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.

scholarly journals Temperature and Pomaceous Flower Age Related to Colonization by Erwinia amylovora and Antagonists

2004 ◽  
Vol 94 (8) ◽  
pp. 901-911 ◽  
Author(s):  
P. L. Pusey ◽  
E. A. Curry
Keyword(s):  
Erwinia Amylovora ◽  
Disease Risk ◽  
Bacterial Colonization ◽  
Field Performance ◽  
Age Related ◽  
Temperature Regimes ◽  
Different Temperatures ◽  
Flower Age ◽  
Crab Apple

Fire blight of apple and pear is initiated by epiphytic populations of Erwinia amylovora on flower stigmas. Predicting this disease and managing it with microbial antagonists depends on an understanding of bacterial colonization on stigmas. Detached ‘Manchurian’ crab apple flowers were inoculated with E. amylovora and subjected to a range of constant temperatures or various fluctuating temperature regimes. Results may have application to disease risk assessment systems such as the Cougarblight model, which now are based on in vitro growth of the pathogen. In other experiments, detached crab apple flowers and attached ‘Gala’ apple flowers were maintained at different temperatures for various periods before inoculation with E. amylovora or antagonists (Pseudomonas fluorescens strain A506 and Pantoea agglomerans strains C9-1 and E325). Maximum stigma age supporting bacterial multiplication decreased as temperature increased, and was reduced by pollination. Stigmas were receptive to bacteria at ages older than previously reported, probably due to less interference from indigenous organisms. The study revealed antagonist limitations that possibly affect field performance (e.g., the inability of strain A506 to grow on relatively old stigmas conducive to the pathogen). Such deficiencies could be overcome by selecting other antagonists or using antagonist mixtures in the orchard.

scholarly journals Fire Blight Symptomatic Shoots and the Presence of Erwinia amylovora in Asymptomatic Apple Budwood

Plant Disease ◽  
2017 ◽  
Vol 101 (1) ◽  
pp. 186-191 ◽  
Author(s):  
K. A. Tancos ◽  
E. Borejsza-Wysocka ◽  
S. Kuehne ◽  
D. Breth ◽  
Kerik D. Cox
Keyword(s):  
New York ◽  
Fire Blight ◽  
Erwinia Amylovora ◽  
Causal Agent ◽  
Economic Losses ◽  
Apple Trees ◽  
The Mean ◽  
Collection Practices ◽  
Time Of Collection ◽  
Young Apple

Erwinia amylovora, the causal agent of fire blight, causes considerable economic losses in young apple plantings in New York on a yearly basis. Nurseries make efforts to only use clean budwood for propagation, which is essential, but E. amylovora may be present in trees that appear to have no apparent fire blight symptoms at the time of collection. We hypothesized that the use of infected budwood, especially by commercial nursery operations, could be the cause, in part, of fire blight outbreaks that often occur in young apple plantings in New York. Our goal was to investigate the presence of E. amylovora in asymptomatic budwood from nursery source plantings as it relates to trees with fire blight symptoms. From 2012 to 2015, apple budwood was collected from two commercial budwood source plantings of ‘Gala’ and ‘Topaz’ at increasing distances from visually symptomatic trees. From these collections, internal contents of apple buds were analyzed for the presence of E. amylovora. E. amylovora was detected in asymptomatic budwood in trees more than 20 m from trees with fire blight symptoms. In some seasons, there were significant (P ≤ 0.05) differences in the incidence of E. amylovora in asymptomatic budwood collected from symptomatic trees and those up to 20 m from them. In 2014 and 2015, the mean E. amylovora CFU per gram recovered from budwood in both the Gala and Topaz plantings were significantly lower in budwood collected 20 m from symptomatic trees. Further investigation of individual bud dissections revealed that E. amylovora was within the tissue beneath the bud scales containing the meristem. Results from the study highlight the shortcomings of current budwood collection practices and the need to better understand the factors that lead to the presence of E. amylovora in bud tissues to ensure the production of pathogen-free apple trees.

scholarly journals Draft Genome Sequences of Four Streptomycin-Sensitive Erwinia amylovora Strains Isolated from Commercial Apple Orchards in Ohio

2021 ◽  
Vol 10 (50) ◽  
Author(s):  
A. M. Jimenez Madrid ◽  
T. Klass ◽  
V. Roman-Reyna ◽  
J. Jacobs ◽  
M. L. Lewis Ivey
Keyword(s):  
Causative Agent ◽  
Fire Blight ◽  
Erwinia Amylovora ◽  
Draft Genome ◽  
Apple Orchards ◽  
Genome Sequences ◽  
Apple Trees ◽  
Content Type

Erwinia amylovora is the causative agent of fire blight, a devastating disease of apples and pears worldwide. Here, we report draft genome sequences of four streptomycin-sensitive strains of E. amylovora that were isolated from diseased apple trees in Ohio.

