First Report of Black Leaf Mold of Tomato Caused by Pseudocercospora fuligena in Ohio

Diseased tomato (Solanum lycopersicum L. cvs. Geronimo, Rebelski, and Big Dena) plants were received for diagnosis from a home gardener in Wayne County, Ohio, in August 2013 and from a 0.14-ha greenhouse in Brown County, Ohio, in September 2013. Approximately 10 and 60% of leaf area was diseased in the home garden and greenhouse, respectively. One or more lesions, each with an indistinct border, were observed on the leaves. Black fungal growth was observed on both sides of the leaf in association with the lesions. Microscopic examination revealed Cercospora-like conidia (2). Three symptomatic leaves from each location were surface-sterilized with 0.5% NaClO for 1 min and cultured on V8 juice agar medium at room temperature under continuous fluorescent lighting. One isolate was selected from each of Wayne Co. (SAM33-13) and Brown Co. (SAM34-13). The fungus produced small, dark-brown colonies within 2 weeks of plating. Mycelium was olive brown and septate, producing fascicles of conidiophores. Conidia were cylindrical, 2 to 14 septate, and 25.8 to 109.7 × 6.5 μm. Genomic DNA was extracted from colonies of isolate SAM33-13 grown on V8 juice agar medium using the Wizard SV Genomic DNA Purification System (Promega, Madison, WI). The internal transcribed spacer (ITS) region of rDNA was amplified by PCR using primer pair ITS1 and ITS4 (5), and the purified amplicon was sequenced (OARDC Molecular and Cellular Imaging Center, Wooster, OH). The ITS sequence was 99% identical to those of GenBank accessions of Pseudocercospora fuligena from Korea (JX290079) and Thailand (GU214675). The sequence was deposited in GenBank (KF931141). Based on morphology (4) and sequence analysis, the fungus was identified as P. fuligena (Roldan) Deighton (basionym Cercospora fuligena). To satisfy Koch's postulates, three 4-week-old tomato plants each of the cultivars L390 (AVRDC, Taiwan) and Mountain Spring (Siegers Seed Co., Holland, MI) were sprayed with a suspension of 1 × 103 conidia/ml of isolates SAM33-13 or SAM34-13 prepared from 3-week-old cultures growing on V8 juice agar medium. Three non-inoculated control plants were sprayed with sterilized water. Plants were maintained in a growth chamber at 25 to 30°C, 80% RH, and a 12 h/12 h day/night cycle. The first symptoms appeared 3 weeks after inoculation as light yellow foliar lesions. The lesions enlarged and turned black due to fungal growth, and the infected leaves dried. Disease severity was 70 and 10% of leaf area for cvs. L390 and Mountain Spring, respectively, for each isolate. Non-inoculated control plants were symptomless, and no fungus was re-isolated from the leaves. P. fuligena was isolated from symptomatic leaves of inoculated plants as described above, and the identity was confirmed based on morphology. In the United States, C. fuligena has not been reported infecting tomato since the first report in Florida in 1974 (1). To our knowledge, this is the first report of black leaf mold of tomato caused by P. fuligena in Ohio. Resistant cultivars, crop sanitation, and fungicides are recommended to manage the disease (3). References: (1) C. H. Blazquez and S. A. Alfieri. Phytopathology 64:443, 1974. (2) U. Braun. IMA Fungus 4:265, 2013. (3) R. Cerkauskas. AVRDC Publication 04-606, 2004. (4) B. Halfeld-Vieira et al. Fitopatol. Bras. 31:3, 2006. (5) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA, 1990.

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First Report of Black Leaf Mold of Tomato Caused by Pseudocercospora fuligena in North Carolina

Plant Disease ◽

10.1094/pdis-06-17-0897-pdn ◽

2018 ◽

Vol 102 (2) ◽

pp. 442-442 ◽

Cited By ~ 1

Author(s):

E. C. Lookabaugh ◽

A. Thomas ◽

B. B. Shew ◽

S. C. Butler ◽

F. J. Louws

Keyword(s):

North Carolina ◽

First Report ◽

Leaf Mold ◽

Black Leaf Mold ◽

Pseudocercospora Fuligena

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Black Leaf Mold of Tomato Caused by Pseudocercospora fuligena in Korea

Research in Plant Disease ◽

10.5423/rpd.2012.18.3.255 ◽

2012 ◽

Vol 18 (3) ◽

pp. 255-258 ◽

Cited By ~ 1

Author(s):

Mun-Haeng Lee ◽

Suk-Soo Lee ◽

Hong-Gi Kim ◽

Youn-Su Lee ◽

Ji-Hye Lee ◽

...

