First Report of Zonate Leaf Spot Caused by Hinomyces moricola on Japanese Hop in Korea

Japanese hop (Humulus japonicus Siebold & Zucc. = H. scandens (Lour.) Merr.), native to East Asia, is an annual, climbing or trailing vine. The vines can spread to cover large areas of open ground or low vegetation, eventually blanketing the land and vegetation. Pollen of H. japonicus is allergenic, and this species is considered as one of the important causes of pollinosis in Korea and China. It is a notorious invasive weed in the United States and also in France, Hungary, and Italy (1). In September 2012, zonate leaf spots were observed on Japanese hops growing in wetlands in Yeongdong County of Korea. A voucher specimen was preserved in the Korea University Herbarium (KUS-F26901). Initial symptoms included grayish-green to grayish-brown spots without border lines. As the lesions enlarged, they coalesced, leading to leaf blight. Sporophores on the leaf lesions were dominantly hypophyllous, rarely epiphyllous, solitary, erect, easily detachable, and as long as 700 μm. The upper portion of the sporophores consisted of a pyramidal head was ventricose, 320 to 520 μm long and 110 to 150 μm wide. The fungus was isolated from leaf lesions and maintained on potato dextrose agar (PDA). Sclerotia were produced on PDA after 4 to 5 weeks at 18°C without light, but conidia were not observed in culture. These morphological and cultural characteristics were consistent with those of Hinomyces moricola (I. Hino) Narumi-Saito & Y. Harada (= Cristulariella moricola (I. Hino) Redhead) (3,4). An isolate was preserved in the Korean Agricultural Culture Collection (Accession No. KACC46955). Genomic DNA was extracted using the DNeasy Plant Mini DNA Extraction Kit (Qiagen Inc., Valencia, CA). The complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced. The resulting sequence of 452 bp was deposited in GenBank (Accession No. KC460209). A BLAST search in GenBank revealed that the sequence showed an exact match with those of C. moricola (JQ036181 ex Acer negundo and JQ036182 ex Glycine max). To determine the pathogenicity of the fungus, according to the procedure of Cho et al. (2), sporophores with the pyramidal head were carefully detached from a lesion on the naturally infected leaf using a needle. Each sporophore was transferred individually onto five places of four detached healthy leaves. The leaves were placed in dew chambers and incubated at 16°C. Symptoms were observed after 2 days on all inoculated leaves. A number of sporophores and immature sclerotia which were morphologically identical to the ones observed in the field were formed on the abaxial surface of the leaf 2 weeks after inoculation. The pathogen was reisolated from lesions on the inoculated leaves, confirming Koch's postulates. No symptoms were observed on the control leaves kept in humid chambers for 2 weeks. H. moricola was known to cause zonate leaf spots and defoliation on a wide range of woody and annual plants (3). To the best of our knowledge, this is the first report of Hinomyces infection on Japanese hops in Korea. References: (1) Anonymous. Humulus japonicus (Cannabaceae): Japanese hop. Eur. Medit. Plant Prot. Org. (EPPO). 2012. (2) S. E. Cho et al. Plant Dis. 96:906, 2012. (3) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab., Online publication, ARS, USDA, Retrieved December 8, 2012. (4) S. A. Redhead. Can. J. Bot. 53:700, 1975.

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First Report of Zonate Leaf Spot of Glycine max Caused by Cristulariella moricola in Korea

Plant Disease ◽

10.1094/pdis-01-12-0028-pdn ◽

2012 ◽

Vol 96 (6) ◽

pp. 906-906 ◽

Cited By ~ 1

Author(s):

S. E. Cho ◽

J. H. Park ◽

J. K. Choi ◽

H. D. Shin

Keyword(s):

