First Report of Acidovorax avenae subsp. citrulli as a Pathogen of Cucumber

H. L. Martin; R. G. O'Brien; D. V. Abbott

doi:10.1094/pdis.1999.83.10.965d

First Report of Acidovorax avenae subsp. citrulli as a Pathogen of Cucumber

Plant Disease ◽

10.1094/pdis.1999.83.10.965d ◽

1999 ◽

Vol 83 (10) ◽

pp. 965-965 ◽

Cited By ~ 26

Author(s):

H. L. Martin ◽

R. G. O'Brien ◽

D. V. Abbott

Keyword(s):

Bacterial Suspension ◽

Bacterial Disease ◽

Cucumis Sativus L ◽

First Report ◽

Plastic Bags ◽

Initial Symptoms ◽

Leaf Surfaces ◽

Commercial Crop ◽

Slow Growing ◽

Dead Tissue

In March 1999, a foliar bacterial disease was observed in a commercial crop of cucumber (Cucumis sativus L.) cv. Jetset in Gumlu in northern Queensland, Australia. Initial symptoms consisted of angular, chlorotic, water-soaked lesions that later dried to necrotic areas of light brown, dead tissue. White bacterial ooze was commonly found on the undersides of young water-soaked lesions. Lesions were delimited by veins and distributed uniformly over leaf surfaces, and more than 20% of the crop was affected. No symptoms were observed on plant stems or fruits. Bacterial streaming from the edges of freshly cut young lesions was clearly visible in a droplet of water under ×100 magnification in the laboratory. Isolations were made from young lesions on King's medium B (1). A slow-growing, white, gram-negative, nonfluorescent bacterium was consistently isolated. Three isolates of the bacterium were identified, using the Biolog software program (Biolog, Hayward CA), and in each instance, the bacterium was confirmed as Acidovorax avenae subsp. citrulli, with a similarity of >0.80. Koch's postulates were completed with 8-day-old glasshouse-grown cucumber (cv. Jetset) seedlings. Seedlings were misted until runoff with a bacterial suspension of 3 × 108 CFU/ml and enclosed in plastic bags for ≈30 h at 22°C. Water-soaked lesions were observed on cucumber cotyledons 4 days after inoculation. This is the first report of A. avenae subsp. citrulli as a pathogen of cucumber. Reference: (1) E. O. King et al. J. Lab. Clin. Med. 44:301, 1954.

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First Report of Acidovorax avenae subsp. citrulli as a Pathogen of Gramma in Australia

Plant Disease ◽

10.1094/pdis.2002.86.12.1406a ◽

2002 ◽

Vol 86 (12) ◽

pp. 1406-1406 ◽

Cited By ~ 10

Author(s):

H. L. Martin ◽

C. M. Horlock

Keyword(s):

Bacterial Suspension ◽

Bacterial Disease ◽

Bacterial Cells ◽

Carbon Source Utilization ◽

Internal Transcribed Spacer Region ◽

First Report ◽

Plastic Bags ◽

Symptomatic Tissue ◽

Polymerase Chain ◽

Slow Growing

In March 2001, a foliar bacterial disease was observed on gramma seedlings (Cucurbita moschata L.) cv. Ken Special Hybrid 864 in a commercial nursery in Bowen, north Queensland, Australia. Symptoms included chlorosis of cotyledons and angular, water-soaked lesions from the tips of the cotyledons to the petioles. Brown, angular, water-soaked lesions that were delimited by the leaf veins were also present on newly emerged true leaves. Streaming of bacterial cells from the edges of cut lesions was seen in a droplet of water with ×100 magnification. Isolations attempted on King's medium B consistently yielded a slow-growing, cream to white, gram-negative bacterium. Bacterium was identified as Acidovorax avenae subsp. citrulli based on carbon source utilization profiles (Biolog, Hayward CA) and polymerase chain reaction (PCR) using a primer pair based on the 16S-23S internal transcribed spacer region. When tested in rep-PCR with the BoxA1R primer (2), the isolate produced a banding pattern similar to other Australian A. avenae subsp. citrulli isolates previously shown to be pathogenic to rockmelon (1). Koch's postulates were completed with 20 2-week-old glasshouse-grown gramma (cv. Ken Special Hybrid 864) seedlings. Seedlings were misted until runoff with a 3 × 108 CFU/ml bacterial suspension and enclosed in plastic bags for 48 h at 23°C. Water-soaked lesions developed on cotyledons of all seedlings 6 days after inoculation, and bacterium was reisolated from symptomatic tissue. To our knowledge, this is the first report of A. avenae subsp. citrulli as a pathogen of C. moschata References: (1) R. G. O'Brien and H. L. Martin. Aust. J. Exp. Agric. 39:479, 1999 (2) J. Versalovic et al. Methods Mol. Cell Biol. 5:25, 1994.

