scholarly journals First Report of Severe Outbreaks of Bacterial Leaf Spot of Leafy Brassica Greens Caused by Xanthomonas campestris pv. campestris in South Carolina

Plant Disease ◽  
2008 ◽  
Vol 92 (7) ◽  
pp. 1134-1134 ◽  
Author(s):  
W. P. Wechter ◽  
A. P. Keinath ◽  
J. P. Smith ◽  
M. W. Farnham
Keyword(s):  
South Carolina ◽  
Leaf Spot ◽  
Xanthomonas Campestris ◽  
Leaf Spot Disease ◽  
Black Rot ◽  
Spot Disease ◽  
Leafy Greens ◽  
Brassica Crops ◽  
Xanthomonas Campestris Pv Campestris ◽  
Severe Leaf

Severe outbreaks of leaf spot disease of leafy vegetable brassica crops have occurred from early spring to late fall for at least the past 7 years in Lexington County, South Carolina, the major growing region for leafy greens in the state. Significant economic losses to this disease totaling $1.7 million have been incurred by large and small growers. In 2005, Pseudomonas syringae pv. maculicola was reported as one of the causal organisms of leaf spot disease in South Carolina (2). Investigations during 2006 and 2007 have led to the isolation of another bacterium causing leaf spotting of brassica crops. Symptoms in the field were nearly identical to symptoms caused by P syringae pv. maculicola, i.e., small, brown necrotic spots, often with chlorotic halos that expand and coalesce to cover the leaves. Colonies recovered from diseased tissues were xanthomonad like, nonfluorescent on Pseudomonas Agar F, mucoid on yeast extract dextrose chalk medium, grew at 35°C, hydrolyzed starch, positive for protein digestion, alkaline in litmus milk, and produce acid from arabinose. Sequence data from the 16S rDNA and fatty acid methyl ester analysis gave the best homology to Xanthomonas campestris pv. campestris with a similarity score index of >0.98 and >0.70, respectively, confirming genus and species. Excised-cotyledon assays, used to differentiate between pathovars campestris and armoraciae, confirmed the pathovar as campestris (1). Pathogenicity assays with spray inoculations (1 × 107 CFU/ml) (3) on eight plants each of ‘Topper’ and ‘Alamo’ turnip, ‘Early Jersey Wakefield’ cabbage, and ‘Money maker’ tomato produced leaf-spot symptoms within 10 days in the greenhouse and growth chamber on the turnip and cabbage plants, but not the tomato. X. campestris pv. campestris, which is common throughout the world, also is the causal agent of black rot in brassica. Typical black rot symptoms are seen often in Lexington County fields in summer and are quite different from the leaf spot symptoms observed. Leaf-spotting X. campestris pv. campestris (LS) strains and black rot (BR) strains, recovered from black rot-symptomatic plants lacking leaf spots, from the same fields were compared in greenhouse pathogenicity assays on six plants each of ‘Topper’ turnip and ‘Early Jersey Wakefield’ cabbage. Spray inoculations with 20 individual LS strains and 10 individual BR strains, collected from 2005 to 2007, produced symptoms unique to each group. These symptoms included chlorotic ‘V’-shaped lesions initiating from the leaf margins with black veining when plants were inoculated with BR strains, versus rapid and severe leaf spotting followed by chlorotic ‘V’-shaped lesions typically lacking black-veining 10 to 16 days postinoculation associated with LS strains. Additional inoculation tests gave similar results. To our knowledge, this is the first report of a severe leaf spotting disease of field-grown brassica leafy greens caused by X. campestris pv. campestris in South Carolina. These findings may have importance in differentiation of bacterial leaf spot pathogens in brassica crops. References: (1) A. M. Alvarez et al. Phytopathology 84:1449, 1994. (2) A. P. Keinath et al. Plant Dis. 90:683, 2006. (3) W. P. Wechter et al. Hortic Sci. 42:1140, 2007.

scholarly journals An Outbreak of a Leaf Spot Disease of Cabbage in Southern Florida Caused by Xanthomonas campestris pv. armoraciae