Glycine Max ◽

Its Region ◽

Economic Losses ◽

Mountainous Area ◽

Potential Threat ◽

Voucher Specimen ◽

First Report ◽

Leaf Spots ◽

Initial Symptoms ◽

Wide Range

Soybean (Glycine max (L.) Merr.) is native to East Asia including Korea and is widely grown and consumed as an edible seed. In August 2011, following a prolonged period of cool and moist weather, zonate leaf spots were observed in local soybean (cultivar unknown) planted in a mountainous area of Goseong, central Korea. A voucher specimen was collected and entered at the Korea University herbarium (KUS-F26049). Initial symptoms included grayish green-to-grayish brown spots without border lines. As the lesions enlarged, they coalesced, leading to leaf blight and premature defoliation. Sporophores on the leaf lesions were dominantly hypophyllous, rarely epiphyllous, solitary, erect, easily detachable, and as long as 750 μm. The upper portion of the sporophores consisted of a pyramidal head that was ventricose, 275 to 500 μm long, and 80 to 160 μm wide. The fungus was isolated from leaf lesions and maintained on potato dextrose agar (PDA). Sclerotia were produced on PDA after 4 to 5 weeks at 18°C without light, but conidia were not observed in culture. The morphological and cultural characteristics were consistent with those of Cristulariella moricola (Hino) Redhead (2,3). An isolate was preserved in the Korean Agricultural Culture Collection (KACC46401). Genomic DNA was extracted with the DNeasy Plant Mini DNA Extraction Kit (Qiagen Inc., Valencia, CA). The complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced. The resulting sequence of 453 bp was deposited in GenBank (Accession No. JQ036182). A BLAST search in GenBank revealed that the sequence showed an exact match with that of C. moricola from Acer negundo (JQ036181) and >99% similarity with that of Grovesinia pyramidalis, teleomorph of C. moricola from Juglans sp. (Z81433). To determine the pathogenicity of the fungus, sporophores with the pyramidal head were carefully detached from a lesion on the naturally infected leaflet with fine needles. Each sporophore was transferred individually onto four places of six detached healthy soybean leaflets. The leaflets were placed in humid chambers at 100% relative humidity and incubated at 16 to 20°C (4). Symptoms were observed after 2 days on all inoculated leaflets (one to four lesions/leaflet). The lesions enlarged rapidly and reached ~20 mm diameter in a week. A number of sporulating structures and immature sclerotia were formed on the abaxial surface of the leaf 2 weeks after inoculation. The pathogen was reisolated from lesions on the inoculated leaflets, confirming Koch's postulates. No symptoms were observed on the control leaflets kept in humid chambers for 2 weeks. C. moricola was known to cause zonate leaf spots and defoliation on a wide range of woody and annual plants (1), but not on G. max. To our knowledge, this is the first report of Cristulariella infection in cultivated soybeans. Since the infections may be limited to the mountainous area with low night temperature and high humidity, economic losses seem to be negligible. However, the disease could be a potential threat to the safe production of soybeans in areas with prolonged periods of cool and moist weather. References: (1) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.arsgrin.gov/fungaldatabases/ , January 7, 2012. (2) H. B. Lee and C. J. Kim. Plant Dis. 86:440, 2002. (3) S. A. Redhead. Can. J. Bot. 53:700, 1975. (4) H. J. Su and S. C. Leu. Plant Dis. 67:915, 1983.

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First Report of Leaf Spot Caused by Phyllosticta yuccae on Yucca filamentosa in Brazil

Plant Disease ◽

10.1094/pdis-04-13-0384-pdn ◽

2013 ◽

Vol 97 (9) ◽

pp. 1257-1257 ◽

Cited By ~ 1

Author(s):

A. D. A. Silva ◽

D. B. Pinho ◽

B. T. Hora Junior ◽

O. L. Pereira

Keyword(s):