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First Report of Bacterial Blight of Romanesco Cauliflower (Brassica oleracea var. botrytis) Caused by Pseudomonas syringae pv. alisalensis in California

Plant Disease ◽

10.1094/pd-90-1551b ◽

2006 ◽

Vol 90 (12) ◽

pp. 1551-1551 ◽

Cited By ~ 10

Author(s):

S. T. Koike ◽

K. Kammeijer ◽

C. T. Bull ◽

D. O'Brien

Keyword(s):

Brassica Oleracea ◽

Pseudomonas Syringae ◽

Bacterial Pathogen ◽

Acid Methyl Ester ◽

Hypersensitive Reaction ◽

Bacterial Suspension ◽

First Report ◽

Plastic Bags ◽

Initial Symptoms ◽

Infested Field

In 2005, a new disease was detected on commercial, organically grown romanesco (green) cauliflower (Brassica oleracea var. botrytis) grown in San Benito County, California. Initial symptoms consisted of small (1 to 2 mm in diameter), angular, water-soaked flecks. These flecks developed into tan-to-gray, angular lesions measuring as much as 5 mm in diameter. Lesions were usually surrounded by chlorotic borders. Coalescing lesions caused the leaf to turn papery in texture and have a blighted appearance. A blue-green fluorescing pseudomonad was consistently isolated from lesions on King's medium B. Strains were levan positive, oxidase negative, and arginine dihydrolase negative. Strains did not rot potato slices but induced a hypersensitive reaction in tobacco (Nicotiana tabacum cv. Samsun). These data indicated that the bacteria belonged to Lelliot's LOPAT group 1 (2). This was confirmed with data from fatty acid methyl ester analysis (MIS-TSBA version 4.10, MIDI, Inc., Newark, DE), which showed that the strains were highly similar (similarity = 0.921 or greater) to Pseudomonas syringae. Amplification of repetitive bacterial sequences (rep-PCR) using the BOXA1R primer and the polymerase chain reaction resulted in identical banding patterns for the romanesco strains and the P. syringae pv. alisalensis pathotype strain. Pathogenicity was demonstrated by growing inoculum of six strains in nutrient broth shake cultures for 48 h (24°C), adjusting the bacterial suspension to 106 CFU/ml, and spraying the resulting suspension onto green cauliflower (cv. Romanesco Precoce). Plants were enclosed in plastic bags for 24 h and then incubated in a greenhouse (24 to 26°C). Control plants were misted with sterile water and treated the same way. After 5 days, foliar symptoms identical to symptoms seen in the field developed on all inoculated plants, and reisolated strains were characterized and found to be identical to P. syringae pv. alisalensis by the tests described above. Control plants remained symptomless. The results of two sets of pathogenicity tests were the same. To our knowledge, this is the first report of commercially grown romanesco green cauliflower as a host of P. syringae pv. alisalensis. The infested field had approximately 30% of the plants affected, with perhaps 10% sustaining some crop loss. This bacterial pathogen has previously been reported on commercial plantings of arugula (Eruca sativa), broccoli (Brassica oleracea var. botrytis), and broccoli raab (Brassica rapa var. rapa) and under experimental (greenhouse) conditions causes disease on additional hosts, including members of the Poaceae (1). References: (1) N. A. Cintas et al. Plant Dis. 86:992, 2002. (2) R. A. Lelliott. J. Appl. Bacteriol. 29:470, 1966.

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First Report of Bacterial Blight of Rutabaga (Brassica napus var. napobrassica) Caused by Pseudomonas syringae pv. alisalensis in California

Plant Disease ◽

10.1094/pd-91-0112c ◽

2007 ◽

Vol 91 (1) ◽

pp. 112-112 ◽

Cited By ~ 12

Author(s):

S. T. Koike ◽

K. Kammeijer ◽

C. T. Bull ◽

Doug O'Brien

Keyword(s):

