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

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.

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

Phytopathology ◽

10.1094/phyto-96-0735 ◽

2006 ◽

Vol 96 (7) ◽

pp. 735-745 ◽

Cited By ~ 25

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.

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

Plant Disease ◽

10.1094/pdis.2003.87.7.873b ◽

2003 ◽

Vol 87 (7) ◽

pp. 873-873 ◽

Cited By ~ 1

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.

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

Plant Disease ◽

10.1094/pdis-91-10-1360b ◽

2007 ◽

Vol 91 (10) ◽

pp. 1360-1360 ◽

Cited By ~ 1

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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First Report of a Leaf Spot Disease of Bells-of-Ireland (Moluccella laevis) Caused by Cercospora apii in California

Plant Disease ◽

10.1094/pdis.2003.87.2.203a ◽

2003 ◽

Vol 87 (2) ◽

pp. 203-203

Author(s):

S. T. Koike ◽

S. A. Tjosvold ◽

J. Z. Groenewald ◽

P. W. Crous

Keyword(s):

Leaf Spot ◽

Sequence Data ◽

Disease Incidence ◽

Leaf Spot Disease ◽

Conidial Suspension ◽

Internal Transcribed Spacer Region ◽

First Report ◽

Spot Disease ◽

Leaf Spots ◽

Initial Symptoms

Bells-of-Ireland (Moluccella laevis) (Lamiaceae) is an annual plant that is field planted in coastal California (Santa Cruz County) for commercial cutflower production. In 2001, a new leaf spot disease was found in these commercially grown cutflowers. The disease was most serious in the winter-grown crops in 2001 and 2002, with a few plantings having as much as 100% disease incidence. All other plantings that were surveyed during this time had at least 50% disease. Initial symptoms consisted of gray-green leaf spots. Spots were generally oval in shape, often delimited by the major leaf veins, and later turned tan. Lesions were apparent on both adaxial and abaxial sides of the leaves. A cercosporoid fungus having fasciculate conidiophores, which formed primarily on the abaxial leaf surface, was consistently associated with the spots. Based on morphology and its host, this fungus was initially considered to be Cercospora molucellae Bremer & Petr., which was previously reported on leaves of M. laevis in Turkey (1). However, sequence data obtained from the internal transcribed spacer region (ITS1, ITS2) and the 5.8S gene (STE-U 5110, 5111; GenBank Accession Nos. AY156918 and AY156919) indicated there were no base pair differences between the bells-of-Ireland isolates from California, our own reference isolates of C. apii, as well as GenBank sequences deposited as C. apii. Based on these data, the fungus was subsequently identified as C. apii sensu lato. Pathogenicity was confirmed by spraying a conidial suspension (1.0 × 105 conidia/ml) on leaves of potted bells-of-Ireland plants, incubating the plants in a dew chamber for 24 h, and maintaining them in a greenhouse (23 to 25°C). After 2 weeks, all inoculated plants developed leaf spots that were identical to those observed in the field. C. apii was again associated with all leaf spots. Control plants, which were treated with water, did not develop any symptoms. The test was repeated and the results were similar. To our knowledge this is the first report of C. apii as a pathogen of bells-of-Ireland in California. Reference: (1) C. Chupp. A Monograph of the Fungus Genus Cercospora. Cornell University Press, Ithaca, New York, 1954.

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First Report of Leaf Spot Disease on Walnut Caused by Colletotrichum fioriniae in China

Plant Disease ◽

10.1094/pdis-09-14-0938-pdn ◽

2015 ◽

Vol 99 (2) ◽

pp. 289-289 ◽

Cited By ~ 9

Author(s):

Y. Z. Zhu ◽

W. J. Liao ◽

D. X. Zou ◽

Y. J. Wu ◽

Y. Zhou

Keyword(s):