Leaf Spot ◽

Its Region ◽

The United States ◽

Leaf Spot Disease ◽

Infected Leaf ◽

Single Spore ◽

First Report ◽

Leaf Spots ◽

Slime Layer ◽

Pure Cultures

Yucca filamentosa L. (Agavaceae), commonly known as Adam's needle, is known in Brazil as “agulha-de-adão.” It is an ornamental garden plant with medicinal properties (4). In 2010, 100% of Y. filamentosa seedlings and plants were observed with a severe leaf spot disease in two ornamental nurseries located in the municipality of Viçosa, Minas Gerais, Brazil. Initially, lesions were dark brown, elliptical, and scattered, and later became grayish at the center with a reddish brown margin, irregular and coalescent. Infected leaf samples were deposited in the herbarium at the Universidade Federal de Viçosa (Accession Nos. VIC32054 and VIC32055). A fungus was isolated from the leaf spots and single-spore pure cultures were obtained on potato dextrose agar (PDA). The sporulating single-spore cultures were deposited at the Coleção de Culturas de Fungos Fitopatogênicos “Prof. Maria Menezes” (CMM 1843 and CMM 1844). On the leaf, the fungus produced pycnidial conidiomata that were scattered or gregarious, usually epiphyllous, immersed, dark brown, unilocular, subglobose, and 95 to 158 × 108 to 175 μm, with a minute, subcircular ostiole. Conidiogenous cells were blastic, hyaline, conoidal, or short cylindrical. Conidia were aseptate, hyaline, smooth walled, coarsely granular, broadly ellipsoidal to subglobose or obovate, usually broadly rounded at both ends, occasionally truncate at the base or indented slightly at the apex, and 7.5 to 13.5 × 6 to 10 μm. Conidia were also surrounded by a slime layer, usually with a hyaline, flexuous, narrowly conoidal or cylindrical, mucilaginous apical appendage that was 10 to 16 μm long. Spermatia were hyaline, dumbbell shaped to cylindrical, both ends bluntly rounded, and 3 to 5 × 1 to 1.5 μm. These characteristics matched well with the description of Phyllosticta yuccae Bissett (1). To confirm this identification, DNA was extracted using a Wizard Genomic DNA Purification Kit and amplified using primers ITS1 and ITS4 (2) for the ITS region (GenBank Accession Nos. JX227945 and JX227946) and EF1-F and EF2-R (3) for the TEF-1α (JX227947 and JX227948). The sequencing was performed by Macrogen, South Korea. The ITS sequence matched sequence No. JN692541, P. yuccae, with 100% identity. To confirm Koch's postulates, four leaves of Y. filamentosa (five plants) were inoculated with 6-mm-diameter plugs from a 7-day-old culture growing on PDA. The leaves were covered with plastic sack and plants were maintained at 25°C. In a similar manner, fungus-free PDA plugs were placed on five control plants. Symptoms were consistently similar to those initially observed in the nurseries and all plants developed leaf spots by 15 days after inoculation. P. yuccae was successfully reisolated from the symptomatic tissue and control plants remained symptomless. P. yuccae has been previously reported in Canada, the Dominican Republic, Guatemala, Iran, and the United States of America. To our knowledge, this is the first report of P. yuccae causing disease in Y. filamentosa in Brazil and it may become a serious problem for the nurseries, due to the severity of the disease and the lack of chemical products to control this pathogen. References: (1) J. Bissett. Can. J. Bot. 64:1720, 1986. (2) M. A. Innis et al. PCR Protocols: A guide to methods and applications. Academic Press, 1990. (3) Jacobs et al. Mycol. Res. 108:411, 2004. (4) H. Lorenzi and H. M. Souza. Plantas Ornamentais no Brasil. Instituto Plantarum, 2001.

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First Report of Anthracnose Caused by Colletotrichum sansevieriae on Sansevieria in Korea

Plant Disease ◽

10.1094/pdis-04-13-0402-pdn ◽

2013 ◽

Vol 97 (11) ◽

pp. 1510-1510 ◽

Cited By ~ 2

Author(s):

J. H. Park ◽

K. S. Han ◽

J. Y. Kim ◽

H. D. Shin

Keyword(s):

