First Report of Leaf Spot Caused by Colletotrichum cf. linicola on Field Bindweed in Turkey

Field bindweed (Convolvulus arvensis L., Convolvulaceae) is one of the most problematic weeds in the world (1) and a target of biological control efforts (2). In the summer of 2006, dying field bindweed plants were found in a wheat field near Bafra, Turkey (41°21.197′N, 36°12.524′E). Plants had water-soaked lesions that developed into necrotic leaf spots on most of the leaves, particularly along the leaf margins, and on some stems. In most cases, the leaf spots coalesced, causing the leaves and later plants to wilt and die. Diseased leaves and stems were taken to the Phytopathology Laboratory of the Faculty of Agriculture, Ondokuz Mayis University, Samsun, Turkey. Diseased tissue was surface disinfested and placed on moist filter paper in petri dishes. Numerous acervuli with setae and conidia typical of a Colletotrichum sp. were observed after 2 to 5 days. A fungus, designated 06-01, was isolated from the diseased leaves. Stems and leaves of seven 12-week-old plants were spray inoculated in the laboratory with an aqueous suspension of conidia (106 spores per ml; 10 ml per plant) harvested from 6- to 8-day-old cultures grown on malt extract agar. The plants and two noninoculated checks were placed in a dew chamber at 22°C in darkness and continuous dew. After 48 h, plants from the dew chamber were moved to a greenhouse bench. All plants were watered twice daily. Symptoms were observed 5 days after inoculation. No symptoms were observed on noninoculated plants. Isolate 06-01 was reisolated from all inoculated plants. In the field, 20 inoculated plants became diseased after 20 days with approximately 36% diseased leaf tissue from which 06-01 was consistently reisolated. Diseased tissue and cultures of the fungus were sent to the Foreign Disease-Weed Science Research Unit, USDA/ARS, Fort Detrick, MD. The fungus conformed to the description of Colletotrichum linicola Pethybr. & Laff., which was noted as distinct from C. lini (3). The original description is also different than the description of C. lini (Westerdijk) Tochinai by Sutton (4). Acervuli were sparse, subepidermal, and erumpent. Conidia were hyaline, oblong or cylindrical or somewhat spindle-shaped with dull-pointed ends, guttulate, and 14 to 19 × 4 to 5 μm (mean 17 × 4 μm). Conidiophores were short, simple, hyaline, and emerged from subepidermal stroma. Setae were simple, erect, 3-septate, and dark with hyaline tips. DNA sequences were obtained for the internal transcribed spacer regions (GenBank Accession No. EU000060) and compared with other sequences in GenBank. Sequences from 06-01 matched 100% with one isolate of C. linicola and 99% with two other isolates of C. linicola. These isolates formed a unique clade. However, 06-01 was also 99% identical to other species of Colletotrichum. Thus, species identification is inconclusive. Isolate 06-01 is a destructive pathogen on field bindweed, and severe disease can be produced by inoculation of foliage with an aqueous suspension of conidia. To our knowledge, this is the first report of Colletotrichum on field bindweed. A voucher specimen has been deposited with the U.S. National Fungus Collections (BPI 878174). References: (1) L. Holm et al. The World's Worst Weeds. University Hawaii Press, Honolulu, Hawaii, 1977. (2) G. Defago et al. BioControl 46:157, 2001. (3) G. H. Pethybridge and H. A. Lafferty. Sci. Proc. R. Dublin Soc. 15:359, 1918. (4) B. C. Sutton. The Coelomycetes. Commonw. Mycol. Inst., Kew, England, 1980.

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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 Leaf Anthracnose Caused by Phomopsis convolvuli on Field Bindweed in Turkey

Plant Disease ◽

10.1094/pdis-93-8-0847b ◽

2009 ◽

Vol 93 (8) ◽

pp. 847-847 ◽

Cited By ~ 1

Author(s):

E. Kuleci ◽

B. Tunali ◽

D. K. Berner ◽

C. A. Cavin ◽

L. A. Castlebury

Keyword(s):

