scholarly journals First Report of Ralstonia (Pseudomonas) solanacearum Infecting Pot Anthurium Production in Florida

Plant Disease ◽  
1999 ◽  
Vol 83 (3) ◽  
pp. 300-300 ◽  
Author(s):  
D. J. Norman ◽  
J. M. F. Yuen
Keyword(s):  
Xanthomonas Campestris ◽  
Polymerase Chain Reaction Amplification ◽  
Methyl Esters ◽  
Electrophoretic Analysis ◽  
Identification System ◽  
Strictly Aerobic ◽  
Pseudomonas Solanacearum ◽  
Triphenyltetrazolium Chloride ◽  
Initial Inoculum ◽  
Microbial Identification

Xanthomonas campestris pv. dieffenbachiae is a common pathogen of pot anthurium production in Florida. While X. campestris pv. dieffenbachiae was isolated from systematically infected plants with chlorotic, necrotic, and wilted leaves, a fluidal, beige bacteria was occasionally isolated on nutrient agar (Difco, Detroit, MI), as opposed to the common, yellow pigmented Xanthomonas sp. Distinction in the symptomology of plants systematically infected with a Xanthomonas sp. or this new bacterium could not be made. Three isolates were obtained of this unidentified bacterium from leaves and stems of three separate plants. With FAME (fatty acid methyl esters) analysis, using MIDI (Microbial Identification System, software version TSBA 3.90 [Newark, DE]), these isolates were classified as Ralstonia (Pseudomonas) solanacearum (syn. Burkholderia solanacearum) with a mean similarity indice of 0.895. Isolates were found to be gram negative, oxidase negative, catalase positive, motile, strictly aerobic, and metabolically classified as biovar 1; they accumulated poly-β-hydroxybutyrate and produced a hypersensitive response on tobacco within 24 h. A characteristic fluidal, white growth with a distinctive, red, swirling, egg-shaped, pigmentation pattern was observed on triphenyltetrazolium chloride medium. Further confirmation of identity as R. solanacearum was obtained by polymerase chain reaction amplification and electrophoretic analysis with species-specific primers (2), which in all cases produced a 148-bp product along with control strains. The three isolates were inoculated onto three plants of anthurium, tomato, triploid banana, and pothos. Inoculations were done at least twice; plants were inoculated either by stabbing the plant stems with a needle dipped in a suspension of bacteria or by applying 10 ml of a 1 × 108 CFU/ml suspension to the soil of the test plants. Chlorosis, necrosis, and wilt symptoms appeared within 2 weeks on all plant species tested. Recently, pothos (Epipremnum aureum) cuttings imported to Florida from Costa Rica have been implicated as a source of R. solanacearum (1). Imported cuttings of pothos were being grown in hanging baskets over the infected anthuriums. Although no R. solanacearum infections were detected in the pothos, these imported plants are the probable source of the initial inoculum for this disease outbreak on anthuriums. References: (1) D. J. Norman and J. M. F. Yuen. Phytopathology 87:S70, 1997. (2) S. E. Seal et al. Appl. Environ. Microbiol. 58:3751, 1992.

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

Plant Disease ◽  
2008 ◽  
Vol 92 (7) ◽  
pp. 1135-1135 ◽  
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.

scholarly journals Identification of Three Strains of Mycobacterium Species Isolated from Clinical Samples Using Fatty Acid Methyl Ester Profiling

2003 ◽  
Vol 31 (2) ◽  
pp. 133-140 ◽  
Author(s):  
A Ozbek ◽  
O Aktas
Keyword(s):  
Fatty Acid ◽  
Methyl Esters ◽  
Acid Methyl Ester ◽  
Cellular Fatty Acid ◽  
Clinical Samples ◽  
Identification System ◽  
Cyclopropane Fatty Acid ◽  
Mycobacterium Species ◽  
Microbial Identification ◽  
Acid Methyl

The cellular fatty acid profiles of 67 strains belonging to three different species of the genus Mycobacterium were determined by gas chromatography of the fatty acid methyl esters, using the MIDI Sherlock® Microbial Identification System (MIS). The species M. tuberculosis, M. xenopi and M. avium complex were clearly distinguishable and could be identified based on the presence and concentrations of 12 fatty acids: 14:0, 15:0, 16:1ω7c, 16:1ω6c, 16:0, 17:0, 18:2ω6,9c, 18:1ω9c, 18:0, 10Me-18:0 tuberculostearic acid, alcohol and cyclopropane. Fatty acid analysis showed that there is great homogeneity within and heterogeneity between Mycobacterium species. Thus the MIS is an accurate, efficient and relatively rapid method for the identification of mycobacteria.

