Leaf Spotting of Turkish Filbert in Colorado Caused by Xanthomonas arboricola pv. corylina and Pseudomonas syringae pv. syringae

Jorge Ibarra; Jacob Snelling; Kathleen Alexander; Ned Tisserat

doi:10.1094/php-2012-0517-01-br

First Report of Alternaria Leaf Spot of Banana Caused by Alternaria alternata in the United States

Plant Disease ◽

10.1094/pdis-01-13-0007-pdn ◽

2013 ◽

Vol 97 (8) ◽

pp. 1116-1116 ◽

Cited By ~ 3

Author(s):

V. Parkunan ◽

S. Li ◽

E. G. Fonsah ◽

P. Ji

Keyword(s):

United States ◽

Alternaria Alternata ◽

Leaf Spot ◽

Morphological Characteristics ◽

The United States ◽

Its Sequencing ◽

Single Spore ◽

First Report ◽

Alternaria Leaf Spot ◽

Leaf Spots

Research efforts were initiated in 2003 to identify and introduce banana (Musa spp.) cultivars suitable for production in Georgia (1). Selected cultivars have been evaluated since 2009 in Tifton Banana Garden, Tifton, GA, comprising of cold hardy, short cycle, and ornamental types. In spring and summer of 2012, 7 out of 13 cultivars (African Red, Blue Torres Island, Cacambou, Chinese Cavendish, Novaria, Raja Puri, and Veinte Cohol) showed tiny, oval (0.5 to 1.0 mm long and 0.3 to 0.9 mm wide), light to dark brown spots on the adaxial surface of the leaves. Spots were more concentrated along the midrib than the rest of the leaf and occurred on all except the newly emerged leaves. Leaf spots did not expand much in size, but the numbers approximately doubled during the season. Disease incidences on the seven cultivars ranged from 10 to 63% (10% on Blue Torres Island and 63% on Novaria), with an average of 35% when a total of 52 plants were evaluated. Six cultivars including Belle, Ice Cream, Dwarf Namwah, Kandarian, Praying Hands, and Saba did not show any spots. Tissue from infected leaves of the seven cultivars were surface sterilized with 0.5% NaOCl, plated onto potato dextrose agar (PDA) media and incubated at 25°C in the dark for 5 days. The plates were then incubated at room temperature (23 ± 2°C) under a 12-hour photoperiod for 3 days. Grayish black colonies developed from all the samples, which were further identified as Alternaria spp. based on the dark, brown, obclavate to obpyriform catenulate conidia with longitudinal and transverse septa tapering to a prominent beak attached in chains on a simple and short conidiophore (2). Conidia were 23 to 73 μm long and 15 to 35 μm wide, with a beak length of 5 to 10 μm, and had 3 to 6 transverse and 0 to 5 longitudinal septa. Single spore cultures of four isolates from four different cultivars were obtained and genomic DNA was extracted and the internal transcribed spacer (ITS1-5.8S-ITS2) regions of rDNA (562 bp) were amplified and sequenced with primers ITS1 and ITS4. MegaBLAST analysis of the four sequences showed that they were 100% identical to two Alternaria alternata isolates (GQ916545 and GQ169766). ITS sequence of a representative isolate VCT1FT1 from cv. Veinte Cohol was submitted to GenBank (JX985742). Pathogenicity assay was conducted using 1-month-old banana plants (cv. Veinte Cohol) grown in pots under greenhouse conditions (25 to 27°C). Three plants were spray inoculated with the isolate VCT1FT1 (100 ml suspension per plant containing 105 spores per ml) and incubated under 100% humidity for 2 days and then kept in the greenhouse. Three plants sprayed with water were used as a control. Leaf spots identical to those observed in the field were developed in a week on the inoculated plants but not on the non-inoculated control. The fungus was reisolated from the inoculated plants and the identity was confirmed by morphological characteristics and ITS sequencing. To our knowledge, this is the first report of Alternaria leaf spot caused by A. alternata on banana in the United States. Occurrence of the disease on some banana cultivars in Georgia provides useful information to potential producers, and the cultivars that were observed to be resistant to the disease may be more suitable for production. References: (1) E. G. Fonsah et al. J. Food Distrib. Res. 37:2, 2006. (2) E. G. Simmons. Alternaria: An identification manual. CBS Fungal Biodiversity Center, Utrecht, Netherlands, 2007.