Aqueous Suspension ◽

Triticum Aestivum L ◽

Distilled Water ◽

Convolvulus Arvensis ◽

Voucher Specimen ◽

Perennial Weed ◽

First Report ◽

5.8S Rdna ◽

Field Bindweed ◽

The World

Field bindweed (Convolvulus arvensis L.; Convolvulaceae) is a troublesome perennial weed found among many important crops in the world (1). In May of 2007, dying field bindweed plants were found along the edge of a wheat (Triticum aestivum L.) field between Bafra and Taflan, Turkey (41°34.395′N, 35°52.215′E). Lesions on leaves were irregular and variable in size and dark black with green margins. Severely diseased leaves were wilted or dead. Fruiting bodies were not evident on field-collected material. Diseased tissue was surface disinfested and placed on moist filter paper in petri plates. Numerous pycnidia with alpha conidia were observed after 2 weeks. A fungus, designated 24-6, was isolated from the diseased leaves. Cultures on potato dextrose agar (PDA) were floccose with white mycelia and small black stromata. Alpha conidia from pycnidia on inoculated plants were biguttulate, one celled, hyaline, oblong to ellipsoid, and 7.0 to 12.8 × 3.0 to 5.5 μm (mean 10.0 × 3.9 μm). Neither beta conidia nor the teleomorph, Diaporthe sp., were observed on diseased tissue or in cultures. Morphology was consistent with that of Phomopsis convolvuli Ormeno-Nunez, Reeleder & A.K. Watson (2). Alpha conidia were harvested from 12-day-old cultures grown on PDA by brushing the surface of the colonies with a small paint brush, suspending the conidia in sterile distilled water, and filtering through cheesecloth. The conidia were then resuspended in sterile distilled water plus 0.1% polysorbate 20 to arrive at a concentration of 107 conidia/ml. Stems and leaves of seven plants at the 3- to 5-leaf stage were spray inoculated with 10 ml per plant of this aqueous suspension. Inoculated plants and two noninoculated plants were placed in a dew chamber at 24°C in darkness and continuous dew. After 48 h, plants from the dew chamber were moved to a greenhouse bench. Disease severity was evaluated 1 week after inoculation with a rating system based on a scale from 0 to 4, in which 0 = no symptoms, 1 = 1 to 25% necrosis, 2 = 26 to 50% necrosis, 3 = 51 to 75% necrosis, and 4 = 76 to 100% necrosis (2). The average disease rating on inoculated plants was 3.75. No disease was observed on noninoculated plants. P. convolvuli was reisolated from all inoculated plants. Comparison of the internal transcribed spacer (ITS) 1 and 2 sequences with available sequences of a vouchered P. convolvuli specimen (GenBank Nos. U11363, U11417; BPI 748009, FAU649) showed 192 of 193 and 176 of 179 identities, respectively, for the two regions. Nucleotide sequences for the ribosomal ITS regions (ITS 1 and 2, including 5.8S rDNA) were deposited in GenBank (Accession No. FJ710810), and a voucher specimen has been deposited with the U.S. National Fungus Collections (BPI 878927). To our knowledge, this is the second report in the world of leaf anthracnose on field bindweed caused by P. convolvuli. The first report was from Canada (3) of an isolate that was later patented for biological control of C. arvensis (4). References: (1) L. Holm et al. The World's Worst Weeds. University Press of Hawaii, Honolulu, 1977. (2) J. Ormeno-Nunez, et al. Can. J. Bot. 66:2228, 1988. (3) J. Ormeno-Nunez et al. Plant Dis. 72:338, 1988. (4) A. K. Watson et al. U.S. Patent 5,212,086, 1993.

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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 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 Leaf Blight Caused by Phoma exigua on Acroptilon repens in Turkey

Plant Disease ◽

10.1094/pdis.2003.87.12.1540c ◽

2003 ◽

Vol 87 (12) ◽

pp. 1540-1540 ◽

Cited By ~ 5

Author(s):

B. Tunali ◽

F. M. Eskandari ◽

D. K. Berner ◽

D. F. Farr ◽

L. A. Castlebury

Keyword(s):