scholarly journals Occurrence of Bacterial Stem Rot, Caused by Erwinia chrysanthemi, on Field-Grown Tomato in Florida

Plant Disease ◽  
1998 ◽  
Vol 82 (7) ◽  
pp. 831-831 ◽  
Author(s):  
D. O. Chellemi ◽  
H. A. Dankers ◽  
K. Hill ◽  
R. E. Cullen ◽  
G. W. Simone ◽  
...  
Keyword(s):  
Pathogenic Bacteria ◽  
Methyl Esters ◽  
Sole Source ◽  
Erwinia Chrysanthemi ◽  
Identification System ◽  
Bacterial Cells ◽  
Sterile Water ◽  
Microbial Identification ◽  
Pure Cultures ◽  
Tomato Isolate

In September 1997, wilted 4-week-old tomato (Lycopersicon esculentum Mill.) plants were observed in a commercial production field in St. Lucie County, FL. Closer inspection of affected plants revealed hollow stems and petioles with dark, water-soaked lesions. Diseased tissue was macerated and streaked onto nutrient agar (NA) and crystal violet pectate (CVP) agar. After incubation for 2 days at 30°C, isolates produced pits on the CVP agar. Isolates were transferred onto NA and the incubation and transfer procedure was performed two additional times to obtain pure cultures. Suspensions of bacterial cells were injected into tomato and tobacco leaves to test for a hypersensitive or pathogenic reaction. Isolates produced collapsed necrotic tissue on tomato while no reaction was observed on tobacco. Tests for differentiating species and subspecies in the ‘carotovora’ group of Erwinia were conducted following the protocol of Dickey and Kelman (1). With known cultures of E. carotovora subsp. carotovora and E. chrysanthemi as controls, the isolate from tomato was determined to function as a facultative anaerobe, utilize asparagine as a sole source of carbon and nitrogen, and give positive reactions for pectate degradation, phosphatase, and growth at 37°C. Known cultures of E. carotovora subsp. carotovora, E. chrysanthemi, and the tomato isolate were grown on trypticase soy broth agar for 24 h at 28°C and their cellular fatty acids derivatized to fatty acid methyl esters (FAMEs). Statistical analyses of FAME profile data (MIDI Microbial Identification System, Newark, DE, version 3.60) identified the tomato isolate as Erwinia chrysanthemi. Pathogenicity was determined by inoculating 50-day-old tomato plants (cv. SunPride) with a suspension of E. chrysanthemi obtained from nutrient broth plates incubated at 24°C for 60 h. Three plants each were inoculated with the E. chrysanthemi identified from tomato, sterile water, and known cultures of E. chrysanthemi and E. carotovora subsp. carotovora by placing a drop at the junction of the petiole and stem and passing a sterile needle through the drop into the stem. Plants were maintained in a greenhouse. Dark, water-soaked cankers were observed on the stems of plants inoculated with E. chrysanthemi, including the tomato isolate and E. carotovora subsp. carotovora, after 7 days. No symptoms were observed on plants inoculated with sterile water. Reisolation of the pathogen and identification was performed with tissue from one of the symptomatic inoculated plants. Analyses of FAMEs confirmed E. chrysanthemi as the causal agent. This is the first report of E. chrysanthemi causing a vascular disease of field-grown tomato in Florida. Reference: (1) R. S. Dickey and A. Kelman. 1988. Pages 44–59 in: Laboratory Guide for Identification of Plant Pathogenic Bacteria. N. W. Schaad, ed. American Phytopathological Society, St. Paul, MN.

scholarly journals Occurrence of Bacterial Stripe of Pearl Millet in Georgia

Plant Disease ◽  
2002 ◽  
Vol 86 (3) ◽  
pp. 326-326
Author(s):  
R. Gitaitis ◽  
J. Wilson ◽  
R. Walcott ◽  
H. Sanders ◽  
W. Hanna
Keyword(s):  
Pearl Millet ◽  
Sweet Corn ◽  
Pennisetum Glaucum ◽  
Methyl Esters ◽  
The United States ◽  
Negative Control ◽  
Identification System ◽  
Breeding Lines ◽  
Microbial Identification ◽  
Atypical Symptoms

