First Report of Fire Blight on Pyrus elaeagrifolia and Amelanchier sp. in Bulgaria

In 2005, a fire blight epidemic occurred for the second time within the last 3 years, and severe damages were observed on pome fruits trees in many regions of Bulgaria. For the first time, we found fire blight on Pyrus elaeagrifolia and Amelanchier sp. grown in a park area (Plovdiv Region), providing evidence of continuing spread of the pathogen in Bulgaria. The symptoms on P. elaeagrifolia were necrotic, immature fruitlets and progressive necrosis toward the adjacent branches, thus forming cankers and leading to death of the plant above the canker. Many Amelanchier sp. shrubs had severely blighted flowers, fruitlets, shoots, and branches and dried, amber ooze droplets on the shoots. All the isolations made from blighted hosts' shoots and cankers on King's medium B (2 to 3 days, 26 to 27°C) yielded whitish, glistening, round bacterial colonies. Infiltration of the suspensions of randomized isolates from both hosts into tobacco leaves resulted in a typical hypersensitive reaction. Subsequently, some strains showed a typical ooze production on immature pear fruits (cv. Conference) and were also successfully reisolated from artificially inoculated quince shoots (1.2 × 109 CFU, cv. Portugalska, three replicates), where typical fire blight symptoms were observed, thereby fulfilling Koch's postulates. No symptoms or bacteria were found within any of the shoots from the same plant species injected with sterile water. The identity of the isolates was confirmed as Erwinia amylovora by an antibody-based slide agglutination test (Neogen_Express; Neogen Europe, Ltd., UK) and PCR test with primers derived from the ams region (1). On the basis of the symptoms, cultural characteristics, and positive results in pathogenicity, serological, and PCR tests, the isolates were considered to be E. amylovora. To our knowledge, this is the first report of fire blight on P. elaeagrifolia and Amelanchier sp. in Bulgaria. Reference: (1) S. Bereswill et al. Appl. Environ. Microbiol. 61:2636, 1995.

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First Report of Fire Blight Caused by Erwinia amylovora on Pyracantha coccinea in Bulgaria

Plant Disease ◽

10.1094/pdis.2004.88.4.427a ◽

2004 ◽

Vol 88 (4) ◽

pp. 427-427 ◽

Cited By ~ 1

Author(s):

S. G. Bobev ◽

S. Baeyen ◽

C. Crepel ◽

M. Maes

Keyword(s):

Fire Blight ◽

Erwinia Amylovora ◽

Hypersensitive Reaction ◽

Nested Polymerase Chain Reaction ◽

New Host ◽

First Report ◽

Specific Pcr ◽

Polymerase Chain ◽

Positive Results ◽

Pyracantha Coccinea

During late May and June of 2003, a fire blight epidemic occurred in southcentral Bulgaria on earlier reported hosts such as apple, pear, quince, and hawthorn (1). A new host was found when fire blight was also observed in mid-June on Pyracantha coccinea grown in the Plovdiv Region. Symptoms were necrotic flowers, shoots, petioles, and the presence of sticky ooze droplets mainly on the shoots. Isolations made from blighted Pyracantha coccinea flowers and shoots onto King's medium B (2 days at 25 to 26°C) yielded whitish, glistening, round bacterial colonies. Infiltration of the suspensions of three of the isolates into tobacco leaves resulted in a typical hypersensitive reaction. When Pyracantha coccinea and Cotoneaster sp. shoots were inoculated with these three isolates, typical fire blight symptoms were obtained. The pathogen was reisolated 2 weeks after inoculation from necrotic tissues (15 to 20 mm above and below the inoculation site), thereby fulfilling the Koch's postulates. No symptoms and bacteria were found within any of the shoots from the same plant species injected with sterile water. The identity of the isolates was also determined by conducting nested polymerase chain reaction (PCR) (2) and target-specific PCR (23S rDNA) (3). On the basis of the symptoms, cultural characteristics, and positive results in pathogenicity and PCR tests, the isolates were considered to be Erwinia amylovora. To our knowledge, this is the first report of fire blight on Pyracantha coccinea in Bulgaria. References: (1) S. G. Bobev et al. Plant Dis. 82:1283, 1998. (2) P. Llop et al. Appl. Environ. Microbiol. 66:2071, 2000. (3) M. Maes et al. Plant Pathol. 45:1139, 1996.