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First Report of Web Blight on Yellow-Sage (Lantana camara) Caused by Rhizoctonia solani in Europe

Plant Disease ◽

10.1094/pdis.2003.87.7.875a ◽

2003 ◽

Vol 87 (7) ◽

pp. 875-875 ◽

Cited By ~ 2

Author(s):

A. Garibaldi ◽

A. Minuto ◽

D. Bertetti ◽

R. Nicoletti ◽

M. L. Gullino

Keyword(s):

United States ◽

Rhizoctonia Solani ◽

The United States ◽

The Philippines ◽

Lantana Camara ◽

First Report ◽

Leaf Spots ◽

Entire Plant ◽

Pathogenicity Tests ◽

Web Blight

Lantana camara is increasingly grown in northern Italy as a potted plant and contributes to the diversification of offerings in the ornamental market. During the spring of 2001, selections of L. camara cuttings growing at a commercial farm located at Albenga (Riviera coast) exhibited tan leaf spots of irregular size and shape. Spots were at first isolated, 4 to 8 mm in diameter, and later coalesced and affected the entire plant. Heavily infected leaves, stems, and branches became blighted and were killed. Infected rooted cuttings also eventually died. Diseased cuttings showed a progressive reduction (to less than 20%) in rooting ability. Isolations from infected leaves and stems on potato dextrose agar (PDA), supplemented with 100 mg/liter of streptomycin sulphate, consistently yielded a fungus with mycelial and cultural characteristics resembling Rhizoctonia solani. The fungal isolates were further characterized as R. solani Kühn AG-4 based on hyphal anastomoses with several AG-4 tester isolates. Pathogenicity tests were performed by placing 5-day-old-fungal mycelial plugs, grown on PDA, at the base of five healthy yellow-sage stems and holding plants in a dew chamber at 18 to 22°C. After 2 days, foliage blight appeared on leaves of inoculated plants, and after 3 days, stems also became infected and entire plants wilted. Five noninoculated plants remained healthy. The fungal pathogen was reisolated from all inoculated plants. R. solani has been observed on L. camara in the United States (1) and the Philippines (2). To our knowledge, this is the first report of R. solani on L. camara in Europe. References: (1) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN, 1989. (2) F. T. Orillo and R. B. Valdez. Philipp. Agric. A. 42:292, 1958.

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First Report of Bacterial Leaf Spot of Spinach Caused by a Pseudomonas syringae Pathovar in California

Plant Disease ◽

10.1094/pdis.2002.86.8.921a ◽

2002 ◽

Vol 86 (8) ◽

pp. 921-921 ◽

Cited By ~ 3

Author(s):

S. T. Koike ◽

H. R. Azad ◽

D. C. Cooksey

Keyword(s):

Brassica Oleracea ◽

Beta Vulgaris ◽

Pseudomonas Syringae ◽

Leaf Spot ◽

The United States ◽

Nutrient Broth ◽

Bacterial Leaf Spot ◽

First Report ◽

Leaf Spots ◽

Initial Symptoms

In 2000 and 2001, a new disease was observed on commercial spinach (Spinacia oleracea) in the Salinas Valley, Monterey County, CA. Initial symptoms were water-soaked, irregularly shaped leaf spots (2 to 3 mm diameter). As the disease developed, spots enlarged to as much as 1 to 2 cm, were vein-delimited, and turned dark brown. Faint chlorotic halos sometimes surrounded the spots. Death of large areas of the leaf occurred if spots coalesced. Spots were visible from the adaxial and abaxial sides of leaves, and no fungal structures were observed. The disease occurred on newly expanded and mature foliage. No fungi were isolated from the spots. However, cream-colored bacterial colonies were consistently isolated on sucrose peptone agar, and these strains were nonfluorescent on King's medium B. Strains were positive for levan and negative for oxidase, arginine dihydrolase, and nitrate reductase. Strains did not grow at 36°C, did not rot potato slices, but induced a hypersensitive reaction in tobacco (Nicotiana tabacum cv. Turk). These results suggested the bacterium was similar to Pseudomonas syringae. Fatty acid methyl ester (FAME) analysis (MIS-TSBA 4.10, MIDI Inc., Newark, DE) indicated the strains were highly similar (80.1 to 89.3%) to P. syringae pv. maculicola. However, in contrast to P. syringae pv. maculicola, the spinach strains did not utilize the carbon sources erythritol, L+tartrate, L lactate, and DL-homoserine. Pathogenicity of 10 strains was tested by growing inoculum in nutrient broth shake cultures for 48 h, diluting to 106 CFU/ml, and spraying 4-week-old plants of spinach cv. Bossanova. Control plants were sprayed with sterile nutrient broth. After 5 to 8 days in a greenhouse (24 to 26°C), leaf spots identical to those observed in the field developed on cotyledons and true leaves of inoculated plants. Strains were reisolated from the spots and identified as P. syringae. Control plants remained symptomless. The 10 strains were also inoculated on beet (Beta vulgaris), Swiss chard (Beta vulgaris subsp. cicla), cilantro (Coriandrum sativum), and spinach. Spinach showed leaf spots after 8 days; however, none of the other plants developed symptoms. Two strains were inoculated onto spinach cvs. Califlay, Lion, Nordic IV, Polka, Resistoflay, Rushmore, RZ 11, Spinnaker, Springfield, Viroflay, and Whitney. Leaf spot developed on all cultivars, and the pathogen was reisolated. Because the FAME data indicated a similarity between the spinach pathogen and P. syringae pv. maculicola, we inoculated sets of spinach cv. Bolero, cabbage (Brassica oleracea subsp. capitata cv. Grenedere), and cauliflower (Brassica oleracea subsp. botrytis cv. White Rock) with three P. syringae pv. maculicola and three spinach strains. Cabbage and cauliflower developed leaf spots only when inoculated with P. syringae pv. maculicola; spinach had leaf spots only when inoculated with the spinach strains. All inoculation experiments were done twice, and the results of the two tests were the same. To our knowledge, this is the first report of bacterial leaf spot of spinach in California caused by a nonfluorescent P. syringae, and the first record of this disease in the United States. Biochemical characteristics and limited host range of the pathogen indicate the California strains are likely the same as the P. syringae pv. spinaciae pathogen that was reported in Italy (1) and Japan (2). References: (1) C. Bazzi et al. Phytopathol. Mediterr. 27:103, 1988. (2) K. Ozaki et al. Ann. Phytopathol. Soc. Jpn. 64:264, 1998.

