First Report of Magnaporthe poae, Cause of Summer Patch Disease on Annual Bluegrass, in Canada

The ectotrophic, root-infecting fungus Magnaporthe poae Landschoot & Jackson, the causal agent of summer patch disease in the U.S. (2), is implicated in the damage and loss of annual bluegrass (Poa annua L.) on golf course greens. This pathogenic fungus, one of the important root pathogens of turfgrass, attacks and colonizes susceptible turfgrass roots suffering from environmental or cultural stresses. Over 100 turf samples that exhibited symptoms (chlorotic circular or irregular patches of ≥15 cm in diameter with necrotic crowns and discolored roots) reminiscent of summer patch were collected from 77 southwestern Ontario golf courses from July to August of 2009 and 2010. Roots and crowns were often covered with dark, ectotrophic runner hyphae, lobed hyphopodia, and growth cessation structures, characteristic of M. poae. Sections of root tissue were surface sterilized in 0.6% sodium hypochlorite (NaOCl) for 5 min. Sterilized root tissue was plated on potato dextrose agar (PDA) containing 50 mg L–1 streptomycin sulfate and incubated at 28°C for 7 to 10 days. A fungus with morphological characteristics (hyaline mycelium that appears gray or olive-brown when mature) similar to those of M. poae (1) was consistently isolated (≥100 isolates were obtained) and used to identify M. poae through molecular techniques and Koch's postulates. DNA was extracted from the fungal mycelium of the collected isolates using the PowerPlant DNA isolation kit (MO BIO Laboratories, Inc., Carlsbad, CA). The rDNA internal transcribed spacer (ITS) regions of the isolates (≥100 isolates) were amplified by PCR using universal fungal rDNA primers ITS 4 (5′-TCCTCCGCTTATTGATATGC-3′) and ITS 5 (5′- GGAAGTAAAAGTCGTAACAAGG-3′) (3). The purified PCR products were sequenced (GenBank Accession No. JX134588 through JX134601) and a BLAST search exhibited seven isolates with 99% (MAG3, MAG6, MAG13, MAG16, and MAG17) and 100% (MAG1 and MAG14) similarity to M. poae in the GenBank database. Pathogenicity of four isolates (MAG1, MAG3, MAG6, and MAG14) was confirmed with Koch's postulates. Sixteen healthy P. annua core samples (four replicates of each treatment/isolate) collected from an Ontario golf course were inoculated with 25 mg M. poae-infested Kentucky bluegrass seed (Poa pratensis L.; 12.5 mg inoculum applied at the surface of the potting medium and 12.5 mg inoculum applied on the foliar surface) and were placed in a growth chamber with 12-h day/night cycles at 30/25°C and approximate relative humidity. After 2 to 3 weeks, inoculated plants exhibited chlorotic foliage and necrotic roots covered with dark ectotrophic runner hyphae and lobed hyphopodia. Infected root sections from each replication were surface sterilized and placed on PDA containing 50 mg L–1 streptomycin sulfate. The fungal cultures exhibited morphological characteristics consistent with M. poae (1). To our knowledge, this is the first report of summer patch caused by M. poae in Canada. References: (1) B. B. Clarke and A. B. Gould, eds. Turfgrass Patch Diseases Caused by Ectotrophic Root-Infecting Fungi. The American Phytopathological Society, St. Paul, MN, 1993. (2) P. J. Landschoot and N. Jackson. Mycol. Res. 93:59, 1989. (3) T. J. White et al. Amplification and direct sequencing of fungal ribosomal RNA genes for phylogenetics. Pages 315-322 in: PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al. eds. Academic Press, San Diego, CA, 1990.

