First Report of Pear Blossom Blast Caused by Pseudomonas syringae pv. syringae in China

In the spring of 2006, a new bacterial disease was noted in pear orchards near Hangzhou, Zhejiang Province, China. The disease caused severe blossom blast on pears (Pyrus pyrifolia; cv. Cuiguan). Early symptoms of the disease included blackening of the calyx end of developing fruit, blackening of blossom clusters while leaves of affected blossom clusters appeared normal, or death of clusters consisting of both blossoms and leaves. Later, tips of twigs turned dark brown and died. No bacterial ooze was observed. Twelve bacterial isolates were recovered from ten samples of buds and blossoms. Six isolates were selected for identification. They were similar to those of the reference strains of Pseudomonas syringae pv. syringae LMG5570 and LMG 2230 from Belgium in phenotypic tests on the basis of the Biolog Microbial Identification System (version 4.2; Biolog Inc., Hayward, CA), pathogenicity tests, gas chromatographic analysis of fatty acid methyl esters (FAMEs) using the Microbial Identification System (MIDI Inc., Newark, DE) with aerobic bacterial library (TABA50), and electron microscopy (TEM, KYKY-1000B, Japan). All isolates tested were gram-negative, aerobic rods measuring 1.5 to 2.4 × 0.5 to 0.6 μm with 2 to 4 polar flagella. Fluorescent green diffusible pigment was produced on King's Medium B. Colonies were gray-white and slightly raised with smooth margins on nutrient agar. They produced levan on sucrose nutrient agar. A hypersensitive reaction was observed on tobacco cv. Benshi 24 h after inoculation. All isolates were identified as P. syringae pv. syringae with Biolog similarity index of 0.57 to 0.86 and FAME similarity index of 0.58 to 0.81. Identification as P. syringae pv. syringae was confirmed using 16S rDNA universal primers (2,3): 5′-AGA GTT TGA TCA TGG CTC AG-3′ forward primer, 5′-ACG GTT ACC TTG TTA CGA CTT-3′ reverse primer. The PCR fragments of the three isolates were sequenced and compared with sequences in GenBank. They had 99% similiarity with P. syringae pv. syringae 16S rRNA gene strain NCPPB 3869. Koch's postulates were conducted on buds of the original pear cultivar growing in pots and detached pear blossoms in flasks by spray inoculation with cell suspensions containing 108 CFU/ml of the six isolates at 18 to 22°C with two replications. The bacteria induced symptoms on buds and blossoms similar to those observed in the field. The bacterium was reisolated from symptomatic pear buds and internal ovary tissues. P. syringae pv. syringae was first reported in England as the cause of pear blossom blast in 1914 (1). After searching all the Chinese agricultural databases and major journals (National Knowledge Infrastructure database, Vip Chinese periodical database, Chinese wanfang database, China InfoBank, Scientia Agricultura Sinica, Acta Phytopathologica Sinica, Acta Phytophylacica Sinica, and Journal of Fruit Science), to our knowledge, this is the first report of pear blossom blast caused by P. syringae pv. syringae in China. The disease cycle on pear trees and the control strategies in the regions are being further studied. References: (1) B. P. Barker et al. Ann. Appl. Biol. 1:85, 1914. (2) U. Edward et al. Nucleic Acids Res. 17:7843,1989. (3) B. Li et al. J. Phytopathol. 34:141, 2006.

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Wildfire of Soybean Caused by Pseudomonas syringae pv. tabaci, a New Disease in Korea

Plant Disease ◽

10.1094/pdis-93-11-1214a ◽

2009 ◽

Vol 93 (11) ◽

pp. 1214-1214 ◽

Cited By ~ 3

Author(s):

I.-S. Myung ◽

J.-W. Kim ◽

S. H. An ◽

J. H. Lee ◽

S. K. Kim ◽

...