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First Report of Fire Blight on Pear Trees Caused by Erwinia amylovora in Kurdistan Province, Iran

Plant Disease ◽

10.1094/pdis-09-12-0876-pdn ◽

2013 ◽

Vol 97 (8) ◽

pp. 1111-1111 ◽

Cited By ~ 1

Author(s):

S. N. Mollaei ◽

B. Harighi

Keyword(s):

Fire Blight ◽

Erwinia Amylovora ◽

Reca Gene ◽

Phylogenetic Position ◽

Bacterial Suspension ◽

Sodium Hypochlorite Solution ◽

Pathogenicity Test ◽

First Report ◽

Appl Environ ◽

Pear Trees

Pear (Pyrus L.) is one of the most widely grown crops in western Iran. Since 2010, an outbreak of a disease with symptoms similar to fire blight has been observed on pear trees in various locations of Kurdistan Province. Initial flower symptoms include water-soaking and rapidly shriveling, infected flowers that remained hanging on the trees. Immature fruits become water-soaked, turned brown, and shriveled. Infected flowers and immature fruits were collected from different locations in the province. Small pieces (about 1 mm2) were excised from infected tissues, surface sterilized with 0.5% sodium hypochlorite solution, followed by rinsing in sterile-distilled water (SDW). Each piece was macerated in 2 to 3 ml of SDW, streaked onto nutrient agar sucrose or eosin methylene blue agar media, and incubated at 27 to 29°C. After 48 to 72 h, single colonies were subcultured onto the same media and stored at 4°C. In total, 74 bacteria were isolated from infected tissues. All isolates were gram-negative and rod-shaped. Based on other phenotypic properties, strains were grouped into three clusters at a similarity level of 65% (data not shown). Forty-one and 23 strains showed properties as expected for Erwinia amylovora and Enterobacter sp., respectively. Other strains showed properties resembling Pantoea agglomerans. All strains identified as E. amylovora produced an expected DNA fragment of about 900 bp by PCR using primers PE29A and PE29B corresponding to plasmid pEA29 (1). The result was confirmed by using primers AMSbL and AMSbR derived from the ams region required for amylovoran synthesis of E. amylovora. E. amylovora strains produced an expected 1,600-bp fragment (2). For the pathogenicity test, a bacterial suspension was adjusted to approximately 1 × 107 CFU/ml from cell cultures grown in nutrient broth at 27°C for 48 h. Immature pear fruits sterilized with 70% ethanol and rinsed with SDW were injected with the bacterial suspension using a 25-gauge sterile needle. Fruits injected with sterile water were used as controls. Pear fruits were kept in a mist chamber at 27 to 29°C. Symptoms were assessed up to 2 weeks after inoculation. All E. amylovora strains produced typical symptoms on inoculated immature pear fruits. Necrosis and oozing of bacterial exudates were observed after 3 to 7 days. The phylogenetic position of two selected strains was analyzed by sequence comparison of recA gene among other species in the genus Erwinia and related bacteria. The recA sequence of bacterial strains identified as E. amylovora revealed high similarity (99%) to the E. amylovora type strain (CFBP 1430). Genetic diversity of selected strains was assessed and compared with E. amylovora reference strain CFBP 1430 using ERIC and REP primers in rep-PCR analysis. (3). UPGMA cluster analysis of the combined data obtained in the rep-PCR experiments using Dice's coefficient revealed that the majority of E. amylovora strains showed the same fingerprint patterns at a similarity level of 93%, indicating genetic homogeneity among strains but clearly separated from Enterobacter sp. and P. agglomerans strains. To our knowledge, this is the first report that characterizes the phenotypic and genetic properties of E. amylovora in western part of Iran. References: (1) S. Bereswill et al. Appl. Environ. Microbiol. 58:3522, 1992. (2) S. Bereswill et al. Appl. Environ. Microbiol. 61:2636, 1995. (3) J. Versalovic et al. Mol. Cell Biol. 5:25, 1994.