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First Report of Stemphylium botryosum Causing Leaf Blight of Kiwi in the Province Imathia, Northern Greece

Plant Disease ◽

10.1094/pdis-92-4-0650b ◽

2008 ◽

Vol 92 (4) ◽

pp. 650-650 ◽

Cited By ~ 1

Author(s):

T. Thomidis ◽

T. J. Michailides

Keyword(s):

Apical Cell ◽

Morphological Characteristics ◽

Leaf Blight ◽

Width Ratio ◽

Northern Greece ◽

Cell Width ◽

Koch’S Postulates ◽

First Report ◽

Stemphylium Botryosum ◽

Koch's Postulates

In Greece, kiwi (Actinidia deliciosa) is mostly found in the northern part of the country where approximately 440,000 ha are grown. In the summer of 2006, a Stemphylium sp. was frequently isolated from leaves of kiwi (cv. Hayward) grown in the province of Imathia. Symptomatic leaves were covered with irregular, necrotic, brown areas. Lesions had a distinct margin that, in some cases, covered a wide part of the diseased leaves. Intense symptoms were frequently observed and associated with defoliation. This Stemphylium sp. was consistently isolated from diseased leaves onto potato dextrose agar (PDA) after surface sterilization with 0.1% chlorine solution. On the basis of morphological characteristics of mycelia, dimensions (length 20 to 29 μm and width 14 to 21 μm) and mean length/width ratio (1.42 μm) of conidia, and width and apical cell width of condiophores, the fungus was identified as Stemphylium botryosum (Wallr.) (2,3) Koch's postulates were completed in the laboratory by inoculating leaves of kiwi (cv. Hayward) with an isolate of S. botryosum originated from a symptomatic leaf of a Hayward kiwi. Twenty leaves were surface sterilized by dipping them into 0.1% chlorine solution for 2 to 3 min, washing in sterile distilled water, and allowing them to dry in a laminar flow hood. A leaf was then placed into a petri plate containing a wet, sterilized paper towel. Inoculation was made by transferring a 5-mm-diameter mycelial disc from the margins of a 7-day-old culture onto the center of each leaf surface. Petri plates were closed and incubated at 25°C with 12 h of light for 6 days. Koch's postulates were satisfied when the same S. botryosum was reisolated from 100% of inoculated leaves that developed symptoms similar to those observed in the vineyards. Leaves inoculated with a PDA plug alone (with no S. botryosum) did not develop any symptoms. Previously, Alternaria alternata was reported as the causal agent of a leaf spot pathogen of kiwi (1,4). To our knowledge, this is the first report of the occurrence of S. botryosum causing leaf blight of kiwi in Greece and worldwide. This pathogen can cause a high level of defoliation in diseased plants. References: (1) L. Corazza et al. Plant Dis. 83:487, 1999. (2) M. B. Ellis. Dematiaceous Hyphomycetes. Mycology Institute. London, England, 1971. (3) E. G. Simmons. Mycologia 61:1, 1969. (4) C. Tsahouridou and C. C. Thanassoulopoulos. Plant Dis. 84:371, 2000

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

Plant Disease ◽

10.1094/pdis-09-14-0938-pdn ◽

2015 ◽

Vol 99 (2) ◽

pp. 289-289 ◽

Cited By ~ 9

Author(s):

Y. Z. Zhu ◽

W. J. Liao ◽

D. X. Zou ◽

Y. J. Wu ◽

Y. Zhou

Keyword(s):

Dna Sequences ◽

Leaf Spot ◽

Juglans Regia ◽

Morphological Characteristics ◽

Leaf Spot Disease ◽

Koch’S Postulates ◽

First Report ◽

Spot Disease ◽

Leaf Spots ◽

Koch's Postulates

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

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First Report of Aspergillus niger Causing Postharvest Fruit Rot of Cherry in the Prefectures of Imathia and Pella, Northern Greece

Plant Disease ◽

10.1094/pdis-07-11-0620 ◽

2012 ◽

Vol 96 (3) ◽

pp. 458-458 ◽

Cited By ~ 1

Author(s):

T. Thomidis ◽

E. Exadaktylou

Keyword(s):

