scholarly journals Antibiosis Activity of Pantoea agglomerans Biocontrol Strain E325 Against Erwinia amylovora on Apple Flower Stigmas

2011 ◽  
Vol 101 (10) ◽  
pp. 1234-1241 ◽  
Author(s):  
P. L. Pusey ◽  
V. O. Stockwell ◽  
C. L. Reardon ◽  
T. H. M. Smits ◽  
B. Duffy
Keyword(s):  
Parental Strain ◽  
Fire Blight ◽  
Erwinia Amylovora ◽  
Pantoea Agglomerans ◽  
Relative Area ◽  
Pathogen Inhibition ◽  
Growth Chambers ◽  
Biocontrol Strain ◽  
Crab Apple

Pantoea agglomerans E325, the active ingredient in a commercial product for fire blight control, was previously shown in vitro to produce a unique alkaline- and phosphate-sensitive antibiotic specific to Erwinia amylovora. Antibiosis was evaluated as a mode of antagonism on flower stigmas using two antibiosis-deficient mutants. On King's medium B, mutants E325ad1 and E325ad2 have stable smooth-butyrous or hypermucoid colony morphologies, respectively, and the parental strain E325 exhibits phenotypic plasticity with predominantly hypermucoid colonies accompanied by slower-growing, smooth-butyrous colonies. Mutants were tested against E. amylovora on stigmas of detached flowers of crab apple (Malus mandshurica) in growth chambers and apple (Malus domestica) in the orchard. Epiphytic fitness of the antibiosis-negative mutants was similar or greater than the parental strain as determined by relative area under the population curve (RAUPC). In laboratory and orchard trials, both mutants had significantly lower inhibitory activity against the pathogen (i.e., less reduction of E. amylovora RAUPC) compared with the parental strain. E325 and the mutants caused similar decreases in pH in a broth medium, indicating that acidification, which was previously reported as a possible mechanism of pathogen inhibition on stigmas, is not directly related to antibiosis. In this study we provide the first evidence for E325 antibiosis involved in E. amylovora growth suppression on apple flower stigmas.

scholarly journals Management of Erwinia amylovora by Potential Bio-Pesticides in vitro and in vivo Conditions

2020 ◽  
Vol 8 (sp1) ◽  
pp. 38-45
Author(s):  
Kubilay Kurtulus Bastas
Keyword(s):  
Fire Blight ◽  
Erwinia Amylovora ◽  
Shoot Length ◽  
Absolute Methanol ◽  
Diffusion Method ◽  
Thymus Vulgaris ◽  
Blight Disease ◽  
Santa Maria

Erwinia amylovora, the causative agent of fire blight disease, threatens a lot of species of the Rosaceae family. Antibiotics and copper compounds in chemical applications are most frequently are applied, but these can be phytotoxic and cause resistant strains of the pathogen. In our experiments, 20 herbal materials were tested for their antimicrobial effectiveness against the fire blight pathogen in vitro and in planta. The air-dried plants ground into fine powder and extraction was performed at room temperature by maceration with 80% (v/v) methanol/distilled water. The minimum inhibitory concentration values were determined by using disc diffusion method and streptomycin was used as control in all experiments. Antimicrobial activity was evaluated by measuring the inhibition zones in reference to the pathogen. Among the tested plants, Szygium aromaticum, Thymus vulgaris and Rhus cararia showed a good antibacterial activity and they inhibited the growth of E. amylovora with inhibition zone diameter ranging from 21 to 27 mm at 20% (w/v) in absolute methanol compared to streptomycin (31 mm) in vitro conditions. In vivo tests were performed by using highly virulent E. amylovora isolate (Eak24b, 91%) grown on TSA medium and inoculation on young shoots of 3-year-old Gala variety of apple and Santa Maria variety of pear seedlings at 107 CFU ml-1 density of the pathogen. Disease severity (%) was assessed by by proportion of blighted shoot length to the whole shoot length and also efficacy of the extracts was determined by using Abbott formula. The highest efficacy was obtained by S. aromaticum and T. vulgaris extracts of reducing shoot blight of cv. Gala and cv. Santa Maria by 67.81% - 64-12% and 51.50% - 51.04% ratios, respectively. Obtaining results showed that some medicinal and aromatic plant extracts might be used against fire blight disease as potential new generation chemicals on pome fruits within integrated and organic control programs.

scholarly journals Evaluation of Kasugamycin for Fire Blight Management, Effect on Nontarget Bacteria, and Assessment of Kasugamycin Resistance Potential in Erwinia amylovora

2011 ◽  
Vol 101 (2) ◽  
pp. 192-204 ◽  
Author(s):  
Gayle C. McGhee ◽  
George W. Sundin
Keyword(s):  
Fire Blight ◽  
Erwinia Amylovora ◽  
Management Strategies ◽  
Resistance Management ◽  
Aminoglycoside Antibiotic ◽  
Relative Fitness ◽  
Industry Standard ◽  
High Concentrations ◽  
New Compounds