Bacterial stripe, caused by Acidovorax avenae subsp. avenae, was observed on breeding lines of pearl millet (Pennisetum glaucum (L.) R. Br.) in Georgia in 1999 and 2001. A gram-negative, oxidase-positive, rod-shaped bacterium that produced circular, cream-colored, nonfluorescent, butyrous colonies with entire margins on King's medium B was consistently isolated from leaf lesions. The bacterium was identified as A. avenae subsp. avenae by gas-chromatography of extracted, whole-cell, fatty acid methyl esters using the Sherlock Microbial Identification System (MIDI, Newark, DE) and by substrate utilization patterns using the Biolog Identification System (Biolog Inc., Hayward, CA). Isolates from pearl millet produced amplicons of expected size (360 bp) from 16S rDNA after conducting polymerase chain reaction (PCR) with primers WFB1 and WFB2, which are specific for A. avenae. When bacterial suspensions of 1 × 108 CFU/ml were infiltrated into the intercellular spaces of leaves of pearl millet seedlings in the greenhouse, typical water-soaked, reddish-brown stripes developed and were identical to those observed in the field. In contrast to previous reports (1), the pearl millet strains produced atypical symptoms on sweet corn (cvs. Merit and Primetime). Necroses were restricted, lacked customary water-soaking, and were similar to symptoms produced by the watermelon pathogen, A. avenae subsp. citrulli, which was used as a negative control. In contrast, three strains of A. avenae subsp. avenae previously isolated from corn in Georgia produced typical water-soaked stripes in both millet and the sweet corn ‘Merit’. However, like the millet strains, A. avenae subsp. avenae strains from corn produced atypical symptoms on the sweet corn ‘Primetime’. Using immunomagnetic separation and PCR (2), A. avenae subsp. avenae was detected in remaining samples of pearl millet seed planted in Georgia in 2001, as well as in remnant samples of seed sent to Puerto Rico for increase in 2000. The A. avenae subsp. avenae strain recovered from seed was identified by the methods listed above, and in the greenhouse it was identified by the production of typical water-soaked stripes after inoculation of pearl millet. This is the first report of A. avenae subsp. avenae infecting pearl millet in the United States. The detection and distribution of seedborne inoculum in breeding lines is significant since the program at Tifton represents a major effort by the U.S. Department of Agriculture to develop higher-yielding, disease-resistant pearl millet hybrids. Furthermore, the strains from pearl millet appear to be different from previous A. avenae subsp. avenae strains isolated from corn in Georgia, because they did not produce typical disease symptoms when infiltrated in corn leaves. References: (1) L. E. Claflin et al. Plant Dis. 73:1010, 1989. (2) R. R. Walcott and R. D. Gitaitis. Plant Dis. 84:470, 2000.

scholarly journals Determination of Whole-Cell Fatty Acid Profiles for the Characterization and Differentiation of Isolates of Rhizoctonia solani AG-4 And AG-7

Plant Disease ◽  
2000 ◽  
Vol 84 (7) ◽  
pp. 785-788 ◽  
Author(s):  
R. E. Baird ◽  
R. D. Gitaitis ◽  
D. E. Carling ◽  
S. M. Baird ◽  
P. J. Alt ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Rhizoctonia Solani ◽  
Euclidean Distance ◽  
Methyl Esters ◽  
Principal Component ◽  
Identification System ◽  
Microbial Identification ◽  
Euclidean Distances