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First Report of Fire Blight Caused by Erwinia amylovora on Meadowsweet (Spirea prunifolia) in Turkey

Plant Disease ◽

10.1094/pdis-03-13-0220-pdn ◽

2014 ◽

Vol 98 (1) ◽

pp. 153-153 ◽

Cited By ~ 2

Author(s):

K. K. Bastas ◽

F. Sahin

Keyword(s):

Pathogenic Bacteria ◽

Fire Blight ◽

Erwinia Amylovora ◽

Natural Infection ◽

Hypodermic Needle ◽

Identification System ◽

Bacterial Strains ◽

First Report ◽

Molecular Tests ◽

Initial Symptoms

Fire blight, caused by Erwinia amylovora (Burr.) Winslow et al., affects plants in the Rosaceae family, which includes trees and shrubs in orchards, nurseries, and landscape plantations. During the springs and summers of 2008 and 2010, dying branches, necrotic leaves attached to shoots, and blighted twigs of meadowsweet (Spirea prunifolia) were observed at three different locations of landscape areas in Konya Province, Turkey. Disease incidence was approximately 1% on the plants during the surveys. Initial symptoms of reddish to brownish streaks on the shoots of infected plants were observed in spring. Nine representative bacterial strains were isolated from the lesions on shoots of seven meadowsweet plants on nutrient sucrose agar (NSA) medium and identified as E. amylovora on basis of biochemical, physiological (2,3) and molecular tests (1). Bacteria were gram-negative, rod shaped, aerobic, fermentative, yellow-orange on Miller and Scroth medium (2), positive for levan formation and acetoin production, did not grow at 36°C, positive for gelatin hydrolysis, and negative for esculin hydrolysis, indole, urease, catalase, oxidase, arginine dehydrolase, reduction of nitrate, acid production from lactose, and inositol. All strains were hypersensitive response-positive on tobacco (Nicotiana tabacum var. White Burley) plants. All strains were identified as E. amylovora using the species-specific primers set, A/B (1), by PCR assay, and by fatty acid methyl ester (FAME) profiles determined by Sherlock Microbial Identification System software (TSBA 6 v. 6.00; Microbial ID, Newark, DE) with similarity indices ranging from of 79 to 99%. Pathogenicity was tested by injecting of petioles and actively growing three shoot tips of 2-year-old S. prunifolia seedlings cv. number 29 using a 0.46 mm-diameter hypodermic needle with bacterial suspensions containing 108 CFU mL–1 in sterile distilled water (SDW) Plants were inoculated with each of the nine bacterial strains and two references strains, Ea29 and NCPPB 2791 (Selcuk University, Department of Plant Protection, Konya, Turkey). Symptoms resembling those associated with natural infection appeared on the inoculated plants 7 days after inoculation. Plants inoculated with SDW served as a negative control treatment, and no symptoms were observed on these plants. All tests were repeated three times with the same results. Bacterial re-isolations were attempted from the control plants as well as shoots and leaves inoculated with the two reference strains and the nine bacteria identified as E. amylovora. Bacteria isolated from inoculated plants were identified as E. amylovora using the biochemical, physiological, and molecular tests described above, but this bacterium was not isolated from the control plants. Phytosanitary measures must be taken to avoid spread of the pathogen to ornamentals in new landscape areas in Turkey. This report is important because infected Spirea spp. can be a potential inoculum source for other rosaceous ornamentals. To our knowledge, this is the first report of the occurrence of fire blight on meadowsweet in Turkey. References: (1) S. Bereswill et al. Appl. Environ. Microbiol. 58:3522, 1992. (2) A. L. Jones and K. Geider. Laboratory Guide for Identification of Plant Pathogenic Bacteria, pp. 40-55. American Phytopathological Society, St. Paul, MN, 2001. (3) R. A. Lelliott and D. E. Stead. Methods for Diagnosis of Bacterial Diseases of Plants (Methods in Plant Pathology). Oxford, UK, 1987.

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Sources and Inheritance of Resistance to Fire Blight (Erwinia amylovora) in Eastern U.S. Blackberry Genotypes

HortScience ◽

10.21273/hortsci.40.1.39 ◽

2005 ◽

Vol 40 (1) ◽

pp. 39-42 ◽

Cited By ~ 6

Author(s):

Philip J. Stewart ◽

John R. Clark ◽

Patrick Fenn

Keyword(s):

Fire Blight ◽

Erwinia Amylovora ◽

Inheritance Of Resistance ◽

Sterile Water ◽

Narrow Sense ◽

Narrow Sense Heritability ◽

Diallel Crossing ◽

Breeding Selection ◽

Breeding Selections ◽

Partial Diallel

Resistance to fire blight in blackberry (Rubus subgenus Rubus Watson) was studied in both seedling populations and clonally propagated plants. Seedling populations resulted from a partial diallel crossing of seven cultivars (Apache, Arapaho, Chester Thornless, Illini Hardy, Navaho, Triple Crown, and Prime-Jim™). Clonal material evaluated included eleven cultivars (Apache, Arapaho, Chester Thornless, Chickasaw, Kiowa, Illini Hardy, Navaho, Ouachita, Shawnee, Triple Crown, and Prime-Jim) and six breeding selections. Inoculations were made by injection of suspensions of Erwinia amylovora in sterile water. Significant differences in resistance were found among genotypes; `Navaho' was the most susceptible, and `Kiowa' and a breeding selection A-2095, the most resistant. Seedling inoculations showed resistance to be quantitatively inherited and mostly additive, with an overall narrow-sense heritability of h2 = 0.32.