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First Report of Leaf Spot Caused by a Cercosporella sp. on Centaurea solstitialis in Greece

Plant Disease ◽

10.1094/pdis.2004.88.12.1382a ◽

2004 ◽

Vol 88 (12) ◽

pp. 1382-1382 ◽

Cited By ~ 1

Author(s):

F. M. Eskandari ◽

D. K. Berner ◽

J. Kashefi ◽

L. Strieth

Keyword(s):

United States ◽

Biological Control ◽

Biological Control Agent ◽

Aqueous Suspension ◽

The United States ◽

Centaurea Solstitialis ◽

Voucher Specimen ◽

Disease Symptoms ◽

First Report ◽

Leaf Spots

Centaurea solstitialis L. (yellow starthistle [YST]), family Asteraceae, an invasive weed in California and the western United States is targeted for biological control. During the spring of 2004, an epidemic of dying YST plants was found near Kozani, Greece (40°22′07″N, 21°52′35″E, 634 m elevation). Rosettes of YST had small, brown leaf spots on most of the lower leaves. In many cases, these spots coalesced and resulted in necrosis of many of the leaves and death of the rosette. Along the roadside where the disease was found, >100 of the YST plants showed disease symptoms. Diseased plants were collected, air dried, and sent to the quarantine facility of the Foreign Disease-Weed Science Research Unit (FDWSRU), USDA, ARS, Fort Detrick, MD. Diseased leaves were surface disinfested and placed on moist filter paper in petri dishes. Conidiophores and conidia were observed after 48 h. The fungal isolate, DB04-011, was isolated from these diseased leaves. Pathogenicity tests were performed by spray inoculating the foliage of 20 4-week-old YST rosettes with an aqueous suspension of 1 × 106 conidia per ml. Conidia were harvested from 2-week-old cultures grown on modified potato carrot agar (MPCA). Inoculated plants were placed in an environmental chamber at 23°C with 8 h of daily light and continuous dew for 48 h. Inoculated and control plants were moved to a 20°C greenhouse bench and watered twice per day. After 7 days, leaf spots were observed first on lower leaves. After 10–12 days, all inoculated plants showed typical symptoms of the disease. No symptoms developed on control plants. The pathogen, DB04-011, was consistently isolated from symptomatic leaves of all inoculated plants. Disease symptoms were scattered, amphigenous leaf spots in circular to subcircular spots that were 0.2 to 7 mm in diameter and brownish with distinct dark green margins. Intraepidermal stromata, 14 to 77 μm in diameter and pale yellow to brown, were formed within the spots. Conidiophores that arose from the stromata were straight, subcylindrical, simple, 70 to 95 × 2.8 to 4 μm, hyaline, smooth, and continuous or septate with conidial scars that were somewhat thickened, colorless, and refractive. Primary conidia were subcylindrical, slightly obclavate or fusiform, ovoid, 21 to 49 × 5 to 7.5 μm, 0 to 5 septate, hyaline, smooth, had a relatively rounded apex, and the hilum was slightly thickened. Conidial dimensions on MPCA were 11.2 to 39.2 × 4.2 to 7 μm (average 25.5 × 5.5 μm). Koch's postulates were repeated two more times with 20 and 16 plants. On the basis of fungal morphology, the organism was identified as a Cercosporella sp., (1,2; U. Braun and N. Ale-Agha, personal communication). To our knowledge, this is the first report of this genus of fungus parasitizing YST. Results of host range tests will establish if this isolate of Cercosporella has potential as a biological control agent of YST in the United States. A voucher specimen has been deposited with the U.S. National Fungus Collections (BPI 844247). Live cultures are being maintained at FDWSRU and European Biological Control Laboratoryt (EBCL), Greece. References: (1) U. Braun. A Monograph of Cercosporella, Ramularia and Allied Genera (Phytopathogenic Hyphomycetes) Vol. 1. IHW-Verlage, Eching-by-Munich, 1995. (2) U. Braun. A Monograph of Cercosporella, Ramularia and Allied Genera (Phytopathogenic Hyphomycetes) Vol. 2. IHW-Verlage, 1998.