Fatty acid methyl esters (FAMEs) of isolates of Rhizoctonia solani AG-4 and AG-7 were characterized by gas chromatography and analyzed with Microbial Identification System software. Palmitic, stearic, and oleic acids were common in all isolates from both anastomosis groups (AGs) and accounted for 95% of the C14 to C18 fatty acids present. Oleic acid, most common in both R. solani AG-4 and AG-7 isolates, accounted for the greatest percentages of total FAMEs. The presence, quantities, or absence of individual fatty acids could not be used for distinguishing AG-4 and AG-7 isolates. Anteisopentadecanoic and 9-heptadecanoic acids, however, were specific to all three AG-7 isolates from Japan but absent in other AG-7 isolates and all AG-4 isolates. Pentadecanoic acid occurred in only two of the R. solani AG-4 isolates, but was not found in any of the AG-7 isolates. The AG-4 isolates could be distinguished from AG-7 isolates when quantities of FAMEs and key FAME ratios were analyzed with cluster analysis and principle components were plotted. Isolates of AG-7 from Arkansas, Indiana, and Georgia appeared to be more closely related to each other than to AG-7 isolates from Japan and Mexico. These differences in FAMEs were sufficiently distinct that isolate geographical variability could be determined. A dendrogram analysis cluster constructed from the FAMEs data showed results similar to that of the principal component analysis. Euclidean distances of total AG-4 isolates were distinct from total AG-7 isolates. The Arkansas and Indiana AG-7 isolates had a similar Euclidean distance to each another but the percentages were different for the AG-7 isolates from Japan and Mexico. In conclusion, variability of the FAMEs identified in this study would not be suitable as the main diagnostic tool for distinguishing individual isolates of R. solaniAG-4 from AG-7.

scholarly journals New Disease on Ornamental Asparagus Caused by Xanthomonas campestris in Florida

Plant Disease ◽  
1997 ◽  
Vol 81 (8) ◽  
pp. 847-850 ◽  
Author(s):  
D. J. Norman ◽  
J. M. F. Yuen ◽  
N. C. Hodge
Keyword(s):  
Xanthomonas Campestris ◽  
Methyl Esters ◽  
Carbon Substrate ◽  
Strictly Aerobic ◽  
University Of Florida ◽  
Fame Analysis ◽  
Similarity Indices ◽  
Utilization Patterns ◽  
Large Round ◽  
The University

From dark, water-soaked lesions on stems of asparagus tree fern (Asparagus virgatus) in commercial nurseries in Florida, 33 xanthomonad strains were isolated. Strains formed large, round, butyrus, bright yellow colonies on yeast dextrose calcium carbonate medium, and were gram negative, oxidase negative, catalase positive, motile, strictly aerobic, and did not hydrolyze starch. Strains were further characterized by carbon substrate utilization patterns (Biolog), and by fatty acid methyl esters (FAME) analyses. The metabolic fingerprints of most strains were similar to Xanthomonas campestris pv. vitians, and X. campestris pv. dieffenbachiae from Xanthosoma or Syngonium. Representative strains from A. virgatus were not pathogenic on Dieffenbachia. X. campestris pv. dieffenbachiae strains that did not hydrolyze starch produced scattered lesions on A. virgatus stems. However, starch-hydrolyzing strains of X. campestris pv. dieffenbachiae did not produce symptoms when inoculated onto A. virgatus. FAME analysis indicated the strains were X. campestris pv. vitians or X. campestris pv. translucens; however, low similarity indices ( x = 0.461) indicated that the asparagus strains were not represented in the MIDI library database. FAME analysis profiles were also compared to the University of Florida database, which contains 1,048 X. campestris strains of which 200 are X. campestris pv. dieffenbachiae. Similarity indices were again low with 15 strains matched to X. campestris pv. secalis (x = 0.412), seven strains to X. fragariae (x = 0.224), six strains to X. campestris pv. translucens ( x = 0.437), and five strains matched < 0.20 to other pathovars. Five representative strains were tested on six Asparagus species or cultivars: A. virgatus, A. setaceus, A. macowanii, A. densiflorus ‘Sprengeri’ , A. densiflorus ‘Myers’, and A. officinalis. All five strains were pathogenic on A. virgatus but were less virulent on A. setaceus and A. densiflorus ‘Sprengeri’.

scholarly journals Bacterial Wilt of Mulberry (Morus alba) Caused by Enterobacter cloacae in China

Plant Disease ◽  
2008 ◽  
Vol 92 (3) ◽  
pp. 483-483 ◽  
Author(s):  
G. F. Wang ◽  
K. Praphat ◽  
G. L. Xie ◽  
B. Zhu ◽  
B. Li ◽  
...  
Keyword(s):  
Bacterial Wilt ◽  
Methyl Esters ◽  
Enterobacter Cloacae ◽  
The United States ◽  
Hypersensitive Reaction ◽  
Identification System ◽  
Bacterial Disease ◽  
Bacterial Strains ◽  
Microbial Identification ◽  
Light Yellow