Dna Sequences ◽

Leaf Spot ◽

Juglans Regia ◽

Morphological Characteristics ◽

Leaf Spot Disease ◽

Koch’S Postulates ◽

First Report ◽

Spot Disease ◽

Leaf Spots ◽

Koch's Postulates

In May 2014, a severe leaf spot disease was observed on walnut tree (Juglans regia L.) in Hechi, Guangxi, China. Leaf spots were circular to semicircular in shape, water-soaked, later becoming grayish white in the center with a dark brown margin and bordered by a tan halo. Necrotic lesions were approximately 3 to 4 mm in diameter. Diseased leaves were collected from 10 trees in each of five commercial orchards. The diseased leaves were cut into 5 × 5 mm slices, dipped in 75% ethanol for 30 s, washed three times in sterilized water, sterilized with 0.1% (w/v) HgCl2 for 3 min, and then rinsed five times with sterile distilled water. These slices were placed on potato dextrose agar (PDA), followed by incubating at 28°C for about 3 to 4 days. Fungal isolates were obtained from these diseased tissues, transferred onto PDA plates, and incubated at 28°C. These isolates produced gray aerial mycelium and then became pinkish gray with age. Moreover, the reverse of the colony was pink. The growth rate was 8.21 to 8.41 mm per day (average = 8.29 ± 0.11, n = 3) at 28°C. The colonies produced pale orange conidial masses and were fusiform with acute ends, hyaline, sometimes guttulate, 4.02 to 5.25 × 13.71 to 15.72 μm (average = 4.56 ± 0.31 × 14.87 ± 1.14 μm, n = 25). The morphological characteristics and measurements of this fungal isolate matched the previous descriptions of Colletotrichum fioriniae (Marcelino & Gouli) R.G. Shivas & Y.P. Tan (2). Meanwhile, these characterizations were further confirmed by analysis of the partial sequence of five genes: the internal transcribed spacer (ITS) of the ribosomal DNA, beta-tubulin (β-tub) gene, glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene, chitin synthase 3(CHS-1) gene, and actin (ACT) gene, with universal primers ITS4/ITS5, T1/βt2b, GDF1/GDR1, CHS1-79F/CHS1-354R, and ACT-512F/ACT-783R, respectively (1). BLAST of these DNA sequences using the nucleotide database of GenBank showed a high identify (ITS, 99%; β-tub, 99%; GAPDH, 99%; CHS-1, 99%; and ACT, 100%) with the previously deposited sequences of C. fioriniae (ITS, KF278459.1, NR111747.1; β-tub, AB744079.1, AB690809.1; GAPDH, KF944355.1, KF944354.1; CHS-1, JQ948987.1, JQ949005.1; and ACT, JQ949625.1, JQ949626.1). Koch's postulates were fulfilled by inoculating six healthy 1-year-old walnut trees in July 2014 with maximum and minimum temperatures of 33 and 26°C. The 6-mm mycelial plug, which was cut from the margin of a 5-day-old colony of the fungus on PDA, was placed onto each pin-wounded leaf, ensuring good contact between the mycelium and the wound. Non-colonized PDA plugs were placed onto pin-wounds as negative controls. Following inoculation, both inoculated and control plants were covered with plastic bags. Leaf spots, similar to those on naturally infected plants, were observed on the leaves inoculated with C. fioriniae within 5 days. No symptoms were observed on the negative control leaves. Finally, C. fioriniae was re-isolated from symptomatic leaves; in contrast, no fungus was isolated from the control, which confirmed Koch's postulates. To our knowledge, this is the first report of leaf disease on walnut caused by C. fioriniae. References: (1) L. Cai et al. Fungal Divers. 39:183, 2009. (2) R. G. Shivas and Y. P. Tan. Fungal Divers. 39:111, 2009.

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First Report of Embellisia hyacinthi Causing a Leaf Spot and Bulb Skin Spot Disease on Scilla peruviana in California

Plant Disease ◽

10.1094/pdis-11-10-0845 ◽

2011 ◽

Vol 95 (3) ◽

pp. 356-356

Author(s):

S. Rooney-Latham ◽

C. L. Blomquist ◽

D. G. Fogle ◽

E. G. Simmons

Keyword(s):