Brassica Napus ◽

Pseudomonas Syringae ◽

Bacterial Pathogen ◽

Acid Methyl Ester ◽

Hypersensitive Reaction ◽

Bacterial Suspension ◽

Experimental Conditions ◽

First Report ◽

Plastic Bags ◽

Initial Symptoms

In 2005, commercial, organically grown rutabaga (Brassica napus var. napobrassica) in San Benito County, CA showed symptoms of a previously undescribed disease on approximately 30% of the plants. Initial symptoms consisted of small (1 to 2 mm in diameter), angular, water-soaked flecks that often were surrounded by chlorotic haloes. These flecks enlarged and coalesced into large, irregularly shaped, gray brown lesions that could be as long as 10 mm. Lesions were visible from both adaxial and abaxial leaf surfaces and generally retained the chlorotic borders. A blue-green fluorescing pseudomonad was consistently isolated from lesions on King's medium B. Eight isolates were characterized and were levan positive, oxidase negative, and arginine dihydrolase negative. Isolates did not rot potato slices but induced a hypersensitive reaction in tobacco (Nicotiana tabacum cv. Samsun). These data indicated that the bacteria belonged to Lelliot's LOPAT group 1 (2). This was confirmed with data from fatty acid methyl ester analysis (MIS-TSBA version 4.10; MIDI, Inc., Newark, DE) that showed that the isolates were highly similar (similarity = 0.922 or greater) to Pseudomonas syringae. Amplification of repetitive bacterial sequences (rep-PCR) using the BOXA1R primer and the polymerase chain reaction resulted in identical banding patterns for the rutabaga isolates and the P. syringae pv. alisalensis pathotype strain. Pathogenicity was demonstrated by growing inocula of six isolates in nutrient broth shake cultures for 48 h (24°C), adjusting the bacterial suspension to 106 CFU/ml, and misting the resulting suspensions onto rutabaga (cv. American Purple Top). Plants were enclosed in plastic bags for 24 h and then incubated in a greenhouse (24 to 26°C). Control plants were misted with sterile water and treated the same way. After 5 to 7 days, foliar symptoms similar to symptoms seen in the field developed on all inoculated plants, and reisolated bacteria were characterized and found to be P. syringae pv. alisalensis. Control plants remained symptomless. The results of two sets of pathogenicity tests were the same. To our knowledge, this is the first report of commercially grown rutabaga as a host of P. syringae pv. alisalensis and the first report of a B. napus host of this pathogen. This bacterial pathogen has previously been reported on commercial plantings of arugula (Eruca sativa), broccoli (Brassica oleracea var. botrytis), and broccoli raab (Brassica rapa var. rapa) in California and under experimental conditions it causes disease on additional hosts, including members of the Poaceae (1). References: (1) N. A. Cintas et al. Plant Dis. 86:992, 2002. (2) R. A. Lelliott. J. Appl. Bacteriol. 29:470, 1966.

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First Report of Impatiens Downy Mildew Outbreaks Caused by Plasmopara obducens Throughout the Hawai'ian Islands

Plant Disease ◽

10.1094/pdis-10-13-1017-pdn ◽

2014 ◽

Vol 98 (5) ◽

pp. 696-696 ◽

Cited By ~ 7

Author(s):

J. A. Crouch ◽

M. P. Ko ◽

J. M. McKemy

Keyword(s):