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First Report of Leaf Spot of Sesame Caused by Xanthomonas sp. In the United States

Plant Disease ◽

10.1094/pdis-03-12-0284-pdn ◽

2012 ◽

Vol 96 (8) ◽

pp. 1222-1222 ◽

Cited By ~ 2

Author(s):

T. Isakeit ◽

B. T. Hassett ◽

K. L. Ong

Keyword(s):

United States ◽

Leaf Area ◽

Its Region ◽

The United States ◽

Pcr Analysis ◽

Sterile Water ◽

First Report ◽

Genomic Dna Isolation ◽

Leaf Spots ◽

Mist Chamber

In July 2010 in Texas, extensive leaf spots (10 to 30% leaf area affected) occurred on a commercial planting of sesame (Sesamum indicum L.) in Hidalgo County and to a lesser extent (1 to 5% leaf area) on leaves of several varieties in experimental trials in Colorado and Victoria Counties. The leaf spots were light to dark brown, somewhat circular, and 1 to 3 mm in diameter. A symptomatic leaf from each of three to five plants per county was sampled for isolations. Leaves were sprayed with 70% ethanol and immediately blotted dry with a paper towel. The margins of spots (2 mm2) were excised with a scalpel and placed in a drop of sterile water for 5 min. Drops were streaked on nutrient agar (NA) and incubated at 30°C. The 12 isolations consistently yielded gram-negative, rod-shaped bacteria with yellow, translucent colonies that were visible after 2 days of incubation. The DNA of 11 isolates was extracted with the Norgen (Thorold, ON) Bacterial genomic DNA isolation kit (Cat. #17900) and the ITS region was amplified by 16S uni 1330 and 23S uni 322 anti primers (1). PCR products were treated with the ZymoResearch (Irvine, CA) DNA clean & concentrator kit (Cat. #D4003) and sequenced. With the NCBI database, a BLAST search of the 1,100 bp amplicons showed 93 to 99% identity with pathovars of either Xanthomonas oryzae or X. axonopodis (GenBank Accession Nos. CP003057.1 and CP002914.1, respectively). Amplicon sequences of the sesame isolates were deposited in GenBank as Accession Nos. JQ975037 through JQ975047. The reported species on sesame is X. campestris pv. sesami (2). To fulfill Koch's postulates, potted sesame plants (var. Sesaco 25), 15 to 20 cm tall, were sprayed until runoff with a suspension of bacteria (106 to 107 CFU/ml) from a 2-day-old NA culture. All 12 isolates were evaluated, with five to seven plants per isolate. Plants were maintained in a mist chamber in a greenhouse at 27 to 30°C and 100% relative humidity. The pathogenicity trial was repeated once. Leaf spots were first seen 7 days after inoculation and were prevalent 14 days after inoculation. All 12 isolates were pathogenic. There were no symptoms on leaves sprayed with sterile water. Bacteria that produced colonies consistent with Xanthomonas were reisolated on NA from symptomatic leaves but not from controls. The identities of three isolates were reconfirmed with PCR analysis and sequencing. In 2007, more than 2,000 ha of sesame were grown in the continental United States, with 80% of that in Texas. Currently, acreage of shatter-free varieties of sesame is increasing in arid areas of Texas, Oklahoma, and Kansas. In such areas, the yield impact of this disease is likely to be minimal, except in years with above-average rainfall. To our knowledge, this is the first report of this disease in the United States. References: (1) E. R. Gonçalves and Y. B. Rosato. Int. J. Syst. Evol. Microbiol. 52:355, 2002. (2) J. M. Young et al., New Zealand J. Agric. Res. 21:153, 1978.