Keyword(s):

Pseudomonas Syringae ◽

Pathogenic Bacteria ◽

Similarity Index ◽

Soft Rot ◽

Universal Primers ◽

Identification System ◽

Bacterial Disease ◽

Bacterial Strains ◽

Microbial Identification ◽

Soybean Leaves

In 2006 and 2007, a new bacterial disease was observed in field-cultivated soybeans in Boeun District and Munkyung City of Korea. The disease caused severe blighting of soybean (Glycine max) leaves. Soybean leaves in fields showed yellowish spots with brown centers. Brown and dead areas of variable size and shape were surrounded by wide, yellow haloes with distinct margins. Spots might coalesce and affected leaves fell readily. Seven bacterial strains were isolated from chlorotic areas of soybean leaves and all produced white colonies on trypticase soy agar. With the Biolog Microbial Identification System, version 4.2, (Biolog Inc., Hayward, CA) all strains and Pseudomonas syringae pv. tabaci CFBP2106T were identified as P. syringae pv. tabaci with a Biolog similarity index of 0.28 to 0.52 and 0.48 after 24 h. Pathogenicity of the strains (three plants per strain) on soybean leaves at the V5 stage (cv. Hwanggeum) was confirmed by rub inoculation with bacterial suspensions (1 × 108 CFU/ml) in sterile distilled water on the lesions cut 1 cm long on the upper side of the leaves with razor blades and by pinprick on 3-week-old leaves of tobacco (Nicotiana tabacum cv. Samsun) in the greenhouse. Wildfire symptoms on the soybean leaves and faint halos on tobacco leaves were observed 4 days after inoculation. The identification of reisolated bacterial strains was confirmed with the metabolic fingerprintings on Biolog. LOPAT tests (1) and phenotypic characteristics (3) of the strains were similar to those of the CFBP2106T. Colonies were levan positive, oxidase negative, potato soft rot negative, arginine dihydrase negative, and tobacco hypersensitivity negative. All strains were gram-negative, aerobic rods with a polar flagellum. Strains were negative for esculin hydrolysis, gelatin liquefaction, urea production, accumulation of poly-β-hydroxy butyrate, starch hydrolysis, ornithine dihydrolase, lysine dihydrolase, growth at 37°C, utilization of geraniol, benzoate, cellobiose, sorbitol, trehalose, l-rhamnose, and adonitol. Positive reactions were catalase and arbutin hydrolysis, utilization of sorbitol, d-arabinose, and dl-serine. The strains were variable in utilization of mannitol, sucrose, and d-arabinose. The 1,472-bp PCR fragments of strains, BC2366 (GenBank Accession No. FJ755788) and BC2367 (No. FJ755789) was sequenced using 16S rDNA universal primers (2). The sequences shared 100% identity with the analogous sequences of P. syringae pv. glycenea (GenBank Accession No. AB001443) available in NCBI databases. Based on the phenotypic, genetic, and pathological characteristics, all strains were identified as P. syringae pv. tabaci. To our knowledge, this is the first report of P. syringae pv. tabaci causing wildfire on soybean in Korea. References: (1) R. A. Lelliott et al. J. Appl. Bacteriol. 29:470, 1966. (2) I.-S. Myung et al. Plant Dis. 92:1472, 2008. (3) N. W. Schaad et al., eds. Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. The American Phytopathological Society, St. Paul, MN, 2001.

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First Report of a Field Outbreak of a Bacterial Leaf Spot of Cantaloupe and Squash Caused by Pseudomonas syringae pv. syringae in Georgia

Plant Disease ◽

10.1094/pdis.2003.87.5.600b ◽

2003 ◽

Vol 87 (5) ◽

pp. 600-600 ◽

Cited By ~ 5

Author(s):

D. B. Langston ◽

F. H. Sanders ◽

J. H. Brock ◽

R. D. Gitaitis ◽

J. T. Flanders ◽

...