United States ◽

Biological Control ◽

Aqueous Suspension ◽

Severe Disease ◽

The United States ◽

Potential Candidate ◽

Voucher Specimen ◽

Phoma Exigua ◽

First Report ◽

Acroptilon Repens

Acroptilon repens (L.) DC. (Russian knapweed, synonym Centaurea repens L., family Asteraceae) is becoming a noxious weed in wheat fields in Turkey. Because it is also an invasive weed in the northwestern United States, A. repens is a target of biological control efforts. In the summer of 2002, approximately 20 dying A. repens plants were found on a roadside near Cankiri, Turkey (40°21′41″N, 33°31′8″E, elevation 699 m). No healthy plants were found in the immediate area. Dying plants had irregular, charcoal-colored, necrotic lesions at the leaf tips and margins, and frequently, whole leaves and plants were necrotic. Symptomatic leaves were air-dried and sent to the Foreign Disease-Weed Science Research Unit, USDA/ARS, Fort Detrick, MD. There, diseased leaves were surface-disinfested and placed on moist, filter paper in petri dishes. Pycnidia producing one-celled hyaline conidia were observed after 4 to 5 days. Internal transcribed spacer regions 1 and 2, including the 5.8S ribosomal DNA, were sequenced for isolate 02-059 (GenBank Accession No. AY367351). This sequence was identical to sequences in GenBank from six well-characterized strains of Phoma exigua Desmaz (1). Morphology was also consistent with P. exigua (2) with the exception that material grown on alfalfa twigs produced pycnidia with 1 to 4 ostioles with necks as much as 80 μm long. Typically, pycnidia of P. exigua produced on agar have 1 to 2 ostioles that lack necks. Conidial dimensions on alfalfa were 4.1 to 7.6 × 1.7 to 3.2 μm (average 5.5 × 2.4 μm). Images of the fungus are located at http://nt.ars-grin.gov under the section ‘Fungi Online’. Stems and leaves of 20 3-week-old plants were spray inoculated with an aqueous suspension (1 × 107 conidia per ml) of conidia harvested from 25-day-old cultures grown on acidified potato dextrose agar, and placed in an environmental chamber at 25°C with constant light and continuous dew for 3 days. Plants were then moved to a greenhouse bench and watered twice daily. After 6 days, symptoms were observed on all plants. Once symptoms had progressed to the midveins of the leaves, the disease progressed rapidly on the plants, indicating the possibility of systemic infection or systemic movement of toxins. Phoma exigua was reisolated from the stems, petioles, and leaves of all inoculated plants. In a separate test, 12 plants were inoculated as described above, and 8 additional plants were sprayed with water only. After inoculation, plants were handled as described above. The first lesions developed after 3 days on all except the youngest leaves of inoculated plants. After 10 days, three inoculated plants were dead, and all other inoculated plants had large necrotic lesions. No symptoms developed on control plants. This isolate of Phoma exigua is a destructive pathogen on A. repens, and severe disease can be produced by inoculation of foliage with an aqueous suspension of conidia. These characteristics make this isolate of P. exigua a potential candidate for biological control of this weed in Turkey and the United States. To our knowledge, this is the first report of P. exigua on A. repens in Turkey. A voucher specimen has been deposited with the U.S. National Fungus Collections (BPI 843350). References: (1) E. C. A. Abeln et al. Mycol. Res. 106:419, 2002. (2) H. A. Van der Aa et al. Persoonia 17:435, 2000.

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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 Periconia igniaria on Yellow Starthistle in Russia

Plant Disease ◽

10.1094/pdis-92-6-0983a ◽

2008 ◽

Vol 92 (6) ◽

pp. 983-983 ◽

Cited By ~ 4

Author(s):

T. Kolomiets ◽

L. Pankratova ◽

Z. Mukhina ◽

D. Kassanelly ◽

T. Matveeva ◽

...

Keyword(s):