Plant Disease ◽  
2003 ◽  
Vol 87 (7) ◽  
pp. 873-873 ◽  
Author(s):  
K. Pernezny ◽  
J. B. Jones ◽  
P. D. Roberts ◽  
E. Dickstein
Keyword(s):  
Leaf Spot ◽  
Xanthomonas Campestris ◽  
Acid Methyl Ester ◽  
Sole Source ◽  
Leaf Spot Disease ◽  
Black Rot ◽  
Red Cabbage ◽  
Spot Disease ◽  
Leaf Spots ◽  
Serological Data

From October to December 2001, a leaf spot disease was observed in numerous commercial fields of red and green cabbage (Brassica oleracea var. capitata L.) in the Everglades Agricultural Area, south and east of Lake Okeechobee and in the environs of Immokalee in southwestern Florida. Discrete water-soaked to greasy appearing spots were observed in the leaf blades with no evidence of marginal V-shaped lesions characteristic of black rot caused by Xanthomonas campestris pv. campestris. Profuse bacterial streaming was observed when cut leaf sections were examined microscopically. A bacterium that formed yellow colonies on nutrient agar was consistently isolated from these lesions. Ten bacteria were isolated, purified, and characterized. All strains were aerobic, gram-negative rods. Strains were positive for esculin hydrolysis, proteolysis in litmus milk, and gelatin liquefaction. Strains were negative for urease production, nitrate reduction, oxidase, and utilization of asparagine as a sole source of carbon and nitrogen. Fatty acid methyl ester analysis indicated a match with Florida library strains of X. campestris pv. raphani (similarity indices 0.605–0.738). Suspensions (2 × 107 CFU/ml in phosphate-buffered saline) of two Oklahoma strains identified as X. campestris pv. armoraciae provided by J. P. Damicone (3) and four representative Florida strains were applied to plants using a hand-held sprayer. Pathogenicity of the strains was tested on three replicate greenhouse-grown plants of the following: green cabbage cv. Market Early; red cabbage cv. Salad Delight; radish cv. Red Silk; tomato cv. Sunny; sweet bell pepper cv. Jupiter; and fresh horseradish roots purchased from a retail grocery chain. A strain of X. campestris pv. campestris originally isolated from Homestead, FL was also included in pathogenicity tests. All Florida and Oklahoma strains produced leaf spots, but no V-shaped lesions, on leaves of green cabbage, red cabbage, radish, tomato, and horseradish. Typical black rot symptoms were observed only in radish and green and red cabbage inoculated with the X. campestris pv. campestris strain. On the basis of these results, we identify the Florida strains as X. campestris pv. armoraciae (1,2,3), recognizing the precedent of X. campestris pv. armoraciae over X. campestris pv. raphani based on extensive genetic and serological data (1). Our strains appear to be more similar to those causing outbreaks on crucifers in Oklahoma (3) than those in Ohio (2), because Florida strains were pathogenic on tomato. References: (1) A. M. Alvarez et al. Phytopathology 84:1449, 1994. (2) F. Sahin and S. A. Miller. Plant Dis. 81:1334, 1997. (3) Y. Zhao et al. Plant Dis. 84:1008, 2000.

TWO NEW SEVERE LEAF SPOT DISEASE ON FOREST TREES OF JALGAON (MAHARASTRA) INDIA

2017 ◽  
Vol 23 (2) ◽  
Author(s):  
S. A. FIRDOUSI
Keyword(s):  
Leaf Spot ◽  
Fungal Disease ◽  
Leaf Spot Disease ◽  
Forest Trees ◽  
First Report ◽  
Spot Disease ◽  
Severe Leaf

During the survey of the forest fungal disease, of Jalgaon district, two severe leaf spot diseases on Lannae coromandelica and ( Ougenia dalbergioides (Papilionaceae) were observed in Jalgaon, forest during July to September 2016-17. The casual organism was identified as Stigmina lanneae and Phomopsis sp. respectively1-4,7. These are first report from Jalgaon and Maharashtra state.

scholarly journals Pyricularia Leaf Spot: A New Disease of Ornamental Plants of the Family Marantaceae

Plant Disease ◽  
1998 ◽  
Vol 82 (5) ◽  
pp. 465-469 ◽  
Author(s):  
Athanassios C. Pappas ◽  
Epaminondas J. Paplomatas
Keyword(s):  
Leaf Spot ◽  
Ornamental Plants ◽  
Assay Method ◽  
Leaf Spot Disease ◽  
Highly Pathogenic ◽  
Banding Patterns ◽  
Spot Disease ◽  
The Family ◽  
Young Leaves ◽  
Severe Leaf

