Evaluation of Mature Apple Fruit from Washington State for the Presence of Erwinia amylovora

Mature fruit from naturally infected apple (Malus sylvestris Mill. ’Wealthy’) trees was free from a detectable population of Erwinia amylovora in the calyx, stem, peel and cortex. The pathogen failed to survive for 24 h on the surface of artificially inoculated fruit of Red and Golden Delicious apple in the orchard. In the laboratory, survival of the bacterium was excellent on the surface of apples when applied as natural ooze, or in a water suspension. Bacteria injected into the cortex of fruit of several cultivars survived as long as the apples were physiologically sound. Apples even from resistant cultivars developed symptoms of fireblight in storage. However, the absence of E. amylovora from symptomless fruit of naturally infected trees suggests that mature fruit presents a negligible risk for dissemination of fireblight bacteria.

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Invasion and colonization of mature apple fruit by Erwinia amylovora tagged with bioluminescence genes

Journal of General Plant Pathology ◽

10.1007/s10327-005-0190-7 ◽

2005 ◽

Vol 71 (1) ◽

pp. 98-98

Author(s):

Koji Azegami ◽

Takanori Tsukamoto ◽

Takayuki Matsuura ◽

Tatsuji Ohara ◽

Yasuhiro Inoue ◽

...

Keyword(s):

Erwinia Amylovora ◽

Apple Fruit ◽

Mature Apple

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Bactericidal Treatment for the Eradication of Erwinia amylovora from the Surface of Mature Apple Fruit

Plant Disease ◽

10.1094/pd-72-0715 ◽

1988 ◽

Vol 72 (8) ◽

pp. 715 ◽

Cited By ~ 2

Author(s):

W. J. Janisiewicz

Keyword(s):

Erwinia Amylovora ◽

Apple Fruit ◽

Mature Apple

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Erwinia amylovora can pass through the abscission layer of fruit-bearing twigs and invade apple fruit during fruit maturation

Journal of General Plant Pathology ◽

10.1007/s10327-005-0242-z ◽

2006 ◽

Vol 72 (1) ◽

pp. 43-45 ◽

Cited By ~ 4

Author(s):

Koji Azegami ◽

Takanori Tsukamoto ◽

Takayuki Matsuura ◽

Yasuhiro Inoue ◽

Hiroshi Uematsu ◽

...

Keyword(s):

Erwinia Amylovora ◽

Apple Fruit ◽

Fruit Maturation ◽

Abscission Layer ◽

Pass Through

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EVALUATION OF BUFFER ZONE SIZE AND INSPECTION NUMBER REDUCTION ON PHYTOSANITARY RISK ASSOCIATED WITH FIRE BLIGHT AND EXPORT OF MATURE APPLE FRUIT

Acta Horticulturae ◽

10.17660/actahortic.2002.590.4 ◽

2002 ◽

pp. 47-53 ◽

Cited By ~ 4

Author(s):

R.G. Roberts

Keyword(s):

Fire Blight ◽

Buffer Zone ◽

Apple Fruit ◽

Zone Size ◽

Mature Apple

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Evaluation of Loop-Mediated Isothermal Amplification for Rapid Detection of Erwinia amylovora on Pear and Apple Fruit Flowers

Plant Disease ◽

10.1094/pdis-09-10-0636 ◽

2011 ◽

Vol 95 (4) ◽

pp. 423-430 ◽

Cited By ~ 29

Author(s):

Todd N. Temple ◽

Kenneth B. Johnson

Keyword(s):

Rapid Detection ◽

Pathogen Detection ◽

Fire Blight ◽

Management Practices ◽

Erwinia Amylovora ◽

Lamp Assay ◽

Apple Fruit ◽

Isothermal Amplification ◽

Loop Mediated Isothermal Amplification ◽

Forecasting Models

Fire blight of pear and apple is frequently an inoculum-limited disease but weather-based forecasting models commonly assume that the pathogen is omnipresent. To improve fire blight risk assessment during flowering, we developed a rapid pathogen detection protocol that uses loop-mediated isothermal amplification (LAMP) to detect DNA of epiphytic Erwinia amylovora on samples of pear and apple flowers. LAMP detected a single flower colonized epiphytically by E. amylovora in a sample of 100 flower clusters (approximately 600 flowers). Samples of 100 flower clusters from orchards (approximately one sample per hectare) were washed and subjected to LAMP, which was completed in 2 h. In three experimental orchards inoculated with E. amylovora, positive LAMP reactions were attained from nine of nine 100-flower cluster samples; pathogen populations in the floral washes averaged 5.2 × 103 CFU per flower as determined by dilution plating. Samples of pear and apple flowers obtained from 60 commercial orchards located in Oregon, Washington, California, and Utah resulted in detection of E. amylovora by LAMP assay from 34 sites, 20 of which developed fire blight. Of samples at early bloom, 10% were positive for epiphytic E. amylovora compared with 28% at petal fall; pathogen density in washes of positive samples averaged 3.2 × 102 CFU per flower. In another 26 orchards, all floral washes were negative for E. amylovora by LAMP and by dilution plating; a light severity of fire blight was observed in 8 of these orchards. Overall, positive detection of epiphytic E. amylovora in commercial orchards by LAMP-based scouting generally occurred at later stages of bloom after heat (risk) units had begun to accumulate, an indication that weather-based forecasting models may be an adequate measure of fire blight risk for many orchardists. Nonetheless, several orchardists communicated that information from the LAMP-based rapid detection protocol resulted in modification of their fire blight management practices.