Leaf Spot ◽

Apical Cell ◽

Leaf Spot Disease ◽

Adaxial Side ◽

Internal Transcribed Spacer Region ◽

California Department ◽

First Report ◽

Spot Disease ◽

Leaf Spots ◽

Food And Agriculture

The genus Scilla (Hyacinthaceae) includes more than 50 species of perennial, flowering bulbs grown in landscapes worldwide. In December 2000 and May 2009, an unknown leaf spot disease on Scilla peruviana was submitted to the California Department of Food and Agriculture Plant Pest Diagnostic Lab. Samples were collected during routine phytosanitary inspections of production fields in Santa Cruz County in 2000 and Monterey County in 2009. The disease was detected before plants flowered in one field at each location each year and appeared to have a scattered distribution. Foliar spots were large, elliptical to oblong with grayish black centers and brown margins. Yellow halos surrounded many of the spots. Examination of the bulb material revealed small necrotic patches on the outer bulb scales. A rapidly growing fungus was isolated on one-half-strength acidified potato dextrose agar (APDA) from the sporulating leaf spots and necrotic patches on the bulbs. The colonies were greenish gray and became dark olivaceous with age. Dictyospores, which formed on simple to branched, geniculate conidiophores, were oblong, fusiform or obclavate and usually had a triangular apical cell. They were initially hyaline, turning olivaceous brown with age. Conidia measured 14 to 39 × 8 to 13 μm (average 24.6 × 9.9 μm) typically with two to four (but up to seven) thick, transverse septa and one to two longitudinal septa. Morphologically, the fungus matched the description of Embellisia hyacinthi de Hoog & Miller (1,3). To confirm pathogenicity, four leaves of four S. peruviana plants were inoculated by taking colonized mycelial plugs from 2-week-old cultures and placing them in a plastic screw-cap lid filled with sterile water. The water plus mycelial plug suspension in the lid was then clipped to the adaxial side of a pushpin-wounded leaf (4). Plants were placed in a dark dew chamber at 20°C for 48 h and then moved to a growth chamber at 20°C with a 12-h photoperiod. After 48 h, the clips, caps, and plugs were removed. An equal number of control plants were wounded and mock inoculated with noncolonized APDA agar plugs and the experiment was repeated. Leaf lesions were visible 3 days after clip removal and expanded to an average of 26 × 10 mm, 14 days after inoculation. Sporulation was observed in the lesions after 5 to 7 days and the fungus was isolated from all inoculated leaves. No symptoms developed on the control leaves. DNA sequencing of the internal transcribed spacer region of the isolate (GenBank Accession No. HQ425562) using primers ITS1 and ITS4 matched the identity of E. hyacinthi (2,4). E. hyacinthi has been reported as a foliar and bulb pathogen on Hyacinthus, Freesia, and Scilla in Japan and Europe including Great Britain. Bulbs infected with E. hyacinthi are generally less sound and less valuable than noninfected bulbs (1). To our knowledge, this is the first report of the disease on S. peruviana in California. References: (1) G. S. de Hoog and P. J. Muller. Neth. J. Plant Pathol. 79:85, 1973. (2) B. Pryor and D. M. Bigelow. Mycologia 95:1141, 2003. (3) E. Simmons. Mycotaxon 17:216, 1983. (4) L. E. Yakabe et al. Plant Dis. 93:883, 2009.

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

Plant Disease ◽

10.1094/pdis-92-7-1134c ◽

2008 ◽

Vol 92 (7) ◽

pp. 1134-1134 ◽

Cited By ~ 1

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.

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Diaporthe perjuncta Does Not Cause Phomopsis Cane and Leaf Spot Disease of Grapevine in Australia

Plant Disease ◽

10.1094/pdis.2004.88.9.1005 ◽

2004 ◽

Vol 88 (9) ◽

pp. 1005-1010 ◽

Cited By ~ 6

Author(s):

B. Rawnsley ◽

T. J. Wicks ◽

E. S. Scott ◽

B. E. Stummer

Keyword(s):