Keyword(s):

Pseudomonas Syringae ◽

Leaf Spot ◽

Tap Water ◽

Acid Methyl Ester ◽

Economic Damage ◽

Identification System ◽

First Report ◽

Microbial Identification ◽

Microbial Identification System ◽

Physiological Tests

In March 2000, a leaf spot was reported affecting yellow summer squash (Cucurbita pepo) and cantaloupe (Cucumis melo) in commercial fields in Colquitt, Echols, and Grady counties in Georgia. All of the crops affected were reported within a 10-day period, and average temperatures during that time were 8 to 22.5°C, which is very close to the 50-year normal temperatures for these areas located in southwest Georgia. Incidence in affected fields was 100%. Lesions on squash leaves appeared irregularly shaped, dark, water soaked, somewhat vein restricted, and were 5 to 10 mm in diameter. Lesions on cantaloupe were angular, light tan, and necrotic with a lesion diameter of 2 to 5 mm. A general chlorosis was observed around lesions of both crops. Leaf distortion was observed on squash. Four isolates collected were used in biochemical, pathogenicity, and physiological tests. Gram-negative, rod-shaped bacteria were isolated from diseased tissue from squash and cantaloupes. Bacteria were aerobic, catalase-positive, fluorescent on King's medium B (1), oxidase-negative, nonpectolytic on potato, arginine dihydrolase-negative, utilized sucrose as a carbon source, produced levan, and gave a hypersensitivity response on tobacco (HR). Analysis of fatty acid methyl ester (FAME) profiles using the Microbial identification system (Sherlock version 3.1, Microbial identification system, Newark, DE) characterized representative strains as Pseudomonas syringae (similarity indices 0.65 to 0.80). Upon further characterization, the strains were negative for l (+)-tartarate utilization but utilized l-lactate and betaine and also exhibited ice nucleation activity. These characteristics are consistent with those of Pseudomonas syringae pv. syringae. Squash and cantaloupes were grown in a greenhouse for 4 weeks. Bacteria were grown in nutrient broth, resuspended in sterile tap water, and standardized using a spectrophotometer. Plants were inoculated by infiltrating leaves with 1 ml of bacterial suspensions (1 × 107 CFU/ml) using sterile syringes. Sterile water was used as a negative control, and 1 ml was infiltrated into leaves of squash and cantaloupes. Water-soaked lesions developed in 4 to 6 days on squash and cantaloupes inoculated with bacterial suspensions, and Pseudomonas syringae pv. syringae was isolated from diseased tissue. No symptoms developed on squash and cantaloupes used as negative controls. This outbreak of Pseudomonas syringae pv. syringae did not cause significant economic damage to either crop as symptoms subsided once daily high temperatures reached 28 to 32°C. This disease has been isolated from several cucurbit transplants reared in greenhouses, but to our knowledge, this is the first report of this disease occurring in the field. Reference: (1) E. O. King et al. J. Lab. Clin. Med. 44:301, 1954.

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First Report of Bacterial Head Rot of Broccoli Caused by Pseudomonas fluorescens in China

Plant Disease ◽

10.1094/pdis-93-11-1219a ◽

2009 ◽

Vol 93 (11) ◽

pp. 1219-1219 ◽

Cited By ~ 2

Author(s):

B. Li ◽

G. L. Wang ◽

Z. Y. Wu ◽

W. Qiu ◽

Q. M. Tang ◽

...

Keyword(s):