The emergence and spread of streptomycin-resistant strains of Erwinia amylovora in Michigan has necessitated the evaluation of new compounds effective for fire blight control. The aminoglycoside antibiotic kasugamycin (Ks) targets the bacterial ribosome and is particularly active against E. amylovora. The efficacy of Ks formulated as Kasumin 2L for control of fire blight was evaluated in six experiments conducted over four field seasons in our experimental orchards in East Lansing, MI. Blossom blight control was statistically equivalent to the industry standard streptomycin in all experiments. E. amylovora populations remained constant on apple flower stigmas pretreated with Kasumin and were ≈100-fold lower than on stigmas treated with water. Kasumin applied to apple trees in the field also resulted in a 100-fold reduced total culturable bacterial population compared with trees treated with water. We performed a prospective analysis of the potential for kasugamycin resistance (KsR) development in E. amylovora which focused on spontaneous resistance development and acquisition of a transferrable KsR gene. In replicated lab experiments, the development of spontaneous resistance in E. amylovora to Ks at 250 or 500 ppm was not observed when cells were directly plated on medium containing high concentrations of the antibiotic. However, exposure to increasing concentrations of Ks in media (initial concentration 25 μg ml–1) resulted in the selection of Ks resistance (at 150 μg ml–1) in the E. amylovora strains Ea110, Ea273, and Ea1189. Analysis of mutants indicated that they harbored mutations in the kasugamycin target ksgA gene and that all mutants were impacted in relative fitness observable through a reduced growth rate in vitro and decreased virulence in immature pear fruit. The possible occurrence of a reservoir of KsR genes in orchard environments was also examined. Culturable gram-negative bacteria were surveyed from six experimental apple orchards that had received at least one Kasumin application. In total, 401 KsR isolates (42 different species) were recovered from apple flowers and leaves and orchard soil samples. Although we have not established the presence of a transferrable KsR gene in orchard bacteria, the frequency, number of species, and presence of KsR enterobacterial species in orchard samples suggests the possible role of nontarget bacteria in the future transfer of a KsR gene to E. amylovora. Our data confirm the importance of kasugamycin as an alternate antibiotic for fire blight management and lay the groundwork for the development and incorporation of resistance management strategies.

scholarly journals The Role of luxS in the Fire Blight Pathogen Erwinia amylovora Is Limited to Metabolism and Does Not Involve Quorum Sensing

2007 ◽  
Vol 20 (10) ◽  
pp. 1284-1297 ◽  
Author(s):  
Fabio Rezzonico ◽  
Brion Duffy
Keyword(s):  
Gene Expression ◽  
Quorum Sensing ◽  
Fire Blight ◽  
Erwinia Amylovora ◽  
Mutational Analysis ◽  
Pome Fruit ◽  
Autoinducer 2 ◽  
Metabolic Genes ◽  
Metabolic Role

Erwinia amylovora is a gram-negative phytopathogen that causes fire blight of pome fruit and related members of the family Rosaceae. We sequenced the putative autoinducer-2 (AI-2) synthase gene luxS from E. amylovora. Diversity analysis indicated that this gene is extremely conserved among E. amylovora strains. Quorum sensing mediated by LuxS has been implicated in coordinated gene expression, growth, and virulence in other enterobacteria; however, our evidence suggests this is not the function in E. amylovora. Mutational analysis pointed to a role in colonization of apple blossoms, the primary infection court for fire blight, although little if any role in virulence on apple shoots and pear fruit was observed. Expression of key virulence genes hrpL and dspA/E was reduced in mutants of two E. amylovora strains. Stronger effects on gene expression were observed for metabolic genes involved in the activated methyl cycle with mutants having greater levels of expression. No quorum-sensing effect was observed in co-culture experiments with wild-type and mutant strains either in vitro or in apple blossoms. Known receptors essential for AI-2 quorum sensing, the LuxPQ sensor kinase or the Lsr ABC-transporter, are absent in E. amylovora, further suggesting a primarily metabolic role for luxS in this bacterium.

scholarly journals Apple Proteins that Interact with DspA/E, a Pathogenicity Effector of Erwinia amylovora, the Fire Blight Pathogen

2006 ◽  
Vol 19 (1) ◽  
pp. 53-61 ◽  
Author(s):  
Xiangdong Meng ◽  
Jean M. Bonasera ◽  
Jihyun F. Kim ◽  
Riitta M. Nissinen ◽  
Steven V. Beer
Keyword(s):  
Fire Blight ◽  
Erwinia Amylovora ◽  
In Silico Analysis ◽  
Physical Interaction ◽  
Susceptibility Factors ◽  
Genes Encoding ◽  
Important Host ◽  
Two Hybrid ◽  
Silico Analysis