Aqueous Suspension ◽

Soil Fungus ◽

Aerial Mycelium ◽

Its Sequences ◽

Yellow Starthistle ◽

Invasive Weed ◽

Voucher Specimen ◽

First Report ◽

Russian State ◽

Nutrition Medium

Yellow starthistle (YST), Centaurea solstitialis L., is a weedy plant that is widely distributed in the Krasnodar Region of Russia. It is also an aggressive invasive weed in the western United States and a target of biological control efforts. In the summer of 2006, several hundred diseased plants were found near Taman, Russia. Symptoms of the disease were yellow, water-soaked leaf spots. Diseased leaves were collected, air dried, and sent to the Russian State Collection of Phytopathogenic Organisms at the All Russia Institute of Phytopathology (ARIP). The fungus isolated from the diseased leaves conformed to Periconia igniaria E.W. Mason & M.B. Ellis (teleomorph Didymosphaeria igniaria C. Booth) (1). Colonies of the fungus grew rapidly on potato glucose nutrition medium with aerial mycelium from fluffy to pressed and colorless at the beginning and darkening to black with age. The medium side of the colonies gradually became violet purple to wine colored. Conidiophores had aerial mycelia as much as 550 μm long and 9 to 13 μm wide tapering to 6 to 10 μm. Conidiophores were dark with short, swollen branched stipes. Conidia, formed in short twisted chains, were spherical, dark brown, 7 to 9 μm in diameter, and covered by 1 μm long spines. Yellow starthistle plants were grown in growth chambers with day/night air temperatures of 26 to 28/20 to 22°C, 60 to 70% relative air humidity, and 10,000 lx light for 16 h. Fifteen plants in the rosette stage were spray inoculated with an aqueous suspension of P. igniaria conidia at 5 × 106 conidia/ml and 5 ml per plant. Disease on leaves was observed on all plants 3 to 4 weeks after inoculation when the plants started to bolt. When the plants reached flowering stage, diffused yellow spots were observed on stems and inflorescences and all flowers died. Diseased leaves were surface disinfested and put on potato saccharose nutrition medium. P. igniaria was reisolated from 3 to 5 leaves of each plant and from flowers and stems that developed from 10 inoculated rosettes. Flowers of 10 YST plants were also inoculated with P. igniaria isolated from the previously inoculated plants. Disease developed in the flowers of all inoculated plants, and the symptoms were identical to those observed when rosettes were inoculated and disease followed bolting and flowering. No symptoms developed on four noninoculated plants included in each test. Internal transcribed spacer (ITS) sequences of the fungus were obtained and compared with sequences from GenBank. An uncultured soil fungus and three isolates of P. macrospinosa Lefebvre & Aar.G. Johnson produced the best homology (96%). No sequences for P. igniaria were available for comparison, but the description of P. macrospinosa (conidia 18 to 32 μm in diameter with 2.5 to 6 μm long spines) is clearly different than our isolate. ITS sequences for our isolate have been deposited in GenBank (Accession No. EU367468) and a voucher specimen has been deposited with the U.S. National Fungus Collection (BPI 878355). To our knowledge, this is the first report of P. igniaria causing disease on YST. Live cultures are being maintained at the Russian State Collection of Phytopathogenic Organisms in ARIP. Reference: (1) M. B. Ellis. Dematiaceous Hyphomycetes. CMI, Kew, UK, 1971.

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Leaf Anthracnose, a New Disease of Swallow-Worts Caused by Colletotrichum lineola from Russia

Plant Disease ◽

10.1094/pdis-04-11-0318 ◽

2011 ◽

Vol 95 (12) ◽

pp. 1586-1586 ◽

Cited By ~ 6

Author(s):

D. Berner ◽

C. Cavin ◽

Z. Mukhina ◽

D. Kassanelly

Keyword(s):