Aspergillus Niger ◽

Fungal Spores ◽

Morphological Characteristics ◽

Fruit Rot ◽

Northern Greece ◽

Centraalbureau Voor ◽

Koch’S Postulates ◽

First Report ◽

Postharvest Rot ◽

Koch's Postulates

In June 2011, symptoms of postharvest rot were observed on approximately 3% of all cherries collected from commercial orchards of cultivars Lapen and Ferrovia in the prefectures of Imathia and Pella (northern Greece). Fruit were harvested in a timely manner to avoid overripeness. No wounds or other predisposing injuries were observed on the infected fruits. Lesions enlarged rapidly and separated easily from healthy tissue when pressure was applied. Infected tissues were pale and water soaked and the associated fungal spores were dark and powdery and easily liberated when mature. The fungus grew rapidly and produced black colonies on acidified potato dextrose agar (2.5 ml of 85% lactic acid per liter of nutrient medium) after 5 days at 24°C. Identification of the pathogen was based on morphological characteristics (1). The conidial head was radiate, vesicles were nearly spherical and covered with metulae and phialides (biseriate). Conidia were globose (3 to 5 μm in diameter) and usually very rough with irregular ridges, bars, and verrucae. Koch's postulates were completed in the laboratory by inoculating mature cherry fruits (cv. Lapen). The fruits were surface sterilized by dipping in 10% chloride bleach solution, allowed to dry in a laminar flow hood, and wounded with a sharp glass rod that was 2 mm in diameter. A 40-μl drop of a suspension containing 20,000 conidia per ml of water was placed on each wound. There were 20 inoculated and 20 control fruits (similarly wounded and inoculated with a 40-μl drop of sterile distilled water) in a randomized design and incubated at 24 to 26°C for 6 days. Koch's postulates were satisfied after reisolating the fungus from inoculated fruit that developed symptoms similar to those observed on fruit collected from orchards. Control fruits did not show any symptom of the disease. To our knowledge, this is the first report of the occurrence of Aspergillus niger as the causal agent of postharvest rots of cherries in Greece. Postharvest fruit rots caused by A. niger have been reported in cherry orchards of other countries around the world (2). Because this disease causes postharvest rots of cherry fruits, measures may need to be implemented to manage the pathogen. References: (1) M. A. Klich. Page 12 in: Identification of Common Aspergillus Species. Centraalbureau Voor Schimmelcultures, Utrecht, the Netherlands, 2002. (2) A. Valiuskaite et al. Phytopathol. Pol. 35:197, 2005.

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First Report of Botryosphaeria dothidea Causing Shoot Blight of Kiwifruit (Actinidia deliciosa) in Greece

Plant Disease ◽

10.1094/pdis-07-10-0528 ◽

2010 ◽

Vol 94 (12) ◽

pp. 1503-1503 ◽

Cited By ~ 4

Author(s):

T. Thomidis ◽

E. Exadaktylou

Keyword(s):

Random Amplified Polymorphic Dna ◽

Morphological Characteristics ◽

Fungal Mycelium ◽

Adhesive Tape ◽

Petroleum Jelly ◽

Koch’S Postulates ◽

First Report ◽

Agar Plug ◽

Dna Primers ◽

Koch's Postulates

In the spring of 2010, in commercial orchards located in the Prefecture of Pieria in northern Greece, wilted shoots of kiwifruit cv. Hayward were observed. Blighted shoots took on a distinct dark color. Isolations from the lower margins of the cankers were made by plating sodium-hypochlorite-treated shoot tissue sections of approximately 3 mm on acidified (2.5 ml of 85% lactic acid per liter of nutrient medium to create a pH = 3.5 after autoclaving) potato dextrose agar. Plates were incubated at 23°C for 5 days, and a fast-growing, mouse-gray colored fungus was consistently isolated from diseased stems. Identification of the pathogen was based on morphological characteristics and confirmed by using the four random amplified polymorphic DNA primers (K19 [CAC AGG CGG A], K20 [GTG TCG CGA G], R13 [GGA CGA CAA G], and R15 [GGA CAA CGA G], suggested by Ma et al. (2). This fungus formed darkly pigmented pycnidia (170 × 155 μm), while the conidia observed in these bodies were one-celled, hyaline, ellipsoidal to fusoid with distinctly truncate bases, and measured 10.9 to 21.55 × 3.25 to 10.10 μm. The pycnidia exuded conidia in white tendrils. Koch's postulates were completed in the laboratory by inoculating 20 segments (6 cm long and 1.5 to 2 cm in diameter) of 1-year-old woody shoots of kiwifruit cv. Hayward. Using a cork borer, a 7-mm-diameter wound was created in the middle of each shoot segment by removing the bark and a 6-mm-diameter agar plug bearing mycelia from a 15-day-old culture of B. dothidea was inserted into the wound. The wound was covered with petroleum jelly and wrapped with adhesive tape to prevent desiccation. Ten control segments were similarly wounded and inoculated with an agar disk without fungal mycelium. All inoculated and noninoculated shoot segments were incubated at 25°C in moist chambers, after which the resulting necrosis was recorded. Koch's postulates were satisfied after reisolating the fungus from inoculated shoots that developed symptoms similar to those observed on shoots collected from orchards. Although B. dothidea has been previously reported to cause dieback on kiwifruit in Japan (1), to our knowledge, this is the first report of the occurrence of B. dothidea on kiwifruit in Greece. This pathogen can cause a high level of shoot blights in diseased plants and presents a significant threat to the commercial kiwifruit production in Greece. References: (1) M. Kinugawa and T. Sato. Ann. Phytopathol. Soc. Jpn. 69:373, 2003. (2) Z. Ma et al. Phytopathology 91:665, 2001.