The disease-specific (dsp) gene dspA/E of Erwinia amylovora encodes an essential pathogenicity effector of 198 kDa, which is critical to the development of the devastating plant disease fire blight. A yeast two-hybrid assay and in vitro protein pull-down assay demonstrated that DspA/E interacts physically and specifically with four similar putative leucine-rich repeat (LRR) receptor-like serine/threonine kinases (RLK) from apple, an important host of E. amylovora. The genes encoding these four DspA/E-interacting proteins of Malus ×domestica (DIPM1 to 4) are conserved in all genera of hosts of E. amylovora tested. They also are conserved in all cultivars of apple tested that range in susceptibility to fire blight from highly susceptible to highly resistant. The four DIPMs have been characterized, and they are expressed constitutively in host plants. In silico analysis indicated that the DIPMs have similar sequence structure and resemble LRR RLKs from other organisms. Evidence is presented for direct physical interaction between DspA/E and the apple proteins encoded by the four identified clones, which may act as susceptibility factors and be essential to disease development. Knowledge of DIPMs and the interaction with DspA/E thus may facilitate understanding of fire blight development and lead to new approaches to control of disease.

scholarly journals Nectar- and stigma-specific expression of a chitinase could partially protect against fire blight in certain apples

2019 ◽  
Author(s):  
Anita Kurilla ◽  
Timea Toth ◽  
Laszlo Dorgai ◽  
Zsuzsanna Darula ◽  
Tamas Lakatos ◽  
...  
Keyword(s):  
Biofilm Formation ◽  
Fire Blight ◽  
Erwinia Amylovora ◽  
Specific Expression ◽  
Physiological Concentration ◽  
Apple Cultivars ◽  
Nectar Protein ◽  
Blight Disease ◽  
Stigma Exudate

AbstractTo attract pollinators many angiosperms secrete stigma exudate and nectar in their flowers. As these nutritious fluids are ideal infection points for pathogens, both secretions contain various antimicrobial compounds. Erwinia amylovora, the causing bacterium of the devastating fire blight apple disease, is the model pathogen that multiplies in flower secretions and infects through the nectaries. Although Erwinia resistant apples are not available, certain cultivars are tolerant. It was reported that in stigma infection assay, the ‘Freedom’ cultivar was Erwinia tolerant while the ‘Jonagold’ was susceptible. We hypothesized that differences in the nectar protein compositions lead to different susceptibility. Indeed we found that an acidic chitinase III protein (Machi3-1) selectively accumulates in the nectar and stigma of the ‘Freedom’ cultivar. We demonstrate that MYB binding site containing repeats of the ‘Freedom’ Machi3-1 promoter are responsible for the strong nectar- and stigma-specific expression. As we found that in vitro the Machi3-1 protein impairs growth and biofilm formation of Erwinia at physiological concentration, we propose that the Machi3-1 contribute to the tolerance by inhibiting Erwinia multiplication in the stigma exudate and in the nectar. We show that the Machi3-1 allele was introgressed from Malus floribunda 821 into different apple cultivars including the ‘Freedom’.HighlightCertain apple cultivars accumulate to high levels in their nectar and stigma an acidic chitinase III protein that can protect against pathogens including fire blight disease causing Erwinia amylovora

scholarly journals Testing the virulence of some Hungarian Erwinia amylovora strains on in vitro cultured apple rootstocks

2000 ◽  
Vol 6 (4) ◽  
Author(s):  
M. Hevesi ◽  
J. Papp ◽  
E. Jámbor-Benczúr ◽  
K. Kaszáné Csizmár ◽  
I. Pozsgai ◽  
...  
Keyword(s):  
Host Plants ◽  
Fire Blight ◽  
Erwinia Amylovora ◽  
Disease Development ◽  
Apple Rootstocks ◽  
Disease Rating ◽  
Different Strains

A useful method was improved to test and to evaluate the susceptibility of plants to fire blight and the virulence of E. amylovora strains. Six Hungarian strains from different host plants were tested on in vitro cultured apple rootstocks. Disease rating was used for the characterization of the process of disease development. The different strains had different capacity to cause disease, mainly in the first period of incubation. There were significant differences between the virulence of the strains.

scholarly journals Relation of Apple Flower Age to Infection of Hypanthium by Erwinia amylovora

Plant Disease ◽  
2008 ◽  
Vol 92 (1) ◽  
pp. 137-142 ◽  
Author(s):  
P. L. Pusey ◽  
T. J. Smith
Keyword(s):  
Fire Blight ◽  
Erwinia Amylovora ◽  
Disease Risk ◽  
Inoculum Potential ◽  
Apple Trees ◽  
Regression Curves ◽  
Different Temperatures ◽  
Flower Age ◽  
Simulated Rain ◽  
Crab Apple