A severe leaf spot disease incited by the fungus Pyricularia oryzae was identified on Ctenanthe oppenheimiana and C. setosa “Greystar.” Primary symptoms on young leaves consisted of individual circular to slightly irregular pinpoint spots with white necrotic centers zonated by narrow brown-yellow halos. On mature leaves, extended necrotic areas resembling those caused by phytotoxicity were formed. Artificially inoculated leaves with a spore suspension of the isolated fungus from the above case showed symptoms after 3 to 4 days' incubation at 25°C and high humidity. Fungal isolates obtained from Ctenanthe plants of Brazilian origin were found to be highly pathogenic on various plants within the family Marantaceae when they were tested by an excised leaf assay method. By contrast, P. oryzae isolates obtained from rice plants grown in Greece caused either hypersensitivity or immune response symptoms in various Marantaceae. Analysis of esterase and lactate dehydrogenase isozymes showed different banding patterns for rice and Ctenanthe isolates of P. oryzae. Conditions of prolonged leaf wetness combined with prevailing high temperature and humidity favored the epidemic appearance of the Pyricularia leaf spot disease on glasshouse-grown plants during the summer months of 1995 in Greece.

scholarly journals First Report of Xanthomonas campestris pv. raphani Causing Leaf Spot Disease of Brassica oleracea in Portugal

Plant Disease ◽  
2015 ◽  
Vol 99 (2) ◽  
pp. 282-282 ◽  
Author(s):  
J. Cruz ◽  
R. Tenreiro ◽  
L. Cruz
Keyword(s):  
Brassica Oleracea ◽  
Leaf Spot ◽  
Type Strain ◽  
Xanthomonas Campestris ◽  
Biochemical Characterization ◽  
Leaf Spot Disease ◽  
Vegetable Production ◽  
Scientific Publications ◽  
Spot Disease ◽  
Leaf Spots

Representing over 25% of the vegetable production, Brassicaceae crops are very important for Portuguese agriculture. Xanthomonas campestris pv. raphani (Xcr) was first described as the causative agent of a leaf spot disease affecting radish and turnip (4). Despite its ability to infect Solanaceae hosts upon inoculation, this pathogen affects mostly Brassicaceae plants. Typical symptoms include circular dark spots that become lighter and are occasionally surrounded by a chlorotic halo. In severely affected leaves, spots were not limited by the veins and coalesced into irregular shapes that perforated the leaves, rendering the plants unsuitable for marketing. In the early 2000s, several isolates causing leaf spots on Brassica oleracea varieties (cauliflower, white cabbage, savoy cabbage, and tronchuda cabbage) were collected in Sintra, near Lisbon. The isolates, identified as putative X. campestris (Xc), formed typical yellow mucoid and convex colonies when grown on YDC medium. Biochemical characterization (2) showed their ability to produce levan and hydrolyze starch and esculin. Isolates were also able to use celobiose, trehalose, glucose, mannose, raffinose, and sucrose. Furthermore, the isolates were oxidase negative and were unable to hydrolyze arginine and to use rhamnose, indol, inositol, and sorbitol, confirming them as Xc. The expected 619-bp amplicon was obtained for all isolates, after PCR using primers DLH120/DLH125 (1). Koch's postulates were fulfilled through pathogenicity tests on B. oleracea cv. Wirosa and Raphanus sativus, hosts susceptible to Xcr as well as to X. campestris pv. campestris (Xcc). Inoculations on B. carinata (Assession No. PI199947) and Solanum lycopersicum, hosts susceptible only to Xcr, were performed to confirm pathovar identification (2). Four plants of each host were inoculated with each isolate by spraying bacterial water suspensions (OD600 = 0.1) onto leaf surfaces. Positive and negative controls were performed using Xcc type strain (CFBP 5241) and sterile distilled water, respectively. Plants were kept 15 days with 16-h light and 8-h dark photoperiods at 24 and 18°C, respectively, at RH >80% and checked daily for symptom development. Leaf spots typical of Xcr were observed for all isolates on all hosts 5 days after inoculation. All isolates were recovered after re-isolation from inoculated plants, retaining their initial features. Negative control plants showed no symptoms, while CFBP 5241 caused V-shaped lesions, typical of Xcc, on B. oleracea cv. Wirosa and R. sativus. Further confirmation of the identification was attained by partial sequencing of the gyrB gene, using primers X.gyr.fsp.s1/X.gyr.rsp3 (3). Sequences from four isolates (CPBF 143, Genbank KM094906; CPBF 207, GenBank KM094907; CPBF 209, GenBank GU596416; and CPBF 1171, GenBank GU596419) were compared by nucleotide blast at NCBI and displayed higher levels of DNA similarity (>98%) to NCPPB 1946, the type strain for Xcr, than to NCPPB 528, the type strain for Xcc. The polyphasic approach combining phenotypic and genomic data confirmed the presence of X. campestris pv. raphani in Portugal for the first time. References: (1) T. Berg et al. Plant Pathol. 54: 416, 2005. (2) R. Lelliot and D. Stead. Methods for the Diagnosis of Bacterial Diseases of Plants. Blackwell Scientific Publications, Oxford, England, 1987. (3) N. Parkinson et al. Int. J. Syst. Evol. Microbiol. 57:2881, 2007. (4) H. White. Phytopathology 20:653, 1930.