United States ◽

Downy Mildew ◽

The United States ◽

Molecular Data ◽

Economic Losses ◽

Voucher Specimen ◽

First Report ◽

Plastic Bags ◽

Leaf Surfaces ◽

Impatiens Walleriana

Downy mildew of impatiens (Impatiens walleriana Hook.f.) was first reported from the continental United States in 2004. In 2011 to 2012, severe and widespread outbreaks were documented across the United States mainland, resulting in considerable economic losses. On May 5, 2013, downy mildew disease symptoms were observed from I. walleriana ‘Super Elfin’ at a retail nursery in Mililani, on the Hawai'ian island of Oahu. Throughout May and June 2013, additional sightings of the disease were documented from the islands of Oahu, Kauai, Maui, and Hawai'i from nurseries, home gardens, and botanical park and landscape plantings. Symptoms of infected plants initially showed downward leaf curl, followed by a stippled chlorotic appearance on the adaxial leaf surfaces. Abaxial leaf surfaces were covered with a layer of white mycelia. Affected plants exhibited defoliation, flower drop, and stem rot as the disease progressed. Based on morphological and molecular data, the organism was identified as Plasmopara obducens (J. Schröt.) J. Schröt. Microscopic observation disclosed coenocytic mycelium and hyaline, thin-walled, tree-like (monopodial branches), straight, 94.0 to 300.0 × 3.2 to 10.8 μm sporangiophores. Ovoid, hyaline sporangia measuring 11.0 to 14.6 × 12.2 to 16.2 (average 13.2 × 14.7) μm were borne on sterigma tips of rigid branchlets (8.0 to 15.0 μm) at right angle to the main axis of the sporangiophores (1,3). Molecular identification of the pathogen was conducted by removing hyphae from the surface of three heavily infected leaves using sterile tweezers, then extracting DNA using the QIAGEN Plant DNA kit (QIAGEN, Gaithersburg, MD). The nuclear rDNA internal transcribed spacer was sequenced from each of the three samples bidirectionally from Illustra EXOStar (GE Healthcare, Piscataway, NJ) purified amplicon generated from primers ITS1-O and LR-0R (4). Resultant sequences (GenBank KF366378 to 80) shared 99 to 100% nucleotide identity with P. obducens accession DQ665666 (4). A voucher specimen (BPI892676) was deposited in the U.S. National Fungus Collections, Beltsville, MD. Pathogenicity tests were performed by spraying 6-week-old impatiens plants (I. walleriana var. Super Elfin) grown singly in 4-inch pots with a suspension of 1 × 104 P. obducens sporangia/ml until runoff using a handheld atomizer. Control plants were sprayed with distilled water. The plants were kept in high humidity by covering with black plastic bags for 48 h at 20°C, and then maintained in the greenhouse (night/day temperature of 20/24°C). The first symptoms (downward curling and chlorotic stippling of leaves) and sporulation of the pathogen on under-leaf surfaces of the inoculated plants appeared at 10 days and 21 days after inoculation, respectively. Control plants remained healthy. Morphological features and measurements matched those of the original inoculum, thus fulfilling Koch's postulates. To our knowledge, this is the first report of downy mildew on I. walleriana in Hawai'i (2). The disease appears to be widespread throughout the islands and is likely to cause considerable losses in Hawai'ian landscapes and production settings. References: (1) O. Constantinescu. Mycologia 83:473, 1991. (2) D. F. Farr and A. Y. Rossman. Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ July 16, 2013. (3) P. A. Saccardo. Syllogue Fungorum 7:242, 1888. (4) M. Thines. Fungal Genet Biol 44:199, 2007.

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First Report of Bacterial Wilt Caused by Ralstonia solanacearum on Plectranthus amboinicus in Martinique

Plant Disease ◽

10.1094/pdis-12-20-2622-pdn ◽

2021 ◽

Author(s):

Peninna Deberdt ◽

Gilles Cellier ◽

Régine Coranson-Beaudu ◽

Mathis Delmonteil--Girerd ◽

Joanye Canguio ◽

...

Keyword(s):