Fatty Acid ◽

Pseudomonas Fluorescens ◽

Pathogenic Bacteria ◽

Disease Incidence ◽

Identification System ◽

Rrna Gene ◽

First Report ◽

Microbial Identification ◽

Microbial Identification System ◽

Head Rot

During warm and humid periods in the winters from 2005 to 2008, head rot symptoms on broccoli (cv. Sijilv) (Brassica oleracea L. var italica Planch) were observed in commercial fields in Ningbo, Zhejiang Province, China. In agreement with the report of Cui and Harling (1), water-soaked lesions developed on the buds and then progressed into a brown-black soft rot. Longitudinal sections of the symptomatic inflorescences showed brown discoloration and rotting of the internal tissues. Broccoli production is hampered by the disease, with disease incidence ranging from 65 to 81%. Bacteria were isolated by streaking on nutrient agar (3) and individual colonies formed after 2 to 3 days of incubation at 28°C. Fifteen of thirty isolates induced hypersensitive reactions (HR) on tobacco leaves (Nicotiana tabacum cv. Samsun) within 48 h. All the HR-positive strains were fluorescent on King's medium B and the colonies were smooth, convex, entire, and round. Classical bacteriological tests indicated that the fluorescent strains were gram negative, obligate aerobes, arginine dihydrolase positive, and oxidase positive. Also, the fluorescent strains were positive for the production of levan from sucrose. Five representative strains were further characterized by the Biolog Microbial Identification System, version 4.2 (Biolog Inc., Hayward, CA) and gas chromatography of fatty acid methyl esters (FAME) using the Microbial Identification System (MIDI Inc., Newark, DE) with the aerobic bacterial library (TSBA50). The five strains were identified as Pseudomonas fluorescens with Biolog and FAME similarity indexes of 0.61 to 0.68 and 0.52 to 0.58, respectively. The 16S rRNA gene sequence of broccoli strain PFB-01 (GenBank Accession No. GQ352649) was determined according to Li et al. (2). A subsequent GenBank search showed that this sequence had 98% nucleotide identity with the type strain of P. fluorescens (ATCC 17386T, GenBank Accession No. AF094726). Koch's postulates were completed by the inoculation of broccoli heads (cv. Sijilv) with cell suspensions (107 CFU/ml) of the above five strains by spraying on the surface of subcorymbs. Each treatment had five replicates. All strains induced head rot symptoms similar to those observed in natural infections. No symptoms were noted on the control plants inoculated with sterile water. Bacteria were successfully reisolated from symptomatic heads and confirmed by the cellular fatty acid composition. To our knowledge, this is the first report in China that P. fluorescens is the causal pathogen of bacterial head rot of broccoli. References: (1) X. Cui and R. Harling. Phytopathology 96:408, 2006. (2) B. Li et al. J. Phytopathol. 154:711, 2006. (3) N. W. Schaad et al. Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. The American Phytopathological Society. St. Paul, MN, 2001.

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First Report of Leaf Spot and Blight Caused by Ralstonia pickettii on Bird of Paradise Tree in Italy

Plant Disease ◽

10.1094/pdis-92-5-0835a ◽

2008 ◽

Vol 92 (5) ◽

pp. 835-835 ◽

Cited By ~ 2

Author(s):

G. Polizzi ◽

M. Dimartino ◽

P. Bella ◽

V. Catara

Keyword(s):

Leaf Spot ◽

Pathogenic Bacteria ◽

Disease Incidence ◽

Similarity Index ◽

Nutrient Agar ◽

23S Rrna ◽

Identification System ◽

Rrna Gene ◽

Small Subunit Rrna ◽

Ralstonia Pickettii

Bird of Paradise tree (Strelitzia alba (L. f.) Skeels) is an ornamental perennial tropical plant grown in southern Italy. In the summer of 2006 and 2007, a widespread, severe leaf disease was observed on seedlings and 1- to 2-year-old plants in two glasshouses located in eastern Sicily. Disease incidence ranged from 10 to 25%. Symptoms on the leaves consisted of dark brown-to-black stripes of varying length and found between the lateral veins. Lesions sometimes coalesced into a large area of necrotic tissue. Symptomatic tissues were ground in a drop of sterile distilled water (SDW) with a scalpel. Suspensions were streaked on King's medium B (KB), nutrient agar, and yeast extract nutrient agar (2). Isolated strains were gram negative and oxidase positive, non-levan, negative in tobacco hypersensitivity test, white and nonmucoid on yeast dextrose calcium carbonate agar, did not produce fluorescent pigments on KB, and utilized glucose, mannitol, trehalose, arabinose, mannose, and N-acetylglucosamine. Bacterial strains were identified as Ralstonia pickettii by using the Biolog Identification System (MicroLogTM System Release 4.2; Biolog, Inc., Hayward, CA) with a similarity index ranging from 0.52 to 0.67. For an additional confirmation of identity, the small subunit rRNA gene (SSUrDNA) was amplified with primers 530F and Uni 1492R (1). The resulting nucleotide sequence was compared with sequences deposited in GenBank and showed the highest identity (99%) to sequences of R. pickettii strains. Pathogenicity tests were performed on 20 cm tall potted plants. Four S. alba plants were inoculated by infiltrating leaf veins with bacterial suspensions for each of the four isolates (107 CFU ml–1 in SDW) with a 25-gauge needle and syringe. Plants were placed in polyethylene bags 1 day before inoculation and maintained there for 3 days after inoculation. Four control plants were inoculated with SDW. Water-soaked areas in the lateral veins of leaves were observed in all inoculated plants 4 days after inoculation. Within 10 days, dark brown-to-black stripes that coalesced into dark necrotic areas were observed. All isolates induced similar symptoms. Control plants did not show any symptoms. The pathogen was reisolated from symptomatic tissue and identified as R. pickettii by Biolog. A similar disease on S. reginae caused by a Pseudomonas sp. was previously reported from Florida (3). To our knowledge, this is the first record in the world of leaf spot and blight caused by R. pickettii. References: (1) D. J. Lane. 16S/23S rRNA sequencing. Page 115 in: Nucleic Acid Techniques in Bacterial Systematics. E. Stackebrandt and M. Goodfellow, eds. John Wiley and Sons, NY, 1991. (2) N. W. Schaad et al. Laboratory Guide for Identification of Plant Pathogenic Bacteria. The American Phytopathological Society, St. Paul, MN, 2001. (3) C. Wehlburg. Plant Dis. Rep. 55:447, 1971.