United States ◽

Agricultural Research ◽

Aerial Mycelium ◽

Its Region ◽

The United States ◽

Culture Collection ◽

Infected Leaf ◽

Conidial Suspension ◽

Voucher Specimen ◽

First Report

Sansevieria, Sansevieria trifasciata Prain, is cultivated in greenhouses and is used as a potted interior foliage plant in Korea. In April 2012, several plants (cv. Moonshine) exhibiting typical anthracnose symptoms from a local nursery were sent to the plant clinic of Gyeonggi-Do Agricultural Research and Extension Services for diagnosis. The leaf lesions began as round, partly water-soaked, pale greenish to grayish spots, which enlarged and ultimately coalesced, resulting in severe leaf blight. Concentric rings of blackish acervuli were formed in the expanding lesions of mostly 2 to 4 cm in diameter. Acervuli were mostly epiphyllous, circular to ellipsoid. Setae were aseptate to 3-septate, dark brown at the base, paler upwards, acicular, and up to 180 μm long. Conidia (n = 30) were oblong-elliptical to obovate, sometimes fusiform-elliptical, guttulate, hyaline, and 14 to 24 × 5 to 7.5 μm (mean 18.6 × 6.4 μm). Hyphopodial appressoria were dark brown to blackish, globose to clavate in outline, and 5 to 12 × 4 to 8 μm. Colonies on potato dextrose agar (PDA) were grayish-white, felted with cottony-white aerial mycelium on a gray to olivaceous gray background in culture. Gelatinous salmon- to orange-colored conidial masses were produced abundantly after one week's incubation. The morphological and cultural characteristics of the fungus were consistent with the description of Colletotrichum sansevieriae M. Nakamura & M. Ohzono (2,3). A voucher specimen was deposited in the Korea University herbarium (KUS-F26637). An isolate was deposited in the Korean Agricultural Culture Collection (Accession No. KACC46835). Fungal DNA was extracted with DNeasy Plant Mini DNA Extraction Kits (Qiagen Inc., Valencia, CA). The complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced. The resulting 569-bp sequences were deposited in GenBank (Accession No. KC847065). A BLAST search in GenBank exhibited 100% nucleotide identity with sequence of C. sansevieriae (JF911349) from the United States and >99% similarity with that of HQ433226 from Australia. To confirm pathogenicity, inoculum was prepared by harvesting conidia from 3-week-old cultures on PDA. A conidial suspension (2 × 106 conidia/ml) was sprayed over the five leaves of sansevieria ‘Moonshine’ wounded with a fine needle. Five leaves sprayed with sterile water served as controls. Plants were covered with plastic bags to maintain 100% relative humidity for 48 h and then kept in a greenhouse (22 to 28°C and 70 to 80% RH). Within 12 days, symptoms identical to those observed in originally infected leaf developed on all inoculated leaves. No symptoms were observed on control plants. C. sansevieriae was reisolated from the lesions of inoculated plants, fulfilling Koch's postulates. Sansevieria anthracnose associated with C. sansevieriae has been reported in Japan (2), Australia (1), and the United States (3). To our knowledge, this is the first report of sansevieria anthracnose in Korea. Our observations in sansevieria nurseries suggest that preventing wound infection as well as maintaining good plant hygiene in greenhouses might be main strategies for this disease. References: (1) R. Aldaoud et al. Australas. Plant Dis. Notes 6:60, 2011. (2) M. Nakamura et al. J. Gen. Plant Pathol. 72:253, 2006. (3) A. J. Palmateer et al. Plant Dis. 96:293, 2012.

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First Report of Stem Canker of Salsola tragus Caused by Diaporthe eres in Russia

Plant Disease ◽

10.1094/pdis-93-1-0110b ◽

2009 ◽

Vol 93 (1) ◽

pp. 110-110 ◽

Cited By ~ 1

Author(s):

T. Kolomiets ◽

Z. Mukhina ◽

T. Matveeva ◽

D. Bogomaz ◽

D. K. Berner ◽

...

Keyword(s):