Keyword(s):

Leaf Mold ◽

Black Leaf Mold ◽

Pseudocercospora Fuligena

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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 Erysiphe fallax Causing Powdery Mildew on Phasey Bean (Macroptilium lathyroides) in the United States

Plant Health Progress ◽

10.1094/php-11-18-0071-br ◽

2019 ◽

Vol 20 (1) ◽

pp. 35-37

Author(s):

Bindu Poudel ◽

Shouan Zhang

Keyword(s):

Phylogenetic Analysis ◽

Powdery Mildew ◽

Genomic Dna ◽

Morphological Characteristics ◽

Fungal Growth ◽

The United States ◽

Bean Plants ◽

The Family ◽

Tropical America ◽

Macroptilium Lathyroides

Phasey bean (Macroptilium lathyroides) is a member of the family Fabaceae and is native to tropical America. During the fall of 2017, the leaves of phasey bean plants in Homestead, FL, showed white powdery fungal growth. The morphological characteristics suggested that the pathogen was powdery mildew. For further identification, genomic DNA was extracted from conidia. BLAST results showed that the sequence of FL-1 shares 99% identity to an Erysiphe fallax. Phylogenetic analysis confirmed the closest proximity of FL-1 isolate to E. fallax. Koch’s postulates were performed to confirm the pathogenicity.

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First Report of Impatiens Downy Mildew Caused by Plasmopara obducens in Kentucky

Plant Disease ◽

10.1094/pdis-10-12-0973-pdn ◽

2013 ◽

Vol 97 (3) ◽

pp. 428-428 ◽

Cited By ~ 3

Author(s):

N. A. Ward ◽

E. Dixon ◽

B. Amsden

Keyword(s):

Downy Mildew ◽

Ribosomal Subunit ◽

Fungal Growth ◽

The United States ◽

Diseased Plant ◽

Distilled Water ◽

First Report ◽

Plastic Bags ◽

Impatiens Walleriana ◽

Black Plastic

Impatiens downy mildew (Plasmopara obducens (J. Schröt.) J. Schröt. (syn Peronospora obducens) was first reported in the United States in 2004, but widespread outbreaks were observed throughout North America in 2011 (5). In June 2012, symptoms, including severe defoliation while plants retained upright stems, were observed on approximately 100 landscape impatiens (Impatiens walleriana Hook.f.) in Franklin County in central Kentucky. All plants in the landscape were affected. Plants were primarily defoliated and remaining leaves were stunted, mottled, and chlorotic with edges curled downward; no flowers were present. Under examination with a dissecting microscope, white downy fungal growth was observed. Closer examination confirmed that the growth consisted of colorless sporangiophores that were mainly unbranched, straight, and rigid (1,3). Sporangiophores consisted of apical branches attached at right angles to main axes, ranging from 67.2 to 89.9 μm long (1). Sporangia were ovoid and hyaline, measuring 11.2 to 13.3 μm × 8.2 to 10.7 μm (3). No oospores were observed. Pathogenicity tests were performed by inoculating 20 to 40 leaves on three plants each of the cvs. Dazzler and Super Elfin with suspensions of 1 × 105 sporangiophores per ml in sterile distilled water. Sporangia were obtained by washing infected leaves with sterile distilled water, and inoculations were completed by spraying leaves until runoff. Plants sprayed with sterile water served as controls. Plants were covered with black plastic bags for 48 h and then maintained under fluorescent lights for 10 days at room temperature (22 to 25°C). Sporangiophores were recovered from inoculated plants after 10 days, and morphology matched original inoculum; symptoms included chlorotic, downward curling leaves with sporulation on the undersides. Non-inoculated plants did not develop symptoms after 21 days. Molecular identification of the pathogen was conducted using three leaves from one plant from each cultivar. PCR was conducted by amplifying the large ribosomal subunit DNA using primers NL-1 and NL-4 (2). Amplicons of 762 to 691 bp were produced from diseased plant tissue that contained visible sporangiophores, and the bands were extracted from the gel and purified. Sequence results confirmed 100% similarity to accessions from Florida (GenBank Accession No. JX217746.1) and Ohio (JX142134.1) and 99% similarity to amplicons reported from Serbia (HQ246451.1) and UK (AY587558.1). This is believed to be the first report of downy mildew infecting impatiens in Kentucky. References: (1) O. Constantinescu. Mycologia 83:473, 1991. (2) W. Maier et al. Can. J. Bot 81:12, 2003. (3) P. A. Saccardo. Syllogue Fungorum 7:242, 1888. (4) S. N. Wegulo et al. Plant Dis. 88:909, 2004.