United States ◽

Biological Control ◽

Dna Sequences ◽

Aqueous Suspension ◽

Science Research ◽

The United States ◽

Research Unit ◽

Leaf Spots ◽

Pure Cultures ◽

Appressoria Formation

Black swallow-wort, Vincetoxicum nigrum (L.) Moench (= Cynanchum louiseae Kartesz & Gandhi), and pale swallow-wort, V. rossicum (Kleopow) Borhidi (= Cynanchum rossicum (Kleopow) Borhidi), are invasive plants belonging to the family Apocynaceae and are the targets of biological control efforts to control their spread in the United States. In 2010, a disease on a related species, V. scandens Sommier & Levier, was observed in the Krasnodar area of Russia. Disease symptoms were many small, dark red-to-purple leaf spots, approximately 2 to 5 mm in diameter, with white centers. Leaf spots were found on the upper leaf surface. Leaf tips and margins of leaves bearing many of these spots were necrotic. Symptomatic leaves were collected and sent to the BSL-3 containment facility at the Foreign Disease-Weed Science Research Unit (FDWSRU) of the USDA, ARS in Frederick MD. Surface-disinfested symptomatic leaves were incubated at 20 to 25°C in sterile moist chambers. After several days, acervuli and brown setae were observed inside the leaf spots. Pure cultures, designated FDWSRU 10-002, were obtained by transferring spore masses with sterile glass needles onto 20% V8 juice agar. Seeds of V. scandens, collected in Russia, were placed in a freezer at –20°C for 6 weeks and then germinated in sterile petri plates on moist filter paper. The seedlings were then transplanted and grown in a 20°C greenhouse under 12 h of light. Koch's postulates were fulfilled as follows: 2-month-old plants each of V. scandens, V. nigrum, and V. rossicum were inoculated with spores from 2-week-old cultures of isolate 10-002. Plants were inoculated by spraying an aqueous suspension of 106 spores per ml onto each plant until all leaves were wet. Plants were placed in 20 to 24°C dew chambers for 18 h and then placed in a 20°C greenhouse. Two weeks later, diseased leaves with the same symptoms observed in the field were harvested from each species, and the fungus was reisolated from seven of seven inoculated V. scandens plants, one of two V. nigrum plants, and four of four V. rossicum plants. Measurements of fungus fruiting structures were taken from cultures grown on synthetic nutrient-poor agar (SNA) (1). Conidiophores were brown, septate, and branched. Conidia were one-celled, hyaline, smooth walled, ovoid to oblong, falcate, and 20.1 to 26.2 × 1.7 to 3.6 μm (mean ± s.d. = 23.5 ± 1.3 × 2.6 ± 0.4 μm). Lengths of the conidia conformed to the description of Colletotrichum lineola Corda (1), but the conidia were slightly narrower than described. To induce appressoria formation, approximately 104 conidia were placed on sterile dialysis membranes on top of SNA in petri dishes that were wrapped in foil and incubated at 24°C for 24 h. After this time, appressoria were observed with a microscope at ×400 magnification. The appressoria were dark brown, smooth walled, ellipsoidal, and 5.5 to 25.5 × 3.6 to 12.1 μm (mean ± s.d. = 13.4 ± 4.0 × 7.3 ± 2.1 μm), which conformed to the description of appressoria of C. lineola Corda (1). DNA sequences of ITS1, 5.8S, and ITS2 were submitted to GenBank (No. HQ731491), and after BLAST analysis, aligned 100% to 15 previously identified isolates of C. lineola in GenBank. Voucher specimens of the fungus have been deposited in the U.S. National Fungus Collection and were designated as BPI 881105 and BPI 881106. Host range and efficacy tests are planned to determine the suitability of C. lineola for biological control of swallow-worts in the United States. Reference: (1) U. Damm et al. Fungal Divers. 39:45, 2009.

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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 a Septoria sp. on Common Ragweed (Ambrosia artemisiifolia) in Europe

Plant Disease ◽

10.1094/pdis.1999.83.7.696d ◽

1999 ◽

Vol 83 (7) ◽

pp. 696-696 ◽

Cited By ~ 1

Author(s):

Gy. Bohár ◽

I. Schwarczinger

Keyword(s):

Ambrosia Artemisiifolia ◽

Voucher Specimen ◽

Common Ragweed ◽

History Museum ◽

First Report ◽

Leaf Spots ◽

Brown Leaf ◽

Detached Leaves ◽

Pure Cultures ◽

Hungarian Natural History Museum

During a survey for potential biocontrol agents of common ragweed (Ambrosia artemisiifolia var. elatior (L.) Descourt) in 1997, plants exhibiting irregular, brown leaf spots were collected repeatedly from six roadside locations in Pest County, Hungary. Many pycnidia developed in the necrotic tissues on detached leaves after 2 days in moist chambers. Pycnidia were globose to slightly flattened, brown, thin walled, 58 to 100 μm in diameter, with a definite ostiole. Conidia were hyaline, filiform with 2 to 3 septa, and 22.0 to 38.0 × 0.7 to 1.3 μm in size. The fungus was isolated on potato dextrose agar and identified as a Septoria sp. To confirm pathogenicity, potted ragweed seedlings were sprayed with a suspension of 5 × 106 conidia per ml from pure cultures of the Septoria sp., placed in a dew chamber for 72 h, and then grown in a greenhouse at 16 to 24°C. After 2 weeks, inoculated plants developed small, brown lesions on leaves and leaf petioles. Three weeks after inoculation, necrotic lesions had enlarged to 1 to 3 mm in diameter with irregular, distinct margins and light brown centers. The lesions on the lower leaves were larger and more numerous than on leaves nearer the tops of the plants. Pycnidia developed on the senescent leaves after 1 month. Infected leaves became completely necrotic and occasionally entire plants died. The pathogen was reisolated from all inoculated plants, thus satisfying Koch's postulates. A voucher specimen was deposited at the Department of Botany of the Hungarian Natural History Museum in Buda-pest (No. BP 92081). Septoria ambrosiae Hemmi et Naito was described on ragweed in Japan (1), but our isolate is morphologically distinct from that species. This is the first report of a Septoria sp. on A. artemisiifolia in Europe. Reference: (1) N. Naito. Mem. Coll. Agric. Kyoto 47:41, 1940.

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