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Bacterial Stem Rot of Poinsettia Caused by a Dickeya sp. (Pectobacterium chrysanthemi) in China

Plant Disease ◽

10.1094/pdis-92-7-1135b ◽

2008 ◽

Vol 92 (7) ◽

pp. 1135-1135 ◽

Cited By ~ 3

Author(s):

K. Rungnapha ◽

S. H. Yu ◽

G. L. Xie

Keyword(s):

Xanthomonas Campestris ◽

Methyl Esters ◽

Similarity Index ◽

Stem Rot ◽

Unknown Etiology ◽

Identification System ◽

Bacterial Strains ◽

Microbial Identification ◽

Pectobacterium Chrysanthemi ◽

Microbial Identification System

In December 2006, a rot symptom of unknown etiology was observed on stems of plants (Euphorbia pulcherrima cv. Fu-xing) at a flower nursery in the Zhejiang Province of China where we had previously reported leaf spot of poinsettia caused by Xanthomonas campestris (2). Chlorotic spots anywhere along the stem and purplish black petioles were the first noticeable symptoms. The spots rapidly coalesced, forming large irregular chlorotic areas. Petioles turned black and shriveled and affected leaves wilted. Infected tissues were soft and water soaked. Ten bacterial strains were isolated from the diseased samples and five were selected for identification. They were similar to those of the standard reference strains of Pectobacterium chrysanthemi (Dickeya sp.), LMG 2804 from Belgium and ZUPB20056 from China, in phenotypic tests based on the Biolog Microbial Identification System, version 4.2 (Biolog Inc., Hayward, CA), pathogenicity tests, gas chromatography of fatty acid methyl esters (FAME) using the Microbial Identification System (MIDI Inc, Newark, DE) with aerobic bacterial library (TABA50), and transmission electron microscopy (TEM,KYKY-1000B, Japan). All strains tested were gram-negative facultative anaerobic rods measuring 1.5 to 3.6 × 0.6 to 1.1 μm, with peritrichous flagella. Colonies were gray-white and slightly raised with smooth margins on nutrient agar. They were negative for trehalose and positive for phosphatase production and reducing substances from sucrose. A hypersensitive reaction was observed on tobacco cv. Benshi, 24 h after inoculation. All five isolates, LMG 2804, and ZUPB20056 were identified as P. chrysanthemi (Dickeya sp.) with a Biolog similarity index of 0.58 to 0.83, 0.68, and 0.72 and a FAME similarity index of 0.52 to 0.80, 0.59, and 0.70, respectively. Identification as P. chrysanthemi (Dickeya sp.) was confirmed by PCR with specific primers used by Nassar et al (3). Koch's postulates were completed with the inoculation of 12 4-month-old intact poinsettia plants of cv. Fu-xing with cell suspensions containing 108 CFU/ml by a pinprick at the base of the stem. All five strains induced stem infection similar to those observed in natural infections. No symptoms were noted on the two control plants inoculated with sterilized distilled water by the same method. The bacterium was reisolated from symptomatic stems of poinsettia plants. P. chrysanthemi (Dickeya sp.) was first reported in United States as the cause of bacterial stem rot of poinsettia in 1972 (1). To our knowledge, this is the first report of poinsettia stem rot caused by P. chrysanthemi (Dickeya sp.) in China. The disease cycle and the control strategies of the bacterial stem rot of poinsettia in the regions are being further studied. References: (1) H. A. J. Hoitink et al. Plant Dis. Rep. 56:480, 1972. (2) B. Li et al. Plant Pathol. 55:293, 2006. (3) A. A. Nassar et al. Appl. Environ. Microbiol. 62:2228, 1996.