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Epiphytic Bacteria and Yeasts on Apple Blossoms and Their Potential as Antagonists of Erwinia amylovora

Phytopathology ◽

10.1094/phyto-99-5-0571 ◽

2009 ◽

Vol 99 (5) ◽

pp. 571-581 ◽

Cited By ~ 48

Author(s):

P. Lawrence Pusey ◽

Virginia O. Stockwell ◽

Mark Mazzola

Keyword(s):

Relative Humidity ◽

Fire Blight ◽

Erwinia Amylovora ◽

Acid Methyl Ester ◽

Washington State ◽

Microbial Populations ◽

Acid Methyl ◽

Population Sizes ◽

Average Relative Humidity ◽

Cryptococcus Spp

Apple blossoms were sampled for indigenous epiphytic populations of culturable microorganisms during different stages of bloom at two locations in central Washington State and one site in Corvallis, OR. Frequencies and population sizes of bacteria on stigmas of apple were lower in Washington than at Corvallis, where average relative humidity was higher and possibly favored greater colonization; however, bacteria at Corvallis were mainly pseudomonads, whereas those in Washington were diverse, composed of several genera. In Washington, yeast as well as bacteria were isolated from both stigmatic and hypanthial surfaces. Sampled blossoms were processed immediately to assess microbial populations, or after a 24-h incubation at 28°C and high relative humidity, which broadened the range of detectable taxa evaluated as potential antagonists. Identifications were based on fatty acid methyl ester profiles and rDNA sequence analyses. Yeasts or yeastlike organisms were detected at frequencies similar to or greater than bacteria, particularly in hypanthia. When microbial isolates were tested for their capacity to suppress Erwinia amylovora on stigmas of detached crab apple flowers, many were ineffective. The best antagonists were the bacteria Pantoea agglomerans and Pseudomonas spp. and a few yeasts identified as Cryptococcus spp. Further evaluation of these taxa on flowers could lead to the discovery of additional biocontrol agents for fire blight.

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Occurrence and Phenotypes of Pyrimethanil Resistance in Penicillium expansum from Apple in Washington State

Plant Disease ◽

10.1094/pdis-07-13-0721-re ◽

2014 ◽

Vol 98 (7) ◽

pp. 924-928 ◽

Cited By ~ 14

Author(s):

R. Caiazzo ◽

Y. K. Kim ◽

C. L. Xiao

Keyword(s):

High Resistance ◽

Apple Fruit ◽

Washington State ◽

Penicillium Expansum ◽

Small Scale ◽

Blue Mold ◽

Resistance Phenotype ◽

Low Resistance

Penicillium expansum is the cause of blue mold in stored apple fruit. In 2010–11, 779 isolates of P. expansum were collected from decayed apple fruit from five packinghouses, tested for resistance to the postharvest fungicide pyrimethanil, and phenotyped based on the level of resistance. In 2010, 85 and 7% of the isolates were resistant to pyrimethanil in packinghouse A and B, respectively, where pyrimethanil had been used for four to five consecutive years. In 2011, pyrimethanil or fludioxonil was used in packinghouse A, and 96% of the isolates from the fruit treated with pyrimethanil were resistant but only 4% of the isolates from the fruit treated with fludioxonil were resistant to pyrimethanil, suggesting that fungicide rotation substantially reduced the frequency of pyrimethanil resistance. No pyrimethanil-resistant isolates were detected in 2010 in the three other packinghouses where the fungicide had been used recently on a small scale. However 1.8% of the isolates from one of the three packinghouses in 2011 were resistant to pyrimethanil. A significantly higher percentage of thiabendazole-resistant than thiabendazole-sensitive isolates were resistant to pyrimethanil. Of the pyrimethanil-resistant isolates, 37 to 52, 4 to 5, and 44 to 58% were phenotyped as having low, moderate, and high resistance to pyrimethanil, respectively. Fludioxonil effectively controlled pyrimethanil-resistant phenotypes on apple fruit but pyrimethanil failed to control phenotypes with moderate or high resistance to pyrimethanil and only partially controlled the low-resistance phenotype.

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