Xanthomonas campestris pv. sesami. [Descriptions of Fungi and Bacteria].

1981 ◽  
Author(s):  
J. F. Bradbury
Keyword(s):  
Geographical Distribution ◽  
Leaf Spot ◽  
Bacterial Blight ◽  
Xanthomonas Campestris ◽  
Seed Transmission ◽  
Sesamum Indicum ◽  
Leaf Spot Disease ◽  
Spot Disease ◽  
Water Splash ◽  
Olive Green

Abstract A description is provided for Xanthomonas campestris pv. sesami. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On Sesamum indicum (Pedaliaceae). DISEASE: Bacterial blight of sesame or simsim; known as 'Marad ed Dum' in the Sudan. Mainly a leaf spot disease, this starts as tiny dark olive green spots, which increase in size, becoming dark red-brown to black, and about 2-3 mm. They may be rounded or angular, and may coalesce to involve larger areas of leaf. Stems and capsules may also be infected, having oval, slightly raised, dark red-brown lesions. GEOGRAPHICAL DISTRIBUTION: Sudan and India (CMI Map 494, ed 2, 1973) to which must be added Venezuela, now confirmed (54, 524; 56, 2615). TRANSMISSION: Within a crop by water splash, wind-driven rain etc. ; from one area to another by seed transmission (47, 593). Survival in seed is up to 16 months (51, 400), in soil up to 6 months.

scholarly journals Identification of Isolates that Cause a Leaf Spot Disease of Brassicas as Xanthomonas campestris pv. raphani and Pathogenic and Genetic Comparison with Related Pathovars

2006 ◽  
Vol 96 (7) ◽  
pp. 735-745 ◽  
Author(s):  
J. G. Vicente ◽  
B. Everett ◽  
S. J. Roberts
Keyword(s):  
Plant Species ◽  
Leaf Spot ◽  
Xanthomonas Campestris ◽  
Leaf Spot Disease ◽  
Avirulence Genes ◽  
Spot Disease ◽  
Leaf Spots ◽  
Brassica Spp ◽  
Polymerase Chain ◽  
Differential Hosts

Twenty-five Xanthomonas isolates, including some isolates received as either X. campestris pv. armoraciae or pv. raphani, caused discrete leaf spot symptoms when spray-inoculated onto at least one Brassica oleracea cultivar. Twelve of these isolates and four other Xanthomonas isolates were spray- and pin-inoculated onto 21 different plant species/cultivars including horseradish (Armoracia rusticana), radish (Raphanus sativus), and tomato (Lycopersicon esculentum). The remaining 13 leaf spot isolates were spray-inoculated onto a subset of 10 plant species/cultivars. The leaf spot isolates were very aggressive on several Brassica spp., radish, and tomato causing leaf spots and dark sunken lesions on the middle vein, petiole, and stem. Based on the differential reactions of several Brassica spp. and radish cultivars, the leaf spot isolates were divided into three races, with races 1 and 3 predominating. A differential series was established to determine the race-type of isolates and a gene-for-gene model based on the interaction of two avirulence genes in the pathogen races and two matching resistance genes in the differential hosts is proposed. Repetitive-DNA polymerase chain reaction-based fingerprinting was used to assess the genetic diversity of the leaf spot isolates and isolates of closely related Xanthomonas pathovars. Although there was variability within each race, the leaf spot isolates were clustered separately from the X. campestris pv. campestris isolates. We propose that X. campestris isolates that cause a nonvascular leaf spot disease on Brassica spp. should be identified as pv. raphani and not pv. armoraciae. Race-type strains and a neopathotype strain for X. campestris pv. raphani are proposed.