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Identification of Mycobacterium neoaurumIsolated from a Neutropenic Patient with Catheter-Related Bacteremia by 16S rRNA Sequencing

Journal of Clinical Microbiology ◽

10.1128/jcm.38.9.3515-3517.2000 ◽

2000 ◽

Vol 38 (9) ◽

pp. 3515-3517 ◽

Cited By ~ 45

Author(s):

Patrick C. Y. Woo ◽

Hoi-Wah Tsoi ◽

Kit-Wah Leung ◽

Peggy N. L. Lum ◽

Andy S. P. Leung ◽

...

Keyword(s):

16S Rrna ◽

Lymphoblastic Leukemia ◽

Similarity Index ◽

16S Rrna Sequencing ◽

Identification System ◽

Rrna Gene ◽

Microbial Identification ◽

First Case ◽

Rrna Sequencing ◽

Mycobacterial Strain

A rapidly growing pigmented mycobacterial strain with an ambiguous biochemical profile was isolated from the blood culture taken through the Hickman catheter of a 9-year-old girl with acute lymphoblastic leukemia. Whole-cell fatty acid analysis showed that the best match profile was that of Mycobacterium aurum, but the similarity index was only 0.217, meaning that there were no good matches between the isolate and the organisms in the database of the Microbial Identification System. The 16S rRNA gene of the mycobacterial strain was amplified, agarose gel purified, and sequenced. There were 44 base differences between the gene sequence of the isolate and that ofM. aurum but only one base difference between the sequence of the isolate and that of Mycobacterium neoaurum, showing that the isolate was indeed a strain of M. neoaurum by using this “gold standard.” This represents the first case ofM. neoaurum infection documented by 16S rRNA sequencing.

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First Report of Leaf Blight of Onion Caused by Xanthomonas campestris in the Continental United States

Plant Disease ◽

10.1094/pdis.2000.84.2.201c ◽

2000 ◽

Vol 84 (2) ◽

pp. 201-201 ◽

Cited By ~ 13

Author(s):

T. Isakeit ◽

M. E. Miller ◽

L. W. Barnes ◽

E. R. Dickstein ◽

J. B. Jones

Keyword(s):