United States ◽

Biological Control ◽

Biological Control Agent ◽

Aqueous Suspension ◽

Stem Canker ◽

The United States ◽

Invasive Weed ◽

Voucher Specimen ◽

First Report ◽

Stem Lesions

Salsola tragus L. (Russian thistle) is a problematic invasive weed in the western United States and a target of biological control efforts. In September of 2007, dying S. tragus plants were found along the Azov Sea at Chushka, Russia. Dying plants had irregular, necrotic, canker-like lesions near the base of the stems and most stems showed girdling and cracking. Stem lesions were dark brown and contained brown pycnidia within and extending along lesion-free sections of the stems and basal portions of leaves. Diseased stems were cut into 3- to 5-mm pieces and disinfested in 70% ethyl alcohol. After drying, stem pieces were placed into petri dishes on the surface of potato glucose agar. Numerous, dark, immersed erumpent pycnidia with a single ostiole were observed in all lesions after 2 to 3 days. Axenic cultures were sent to the Foreign Disease-Weed Science Research Unit, USDA, ARS, Ft. Detrick, MD for testing in quarantine. Conidiophores were simple, cylindrical, and 5 to 25 × 2 μm (mean 12 × 2 μm). Alpha conidia were biguttulate, one-celled, hyaline, nonseptate, ovoid, and 6.3 to 11.5 × 1.3 to 2.9 μm (mean 8.8 × 2.0 μm). Beta conidia were one-celled, filiform, hamate, hyaline, and 11.1 to 24.9 × 0.3 to 2.5 μm (mean 17.7 × 1.2 μm). The isolate was morphologically identified as a species of Phomopsis, the conidial state of Diaporthe (1). The teleomorph was not observed. A comparison with available sequences in GenBank using BLAST found 528 of 529 identities with the internal transcribed spacer (ITS) sequence of an authentic and vouchered Diaporthe eres Nitschke (GenBank DQ491514; BPI 748435; CBS 109767). Morphology is consistent with that of Phomopsis oblonga (Desm.) Traverso, the anamorph of D. eres (2). Healthy stems and leaves of 10 30-day-old plants of S. tragus were spray inoculated with an aqueous suspension of conidia (1.0 × 106 alpha conidia/ml plus 0.1% v/v polysorbate 20) harvested from 14-day-old cultures grown on 20% V8 juice agar. Another 10 control plants were sprayed with water and surfactant without conidia. Plants were placed in an environmental chamber at 100% humidity (rh) for 16 h with no lighting at 25°C. After approximately 24 h, plants were transferred to a greenhouse at 20 to 25°C, 30 to 50% rh, and natural light. Stem lesions developed on three inoculated plants after 14 days and another three plants after 21 days. After 70 days, all inoculated plants were diseased, four were dead, and three had more than 75% diseased tissue. No symptoms occurred on control plants. The Phomopsis state was recovered from all diseased plants. This isolate of D. eres is a potential biological control agent of S. tragus in the United States. A voucher specimen has been deposited with the U.S. National Fungus Collections (BPI 878717). Nucleotide sequences for the ribosomal ITS regions (ITS 1 and 2) were deposited in GenBank (Accession No. EU805539). To our knowledge, this is the first report of stem canker on S. tragus caused by D. eres. References: (1) B. C. Sutton. Page 569 in: The Coelomycetes. CMI, Kew, Surrey, UK, 1980. (2) L. E. Wehmeyer. The Genus Diaporthe Nitschke and its Segregates. University of Michigan Press, Ann Arbor, 1933.

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First Report of Leaf Spot Caused by Cercospora bizzozeriana on Hoary Cress in Russia

Plant Disease ◽

10.1094/pdis-92-2-0316c ◽

2008 ◽

Vol 92 (2) ◽

pp. 316-316

Author(s):

Z. M. Mukhina ◽

D. Kassanelly ◽

D. K. Berner ◽

H. J. Dubin

Keyword(s):

Biological Control Agent ◽

Aqueous Suspension ◽

Science Research ◽

Research Unit ◽

Invasive Weed ◽

Voucher Specimen ◽

First Report ◽

Leaf Spots ◽

White Leaf ◽

Hoary Cress

Hoary cress (Lepidium draba (L.) subsp. draba (synonym = Cardaria draba (L.) Desv.) (1), family Brassicaceae, is a common weed in Russia but it is an aggressive invasive weed in the northwestern United States. In the summer of 2006, dying hoary cress plants were found near Kugoyeyskoye in the Krylovskoy area of the Krasnodar Region of Russia. Plants had grayish white leaf spots on most of the leaves. In some cases, the diseased 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 leaves within and around the lesions. The fungus isolated (DB06-018) conformed to the description of Cercospora bizzozeriana Saccardo & Berlese (2). Conidiophores were 1 to 5 geniculate, unbranched, pale olive-brown, and uniform in color and width (4 μm). Conidia were multiseptate, hyaline, cylindric, straight to slightly curved, and measured 57 to 171 μm (average 103) long × 3.8 to 6.7 μm (average 4.6) wide. Leaves of rosettes (10 to 15 cm in diameter) of four hoary cress plants were spray inoculated with an aqueous suspension of conidia (1 × 105/ml) and mycelia harvested from 6- to 8-day-old cultures grown on V8 medium. Inoculated plants and two noninoculated plants were placed in a dew chamber at 20°C in darkness and continuous dew. After 96 h, plants were moved from the dew chamber to a greenhouse bench. All plants were watered twice daily. After 12 days, symptoms were observed on all inoculated plants. Symptoms were identical to those observed in the field in Russia. No symptoms were observed on noninoculated plants. C. bizzozeriana was reisolated from the leaves of all symptomatic plants. Nucleotide sequences were obtained for the internal transcribed spacer regions ITS1 and ITS2 and the 5.8S ribosomal RNA gene (GenBank Accession No. EU031780) and aligned with the same sequences obtained from another C. bizzozeriana isolate (GenBank Accession No. DQ370428) collected in Tunisia. There was 100% alignment of the two sequences with no gaps. Both isolates of C. bizzozeriana are destructive pathogens on hoary cress and locally severe epidemics have been observed in both Russia and Tunisia (4). This fungus has also been reported in North America (3) and has the potential as a biological control agent where the weed is a problem. To our knowledge, this is the first report of C. bizzozeriana on L. draba subsp. draba in Russia. A voucher specimen has been deposited with the U.S. National Fungus Collections (BPI 878175). Live cultures are being maintained at FDWSRU. 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. (3) I. L. Conners. Res. Bra. Can. Dep. Agric. 1251:1, 1967. (4) T. Souissi et al. Plant Dis. 89:206, 2005.