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First Report of Phomopsis amygdali Causing Fruit Rot on Peaches in Greece

Plant Disease ◽

10.1094/pd-90-1551c ◽

2006 ◽

Vol 90 (12) ◽

pp. 1551-1551 ◽

Cited By ~ 3

Author(s):

T. J. Michailides ◽

T. Thomidis

Keyword(s):

Prunus Persica ◽

Morphological Characteristics ◽

Fruit Rot ◽

Peach Fruit ◽

Koch’S Postulates ◽

Canker Disease ◽

First Report ◽

Immature Fruit ◽

Diseased Fruit ◽

Koch's Postulates

In the summer of 2005, the fungus Phomopsis amygdali (Del.) Tuset & Portilla was frequently isolated from decayed peaches (Prunus persica cv. Andross) grown in the province of Imathia, Greece. Fruit infected by P. amygdali developed gray-to-brown decay lesions with white mycelium forming on the surface of lesions. Identification of the pathogen was based on morphological characteristics. Dark-pigmented pycnidia (flask-shaped, conidia-bearing fruiting bodies) were produced over the surface of potato dextrose agar. The pycnidia exuded conidia in white tendrils 7 days later. Koch's postulates were completed in the laboratory by inoculating mature and immature cv. Andross peach fruits with an isolate of P. amygdali isolated from decayed cv. Andross peaches. Thirty peach fruit were surface sterilized by dipping them into 0.1% chlorine solution and allowing them to dry in a laminar flow hood. The peach fruit were wounded with a 2-mm diameter glass rod and a 40-μl drop of 5 × 105 conidia of P. amygdali per milliliter suspension was applied to the wound. Thirty control fruits were similarly wounded and inoculated with a 40-μl drop of sterile water. All inoculated and noninoculated fruit were incubated at 24 to 26°C for 7 days. Koch's postulates were satisfied when the same fungus was reisolated from 100% of inoculated mature and immature fruit that developed symptoms similar to diseased fruit collected from orchards. Although P. amygdali has been previously reported as a causal agent of canker disease (2) and fruit rots of peaches (1) in other countries, to our knowledge, this is the first report of the occurrence of P. amygdali causing a fruit rot of peaches in Greece. References: (1) Y. Ko and S. Sun. Plant Pathol. Bull. 12:212, 2003. (2) E. I. Zehr, Constriction canker. Page 31 in: Compendium of Stone Fruit Diseases. J. M. Ogawa et al., eds. The American Phytopathological Society, St. Paul, MN, 1995.