United States ◽

Xanthomonas Campestris ◽

Acid Methyl Ester ◽

Leaf Blight ◽

Nutrient Agar ◽

Identification System ◽

Sterile Water ◽

First Report ◽

Microbial Identification ◽

Similarity Indices

In March 1998, a leaf blight of onion (Allium cepa L. ‘1015’) was found on many plants in a plot on the Texas A&M Agricultural Experiment Station in Weslaco. The symptoms were longitudinal chlorotic areas on one side of the leaf, containing sunken, elliptical necrotic lesions. Affected leaves ultimately died. Chlorotic lesions were swabbed with 70% ethanol, and tissue from beneath the epidermis was placed in a drop sterile water for 20 min. Drops were streaked on nutrient agar and incubated at 30°C. Isolations yielded gram-negative, rod-shaped bacteria that formed dark yellow, gummy colonies on yeast dextrose carbonate agar medium, hydrolyzed starch, and had a single, polar flagellum. Analysis of fatty acid methyl ester (FAME) profiles, using the Microbial Identification System (MIS, version 4.15; Microbial Identification, Newark, DE), done at the Texas Plant Disease Diagnostic Laboratory, College Station, identified nine isolates as Xanthomonas campestris (similarity indices of 0.31 to 0.54). Tests at the University of Florida supported this identification: FAME profiles using MIS version 3.9 gave similarity indices of 0.89 to 0.95, and profiles using Biolog GN Microplates, MicroLog database release 3.50 (Biolog, Hayward, CA), gave similarity indices of 0.03 to 0.76. Leaves (15 to 20 cm long) of potted onions (cv. 1015 at the five- to six-leaf stage) were infiltrated with a suspension of bacteria (107 CFU per ml), using a needle and syringe. Plants were maintained in mist chamber in a greenhouse at 24°C. Water-soaking and development of pale green color of the inoculated leaf occurred after 2 days, followed by death after 4 days. There were no symptoms on leaves inoculated with sterile water. Pathogenicity tests on four isolates were repeated once. Bacteria were reisolated on nutrient agar from symptomatic tissue but not from controls. In the field plot, disease severity did not increase as season progressed nor were there any symptoms on bulbs. Symptoms were not observed on onion during the 1999 season. X. campestris was first reported on onion from Hawaii (1). This is the first report of this pathogen on onion in the continental United States. Reference: (1) A. M. Alvarez et al. Phytopathology 68:1132, 1978.

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First Report of Bacterial Soft Rot on Vanda Orchids Caused by Dickeya chrysanthemi (Erwinia chrysanthemi) in the United States

Plant Disease ◽

10.1094/pdis-92-6-0977a ◽

2008 ◽

Vol 92 (6) ◽

pp. 977-977 ◽

Cited By ~ 6

Author(s):

R. A. Cating ◽

J. C. Hong ◽

A. J. Palmateer ◽

C. M. Stiles ◽

E. R. Dickstein

Keyword(s):

Pathogenic Bacteria ◽

Soft Rot ◽

The United States ◽

Erwinia Chrysanthemi ◽

Disease Spread ◽

Rrna Gene ◽

Bacterial Disease ◽

Water Control ◽

First Report ◽

Microbial Identification

Vanda orchids are epiphytes grown for their attractive flowers by commercial producers and hobbyists throughout Florida. In August 2007, five Vanda hybrids, with an economic value of $150 each, were found at a nursery in central Florida with leaves that were macerated, brown, and water soaked. According to the growers, the plants were normal the previous day but symptoms developed rapidly. The plants were immediately removed from the greenhouse to prevent potential disease spread. Bacteria were isolated according to the method of Schaad et al. (1). Isolated bacteria grew at 37°C, were gram negative, degraded pectate, and produced phosphatase. MIDI (Sherlock version TSBA 4.10; Microbial Identification 16 System, Newark, DE) (SIM 0.906) identified the bacteria as Erwinia chrysanthemi (Dickeya chrysanthemi Burkholder et al. 1953) Samson et al. 2005. PCR was performed on the 16S rRNA gene (GenBank Accession No. EU526397) with primers 27f (5′-GAGAGTTTGATCCTG GCTCAG-3′) and 1495r (5′-TACGGCTACCTTGTTACGA-3′) (2). Subsequent DNA sequencing and GenBank search showed the isolated strain is 99% identical to that of Dickeya chrysanthemi. Four leaves each of six Vanda hybrids were inoculated by injecting approximately 150 μl of a bacteria suspension at 1 × 108 CFU/ml into each leaf. One plant was inoculated with water in each of four leaves. Plants were enclosed in plastic bags and returned to the greenhouse under 50% shade at 29°C day and 17°C night temperatures. Within 24 h, soft rot symptoms appeared on inoculated leaves. The water control appeared normal. D. chrysanthemi was reisolated and identified with the above method, thus Koch's postulates were fulfilled. To our knowledge, this is the first report of a soft rot caused by D. chrysanthemi on Vanda hybrids. Because of the popularity and high value of Vanda orchids, proper identification of this rapidly progressing bacterial disease is of great importance for the commercial producer and homeowner alike. References: (1) N. W. Schaad et al. Erwinia soft rot group. Page 56 in: Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. N. W. Schaad et al., eds. American Phytopathological Society. St. Paul, MN, 2001. (2) W. G. Weisburg. J. Bacteriol. 173:697, 1991.