Bacterial Wilt ◽

Ralstonia Solanacearum ◽

Disease Incidence ◽

Bacterial Suspension ◽

Diagnostic Pcr ◽

Tomato Plants ◽

First Report ◽

Initial Symptoms ◽

Plectranthus Amboinicus ◽

Negative Controls

Plectranthus amboinicus, commonly known as Gwo ten in the French West Indies (Martinique), is a semi-succulent perennial plant of the Lamiaceae family. This aromatic plant wich is widespread naturally throughout the tropics is of economic importance because of the therapeutic and nutritional properties attributed to its natural phytochemical compounds wich are highly valued in the pharmaceutical industry. In March 2019, wilted P. amboinicus plants intercropped with tomato plants (cv. Heatmaster) in order to reduce the insect-pest damages on tomato, were observed in a field located at the CIRAD experimental station in Lamentin, Martinique (14.663194 N, -60.999167 W). Average disease incidence of 65.74% was recorded on P. amboinicus, in 3 plots with an area of 22.04 m2. The initial symptoms observed were irregular, black, necrotic lesions on leaves. After 10 days, plants wilted and black stripes were observed on stems. Within 4 weeks, more than 50% of plants were fully wilted. Longitudinal stem sections of the wilted plants showed brown vascular discoloration. The cut stems of the wilted plants released a whitish bacterial ooze in water. In all, 108 stem sections were collected, surface disinfected with 70% ethanol and each was crushed in 2 mL of Tris-buffer, then processed for bacterial isolation by plating on modified Semi-Selective Medium from South Africa SMSA (Engelbrecht 1994). Typical Ralstonia solanacearum colonies grew on SMSA medium for 100 of the 108 samples after incubation for 48h at 28°C and were identified as Ralstonia solanacearum using diagnostic PCR with 759/760 primers (Opina et al. 1997). A phylotype-specific multiplex PCR (Fegan and Prior 2005) classified all the strains in R. solanacearum Phylotype IIA. A subset of 11 strains was selected for sequevar identification. All the strains were identified as sequevar I-39 (100% nucleotide identity with strain ANT92 - Genbank accession EF371828), by partial egl sequencing (Fegan and Prior 2005) (GenBank Accession Nos. MT314067 to MT314077). This sequevar has been reported to be widespread in the Caribbean and tropical America on vegetable crops (particularly on tomato), but not on P. amboinicus (Deberdt et al. 2014; Ramsubhag et al. 2012; Wicker et al. 2007). To fulfil Koch’s postulates, a reference strain, isolated from diseased P. amboinicus (CFBP 8733, Phylotype IIA/sequevar 39), was inoculated on 30 healthy P. amboinicus plants. A common tomato cultivar grown in Martinique (cv. Heatmaster) was also inoculated on 30 plants with the same bacterial suspension. Three-weeks-old plants of both crops grown in sterilized field soil were inoculated by soil drenching with 20 ml of a calibrated suspension (108 CFU/mL). P. amboinicus and tomato plants drenched with sterile water served as a negative controls. Plants were grown in a fully controlled environment at day/night temperatures of 30–26°C ± 2°C under high relative humidity (80%). The P. amboinicus plants started wilting 9 days after inoculation, and within four weeks 60% of the P. amboinicus plants had wilted. The tomato plants started wilting 5 days after inoculation with 62% of wilted plants within four weeks. R. solanacearum was recovered from all symptomatic plants on modified SMSA medium. No symptoms were observed and no R. solanacearum strains were isolated from negative controls plants. To our knowledge, this is the first report of R. solanacearum causing bacterial wilt on Gwo ten (P. amboinicus) in Martinique. The importance of this discovery lies in the reporting of an additional host for R. solanacearum, which can be associated with other crops as tomato crop in order to reduce the abundance of insect-pests. Further studies need to be conducted to assess the precise distribution of bacterial wilt disease on P. amboinicus in Martinique and to develop a plan of action avoiding its association with R. solanacearum host crops as tomato for reducing epidemic risk.

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First Report of Powdery Mildew on Azalea Cv. Mollis (Rhododendron japonicum × R. molle) in Italy

Plant Disease ◽

10.1094/pdis.2002.86.3.329c ◽

2002 ◽

Vol 86 (3) ◽

pp. 329-329

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

D. Bertetti ◽

M. L. Gullino

Keyword(s):

United Kingdom ◽

Powdery Mildew ◽

Northern Italy ◽

First Report ◽

The United Kingdom ◽

Powdery Mildews ◽

Initial Symptoms ◽

Leaf Surfaces ◽

Microscopy Examination ◽

Selection Of

Rhododendron cultivation has a long history in northern Italy, where a wide selection of varieties and hybrids are grown. In summer 2001, a previously unknown powdery mildew was observed on azalea cv. Mollis (Rhododendron japonicum × R. molle) grown in several gardens in the province of Biella. Initial symptoms included chlorotic spots, followed by white fungal mycelia on both leaf surfaces. Eventually, infected leaves turned reddish and dropped prematurely. Fruit were also infected. On infected tissues, dark brown-to-black spherical cleistothecia developed, alone or in groups. The teleomorph was identified by light microscopy examination of cleistothecia. Cleistothecia measured 110 to 140 µm and were dark brown. They contained four to eight stalked or sessile asci that measured 35 to 45 µm × 40 to 55 µm, each containing six to eight ascospores. Ascospores were ellipsoid to ovoid and measured 12 to 18 µm × 20 to 25 µm. Cleistothecial characteristics were consistent with those described for Microsphaera azaleae but were different from those of the recently described species M. digitata reported in Belgium (1). The presence of conidia was rare in the specimens, so the anamorph could not be identified. To our knowledge, this is the first report of M. azaleae in Italy, but three outbreaks of powdery mildew on rhododendron were first reported in the United Kingdom on plants grown in glasshouses in the mid-1950s, 1969 and 1973 (1). Outdoors, powdery mildew was first reported on rhododendron in Europe in 1981. M. azaleae has been identified as the causal agent of rhododendron powdery mildew in the United Kingdom, Germany, and Switzerland (1). In most cases the disease is readily controlled by regular application of fungicides commonly used against powdery mildews of other crops. Reference: (1) A. J. Inman et al. J. Phytopathol. 148:17, 2000.