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First Report of Azalea Petal Blight Caused by Pestalotiopsis guepini in Argentina

Plant Disease ◽

10.1094/pdis.2000.84.1.100c ◽

2000 ◽

Vol 84 (1) ◽

pp. 100-100 ◽

Cited By ~ 6

Author(s):

M. C. Rivera ◽

E. R. Wright

Keyword(s):

Buenos Aires ◽

Morphological Characteristics ◽

Potato Dextrose Agar ◽

Commonwealth Mycological Institute ◽

Conidial Suspension ◽

Koch’S Postulates ◽

First Report ◽

Pure Cultures ◽

Pathogenicity Testing ◽

Koch's Postulates

The most important azalea (Rhododendron spp.) growing area in Argentina is located in the outskirts of Buenos Aires. A disease of the azalea flower was detected during surveys conducted during September 1998. Irregular brown spots were uniformly distributed on petals and resulted in a flower blight that did not lead to abscission of petals. Pieces of infected petals were surface-sterilized for 1 min in 2% NaOCl, plated on potato dextrose agar, and incubated at 24 ± 2°C. Pure cultures were identified as Pestalotiopsis guepini (Desmaz.) Steyaert (synamorph P. guepini Desmaz.) based on morphological characteristics (1,2). Inoculation for pathogenicity testing was carried out by spraying a conidial suspension (1 × 106 conidia per ml) on plants with previously punctured petals. Inoculated plants with unwounded flowers, as well as noninoculated controls, were included. Plants were incubated in moist chambers at 24°C. Symptoms appeared on all punctured flowers within 4 to 5 days. Petals were blighted by 9 days after inoculation and were covered with black acervuli by 12 days after inoculation. Unwounded and noninoculated controls remained symptomless. The pathogen was reisolated from inoculated flowers, completing Koch's postulates. Pathogenicity of P. guepini on azalea leaves in Argentina was reported in 1991. This is the first report of P. guepini causing disease on azalea flowers in Argentina. References: (1) J. E. M. Mordue. CMI Descr. Pathog. Fungi Bact. No. 320, 1971. (2) B. C. Sutton. 1980. The Coelomycetes. Commonwealth Mycological Institute, Kew, England.

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First Report of Neofusicoccum mediterraneum and N. australe Causing Decay in Vitis vinifera in Castilla y León, Spain

Plant Disease ◽

10.1094/pdis-03-11-0172 ◽

2011 ◽

Vol 95 (7) ◽

pp. 876-876 ◽

Cited By ~ 7

Author(s):

M. T. Martin ◽

L. Martin ◽

M. J. Cuesta

Keyword(s):

Elongation Factor ◽

Morphological Characteristics ◽

Genetic Identity ◽

Malt Extract ◽

Koch’S Postulates ◽

First Report ◽

Castilla Y Leon ◽

Agar Plug ◽

Koch's Postulates ◽

Β Tubulin

During a survey for grapevine decline, five young grapevines (cvs. Tempranillo and Viura) with low vigor and reduced foliage were collected (June and August 2009). Fungal isolations were performed from vascular and brown wood. Small pieces of brown wood were placed onto malt extract agar supplemented with 0.25 g/liter of chloramphenicol and incubated at 25°C in darkness. Five resulting colonies were transferred to potato dextrose agar (PDA). Isolates were characterized by abundant, gray, aerial mycelium that reached a radius of 45 mm after 4 days. Pycnidia induced on water agar with pine needles and UV light contained conidia that were hyaline, smooth, thin walled, fusiform, (20-) 22 to 26 (-28) × (5.5-) 6 (-6.5) μm, with granular cytoplasm. On the basis of morphological characteristics Neofusicoccum mediterraneum was suspected (1). Single-conidial cultures were generated from each isolate. DNA analyses were described in Martin and Cobos (2). Sequences of the internal transcribed spacer (ITS) region confirmed the identification and revealed 99% genetic identity with N. mediterraneum (GenBank Accession No EU040221). A sequence of the ITS fragment was deposited with Accession No. JF437919. Partial sequences of β-tubulin and 1-α elongation factor genes were amplified and deposited in the GenBank with Accession Nos. JF437921 and JF437923, showing 100 and 99% similarity to Accession Nos. GU292786 and GU251350, respectively. Pathogenicity tests were conducted with two isolates. The inoculations were carried out on a fresh wound on which an agar plug was applied; on 110R-rootstock woods of 12 young vines with N. mediterraneum and 12 other control plants were treated with agar only. Grapevines were maintained in a greenhouse at 20 to 25°C. After 4 months, N. mediterraneum was reisolated from vascular and brown tissues in 92% of inoculated plants, fulfilling Koch's postulates. Control plants were asymptomatic and N. mediterraneum was not recovered. With the same methodology, isolate Y264-21-1 reached a radius of 43 mm after 4 days at 25°C on PDA, presented colonies becoming olivaceous with a moderately dense mycelia, mat in center, and aerial around. Conidia were hyaline, fusiform, base subtruncate (19-) 23 to 26 (-31) × 5 to 6 (7.5) μm, unicellular, and smooth with granular contents. Based on these descriptions, N. australe was suspected (3). ITS sequence comparison revealed 99% genetic identity with N. australe (Accession No. FJ150697), a sequence of the fragment was deposited with Accession No. JF437920. Partial sequences of β-tubulin and 1α-elongation factor were deposited in the GenBank (Accession Nos. JF437922 and JF437924) showing 100 and 99% similarity to Accession Nos. AY615149 and GU251352, respectively. Koch's postulates were completed as described above. After 4 months, N. australe was reisolated from internal brown lesions in 92% of inoculated plants. Control plants were asymptomatic and N. australe was not recovered. The streaking length average from inoculation point for N. mediterraneum was 42 ± 22 mm and 53 ± 7 mm for N. australe. To our knowledge this is the first report of N. mediterraneum and N. australe in Castilla y León (Spain). References: (1) P. W. Crous et al. Fungal Planet 19:2, 2007. (2) M. T. Martin and R. Cobos. Phytopathol. Mediterr. 46:18, 2007. (3) B. Slippers et al. Mycologia 96:1030, 2004.