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Grain Discoloration of Rice Caused by Pantoea ananatis (synonym Erwinia uredovora) in China

Plant Disease ◽

10.1094/pdis-94-4-0482b ◽

2010 ◽

Vol 94 (4) ◽

pp. 482-482 ◽

Cited By ~ 7

Author(s):

H. Yan ◽

S. H. Yu ◽

G. L. Xie ◽

W. Fang ◽

T. Su ◽

...

Keyword(s):

Oryza Sativa L ◽

Universal Primers ◽

Identification System ◽

Bacterial Disease ◽

Rice Grain ◽

Pantoea Ananatis ◽

Microbial Identification ◽

Rice Grains ◽

Similarity Indices ◽

Microbial Identification System

In the autumn of 2008, a new bacterial disease of rice was noted in paddy fields near Hangzhou, Zhejiang Province, China. The disease caused severe discoloration of rice grains on cv. Zhong-zhe-you 1 (Oryza sativa L.). It often occurred at early flowering of hybrid rice. Initially, light, rusty, water-soaked lesions appeared on the lemma or palea and then turned brown. More immature and lighter grains were observed on panicles at harvest. No bacterial ooze was observed. Ten bacterial isolates were recovered from eight samples of discolored rice grains (1). Six isolates were selected for identification. They were similar to those of the reference strain of Pantoea ananatis (Serrano, synonym Erwinia uredovora) LMG 2665T (ATCC 33244) from Belgium in phenotypic tests based on the Biolog Microbial Identification System, version 4.2 (Biolog Inc., Hayward, CA), pathogenicity tests, gas chromatographic analysis of fatty acid methyl esters (FAME) using the Microbial Identification System (MIDI Inc, Newark, DE) with the aerobic bacterial library (TAB 5.0), and electron microscopy (TEM,KYKY-1000B, Japan). All isolates were facultatively anaerobic, gram-negative rods that measured 1.6 to 2.5 × 0.5 to 0.7 μm and had three to six peritrichous flagella. Colonies on nutrient agar were yellow and raised with smooth margins. A hypersensitive reaction was observed on tobacco (Nicotiana tobacum cv. Benshi) 24 h after inoculation. All isolates were identified as P. ananatis with Biolog similarity indices of 0.716 to 0.852 and FAME similarity indices of 0.783 to 0.903. Further identification as P. ananatis was done by 16S rDNA sequence analysis. Amplicons were produced from three strains using the universal primers (3) fD2: 5′-AGA GTT TGA TCA TGG CTC AG-3′ forward primer and rP1: 5′-ACG GTT ACC TTG TTA CGA CTT-3′ reverse primer and then sequenced (GenBank Accession Nos. GU324769, GU324770, and GU338399). A BlastN search of GenBank revealed that they had 97 to 98% nt identity with P. ananatis strain 3Pe76 (GenBank Accession No. EF178449). Koch's postulates were completed by spray inoculating panicles of rice cv. Zhong-zhe-you 1 at booting stage, grown in pots, with cell suspensions containing 108 CFU/ml of the six strains at 25 to 29°C. Three plants were inoculated with each strain, controls were sprayed with water, and the experiment was repeated once. Three weeks after inoculation, all strains produced symptoms on panicles similar to those observed in the field. Yellow pigmented bacteria were reisolated from symptomatic panicles and their identity was confirmed by FAMEs. These results indicate that the pathogen is P. ananatis (2), which also causes leaf blight and bulb decay of onion. To our knowledge, this is the first report of rice grain discoloration caused by P. ananatis in China. The disease cycle on rice and the control strategies in the regions are being further studied. References: (1) J. Y. Luo et al. Plant Dis. 91:1363, 2007. (2) H. G. Truper and L. de Clari. Int. J. Syst. Bacteriol. 47:908, 1997. (3) W. G. Weisburg et al. J. Bacteriol. 173:697, 1991.

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