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First Report of Root Rot Caused by Pythium aphanidermatum on Bell Pepper (Capsicum annuum L.) in Italy

Plant Disease ◽

10.1094/pdis-11-13-1148-pdn ◽

2014 ◽

Vol 98 (6) ◽

pp. 854-854 ◽

Cited By ~ 1

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

G. Ortu ◽

M. L. Gullino

Keyword(s):

Capsicum Annuum ◽

Root Rot ◽

Agar Medium ◽

The United States ◽

Pythium Aphanidermatum ◽

Northern Italy ◽

Bell Pepper ◽

Growth Chamber ◽

Sodium Hypochlorite Solution ◽

First Report

During July 2012, symptoms of root rot were observed on bell pepper (Capsicum annuum) grown in 2,000 m2 of commercial greenhouses near Cuneo in northern Italy. Symptoms first developed 30 to 40 days after transplanting, when greenhouse temperatures ranged from 25 to 30°C, and 10% of the plants were affected. Affected plants were stunted with leaf chlorosis, reduced growth, and sudden wilting. Roots were severely affected with a brown discoloration, water-soaking, and soft rot. Eventually, affected plants collapsed. Tissue fragments of 1 mm2 were excised from symptomatic roots, dipped in a 1% sodium hypochlorite solution, and placed on potato dextrose agar (PDA) and an agar medium selective for oomycetes (3). Plates were incubated under constant fluorescent light at 22 ± 1°C for 5 days. An isolate grown for 12 days on V8 agar medium (200 ml V8 Campbell Soup, 15 g agar, 0.5 g CaCO3, and 1 liter distilled water) showed aseptate hyphae that were 3.5 to 6.3 μm (avg. 5.2 μm) wide. Oogonia were globose, smooth, and 24.3 to 29.0 (avg. 25.1) μm in diameter. Antheridia were barrel-shaped, while oospores were globose, and 17.3 to 23.5 μm (avg. 21.2 μm) in diameter. These morphological characters identified the microorganism as a Pythium sp. (4). The ITS region of rDNA of a single isolate was amplified using the primers ITS1/ITS4 and sequenced. BLAST analysis (1) of the 781-bp segment (GenBank Accession KF840479) showed 100% homology with the ITS sequence of an isolate of Pythium aphanidermatum in GenBank (AY598622.2). Pathogenicity tests were performed twice on 30-day-old plants of C. annuum cv. Cuneo grown in 2-L pots (4 plants/pot), containing a steam-disinfested, organic peat substrate (70% black peat and 30% white peat, pH 5.5 to 6.0, N 110 to 190 mg/liter, P2O5 140 to 230 mg/liter, K2O 170 to 280 mg/liter) that was infested with wheat and hemp kernels colonized by the isolate of P. aphanidermatum, at a rate of 1 g colonized kernels/liter potting medium. The inoculum was prepared by autoclaving at 121°C for 30 min a mixture of wheat-hemp kernels (2:1 v/v) in a 1-liter flask, to which the bell pepper isolate of P. aphanidermatum was added in the form of colonized agar medium selective for oomycetes plugs. Before use, the inoculated flask was incubated for 10 days at 22°C in the dark. Four plants/pot were transplanted into each of four pots filled with the infested medium/growth chamber, while the same number of plants were grown in non-infested substrate in pots in each growth chamber. Plants were kept in two growth chambers, one set at 20°C and the other at 28°C. Symptoms first developed 7 days after inoculation. After 30 days, 50% of inoculated plants showed brown roots and died in the growth chamber set at 28°C, while only 10% of the plants were symptomatic at 20°C. Control plants remained asymptomatic at both temperatures. P. aphanidermatum was re-isolated consistently from the symptomatic roots of plants grown in the infested soil by using the same protocol as the original isolations, while no fungal colonies were obtained from asymptomatic roots of the non-inoculated control plants. To our knowledge, this is the first report of the presence of P. aphanidermatum on C. annuum in Italy. The same disease was reported in the United States (2). The importance of the disease, although limited in distribution at present to the greenhouses surveyed in northern Italy, could increase in areas where sweet pepper is grown intensively. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) D. O. Chellemi et al. Plant Dis. 84:1271, 2000. (3) H. Masago et al. Phytopathology 67:425, 1977. (4) T. Watanabe. Pictorial Atlas of Soil and Seed Fungi. CRC Press, Boca Raton, FL, 2002.