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First Report of Acidovorax avenae subsp. avenae Causing Bacterial Leaf Stripe of Strelitzia nicolai

Plant Disease ◽

10.1094/pdis-03-11-0160 ◽

2011 ◽

Vol 95 (11) ◽

pp. 1474-1474 ◽

Cited By ~ 2

Author(s):

T. E. Seijo ◽

N. A. Peres

Keyword(s):

Pathogenic Bacteria ◽

Fatty Acid Analysis ◽

South Florida ◽

Metabolic Phenotype ◽

Bacterial Suspension ◽

Rrna Gene ◽

First Report ◽

Plastic Bags ◽

Young Leaves ◽

Symptomatic Tissue

White bird of paradise (Strelitzia nicolai Regel & K. Koch) is a commonly grown ornamental in central and south Florida. Each summer of 2004 to 2007, a reoccurring disease was observed at a commercial nursery in central Florida. Diseased plants had brown, necrotic stripes between the lateral leaf veins, which usually appeared along the midvein and spread toward the leaf edge. Lesions developed on the youngest leaves as they emerged from the central whorl. During 2004 and 2005, 20 symptomatic leaves were sampled. A white, nonfluorescent bacterium was consistently isolated from symptomatic tissue. It induced a hypersensitive response (HR) on tomato, grew at 41°C, and was identified as a Acidovorax sp. based on fatty acid analysis and as Acidovorax avenae subsp. avenae by Biolog metabolic phenotype analysis (similarity 0.76 to 0.86). A partial 16S rRNA gene sequence (1,455 bp) (Accession No. EF418616) was identical to four sequences in the NCBI (National Center for Biotechnology Information) database: one from A. avenae subsp. avenae and three from A. avenae of undetermined subspecies. To confirm pathogenicity, a bacterial suspension (O.D590 = 0.1) was applied to fill the central whorl (~0.5 to 1 ml) of potted S. nicolai. Plants were incubated for 7 to 10 days inside plastic bags at ambient temperature. Plants were inoculated individually with five strains of A. avenae subsp. avenae, four from S. nicolai, and one from corn (ATCC19860). Two to nine plants per strain were inoculated in each experiment. All strains were tested at least twice and noninoculated control plants were included. Symptoms were reproduced on the emerging leaf of 50 to 100% of inoculated plants with all five A. avenae subsp. avenae strains. No symptoms were observed on the controls. The bacteria recovered from symptomatic tissue were confirmed to be A. avenae subsp. avenae. Corn seedlings were inoculated as described above, except that entire seedlings were sprayed. Water-soaked lesions along the length of older leaf blades developed in 4 to 7 days. Only the corn strain was pathogenic (>80% of seedlings symptomatic), indicating host specificity. To our knowledge, this is the first report of A. avenae subsp. avenae infecting S. nicolai. In 1971, Wehlburg (2) described the same symptoms on orange bird of paradise (S. reginae) as being caused by a nonfluorescent Pseudomonas sp. This report likely describes the same disease since the published description is consistent with symptoms caused by A. avenae subsp. avenae. The pathogen reported by Wehlburg (2) had one polar flagellum, reduced nitrate, produced oxidase and a HR, and utilized arabinose, but not sucrose or arginine, characteristics consistent with those of A. avenae subsp. avenae (1). The only difference was A. avenae subsp. avenae has a delayed positive starch hydrolysis (1), whereas Welhburg's strain was negative. This disease occurs mainly on young leaves when plants receive daily overhead irrigation. Incidence can be as high as 40%, occasionally causing mortality, but even mild symptoms affect appearance and reduce marketability as an ornamental. References: (1) N. W. Schaad et al. Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. The American Phytopathological Society, St. Paul, MN, 2001. (2) C. Wehlburg. Plant Dis. Rep. 55:447, 1971.

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First Report of Fulvia fulva, Causal Agent of Tomato Leaf Mold, in Greenhouses in Southeastern Spain

Plant Disease ◽

10.1094/pdis-92-9-1371b ◽

2008 ◽

Vol 92 (9) ◽

pp. 1371-1371 ◽

Cited By ~ 1

Author(s):

M. de Cara ◽

F. Heras ◽

M. Santos ◽

J. C. Tello Marquina

Keyword(s):