In August of 2006, a new bacterial disease was noted in Hangzhou mulberry orchards of Zhejiang Province, China where bacterial wilt of mulberry caused by Ralstonia solanacearum was previously reported (3). In the summer, the disease caused severe wilt, especially on 1- or 2-year-old mulberry plants, that resulted in premature plant death. Leaf wilt symptoms generally started on older leaves at the bottom of the plant and spread to the younger leaves. The leaves of infected plants became withered and dry, turned dark brown, and eventually the plants became defoliated. The root xylem of infected plants was moist and discolored with brown stripes. The phloem was asymptomatic, however, in severe infections, the phloem was decayed. The observation of wilting proceeding from the bottom of the plant to the top distinguishes this disease from bacterial wilt caused by R. solanacearum. Five bacterial strains isolated from infected mulberry plants showed characteristics similar to those of the standard reference strain of Enterobacter cloacae subsp. cloacae IBJ0611from China, but differed from R. solanacearum IBJ35, E. cancerogenus LMG2693T, and E. cloacae subsp. dissolvens LMG2683T from the University of Gent, Belgium in phenotypic tests, including the Biolog Identification System version 4.2 (Biolog Inc., Hayward CA), pathogenicity tests, transmission electron microscopy (TEM,KYKY-1000B, Japan) observation, and gas chromatographic analysis of fatty acid methyl esters (FAMEs) using the Microbial Identification System (MIDI Company, Newark, DE) with the aerobic bacterial library (TABA50). Isolates were gram negative, facultative anaerobic, rod shaped, 0.3 to 1.0 × 1.0 to 3.0 μm with peritrichous flagella. Colonies on nutrient agar were light yellow, smooth, circular, entire, and convex with no green fluorescent diffusible pigment on King's medium B (3). Weak hypersensitive reaction was observed on tobacco 3 days after inoculation. All five strains were identified as E. cloacae with Biolog similarity of 0.662 to 0.863 and FAMEs similarity of 0.632 to 0.701. Inoculation of 10 6-month-old intact mulberry plants of cv Husang with cell suspensions containing 109 CFU/ml by pinprick at the base of the stem reproduced symptoms observed in natural infections. No symptoms were noted on the two control plants inoculated by the same method but with sterilized distilled water. The bacterium was reisolated from the symptomatic mulberry plants. E. cloacae has been reported from the United States as the cause of internal yellowing of papaya fruits (1) and rhizome rot of edible ginger (2). To our knowledge, this is the first report of mulberry wilt caused by E. cloacae in China. References: (1) K. Nishijima et al. Plant Dis. 71:1029, 1987. (2) K. Nishijima et al. Plant Dis. 88:1318, 2004. (3) L. Xu et al. Acta Phytophylacica. Sin. 34:141, 2007.

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

Plant Disease ◽  
2000 ◽  
Vol 84 (2) ◽  
pp. 201-201 ◽  
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.

scholarly journals First Report of a Leaf Blight of Onion Caused by Xanthomonas spp. in Georgia

Plant Disease ◽  
2003 ◽  
Vol 87 (6) ◽  
pp. 749-749 ◽  
Author(s):  
F. H. Sanders ◽  
D. B. Langston ◽  
J. H. Brock ◽  
R. D. Gitaitis ◽  
D. E. Curry ◽  
...  
Keyword(s):  
Disease Incidence ◽  
Methyl Esters ◽  
Economic Loss ◽  
Leaf Blight ◽  
Identification System ◽  
Sterile Water ◽  
Disease Symptoms ◽  
First Report ◽  
Microbial Identification ◽  
Dry Conditions