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First Report of Canola Powdery Mildew Caused by Erysiphe polygoni in Argentina

Plant Disease ◽

10.1094/pdis.2004.88.10.1163c ◽

2004 ◽

Vol 88 (10) ◽

pp. 1163-1163 ◽

Cited By ~ 5

Author(s):

S. Gaetán ◽

M. Madia

Keyword(s):

Powdery Mildew ◽

Buenos Aires ◽

Disease Incidence ◽

Fungal Growth ◽

The United States ◽

Climatic Conditions ◽

Width Ratio ◽

Infected Leaf ◽

First Report ◽

Erysiphe Polygoni

Canola (Brassica napus) is a developing oleaginous crop grown commercially in the Buenos Aires and Santa Fe provinces of Argentina. During the autumn of 2003, typical signs of powdery mildew were observed on canola plants in experimental field plots in Buenos Aires. Average disease incidence was 42% on 3- to 6-month-old canola cultivars developed in the following countries: Argentina (Eclipse, Impulse Master, Mistral, and Nolza); Australia (Oscar and Rainbow); Canada (Sentry); France (Cadillac, Camberra, and Capitol); and Sweden (Maskot, Sponsor, and Wildcat). The range of incidence on these cultivars was 35 to 93%. Other cultivars exhibited an apparent high level of resistance or escaped disease. These included: Charlton (Argentina); 46CO3, Dunkeld, Insignia, Mystic, Monty, Outback, Rivette, and Surpass 400 (Australia), and Caviar (France). Climatic conditions in Buenos Aires, especially rainfall, from March to May 2003 were apparently favorable for powdery mildew development. On susceptible cultivars, fungal growth was observed on leaves, stems, and pods that resulted in premature senescence of the tissues. The mycelium, with multilobed hausthoria, was white to gray, dense or fine, and in patches or covering the entire adaxial leaf surfaces. Appressoria were lobed and conidiophores were straight. Foot cells were cylindrical, straight, measured 35 to 42 × 7 to 10 μm, and were followed by two cells. Conidia were produced singly, cylindrical to ovoid, and measured 36 to 40 × 18 to 20 μm. The conidial length-to-width ratio was 2.0. No fibrosin bodies were observed in the conidia and conidia germinated at the ends. Cleistothecia were not observed. On the basis of mycelial, conidial, and hausthoria characteristics observed on six leaves for each affected cultivar, the fungus was identified as Erysiphe polygoni DC (1). Pathogenicity was confirmed on 5-week-old canola plants of cvs. Eclipse, Impulse, Master, Mistral, and Maskot by gently pressing (1 min) one adaxial infected leaf with abundant sporulation onto one adaxial healthy leaf. The experiment, which included five inoculated plants and three noninoculated control plants for each cultivar, was conducted in a greenhouse at 22 to 24°C and maintained at 75% relative humidity with no supplemental light. Inoculated and control plants were covered with polyethylene bags for 48 h after inoculation. Powdery mildew developed on all inoculated plants of all cultivars after 12 to14 days. The control plants did not develop disease. The experiment was repeated with similar results. E. polygoni has a worldwide distribution (2); however, the results suggest that this fungus may be a threat to the main cultivars being grown in Argentina (Eclipse, Impulse, Master, Mistral, and Nolza), since high levels of disease incidence, as much as 70%, were observed. Under propitious environments, this pathogen could cause severe yield losses in commercially grown canola in Argentina. To our knowledge, this is the first report of canola powdery mildew caused by E. polygoni in Argentina. References: (1) H. J. Boesewinkel. Rev. Mycol. Tome 41:493, 1977. (2) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St.Paul, MN, 1989.