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First Report of Leaf Spot Caused by Cercospora bizzozeriana on Lepidium draba in the United States

Plant Disease ◽

10.1094/pdis-93-1-0108b ◽

2009 ◽

Vol 93 (1) ◽

pp. 108-108 ◽

Cited By ~ 1

Author(s):

A. J. Caesar ◽

R. T. Lartey ◽

D. K. Berner ◽

T. Souissi

Keyword(s):

United States ◽

North America ◽

Sugar Beet ◽

Leaf Spot ◽

The United States ◽

Initial Report ◽

Voucher Specimen ◽

First Report ◽

Leaf Spots ◽

Lepidium Draba

The herbaceous perennial Lepidium draba L. is an invasive weed of rangelands and riparian areas in North America and Australia. As of 2002, it had infested 40,500 ha of rangeland in Oregon and large areas in Wyoming and Utah. Little is known of plant pathogens occurring on L. draba, especially in the United States, that could be useful for biological control of the weed. Leaf spots were first noted on a stand of L. draba near Shepherd, MT in 1997. The spots were mostly circular but sometimes irregularly shaped and whitish to pale yellow. The pathogen was erroneously assumed to be Cercospora beticola since its morphological traits closely resembled that species and the area had large fields of sugar beet with heavy Cercospora leaf spot incidence. Diseased leaves of L. draba were collected in 1997 and 2007. Conidia, borne singly on dark gray, unbranched conidiophores produced on dark stromata late in the season, were elongate, hyaline, multiseptate, 38 to 120 × 2 to 6 μm (mostly 38 to 50 × 2 to 5 μm) and had bluntly rounded tips and wider, truncate bases. These characteristics were consistent with the description of C. bizzozeriana Saccardo & Berlese (2). To isolate the fungus, spores were picked from fascicles of conidiophores with a fine-tipped glass rod, suspended in sterile water, and spread on plates of water agar. Germinated spores were transferred to potato dextrose agar (PDA). The ITS1, 5.8S, and ITS2 sequences of this fungus (GenBank Accession No. EU887131) were identical to sequences of an isolate of C. bizzozeriana from Tunisia (GenBank Accession No. DQ370428). However, these sequences were also identical to those of a number of Cercospora spp. in GenBank, including C. beticola. We also compared the actin gene sequences of the Montana isolate of C. bizzozeriana (GenBank Accession No. FJ205397) and an isolate of C. beticola from Montana (GenBank Accession No. AF443281); the sequences were 94.6% similar, an appreciable difference. For pathogenicity tests, cultures were grown on carrot leaf decoction agar. Aqueous suspensions of 104 spores per ml from cultures were sprayed on 6-week-old L. draba plants. Plants were covered with plastic bags and placed on the greenhouse bench at 20 to 25°C for 96 h. Koch's postulates were completed by reisolating the fungus from the circular leaf spots that appeared within 10 days, usually on lower leaves. Spores of C. bizzozeriana were also sprayed on seedlings of sugar beet, collard, mustard, radish, cabbage, and kale under conditions identical to those above. No symptoms occurred. After the discovery of the disease in 1997, plants of L. draba in eastern Montana, Wyoming, and Utah were surveyed from 1998 to 2003 for similar symptoms and signs, but none were found. This, to our knowledge, is the first report of C. bizzozeriana in the United States. The initial report of the fungus in North America was from Manitoba in 1938 (1). It has recently been reported as occurring on L. draba in Tunisia (4) and Russia (3) and is reported as common in Europe (2). A voucher specimen has been deposited with the U.S. National Fungus Collections (BPI No. 878750A). References: (1) G. R. Bisby. The Fungi of Manitoba and Saskatchewan. Natl. Res. Council of Canada, Ottawa, 1938. (2) C. Chupp. A Monograph of the Fungus Genus Cercospora. C. Chupp, Ithaca, NY, 1953. (3) Z. Mukhina et al. Plant Dis. 92:316, 2008. (4) T. Souissi et al. Plant Dis. 89:206, 2005.