In October of 2001 and 2002, a leaf blight was reported affecting Vidalia onion (Allium cepa) cvs. Pegasus and Sweet Vidalia, respectively, in one field each. Lesions on onion seedlings began as a water-soaked, tip dieback that gradually blighted the entire leaf. Symptoms on onion transplants appeared as elongated, water-soaked lesions that typically collapsed at the point of initial infection. In both cases, disease was very severe on seedlings, and disease incidence was 50% or more in both fields. Warm temperatures combined with overhead irrigation and above average rainfall likely enhanced the severity and spread of disease. Disease was not detected on more mature onions once cool, dry conditions occurred later in the season, and no significant economic loss occurred. Seed was tested from seed lots of the aforementioned cultivars and Xanthomonas spp. were not found. Diseased tissue was macerated in sterile, phosphate-buffered saline, and 10 μl of the resulting suspension was streaked on nutrient agar plates. Yellow-pigmented, gram-negative, rod-shaped bacteria were isolated routinely from diseased tissue. Bacteria were catalase-positive, cellulolytic, oxidase-negative, amylolytic, proteolytic, and utilized glucose in an oxidative manner. Analysis of whole cell, fatty acid methyl esters (FAME) using the Microbial Identification System (MIS, Sherlock version 3.1; MIDI, Inc., Newark, DE) identified four representative strains of the bacterium as a pathovar of Xanthomonas axonopodis (similarity indices 0.75 to 0.83). Known Xanthomonas spp. from onion from Colorado and Texas (1,2) had similar FAME profiles when analyzed by the MIDI system. Onion plants were grown under greenhouse conditions for 2 months and inoculated by injecting the base of a quill with 1.0 ml of bacterial suspensions (1 × 107 CFU ml-1) of the Xanthomonas sp. isolated from Georgia, and negative controls were inoculated with 1 ml of sterile water. Disease symptoms developed on plants inoculated with bacterial suspensions in 4 to 7 days and Xanthomonas sp. was isolated from the lesions produced. Disease symptoms occurred when the same suspension was sprayed on onion foliage. No symptoms occurred on plants inoculated with 1 ml of sterile water. To our knowledge, this is the first report of Xanthomonas spp. affecting Vidalia onions. References: (1) T. Isakeit et al. Plant Dis. 84:201, 2000. (2) H. F. Schwartz and K. Otto. Plant Dis. 84:922, 2000.

scholarly journals Recent Outbreaks of Black Rot of Brassicas Caused by Xanthomonas campestris pv. campestris in Southern Mozambique

Plant Disease ◽  
2009 ◽  
Vol 93 (11) ◽  
pp. 1218-1218
Author(s):  
J. Bila ◽  
A. M. Mondjana ◽  
E. G. Wulff ◽  
C. N. Mortensen
Keyword(s):  
Xanthomonas Campestris ◽  
Pathogenic Bacteria ◽  
Identification System ◽  
Black Rot ◽  
Microbial Identification ◽  
Brassica Spp ◽  
Brassica Crop ◽  
Leaf Tissues ◽  
Pathogenicity Tests ◽  
Xanthomonas Campestris Pv Campestris

In August and September of 2007, black rot symptoms were observed on seedbed and field plants of Brassica spp. grown in the southern districts of Boane, Mahotas, and Chòkwé in Mozambique. One hundred eighty-two cabbage-growing households were evaluated for the incidence of Xanthomonas campestris pv. campestris. Five Brassica cultivars, Glory F1, Glory of Enkhuizen, Copenhagen Market, Starke (Brassica oleracea pv. capitata L.), and Tronchuda (B. oleracea L. var. costata DC) were grown in the areas for several years. The hybrid Glory F1 was the most popular grown cultivar in the surveyed areas. In the Boane district, the highest incidence of black rot was recorded on Copenhagen Market (70%), Starke (67.9%), and Glory F1 (67.3%). In Chòkwé, Tronchuda (Portuguese kale) was the least affected Brassica crop. Water-soaked lesions starting at the edge of leaves with typical V-shaped necrotic lesions and vein discoloration were the most commonly observed symptoms. When examined with a microscope, cut edges of symptomatic stem and leaf tissues consistently exhibited bacterial streaming. The bacteria were isolated from commercial seed and field-grown plants on semiselective agar media (2). Forty-six X. campestris pv. campestris strains that were gram negative, aerobic, starch positive, nitrate negative, and oxidase negative or weakly positive (3) were further identified on the basis of ELISA (Agdia Inc., Elhart, IN), GN Biolog Microbial Identification System, version 4.2 (Biolog Inc., Hayward, CA), and PCR-specific primers (1). Pathogenicity tests were conducted by pin inoculating two upper leaves of cabbage (cv. Wirosa) in the 2- to 3-leaf stage with bacterial growth from 24-h-old agar cultures (2). Black rot symptoms developed on nearly all inoculated plants within 7 to 14 days. No symptoms were observed on control plants inoculated with a sterile pin without bacterial inoculum. The severity of black rot of Brassica spp. in three important farming districts caused significant losses in Mozambique. References: (1) T. Berg et al. Plant Pathol. 54:416, 2005. (2) S. J. Roberts and H. Koenraadt. Page 1 in: International Rules for Seed Testing: Annexe to Chapter 7 Seed Health Methods. ISTA, 2007. (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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