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First Report of a Leaf Spot Caused by Alternaria brassicae on the Invasive Weed Lepidium draba in North America

Plant Disease ◽

10.1094/pdis-93-8-0846a ◽

2009 ◽

Vol 93 (8) ◽

pp. 846-846 ◽

Cited By ~ 1

Author(s):

A. J. Caesar ◽

R. T. Lartey

Keyword(s):

North America ◽

Chinese Cabbage ◽

Leaf Spot ◽

The United States ◽

Alternaria Brassicae ◽

Voucher Specimen ◽

First Report ◽

Leaf Spots ◽

Black Spots ◽

Lepidium Draba

The exotic, rangeland weed Lepidium draba L., a brassicaceous perennial, is widely distributed in the United States. For example, Oregon contains 100,000 ha of land infested with L. draba (2). Because it is capable of aggressive spread and has the potential to reduce the value of wheat-growing land (4), it is the target of biological control research. The application of multiple pathogens has been advocated for control of other brassicaceous weeds, including the simultaneous application of biotrophic and necrotrophic pathogens (3). In pursuit of this approach, in 2007, we discovered the occurrence of leaf spots on approximately 90% of L. draba plants near Shepherd, MT, which were distinct from leaf lesions caused by Cercospora bizzozeriana (1). The lesions were initially tiny, black spots enlarging over time to become circular to irregular and cream-colored around the initial black spots and sometimes with dark brown borders or chlorotic halos. Conidia from the lesions were light brown, elongate and obclavate, produced singly from short conidia, with 8 to 12 transverse septa, and 2 to 6 longitudinal septa. The spore body measured 25 to 35 × 200 to 250 μm with a beak cell 42 to 100 μm long. On the basis of conidial and cultural characteristics, the fungus was identified as Alternaria brassicae (Berk.) Sacc. Leaf tissues bordering lesions were plated on acidified potato dextrose agar. Colonies on V8 and alfalfa seed agar were black with concentric rings, eventually appearing uniformly black after 10 to 14 days. The internal transcribed spacer region of rDNA was amplified using primers ITS1 and ITS4 and sequenced. BLAST analysis of the 575-bp fragment showed a 100% homology with a sequence of A. brassicae Strain B from mustard (GenBank Accession No. DQ156344). The nucleotide sequence has been assigned GenBank Accession No. FJ869872. For pathogenicity tests, aqueous spore suspensions approximately 105/ml were prepared from cultures grown at 20 to 25°C for 10 to 14 days on V8 agar and sprayed on leaves of three L. draba plants. Inoculated plants were enclosed in plastic bags and incubated at 20 to 22°C for 72 to 80 h. In addition, three plants of the following reported hosts of A. brassicae were inoculated: broccoli, canola, Chinese cabbage, collards, broccoli raab, kale, mustard greens, radish, rape kale, and turnip. Within 10 days, leaf spots similar to those described above developed on plants of radish, canola, Chinese cabbage, and turnip and A. brassicae was reisolated and identified. Control plants sprayed with distilled water remained symptomless. These inoculations were repeated and results were the same. To our knowledge, this is the first report of a leaf spot disease caused by A. brassicae on L. draba in North America. A voucher specimen has been deposited with the U.S. National Fungus Collections (BPI No. 878750A). References: (1) A. J. Caesar et al. Plant Dis. 93:108, 2009. (2) G. L. Kiemnec and M. L. McInnis. Weed Technol. 16:231, 2002. (3) A. Maxwell and J. K. Scott. Adv. Bot. Res. 43:143, 2005. (4) G. A. Mulligan and J. N. Findlay. Can. J. Plant Sci. 54:149, 1974.

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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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