Pathogenic Fungi ◽

Malt Extract ◽

Conidial Suspension ◽

First Report ◽

Leaf Mold ◽

Southeastern Spain ◽

Solanum Lycopersicum L ◽

Plastic Bags ◽

Leaf Surfaces ◽

Fulvia Fulva

Tomato (Solanum lycopersicum L.) is produced in more than 9,000 ha of greenhouses in Almería (southeastern Spain). During 2006 and 2007, a new disease was observed on almost all plants in 37 greenhouses. Yellow spots on upper and lower leaf surfaces were accompanied by gray-to-dark brown mycelia, conidiophores, and conidia on lower leaf surfaces. Affected leaves became necrotic and withered. Six isolates grown on malt extract agar (MEA) were identified as Fulvia fulva (1). The one- to three-celled conidia ranged from 21.8 × 7.8 μm to 21.5 × 6.5 μm. On MEA, potato dextrose agar, and V8 juice agar, the pathogen grew slowly; colonies were only 1 cm in diameter after 30 days. Colony color was initially intense yellow but became dark brown with age. In a growth chamber (12,000 lux for 16 h per day, 23 to 28°C, and 60 to 95% relative humidity), six pots containing five tomato plants (cv. SanPedro) at the four-true-leaf stage were inoculated with a conidial suspension (103 CFU/ml) of F. fulva. Control plants were sprayed with water. The trial was repeated once. Immediately after inoculation, plants were sealed in plastic bags for 8 days. Symptoms of the disease and signs of the pathogen were observed on all inoculated plants 18 days after inoculation. To our knowledge, this is the first report of leaf mold of tomato in Almería and it is becoming common in the greenhouse industry in this region. Reference: (1) P. Holliday and J. L. Mulder. No. 487 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1976.

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First Report of Leaf Blight in Chinese Hickory (Carya cathayensis) Caused by Alternaria petroselini in China

Plant Disease ◽

10.1094/pdis-02-13-0176-pdn ◽

2013 ◽

Vol 97 (9) ◽

pp. 1253-1253 ◽

Cited By ~ 1

Author(s):

Y. H. Liu ◽

C. Q. Zhang ◽

B. C. Xu

Keyword(s):

Management Practices ◽

Morphological Characteristics ◽

Morphological Characterization ◽

Leaf Blight ◽

Internal Transcribed Spacers ◽

Infected Leaf ◽

First Report ◽

Plastic Bags ◽

Initial Symptoms ◽

Carya Cathayensis

Chinese hickory (Carya cathayensis) is one of the important economic forest crops in Zhejiang and Anhui Provinces, China. In 2012, nearly 40% of hickory orchards and 6.8% of hickory trees were affected by leaf blight in Zhejiang. Initial symptoms consisted of small, brown, water-soaked lesions, which subsequently enlarged and developed a black sporulating necrotic center surrounded by a chlorotic halo. Infected leaf samples collected from 25 different orchards in Lin'an and 13 different orchards in Chun'an were surface sterilized with 1.5% sodium hypochlorite for 1.5 min, rinsed in water, plated on 2% potato dextrose agar (PDA), and incubated at 25°C in the dark for 1 week. Single conidium cultures were consistently isolated and cultured on PDA and V8 agar for morphological characterization (1,3). On both agar media, colonies were dark olive brown with smooth margins and concentric rings of sporulation. Conidia were solitary, darkly pigmented, predominantly ovoid-subsphaeroid, and 23 to 52 × 13 to 23 μm with up to six or seven transepta and one to three longisepta. The ribosomal internal transcribed spacers ITS1 and ITS2 of 10 isolates were amplified using primers ITS1/ITS4 on DNA extracted from mycelium and nucleotide sequences showed 100% similarity to that of A. petroselini (GenBank Accession Nos. AY154685.1 and EU807868.1). To confirm pathogenicity, 10 uninfected leaves from each of 10 C. cathayensis trees were sprayed either with a conidia suspension (105 conidia per ml) or with distilled water only to serve as an un-inoculated control. Leaves were subsequently wrapped in plastic bags to retain moisture, and incubated for 48 h. After 1 week, 8 of 10 isolates caused lesions identical to those initially described whereas no symptoms developed on water inoculated leaves. Cultures reisolated from lesions and cultured on PDA exhibited morphological characteristics identical to A. petroselini (1,2,3), confirming Koch's postulates. To our knowledge, this is the first report of leaf blight in C. cathayensis, and this identification would allow producers to identify for appropriate management practices. References: (1) P. M. Kirk et al. The Dictionary of the Fungi, 10th edition, page 159. CABI Bioscience, UK, 2008. (2) B. M. Pryor et al. Mycologia 94:49, 2002. (3) E. G. Simmons. Alternaria: An Identification Manual. CBS Fungal Biodiversity Centre, Utrecht, The Netherlands, 2007.