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First Report of Fire Blight Caused by Erwinia amylovora on Cotoneaster dammeri cv. Skogholm in Croatia

Plant Disease ◽

10.1094/pdis-92-10-1468a ◽

2008 ◽

Vol 92 (10) ◽

pp. 1468-1468

Author(s):

I. Križanac ◽

A. Vukadin ◽

E. Ðermić ◽

B. Cvjetković

Keyword(s):

Fire Blight ◽

Erwinia Amylovora ◽

Polyclonal Antibodies ◽

Immunofluorescence Assay ◽

Plant Tissues ◽

Species Identity ◽

First Report ◽

Appl Environ ◽

Inoculation Site ◽

Plant Pathol

In July of 2007, fire blight symptoms were observed on Cotoneaster dammeri cv. Skogholm in a nursery near Županja, Vukovarsko-Srijemska County, in eastern Croatia. In this region, the first outbreak of fire blight was noted on apple in 1995 (2). Symptoms on cotoneaster were necrotic shoots and petioles. Immunofluorescence assay (IFA) with polyclonal antibodies (Loewe Biochemica GmbH, Sauerlach, Germany) was performed on extracts from blighted C. dammeri cv. Skogholm shoots and were found to be positive for Erwinia amylovora. Round, mucoid, whitish colonies were isolated from extracts of plant tissues with symptoms of fire blight spread on King's medium B and incubated for 2 days at 28°C. Bacterial ooze and necrosis of the inoculation site were observed on immature pear fruits inoculated with a 106 CFU/ml suspension of the isolate. Bacteria were reisolated and the species identity was confirmed by PCR and primers targeting pEA29 DNA (1). E. amylovora was previously reported only on native Cotoneaster spp. (3). To our knowledge, this is the first report of fire blight on C. dammeri cv. Skogholm from a commercial ornamental nursery in Croatia. References: (1) S. Bereswill et al. Appl. Environ. Microbiol. 58:3522, 1992. (2) B. Cvjetković et al. Glas. zaštite bilja 1:13, 1996. (3) E. Halupecki et al. Eur. J. Plant Pathol. 114:435, 2006.

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Bacterial species recognized for the first time for its biocontrol activity against fire blight (Erwinia amylovora)

European Journal of Plant Pathology ◽

10.1007/s10658-019-01885-x ◽

2019 ◽

Vol 156 (1) ◽

pp. 257-272 ◽

Cited By ~ 1

Author(s):

Artur Mikiciński ◽

Joanna Puławska ◽

Assel Molzhigitova ◽

Piotr Sobiczewski

Keyword(s):

Fire Blight ◽

Dna Analysis ◽

Erwinia Amylovora ◽

Bacterial Species ◽

Antagonistic Activity ◽

Protective Capacity ◽

Biocontrol Activity ◽

Enterobacter Ludwigii ◽

First Time ◽

Do So

AbstractThis study included eight bacterial isolates originating from the apple phyllosphere or soil environment that were previously selected using the pear fruitlet test (Mikiciński 2017). Identification of these isolates based on phenotypic assays and DNA analysis showed that five of them belonged to species for which an antagonistic activity against Erwinia amylovora and the protective capacity of apple and pear against fire blight were not previously demonstrated. These were L16 identified as Pseudomonas vancouverensis, 3 M as Pseudomonas chlororaphis subsp. aureofaciens, 35 M – Pseudomonas congelans, 43 M – Enterobacter ludwigii, and 59 M – Pseudomonas protegens. Investigation of the biotic relationships between the tested strains and E. amylovora showed that 3 M, 35 M and 59 M inhibited the growth of the pathogen on five out of six media used (NAS, KB, LB, R2A, NAG), but 43 M did not do so on any of these media. Strain L16 did not inhibit the growth of the pathogen on LB or R2A medium. In contrast, all strains grown on medium 925 stimulated the growth of the pathogen, which showed no growth without co-cultivation with these strains. The experiments on apple trees and detached apple branches showed the ability of the tested bacteria to protect flowers at medium to high levels, depending on the experiment (55–93%). In some cases, this protection was even higher than that of the copper product used for comparison. In studies assessing the bacterial ability to protect shoots of M.26, the highest efficacy was observed for strains 35 M (96%) and 43 M (93%) but on ‘Gala Must’ all tested strains showed 100% of efficacy.