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Controlling Annual Bluegrass (Poa annua L.) Summer Patch Disease with Faeriefungin

HortScience ◽

10.21273/hortsci.28.3.195 ◽

1993 ◽

Vol 28 (3) ◽

pp. 195-196

Author(s):

Brad P. Melvin ◽

Muraleedharan G. Nair ◽

Joe M. Vargas ◽

A. Ronald Detweiler

Keyword(s):

Streptomyces Griseus ◽

Field Trials ◽

Poa Annua ◽

Golf Course ◽

Annual Bluegrass ◽

Magnaporthe Poae ◽

History Of ◽

Patch Disease

Faeriefungin, an antibiotic produced by the actinomycete Streptomyces griseus var. autotrophicus MSU-32058/ATCC 53668, was tested in field trials on golf course fairways to determine if it could control annual bluegrass (Poa annua L.) summer patch effectively. Test sites with a history of severe summer patch outbreaks caused by Magnaporthe poae Landschoot and Jackson were chosen for study. Faeriefungin, when applied as a drench at 0.74 kg·ha-1, effectively controlled summer patch and was not significantly different than the fungicide fenarimol in three of four field trials. Faeriefungin may be an alternative to chemically controlling summer patch disease.

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First Report of Leaf Spot Caused by Didymella americana on Cassia nomame in China

Plant Disease ◽

10.1094/pdis-08-21-1799-pdn ◽

2021 ◽

Author(s):

Weiming Sun ◽

Lina Feng ◽

Xiaolei Wen ◽

Bojia Han ◽

Danrun Xing ◽

...

Keyword(s):