Blossom age as related to hypanthial susceptibility to Erwinia amylovora is not well established, but is relevant to disease risk assessment. To test this, detached crab apple blossoms were maintained for various periods and at different temperatures before applying inoculum to hypanthia. Inoculum potential on hypanthia due to wetting was evaluated by subjecting detached stigma-inoculated blossoms (~106 CFU per flower) to varying amounts and durations of simulated rain (or dew) at 14°C. Blossoms of varying age on mature ‘Gala’ apple trees were inoculated on hypanthia with 102, 104, or 106 CFU per flower. In the laboratory, susceptibility decreased with flower age at rates that increased with temperature. Wetness periods up to 12 h resulted in populations on hypanthia of <103 CFU per flower; 24 h of wetness resulted in ~104 or ~105 CFU. A dose response was shown in the orchard, and regression curves indicated steepest decline of susceptibility during initial days after petal expansion. Disease models incorporating a blossom-age component may be effective because they indicate the potential for infection when temperatures favor rapid bacterial growth on stigmas within a window of high hypanthial susceptibility. Further investigation of these relationships could lead to advancements in determining fire blight risk.

LACK OF REDUCTION OF FIRE BLIGHT INCIDENCE USING NATURAL PRODUCTS WHICH INHIBIT ERWINIA AMYLOVORA IN VITRO

2006 ◽  
pp. 349-352
Author(s):  
J.L. Vanneste ◽  
G. Fischer ◽  
A. Spornberger ◽  
H.C. Pechhacker ◽  
F. Berger
Keyword(s):  
Natural Products ◽  
Fire Blight ◽  
Erwinia Amylovora

scholarly journals Genome Sequence of the Biocontrol Agent Pantoea vagans Strain C9-1

2010 ◽  
Vol 192 (24) ◽  
pp. 6486-6487 ◽  
Author(s):  
Theo H. M. Smits ◽  
Fabio Rezzonico ◽  
Tim Kamber ◽  
Alexander Goesmann ◽  
Carol A. Ishimaru ◽  
...  
Keyword(s):  
Biological Control ◽  
Genome Sequence ◽  
Fire Blight ◽  
Erwinia Amylovora ◽  
Biocontrol Agent ◽  
Pantoea Agglomerans ◽  
Apple Trees ◽  
Gram Negative ◽  
Pantoea Vagans

ABSTRACT Pantoea vagans is a Gram-negative enterobacterial plant epiphyte of a broad range of plants. Here we report the 4.89-Mb genome sequence of P. vagans strain C9-1 (formerly Pantoea agglomerans), which is commercially registered for biological control of fire blight, a disease of pear and apple trees caused by Erwinia amylovora.

scholarly journals Effectiveness of Kasugamycin Against Erwinia amylovora and its Potential Use for Managing Fire Blight of Pear

Plant Disease ◽  
2011 ◽  
Vol 95 (4) ◽  
pp. 448-454 ◽  
Author(s):  
J. E. Adaskaveg ◽  
H. Förster ◽  
M. L. Wade
Keyword(s):  
Fire Blight ◽  
Erwinia Amylovora ◽  
Field Studies ◽  
The United States ◽  
Mean Value ◽  
Natural Occurrence ◽  
Baseline Sensitivity ◽  
Inhibition Of Growth ◽  
Industry Standards

Comparative field studies on the management of fire blight were conducted in California on Asian and Bartlett pear using single-bactericide, mixture, and rotation treatments of selected compounds. Treatment efficacy was evaluated based on the natural occurrence of the disease or after inoculation with Erwinia amylovora. Kasugamycin at 100 mg/liter demonstrated similar or higher pre- and post-infection activity than the industry standards, streptomycin and oxytetracycline. Phytotoxicity caused by kasugamycin was observed only when five or six sequential weekly applications were done. In a six-spray rotation program including three bactericides (copper, kasugamycin, and oxytetracycline), with each being used twice, phytotoxicity was minor. Baseline sensitivity concentrations for kasugamycin were established for growth of 376 isolates of E. amylovora from California. Values for the lowest concentration where a reduction in growth on nutrient agar was observed ranged from 3.5 to 18.3 mg/liter, with a mean value of 8.7 mg/liter. Values for ≥95% inhibition of growth ranged from 6.9 to 46.7 mg/liter, with a mean value of 18.5 mg/liter. These inhibitory values for kasugamycin were higher than those for streptomycin or oxytetracycline. The in vitro activity of all three compounds was highly dependent on the agar medium used in the sensitivity assay. The activity of kasugamycin was also highly dependent on the pH of the medium and was significantly higher at pH 5.1 than pH 7.3. With the planned registration in the United States, kasugamycin represents the first new, highly effective bactericide for managing fire blight in over 40 years.

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