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First Report of Erwinia amylovora, the Causal Agent of Fire Blight, on Pear in Finland

Plant Disease ◽

10.1094/pdis-11-14-1221-pdn ◽

2015 ◽

Vol 99 (7) ◽

pp. 1033 ◽

Cited By ~ 3

Author(s):

M. Soukainen ◽

J. Santala ◽

J. Tegel

Keyword(s):

Fire Blight ◽

Erwinia Amylovora ◽

Causal Agent ◽

First Report

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First Report of Fire Blight Disease on Asian Pear Caused by Erwinia amylovora in Korea

Plant Disease ◽

10.1094/pdis-11-15-1364-pdn ◽

2016 ◽

Vol 100 (9) ◽

pp. 1946-1946 ◽

Cited By ~ 3

Author(s):

D. H. Park ◽

J.-G. Yu ◽

E.-J. Oh ◽

K.-S. Han ◽

M. C. Yea ◽

...

Keyword(s):

Fire Blight ◽

Erwinia Amylovora ◽

First Report ◽

Asian Pear ◽

Blight Disease

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First Report of Erwinia amylovora Causing Fire Blight on Plum (Prunus domestica) in Hungary

Plant Disease ◽

10.1094/pdis-12-11-1013-pdn ◽

2012 ◽

Vol 96 (5) ◽

pp. 759-759 ◽

Cited By ~ 3

Author(s):

A. Végh ◽

Zs. Némethy ◽

L. Hajagos ◽

L. Palkovics

Keyword(s):

16S Rdna ◽

Sequence Homology ◽

Fire Blight ◽

Plasmid Vector ◽

Fruit Production ◽

Hypersensitive Reaction ◽

Bacterial Suspension ◽

Prunus Domestica ◽

Biochemical Tests ◽

First Report

During July 2011, a severe, unusual disease symptom was observed on young shoots on a 10-year old plum tree (Prunus domestica L. ‘d'Agen’) in the city of Budaörs, near Budapest. The naturally infected shoots showed typical symptoms of fire blight including terminal shoots with brown-to-black necrotic lesions and later, shepherd's crook deformation. Symptoms were the same as fire blight, symptoms reported from other hosts and locations. The first occurrence of fire blight on European plum was recorded in Germany in 2002 (4). Shoots containing regions of dead and healthy tissue were surface sterilized with ethanol (50-mg sample homogenized with 500 μl of sterile water and 50 μl of the homogenate streaked to King's B agar medium). After 48 h of incubation at 26°C, the medium contained pure cultures of a bacterium with white mucoid colonies, which is morphologically consistent with E. amylovora (1). Isolates were gram negative and induced a hypersensitive reaction in tobacco (Nicotiana tabacum L. ‘White Burley’) leaves (2). Biochemical tests were also used for identification, and the results of API 20E and API 50 CH kits (Biomérieux, Marcy l'Etoile, France), demonstrated that the bacterium belongs to Enterobacteriaceae. Pathogenicity was tested by injecting five healthy young plum shoots from the same tree with a 10-μl bacterial suspension of 107 CFU/ml. Controls were injected with sterile distilled water. Shoots were kept at 26°C and 80 to 100% relative humidity. Five days after inoculation, dark brown-to-black lesions and shepherd's crook symptoms were observed only on inoculated shoots. The bacterium was reisolated from lesions on inoculated shoots, fulfilling Koch's postulates. No lesions were observed on controls. For molecular identification of the pathogen, the 16S rDNA region was amplified from isolate EA-PlumBo1 with a general bacterial primer pair (63f forward and 1389r reverse) (3). The PCR products were cloned into a pGEM T-Easy plasmid vector (Promega, Madison, WI) and were transformed into Escherichia coli DH5α cells. A recombinant plasmid (2A2.5) was sequenced by M13 forward and reverse primers. The sequence was deposited in GenBank (Accession No. HE610678) and showed 99 to 100% sequence homology with a number of E. amylovora isolates, including type strain AJ233410 with 99% similarity and 100% homology with sequences FN434113 and FN666575, where the complete genomes are known. On the basis of the symptoms, colony morphology, biochemical tests, and 16S rDNA sequence homology, the pathogen was identified as E. amylovora. To our knowledge, this is the first report of a natural outbreak of fire blight on plum in Hungary and the presence of the pathogen may seriously influence local stone fruit production in the future. References: (1) E. O. King et al. J. Lab. Clin. Med. 44:301, 1954. (2) Z. Klement. Nature 199:299, 1963. (3) A. M. Osborn et al. Environ. Microbiol. 2:39, 2000. (4) J. L. Vanneste et al. Acta Hortic. 590:89, 2002.