scholarly journals First Report of a Leaf Spot Disease of Wild Rocket (Diplotaxis tenuifolia) in Florida Caused by Xanthomonas campestris pv. raphani

Plant Disease ◽  
2007 ◽  
Vol 91 (10) ◽  
pp. 1360-1360 ◽  
Author(s):  
K. Pernezny ◽  
R. N. Raid ◽  
J. B. Jones ◽  
E. Dickstein
Keyword(s):  
Leaf Spot ◽  
Xanthomonas Campestris ◽  
Acid Methyl Ester ◽  
Leaf Spot Disease ◽  
Strictly Aerobic ◽  
Spot Disease ◽  
Leaf Spots ◽  
Biolog System ◽  
Wild Rocket ◽  
Phosphate Buffered Saline

Wild rocket, also known as wall rocket or sand rocket (Diplotaxis tenuifolia (L.) DC, family Brassicaceae), is grown in Florida as a salad green and herb, especially for addition to “spring mix” and other bagged salad blends. It is similar in texture and flavor to the more widely known garden arugula (Eruca vesicatoria (L.) Cav. subsp. sativa). During the winter vegetable season of 2006–2007, a leaf spot disease causing severe economic loss was seen in commercial fields of wild rocket near the town of Sebastian in Indian River County, FL. Discrete water-soaked to greasy appearing spots were observed on leaf blades that rarely exceeded 1 mm in diameter with some surrounded by a narrow, yellow halo. There was no evidence of marginal V-shaped lesions suggestive of vascular black rot disease caused by Xanthomonas campestris pv. campestris. A bacterium that formed yellow colonies on nutrient agar was consistently isolated from these lesions. Four strains were isolated, purified, and characterized. All strains were strictly aerobic, gram-negative rods. Strains were positive for esculin hydrolysis and gelatin liquefaction and negative for oxidase, nitrate reduction, urease production, fluorescence on King's B medium, and utilization of asparagine as a sole source of carbon and nitrogen. Proteolysis and an alkaline reaction were observed in inoculated tubes of litmus milk. Colonies were bright yellow and mucoid on plates of yeast extract-glucose-calcium carbonate agar. Carbon source utilization, as revealed by the Biolog system, indicated a match to X. campestris. Fatty acid methyl ester analysis indicated a match with Florida library strains of X. campestris pv. raphani (similarity indices of 0.737 to 0.779). Suspensions (2 × 107 CFU/ml in sterile phosphate-buffered saline) of the four wild rocket strains and a strain isolated in 2003 as a cause of a discrete leaf spot disease of cabbage in southern Florida (1) were sprayed onto plants until runoff with a hand-held plastic mist bottle. Pathogenicity of strains was tested in the greenhouse on seven replicate plants of green cabbage cv. Copenhagen Market, salad arugula cv. Rocket, and wild rocket (an unnamed selection propagated from seed provided by a Florida grower). Symptoms appeared within 6 to 7 days. The wild rocket strains and the cabbage strain were pathogenic on all wild rocket and cabbage test plants, producing small, nonvascular leaf spots. No symptoms were seen on salad arugula or on control plants of wild rocket, cabbage, or arugula sprayed with phosphate-buffered saline. The bacterium was reisolated from infected plants and identified as X. campestris pv. raphani, thus completing Koch's postulates. We have classified the bacterial leaf spot pathogen of wild rocket as X. campestris pv. raphani using the nomenclature of Vincente et al. (2) for X. campestris strains producing nonvascular leaf spots on brassicas. This disease problem seems to be related to widespread use of overhead irrigation in the fields where the disease is prevalent. We have not observed the disease in seepage-irrigated fields of wild rocket. References: (1) K. Pernezny et al. Plant Dis. 87:873, 2003. (2) J. G. Vincente et al. Phytopathology 96:735, 2006.

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