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First Report of a Leaf Spot Caused by Cercospora bizzozeriana on Lepidium draba subsp. draba in Tunisia

Plant Disease ◽

10.1094/pd-89-0206a ◽

2005 ◽

Vol 89 (2) ◽

pp. 206-206

Author(s):

T. Souissi ◽

D. K. Berner ◽

H. J. Dubin

Keyword(s):

United States ◽

Biological Control ◽

Biological Control Agent ◽

Aqueous Suspension ◽

The United States ◽

Voucher Specimen ◽

First Report ◽

Leaf Spots ◽

White Leaf ◽

Lepidium Draba

Lepidium draba (L.) subsp. draba (synonym = Cardaria draba (L.) Desv.), commonly known as white-top or hoary-cress (1), family Brassicaceae, is a common weed and emerging problem in wheat in Tunisia. It is also a problematic invasive weed in the northwestern United States and a target of biological control efforts. During the summer of 2002, dying L. draba plants were found around Tunis, Tunisia. Plants had grayish white leaf spots on most of the leaves. In some cases, the leaf spots dropped out of the leaves producing “shot-holes”. In most cases, the leaf spots coalesced, and the leaves wilted and died. Diseased leaves were collected, air-dried, and sent to the quarantine facility of the Foreign Disease-Weed Science Research Unit (FDWSRU), USDA/ARS, Fort Detrick, MD. The air-dried leaves were observed microscopically, and numerous conidiophores and conidia were observed on both sides of the leaves within and around the lesions. The fungus isolated (DB03-009) conformed to the description of Cercospora bizzozeriana Saccardo & Berlese (2). Conidiophores were unbranched, pale olive-brown, 1 to 5 geniculate, and uniform in color and width. Conidia were hyaline, straight to slightly curved, multiseptate, and 57 to 171 × 3.8 to 6.7 µm (average 103 to 4.6 µm). Stems and leaves of 12 rosettes (10 to 15 cm in diameter) of 6-week-old L. draba plants were spray inoculated with an aqueous suspension of conidia (1 × 105/ml) harvested from 6- to 8-day-old cultures grown on carrot leaf decoction agar. Six of the plants and two noninoculated plants were placed in a dew chamber at 22°C in darkness and continuous dew. The other half of the plants and two noninoculated plants were placed on a greenhouse bench at approximately 25°C and covered with clear polyethylene bags. After 72 h, plants from the dew chamber were moved to a greenhouse bench, and the bagged plants were uncovered. All plants were watered twice daily. After 9 days, symptoms were observed on the plants that had been bagged but not on the plants from the dew chamber. Symptoms were identical to those observed in the field in Tunisia and included “shot holes”. No symptoms were observed on noninoculated plants. C. bizzozeriana was reisolated from the leaves of all symptomatic plants. Completion of Koch's postulates was repeated with an additional five plants. This isolate of C. bizzozeriana is a destructive pathogen on L. draba subsp. draba, and severe disease can be produced by inoculation of foliage with an aqueous suspension of conidia. This isolate is a good candidate for mycoherbicide development in Tunisia where the weed and pathogen are indigenous. However, some commercially grown Brassica species were found susceptible to this isolate, which will preclude its use as a classical biological control agent in the United States. To our knowledge, this is the first report of C. bizzozeriana on L. draba subsp. draba in Tunisia. A voucher specimen has been deposited at the U.S. National Fungus Collections (BPI 843753). Live cultures are being maintained at FDWSRU and the Institut National Agronomique de Tunisie, Tunis, Tunisia. References: (1) I. A. Al-Shehbaz and K. Mummenhoff. Novon 12:5, 2002. (2) C. Chupp. A Monograph of the Fungus Genus Cercospora. C. Chupp, Ithaca, New York, 1953.

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First Report of Bacterial Spot of Tomato Caused by Xanthomonas gardneri in Pennsylvania

Plant Disease ◽

10.1094/pdis-94-5-0638b ◽

2010 ◽

Vol 94 (5) ◽

pp. 638-638 ◽

Cited By ~ 9

Author(s):

S. H. Kim ◽

T. N. Olson ◽

N. D. Peffer ◽

E. V. Nikolaeva ◽

S. Park ◽

...

Keyword(s):