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First report of Cercospora cf. citrulina causing leaf spot of Ipomoea pes-caprae in China

Plant Disease ◽

10.1094/pdis-05-20-1081-pdn ◽

2020 ◽

Author(s):

Min Li ◽

Meijiao Hu ◽

Zhaoyin Gao ◽

Xiaoyu Hong ◽

Chao Zhao ◽

...

Keyword(s):

Molecular Identification ◽

Leaf Spot ◽

Plant Protection ◽

Morphological Characteristics ◽

Pathogenicity Test ◽

Conidial Suspension ◽

Xisha Islands ◽

First Report ◽

Initial Symptoms ◽

Leaf Surfaces

Ipomoea pes-caprae plays an important role in protecting the tropical and subtropical coastal beach of the world. In 2018, a leaf spot was observed on I. pes-caprae in Xisha islands of China, 13.2–25.8% of leaves were infected. The initial symptoms were small (1–3 mm diameter), single, circular, dark gray spots with a light-yellow center on the leaves. The lesions enlarged and were scattered or confluent, distinct and circular, subcircular or irregular, occasionally vein-limited, pale to dark gray-brown, with a narrow dark brown border surrounded by a diffuse yellow margin. Microscopic observations of the spots revealed that caespituli were dark brown and amphigenous, but abundant on the underside of the leaves. Mycelia were internal. Conidiophores were fasciculate, occasionally solitary, pale olivaceous-brown throughout, 0- to 3-septate, 27.9–115.8 (63.4±22.5) µm × 3.2–5.3 (4.3±0.87) µm (n=100). Conidial scars were conspicuously thickened. Conidia were solitary, hyaline, filiform, acicular to obclavate, straight to slightly curved, subacute to obtuse at the apex, truncate at the base, multi-septate, 21.0–125.5 (60.2±20.1) µm × 2.0–5.0 (3.8±0.83) µm (n=100). Single-conidium isolates were obtained from representative colonies grown on potato dextrose agar (PDA) incubated at 25℃ in the dark. The colonies grew slowly and were dense, white to gray and flat with aerial mycelium. Mycelia were initially white, and then became gray. Conidia were borne on the conidiophores directly. The pure isolate HTW-1 was selected for molecular identification and pathogenicity test, which were deposited in Microbiological Culture Collection Center of Environment and Plant Protection Institute, Chinese Academy of Tropical Agricultural Sciences. The internal transcribed spacer (ITS) region of rDNA, translation elongation factor 1-alpha (tef1) and histone H3 (his3) genes were amplified with ITS1/ITS4, EF-1 / EF-2, and CYLH3F / CYLH3R primers, respectively (Groenewald et al. 2013). The obtained sequences of HTW-1 were all deposited in GenBank with accession numbers MT410467 for ITS, MT418903 for tef1 and MT418904 for his3. The ITS, tef1 and his3 genes all showed 100% similarity for ITS (JX143582), tef1 (JX143340) and his3 (JX142602) with C. cf. citrulina (MUCC 588; MAFF 239409) from I. pes-caprae in Japan. Based on the morphological characteristics and molecular identification, the pathogen was identified as Cercospora cf. citrulina (Groenewald et al. 2013). The pathogenicity test was conducted by spraying conidial suspension (1×104 conidia/mL) on wounded and unwounded leaves for seedling of I. pes-caprae in greenhouse and in sterile vitro condition. The conidial suspension was prepared using conidia from 30-day-old culture grown on PDA at 25℃ in the dark. Leaf surfaces of seedling in greenhouse were wounded by lightly rubbing with a steel sponge and detached leaf surfaces were wounded by sterile needles. the treatments were sprayed with conidial suspensions on wounded and unwounded leaf surfaces. The control was sprayed with sterile water. After eight days, the typical symptoms of spots which were small, single, circular and dark gray appeared on the inoculated wounded leaves, while the inoculated unwounded leaves and the control leaves were symptomless. The pathogen was only re-isolated from the inoculated wounded leaves. The pathogen may be infected by wound. A total of 20 Cercospora and related species was found on Ipomoea spp. (García et al. 1996). Cercospora cf. citrulina has been reported on I. pes-caprae in Japan, although it was unclear if it was a pathogen or saprophyte (Groenewald et al. 2013). To our knowledge, this is the first report of C. cf. citrulina causing leaf spot of I. pes-caprae in China. This disease could threat the cultivation of I. pes-caprae in China.

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