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 Influence of Age of Apple Flowers on Growth of Erwinia amylovora and Biological Control Agents

Plant Disease ◽  
2003 ◽  
Vol 87 (5) ◽  
pp. 502-509 ◽  
Author(s):  
S. V. Thomson ◽  
S. C. Gouk
Keyword(s):  
Biological Control ◽  
Fire Blight ◽  
Erwinia Amylovora ◽  
Antagonistic Bacteria ◽  
Biological Control Agents ◽  
Limited Growth ◽  
Bacterial Populations ◽  
Arid Conditions ◽  
Flower Age ◽  
Causal Pathogen

The influence of flower age on growth of Erwinia amylovora, the causal pathogen of fire blight of apples and pears, was investigated under humid and arid conditions in Hamilton, New Zealand (NZ), and Logan, UT, USA, respectively. ‘Royal Gala’ apple flowers ranging from 1 to 8 days old were atomized with E. amylovora. Pistils were dissected and washed separately from the remaining floral parts (flowers ex pistils) for estimation of bacterial numbers. Pistils, 1 to 3 days old (USA) and 1 to 4 days old (NZ), supported exponential growth of E. amylovora, but bacterial populations did not increase when older flowers were inoculated. Scanning electron microscopy showed round and turgid papillae on stigmas of 1-day-old flowers. Papillae on 4- to 6-day-old stigmas were completely collapsed and covered in mucilage. Populations of E. amy-lovora on the flowers ex pistils were characteristically lower than pistil populations. High populations of saprophytic bacteria were found on both floral parts of all ages, but there was no difference in their numbers on 3- to 6-day-old pistils. This suggests their presence did not inhibit the growth of E. amylovora on older stigmas. The results demonstrate that stigmas on 1- to 3-day-old flowers often support rapid growth of E. amylovora, but flowers inoculated when more than 4 to 5 days old do not support growth or only limited growth. The same location and pattern of bacterial growth occurred with the biological control agents Pseudomonas fluorescens PfA506n and Pantoea agglomerans (Erwinia herbicola) Eh318nr. The distinct effect of flower age on growth of antagonistic bacteria and E. amylovora may be important in deciding when to treat with biological control organisms or bactericides.

scholarly journals Survival of Apple Rootstocks to Natural Infections of Fire Blight

2002 ◽  
Vol 12 (2) ◽  
pp. 239-241 ◽  
Author(s):  
D.C. Ferree ◽  
J.C. Schmid ◽  
B.L. Bishop
Keyword(s):  
Fire Blight ◽  
Erwinia Amylovora ◽  
Apple Rootstocks ◽  
Apple Trees ◽  
Wide Range ◽  
Dwarfing Rootstocks

Survival of replicated rootstock plantings of apple trees (Malus ×domestica) to fire blight (Erwinia amylovora) infection shows that a wide range of rootstock susceptibility exists. Trees on `Malling 26' (M.26), `Malling 9' (M.9), and `Mark' consistently had significant losses. Of the dwarfing rootstocks widely available commercially, `Budagovsky 9' (B.9) survived well with productive trees, but was not resistant to fire blight infection. The following experimental rootstocks had good survivability with many live productive trees in one or more trials: `Poland 2' (P.2), `Vineland 1' (V.1), `Malling 27 EMLA' (M.27 EMLA), `Budagovsky 491' (B.491), `Budagovsky 409' (B.409), `Vineland 7' (V.7), `Vineland 4' (V.4), and `Oregon Rootstock 1' (OAR1).

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 Temporal Dynamics of the Biocontrol Agent Pseudomonas fluorescens Strain A506 in Flowers in Inoculated Pear Trees

2003 ◽  
Vol 93 (6) ◽  
pp. 727-737 ◽  
Author(s):  
Steven E. Lindow ◽  
Trevor V. Suslow
Keyword(s):  
Pseudomonas Fluorescens ◽  
Fire Blight ◽  
Erwinia Amylovora ◽  
Biocontrol Agent ◽  
Temporal Dynamics ◽  
Flower Opening ◽  
Bacterial Populations ◽  
Flower Age ◽  
Pear Trees ◽  
Over Time

The colonization of individual flowers in mature pear orchards by Pseudomonas fluorescens strain A506 applied at different times during bloom was measured to determine the receptivity of flowers to colonization and the extent of intra-tree movement over time. Strain A506 populations in flowers open at inoculation were initially about 104 cells per flower and increased to approximately 106 cells per flower in flowers that were inoculated within about 5 days of opening. However, eventual populations decreased with further increases in flower age at inoculation to as few as about 103 cells per flower when inoculated flowers were more than 10 days old. Populations of strain A506 on flowers that opened after inoculation was initially very low at the time of petal expansion (<100 cells per flower) but increased rapidly with time after flower opening. The maximum population of strain A506 that developed on such flowers decreased with increasing time between inoculation and petal expansion; 104 to 105 cells of strain A506 eventually colonized flowers that opened within 7 days of inoculation, whereas fewer than 100 cells colonized flowers that opened 24 days or more after inoculation. Large total bacterial populations on A506-treated trees were associated with significant reductions in populations of Erwinia amylovora and reduced incidence of fire blight and severity of fruit russet.

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