United States ◽

Type Strain ◽

Tap Water ◽

The United States ◽

Nutrient Broth ◽

Rrna Gene ◽

Bacterial Spot ◽

Tomato Plants ◽

First Report ◽

Leaf Spots

Recent investigation of bacteria isolated from samples submitted to the Plant Disease Diagnostic Laboratory, Pennsylvania Department of Agriculture indicated that in 1995, Xanthomonas gardneri (ex Sutic 1957) (2) caused a leaf spot on tomato plants (Lycopersicon esculentum Mill.). In 1995, we examined 185 tomato and 36 pepper samples (13 field, 2 garden center, 38 greenhouse, 4 residence, 16 field-grown transplant, and 148 greenhouse-grown transplant samples). A processing company representative collected samples showing symptoms of bacterial spot of tomato on a hybrid, whole pack processing tomato, from a 16-ha field in Northumberland County, PA exhibiting almost 50% crop infection. Symptoms consisted of circular- to irregularly shaped, dark brown spots, <5 mm in diameter, and frequently with chlorotic haloes on leaves and stems. The center of a spot may be raised and scabby. Several spots on a single leaflet may coalesce and a portion or the entire leaflet may turn yellow or die. These symptoms were indistinguishable from those of bacterial spot caused by X. euvesicatoria, X. vesicatoria, and X. perforans. Bacterial streaming from lesions was evident under dark-field microscopy. Aerobic, gram-negative, yellow-pigmented, mucoid bacteria were isolated from the leaf spots and purified and stored in nutrient broth with 10% glycerol at –80°C. The 16S rRNA gene from a strain (PDA80951-95) typical of the cultures from these samples was sequenced (GenBank Accession No. GU573763). A BlastN search of GenBank revealed 100% nucleotide identity with the type strain of X. gardneri (XCGA2; No. AF123093). This strain also exhibited repetitive sequence-based (rep)-PCR profiles (4) identical to profiles of X. gardneri type strain XCGA2 DNA and produced a ~425-bp PCR product with BSX primers, a genetic marker indicative of X. gardneri (1). The strain was not amylolytic or pectolytic (2) and failed to utilize maltose, gentiobiose, and melezitose (3). For pathogenicity tests, inoculum was grown in nutrient broth with shaking for 24 h at 28°C. Inoculum was centrifuged, resuspended in sterile tap water, and adjusted to 2.5 × 108 CFU/ml. Lower leaf surfaces of tomato (cvs. Bonnie Best and Walter) and pepper (cvs. California Wonder and Early Niagara) plants were gently rubbed with sterile cheesecloth that was moistened with the inoculum. Strain PDA80951-95 caused leaf spots, with chlorotic haloes and occasional coalescence on both tomato and pepper, within 2 weeks at 15 s of mist per 20 min at 20 to 35°C in a secured greenhouse chamber. X. gardneri was only reisolated from symptomatic plants and its identity was confirmed by rep-PCR and absence of amylolytic and pectolytic activities. Negative controls consisting of X. campestris pv. campestris and sterile tap water did not show symptoms. A known type strain of X. gardneri was not included as a positive control for pathogenicity studies because this species is not known to occur in the United States (2). To our knowledge, this is the first report of bacterial spot on tomato plants caused by X. gardneri in Pennsylvania and the United States. Since the first occurrence in 1995, bacterial spot caused by X. gardneri reoccurred in Pennsylvania tomato fields in 2001 and consecutively from 2003 to 2009. Reference: (1) D. A. Cuppels et al. Plant Dis. 90:451, 2006. (2) J. B. Jones et al. Syst. Appl. Microbiol. 27:755, 2004. (3) A. M. Quezado-Duval et al. Plant Dis. 88:15, 2004. (4) D. J. Versalovic et al. Methods Mol. Cell Biol. 5:25, 1994.

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First Report of Downy Mildew Caused by Peronospora lamii on Salvia splendens and Salvia coccinea

Plant Disease ◽

10.1094/pdis.2000.84.10.1154b ◽

2000 ◽

Vol 84 (10) ◽

pp. 1154-1154 ◽

Cited By ~ 5

Author(s):

G. E. Holcomb

Keyword(s):

