::gfp, was applied to flowers and a subset of the population expressed the green fluorescent protein while growing epiphytically on stigmas of apple. These results are consistent with the hypothesis that virulent E. amylovora modifies the epiphytic habitat presented by the stigma through a pathogenesis-related process, which increases host resources available to itself and, coincidentally, to nonpathogenic competitors. Over nine orchard trials, avirulent Ea153 hrpL significantly suppressed the incidence of fire blight four times compared with six for the antagonist mixture. The degree of biological control achievable with an avirulent strain of E. amylovora likely is limited by its inability to utilize the stigmatic habitat to the same degree as a virulent strain.
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Claims 9
Claim · model-written summary
Individually inoculated virulent Ea153N reached about twice the stigma population of avirulent Ea153 hrpL or bacterial antagonists.
- Taxon
- Rosaceoust0
- Material
- Ea153Ne0
- Interactor
- E. amylovora
Erwinia amylovorae0pathogen - Outcome
- population size on stigmase0
- Direction
- higheste0
- Value
- approximately doublee0
- Comparator
- an avirulent hrpL mutant of Ea153 or the bacterial antagonistse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When strains were inoculated individually, virulent E. amylovora strain Ea153N attained the highest population size on stigmas, with population sizes that were approximately double those of an avirulent hrpL mutant of Ea153 or the bacterial antagonists.”
t0“Rosaceous Stigmas”
Claim · model-written summary
The antagonist mixture suppressed the avirulent derivative more than the virulent strain.
- Taxon
- pear, apple, and blackberry
Malus domestica_Poirier_Fleurs_et_feuilles.jpg?width=60)
Pyrus communis
Rubuse1 - Treatment
- antagonist mixturee0
- Interactor
- avirulent derivativee0pathogen
- Outcome
- growth of the avirulent derivativee0
- Direction
- suppressede0
- Comparator
- virulent straine0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
_Poirier_Fleurs_et_feuilles.jpg?width=500)
Verbatim
e0“growth of the avirulent derivative was suppressed by the antagonist mixture to a greater extent than the virulent strain”
e1“stigmas of pear, apple, and blackberry”
Claim · model-written summary
The virulent strain increased the antagonist mixture population.
- Taxon
- pear, apple, and blackberryMalus domesticaPyrus communisRubuse1
- Treatment
- virulent straine0
- Interactor
- antagonist mixturee0biocontrol_agent
- Outcome
- population size of the antagonist mixturee0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the virulent strain enhanced the population size of the antagonist mixture”
e1“stigmas of pear, apple, and blackberry”
Claim · model-written summary
Adding a small dose of virulent Ea153N significantly increased the avirulent mutant population.
- Taxon
- pear, apple, and blackberryMalus domesticaPyrus communisRubuse1
- Treatment
- a small dose of virulent Ea153Ne0
- Interactor
- avirulent hrpL mutant of Ea153e0pathogen
- Outcome
- population size of the avirulent straine0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a small dose of virulent Ea153N added to inoculum of an avirulent hrpL mutant of Ea153 significantly increased the population size of the avirulent strain”
e1“stigmas of pear, apple, and blackberry”
Claim · model-written summary
A subset of the reporter strain population expressed green fluorescent protein on apple stigmas.
- Taxon
- appleMalus domesticae0
- Material
- Ea153 dspE::gfpe1
- Organ / stage
- stigmase0
- Interactor
- Ea153 dspE::gfpe1pathogen
- Outcome
- expressed the green fluorescent proteine0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a subset of the population expressed the green fluorescent protein while growing epiphytically on stigmas of apple”
e1“Ea153 dspE::gfp”
Claim · model-written summary
Avirulent Ea153 hrpL suppressed fire blight incidence in four of nine orchard trials.
- Taxon
- pear, apple, and blackberryMalus domesticaPyrus communisRubuse1
- Treatment
- avirulent Ea153 hrpLe0
- Interactor
- Ea153 hrpLe0pathogen
- Outcome
- incidence of fire blighte0
- Direction
- suppressede0
- Value
- four timese0
- Comparator
- antagonist mixturee0
- Setting
- orchard trialse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Over nine orchard trials, avirulent Ea153 hrpL significantly suppressed the incidence of fire blight four times compared with six for the antagonist mixture”
e1“stigmas of pear, apple, and blackberry”
Claim · model-written summary
The antagonist mixture suppressed fire blight in six of nine orchard trials.
- Taxon
- pear, apple, and blackberryMalus domesticaPyrus communisRubuse1
- Treatment
- antagonist mixturee0
- Interactor
- antagonist mixturee0biocontrol_agent
- Outcome
- incidence of fire blighte0
- Direction
- suppressede0
- Value
- sixe0
- Setting
- orchard trialse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Over nine orchard trials, avirulent Ea153 hrpL significantly suppressed the incidence of fire blight four times compared with six for the antagonist mixture”
e1“stigmas of pear, apple, and blackberry”
Claim · model-written summary
The authors infer virulent E. amylovora alters the stigma habitat via pathogenesis and increases host resources available to competitors.
- Taxon
- pear, apple, and blackberryMalus domesticaPyrus communisRubuse1
- Interactor
- E. amylovoraErwinia amylovorae0pathogen
- Outcome
- host resources available to itself and, coincidentally, to nonpathogenic competitorse0
- Qualifier
- pathogenesis-related processe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“virulent E. amylovora modifies the epiphytic habitat presented by the stigma through a pathogenesis-related process, which increases host resources available to itself and, coincidentally, to nonpathogenic competitors”
e1“stigmas of pear, apple, and blackberry”
Claim · model-written summary
The authors conclude avirulent E. amylovora has limited biological control because it uses the stigma habitat less effectively than virulent strains.
- Taxon
- pear, apple, and blackberryMalus domesticaPyrus communisRubuse1
- Interactor
- E. amylovoraErwinia amylovorae0pathogen
- Outcome
- degree of biological controle0
- Qualifier
- inability to utilize the stigmatic habitat to the same degree as a virulent straine0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The degree of biological control achievable with an avirulent strain of E. amylovora likely is limited by its inability to utilize the stigmatic habitat to the same degree as a virulent strain.”
e1“stigmas of pear, apple, and blackberry”
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See all 16 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.