Sequence Analysis ◽

Leaf Spot ◽

Disease Incidence ◽

Morphological Characteristics ◽

Rrna Gene ◽

Pathogenicity Test ◽

Koch’S Postulates ◽

First Report ◽

Initial Symptoms ◽

Koch's Postulates

Cassia nomame (Sieb.) Kitagawa is an annual plant in the Leguminousae family. The aerial parts of C. nomame have been used as tonic and diuretic in Korea and Japan (Syed et al. 2019). A leaf spot was observed on the leaves of a 1-year-old C. nomame landrace in Changli County (39.42°N, 119.10°E), Qinhuangdao City, Hebei Province during August to October in 2018. In many fields (n≥3), the disease incidence over 80% in the middle and late stage of plant growth. Symptoms on leaves in one field began with many small, dark necrotic spot lesions. Later, the lesions spread to round-to-oval, slightly sunken in the center, and large necrotic patches with indefinite margins. Finally, lesions coalesced and resulted in defoliation. Lesions were occasionally observed on the pods. Symptoms on the pods were initially small, dark spots and then expanded to large necrotic patches with irregular edges. Symptomatic tissues (n=32) from pods and leaves were cut into 3 to 8 mm2 squares, surface disinfested with 75% ethanol for 10 s, rinsed with sterile distilled water, then placed on potato dextrose agar (PDA) at 28℃. After 3 days, ten isolates with consistent characteristics were obtained with a frequency 52.6%. The isolates on PDA were round, initially pale and had little aerial mycelium, gradually turned olive green and had dense wool-like dense aerial mycelia after 3 days. Conidia were hyaline, smooth, solitary, and elliptical. The conidia measured 5.4 to 8.2 μm × 2.5 to 3.8 μm (n=50), and has two oil bodies positioning at opposite poles. Pigmented chlamydospores were spherical or nearly pear-shaped, and solitary. Black fructifications (pycnidia) were produced profusely on PDA after subculture for 3 days. All the isolates were similar to Didymella sp. in morphology (Aveskamp et al. 2009). Choice three isolates YSGUO8 YSGGUO8-a and YSGGUO8-b to be further characterized by sequencing of the internal transcribed spacer (ITS), actin gene, and 28S large subunit of the nuclear rRNA gene (LSU) (Zhang et al. 2017). The sequences of three strains (MK836417 MZ484072 and MZ484073 for ITS, MK837604 MZ593675 and MZ593676 for actin, MK843781 MZ836208 and MZ836207 for LSU, respectively) showed 99% to 100% similarity with Didymella americana K-004 (KY070279 for ITS,KY070285 for LSU), Phoma americana CBS 256.65 (FJ426973 for ITS, FJ426871 for actin, MH870196 for LSU) and P. americana CBS 185.85 (FJ426972 for ITS, FJ426870 for actin, GU237990 for LSU) in GenBank. The fungi were identified as D. americana (formerly P. americana or Peyronellaea americana) on the basis of morphological characteristics and sequence analysis. A pathogenicity test was conducted with three times on 1-year-old C. nomame strain at the 4 to 6 compound leaf stage. Conidia were obtained from 7-day-old PDA cultures grown at 28℃ with a 12-h photoperiod. Koch’s postulates were fulfilled by spray inoculating ten healthy young plants with 106 conidia per milliliter of D. americana strain YSGUO8, and sterile water as the control. After inoculation, the plants were managed at 28℃, 60% relative humidity and a 12-h photoperiod. After 5 to 8 days, the inoculated leaves developed small and dark spots lesions similar to those observed on the leaves with initial symptoms in the field. The control leaves remained symptomless. The same fungi were re-isolated from infected leaves by morphology observation and sequence analysis, confirming Koch's postulates. D. americana has caused leaves spot on Table Beet in New York (Vaghefi et al. 2016). To our knowledge, this is the first report of D. americana causing leaf spot of C. nomame in China.

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First Report of Pathogenicity of Fusarium sporotrichioides and Fusarium acuminatum on Sunflowers in the United States

Plant Health Progress ◽

10.1094/php-2010-0915-02-br ◽

2010 ◽

Vol 11 (1) ◽

pp. 42 ◽

Cited By ~ 4

Author(s):

F. Mathew ◽

B. Kirkeide ◽

T. Gulya ◽

S. Markell

Keyword(s):

United States ◽

Helianthus Annuus ◽

The United States ◽

Fusarium Sporotrichioides ◽

Charcoal Rot ◽

Koch’S Postulates ◽

First Report ◽

Fusarium Acuminatum ◽

Helianthus Annuus L ◽

Koch's Postulates

Widespread infection of charcoal rot was observed in a commercial sunflower field in Minnesota in September 2009. Based on morphology, isolates were identified as F. sporotrichioides and F. acuminatum. Koch's postulates demonstrated pathogencity of both species. To our knowledge, this is the first report of F. sporotrichoides and F. acuminatum causing disease on Helianthus annuus L. in the United States. Accepted for publication 23 August 2010. Published 15 September 2010.

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