Leaf Spot ◽

Pure Culture ◽

Vascular Tissue ◽

Leaf Spot Disease ◽

Symptom Expression ◽

Stem Tissue ◽

Spot Disease ◽

Phomopsis Viticola ◽

Leaf Spots

In Australia, Diaporthe perjuncta (formerly known as Phomopsis taxon 1) and Phomopsis viticola (Phomopsis taxon 2) have been associated with Phomopsis cane and leaf spot of grapevine. Although P. viticola causes distinct leaf spots, as well as lesions on shoots and canes, the pathogenicity of D. perjuncta is relatively unknown. The pathogenicity of D. perjuncta and P. viticola was studied in relation to symptom expression and bud loss. Only P. viticola caused brown-black, longitudinal, necrotic lesions on stem tissue and leaf spots characteristic of the disease, whereas both D. perjuncta and P. viticola induced bleaching of dormant canes. Inoculation of dormant buds with D. perjuncta did not cause bud death. D. perjuncta and P. viticola were reisolated from inoculated tissue and into pure culture. D. perjuncta colonized the epidermis and cortex of the grapevine shoot but not the vascular tissue. D. perjuncta appears to be an endophyte, rather than a pathogen of grapevine.

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KAJIAN MACAM PUPUK HAYATI TERHADAP INTENSITAS PENYAKIT BERCAK DAUN Cercospora sp PADA TANAMAN JAGUNG HITAM

Innofarm:Jurnal Inovasi Pertanian ◽

10.33061/innofarm.v22i1.3534 ◽

2020 ◽

Vol 22 (1) ◽

pp. 50

Author(s):

Nining Saputri ◽

Sartono Joko Santosa ◽

Saiful Bahri

Keyword(s):

Leaf Spot ◽

Block Design ◽

Leaf Spot Disease ◽

Spot Disease ◽

Corn Husk ◽

Central Java ◽

Leaf Spots ◽

Randomized Block Design ◽

Disease Attack ◽

Biological Fertilizer

This study is titled Study of Biological Fertilizers on the intensity of Leaf Spots (Cercospora sp.) On Black Corn (Black Aztec) with the aim to study the types of biological fertilizers on the intensity of Cercospora sp. which began on November 9, 2019, in Jembangan Village, Gagaksipat Village, Ngemplak District, Boyolali District, Central Java, with a height of 150m (asl). This study uses a single factor Complete Randomized Block Design (RCBD) consisting of 10 treatments and 3 replications. The data from the results of this study were analyzed with the Duncan at the 5% level. The parameters observed include: intensity of leaf spot disease, weight of cob with corn husk per plant (gram), weight of cob without corn husk per plant (gram), weight of 100 corn seeds (gram). The results showed that: (1) Symptoms of leaf spot disease appear evenly on all biological fertilizers, symptoms of disease attack began to appear at the age of 30 days after planting. (2) In the treatment of biological fertilizer Megharizo on black corn concertration 10 ml/1,2 l (B2) can reduce the intensity of leaf spot disease. (3) The application of biological fertilizer from three doses has not been able to increase the yield of black corn to the weight of corn with corn husk, weight of corn without corn husk, and weight of 100 seeds.

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Identification Causes Leaf Spot Disease in Cempaka (Magnolia elegans (Blume.) H.Keng) Seedling and Its Control Techniques

Jurnal Wasian ◽

10.20886/jwas.v2i2.843 ◽

2015 ◽

Vol 2 (2) ◽

pp. 87

Author(s):

Arif Irawan ◽

Ilaa Anggraeni ◽

Margaretta Christita

Keyword(s):

Leaf Spot ◽

Fungal Pathogen ◽

Leaf Surface ◽

Control Technique ◽

Leaf Spot Disease ◽

Spot Disease ◽

Control Techniques ◽

Leaf Spots ◽

Early Signs ◽

Determination Key

This research purposes to identify the pathogen causing leaf spot in cempaka seedling and its control technique. Identify cause of disease is necessary to know precise technique control. Identification of disease was conducted in macroscopic appearances and microscopically to determine pathogens. Identification is done by using the determination key of fungi. The results showed that the early signs of leaf spot disease on cempaka seedlings in the nursery are streaks or spots on the leaf surface with distinct boundaries. Leaf spots are formed generally brown surrounded by darker boundaries. The result shows leaf spot disease on cempaka seedling was caused by fungal pathogen Colletotrichum sp. Techniques for controlling the disease can be done by isolating the infected seeds, reducing the intensity of canopy, and using the appropriate fungicides.

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