United States ◽

Downy Mildew ◽

Pathogenic Fungi ◽

The United States ◽

Commonwealth Mycological Institute ◽

First Report ◽

Leaf Spots ◽

Salvia Splendens ◽

Leaf Surfaces ◽

Pathogenicity Tests

Angular chlorotic spots were observed on adaxial leaf surfaces of Salvia splendens (scarlet sage cvs. Empire Purple, Empire White, Red Pillar, and Red Hot Sally) and S. coccinea (scarlet or Texas sage cv. Lady in Red) in early May in Baton Rouge area nurseries. Leaf spots sometimes became necrotic and resulted in leaf drop. Abaxial leaf surfaces contained scattered patches of white mycelia with brown spores. Microscopic examination of mycelia revealed irregular dichotomously branched conidiophores with pointed tips and brown oval conidia. Conidiophores averaged 485 × 9 µm and conidia averaged 21 × 18 µm (16 to 26 × 15 to 23 µm) in dimensions. The fungus was identified as Peronospora lamii A. Braun (= P. swinglei Ellis & Everh.) based on these characters and its known occurrence on Salvia spp. and five other genera in the family Lamiaceae (2). Pathogenicity tests were performed by washing conidia from infected leaves into distilled water and mistinoculating S. coccinea cv. Lady in Red and S. splendens cv. Empire Purple with 50,000 spores/ml. Plants were held in a dew chamber at 20°C for 3 days, then moved to a greenhouse where temperatures ranged from 18 to 32°C. Typical angular chlorotic leaf spots developed on inoculated plants within 6 to 8 days and noninoculated plants remained healthy. The fungus did not sporulate under these greenhouse temperatures, but infected leaves that were removed and placed in a moist chamber at 25°C produced conidiophores and brown conidia typical of P. lamii within 2 to 3 days. P. lamii has been reported previously on S. officinalis (3) and S. reflexa (1) in the United States. This is the first report of downy mildew on S. coccinea and S. splendens. Appearance of the disease in retail nurseries that obtained plants from out of state (Arkansas) suggests a widespread occurrence of the disease on these host plants. References: (1) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN. (2) S. M. Francis. 1981. Peronospora lamii. Descriptions of Pathogenic Fungi and Bacteria No. 688. Commonwealth Mycological Institute, Kew, England. (3) R. T. McMillan and W. R. Graves. Plant Dis. 78:317, 1994.

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First Report of Botrytis cinerea Causing Leaf Spot of Aquilegia vulgaris in Japan

Plant Disease ◽

10.1094/pdis-93-4-0425a ◽

2009 ◽

Vol 93 (4) ◽

pp. 425-425 ◽

Cited By ~ 2

Author(s):

M. Zhang ◽

T. Tsukiboshi ◽

I. Okabe

Keyword(s):

United States ◽

Botrytis Cinerea ◽

Leaf Spot ◽

Leaf Tissue ◽

The United States ◽

Plant Diseases ◽

Its2 Region ◽

Commonwealth Mycological Institute ◽

First Report ◽

Leaf Spots

European columbine, Aquilegia vulgaris L., Ranunculaceae, is an herbaceous flower widely used in gardens, parterres, and courtyards and is a traditional herbal plant. During the summer of 2008, leaf spots were observed on a plant cultivated along a roadside area in Nasushiobara, Tochigi, Japan. In some courtyards, the leaf spot affected more than 60% of the plants. Early symptoms appeared as small, round or elliptic, brown lesions on the leaves. Lesions expanded to 5 to 15 × 4 to 10 mm, irregular spots that were dark brown to black in the middle, with pale yellow-brown or purple-brown margins. In continuously wet or humid conditions, thick, gray mycelium and conidia appeared on the surface of leaf spots. Conidiophores were melanized at the base and hyaline near the apex, branched, and septated (approximately 3 mm × 16 to 18 μm). Conidia were hyaline, aseptate, ellipsoidal to obovoid, with a slightly protuberant hilum, and ranged from 9 to 14.5 × 5.5 to 6.5 μm. The pathogen was identified as Botrytis cinerea Pers.:Fr on the basis of morphology and sequence of ITS1-5.8s-ITS2 region of rDNA. The sequence (GenBank Accession No. FJ424510) exactly matched the sequences of two Botryotinia fuckeliana (anamorph Botrytis cinerea), (e.g., GenBank Accession Nos. AY686865 and FJ169666) (2). The fungus was isolated on potato dextrose agar (PDA) from a single conidium found on the symptomatic leaf tissue. Colonies of B. cinerea were first hyaline and later turned gray to black when the spores differentiated. Koch's postulates were performed with three whole plants of potted aquilegia. Leaves were inoculated with mycelia plugs harvested from the periphery of a 7-day-old colony; an equal number of plants were inoculated with the plugs of PDA medium only and served as controls. All plants were covered with plastic bags for 24 h to maintain high relative humidity and incubated at 25°C. After 8 days, all mycelium-inoculated plants showed symptoms identical to those observed on leaves from A. vulgaris infected in the field, whereas controls remained symptom free. Reisolation of the fungus from lesions on inoculated leaves confirmed that the causal agent was B. cinerea. B. cinerea has been previously reported on A. vulgaris in the United States and China (1,3). To our knowledge, this is the first report of leaf spots caused by B. cinerea on A. vulgaris in Japan. References: (1) Anonymous. Index of Plant Diseases in the United States. USDA Agric. Handb. No 165, 1960. (2) M. B. Ellis. Dematiaceous Hyphomycetes. Commonwealth Mycological Institute, Kew, England, 1971. (3) Z. Y. Zhang. Flora Fungorum Sinicorum. Vol. 26. Botrytis, Ramularia. Science Press, Beijing, 2006.

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