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First Report of Fire Blight Caused by Erwinia amylovora on Pear, Apple, and Quince in Morocco

Plant Disease ◽

10.1094/pdis-92-2-0314a ◽

2008 ◽

Vol 92 (2) ◽

pp. 314-314 ◽

Cited By ~ 3

Author(s):

M. Fatmi ◽

M. Bougsiba ◽

H. Saoud

Keyword(s):

Fire Blight ◽

Erwinia Amylovora ◽

Hypersensitive Reaction ◽

Colony Morphology ◽

Bacterial Suspension ◽

Pome Fruit ◽

Detached Leaves ◽

Physiological Tests ◽

Negative Controls ◽

Reference Strains

In the spring of 2006, symptoms similar to those of fire blight were observed on pear (Pyrus communis), apple (Malus pumila), and quince (Cydonia oblonga) trees at the flowering and early fruit set stages in an orchard in the Meknès Region, 140 km east of Rabat. Symptoms consisted of i) water-soaked flowers that became wilted, shrivelled, and then turned brown to black; ii) “shepherd's crook” of the shoots; iii) dark green pedicles that became brown to black; iv) wilted and shrivelled leaves that turned brown but remained attached; and v) water-soaked fruits that became brown to black with droplets of exudates on the surface. In an effort to eradicate the disease, 42 ha of pears were dug up and burned in October 2006. In the spring of 2007, fire blight reappeared in the same orchard and was encountered in five other orchards with disease incidences from 1 to 60%. Three hectares of pears were removed and burned. Samples of diseased young shoots and fruits were collected. Bacteria were isolated either from washed tissues or directly from bacterial ooze on the host with King's B (KB) and semiselective CCT media (1,4). Colonies with morphology similar to that of Erwinia amylovora were purified through repetitive plating on KB medium. The isolates were first characterized based on colony morphology and biochemical and physiological tests (1). All isolates showed typical colony morphology on both media as compared with the reference strains of E. amylovora. They produced white colonies on KB medium, were gram negative, did not produce fluorescent pigment on KB, did not grow at 36°C, were levan positive, facultative anaerobes, and induced a hypersensitive reaction when infiltrated on tobacco leaves (cv. Xanthi). The isolates reacted negatively for oxidase, urease, indol, H2S production, and potato rotting tests, but they reacted positively for catalase and citrate tests. More than 87% of the isolates induced gelatine liquefaction, did not reduce nitrate, and produced acid from sorbitol but not from inositol, raffinose, and salicin. Thirty-three isolates were identified as E. amylovora by immunofluorescence microscopy with a polyclonal antibody (IF), double-antibody sandwich indirect-ELISA (3), and PCR (2). Pathogenicity was performed with a detached-leaf test tube assay (1). Each isolate was inoculated by wounding three young leaves of pears (cv. William's) along the main vein with a scalpel dipped in a 109 CFU/ml bacterial suspension. The inoculated detached leaves were kept at 25°C and 80% relative humidity in tubes with sterile 1% agar. Positive controls consisted of reference strains of E. amylovora. For negative controls, detached leaves were wounded with a scalpel dipped in sterile phosphate-buffered saline and the leaves were kept separate from the inoculated ones. Within a week, symptoms similar to those observed on leaves inoculated with the reference strains of E. amylovora, including discoloration, browning, and production of bacterial ooze along inoculated vein leaf, appeared. No symptoms developed on negative controls. Reisolation of bacteria produced colonies with characteristics like E. amylovora. Representative colonies were confirmed by IF. The occurrence of fire blight in Morocco creates a serious threat to the pome fruit industry. References: (1) Anonymous. OEPP/EPPO Bull. 34:159, 2004. (2) S. Bereswill et al. Appl. Environ. Microbiol. 58:3522, 1992. (3) M. T. Gorris et al. Acta Hortic. 411:41, 1996. (4) C. Ishimaru and E. J. Klos. Phytopathology 74:1342, 1984.

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