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Survey and Screening of Fungicide for the Control of Tomato Black Leaf Mold Pseudocercospora fuligena

Research in Plant Disease ◽

10.5423/rpd.2015.21.2.094 ◽

2015 ◽

Vol 21 (2) ◽

pp. 94-98 ◽

Cited By ~ 1

Author(s):

Mun Haeng Lee ◽

Hee Keyung Lee ◽

Pyeng Hwa Cho ◽

Young Shik Kim ◽

Suk Keyung Cho ◽

...

Keyword(s):

Leaf Mold ◽

Black Leaf Mold ◽

Pseudocercospora Fuligena

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First Report of Powdery Mildew Caused by Podosphaera (Sphaerotheca) fusca on Euryops pectinatus in North America

Plant Disease ◽

10.1094/pdis.2000.84.9.1048a ◽

2000 ◽

Vol 84 (9) ◽

pp. 1048-1048 ◽

Cited By ~ 1

Author(s):

G. S. Saenz ◽

S. T. Koike ◽

N. Shishkoff

Keyword(s):

United States ◽

New York ◽

North America ◽

Powdery Mildew ◽

Fungal Growth ◽

The United States ◽

Voucher Specimen ◽

First Report ◽

Humidity Chamber ◽

Powdery Mildew Pathogen

Gray-leaved Euryops (Euryops pectinatus Cass., Asteraceae) is an evergreen shrub that is widely planted in landscapes in the United States. In the fall of 1999, powdery mildew was observed on E. pectinatus planted in landscapes in Redlands (San Bernardino County), CA. Symptoms consisted only of slight cupping of leaves. Fungal growth was observed on stems, leaves, petioles, and pedicels and was ectophytic and amphigenous. The white mycelium was patchy to effuse. Hyphal appressoria were indistinct (1). Conidiophore foot cells were cylindric and sometimes were tapered toward or constricted at the base. Foot cells measured 30 to 50 by 10 to 12 μm and were followed by one to two shorter cells. Conidia were cylindric to slightly doliform, borne in chains of two to three, and measured 26 to 38 by 14 to 18 μm. Conidial length to width ratios ranged from 1.7 to 2.4. Catenate conidia had crenate edge lines (3). Conidia possessed conspicuous fibrosin bodies and from their sides produced short germ tubes without appressoria. Cleistothecia were not observed. Based on these characters, the fungus was identified as Podosphaera fusca (Fr.) U. Braun & N. Shishkoff (Podosphaera sect. Sphaerotheca) (1,2). Pathogenicity was confirmed by gently pressing diseased leaves onto leaves of healthy E. pectinatus plants. Plants were incubated in a humidity chamber at 22 to 24°C and after 12 to 14 days powdery mildew colonies developed. E. pectinatus cv. Viridis, a cultivar that lacks the extensive pubescence of E. pectinatus, also developed disease when inoculated. This appears to be the first report of powdery mildew on E. pectinatus in North America. A voucher specimen has been deposited into the University of California Herbarium (accession # UC1738635). P. fusca was also observed on cv. Viridis in a nursery in New York in 1999. It is unclear where this pathogen originated. P. fusca parasitizes a large number of asteraceous species including dandelion (Taraxacum officinalis) and sowthistle (Sonchus spp.) weeds, which occur in the area and sometimes are infected with powdery mildew. The Euryops powdery mildew pathogen may be a race that is different than those found on other composites in the United States. The fungus was observed on plants in shaded areas but not on plants in full sun. References: (1) U. Braun. Nova Hedwigia 89:1, 1987. (2) U. Braun and S. Takamatsu. Schlechtendalia 4:1, 2000. (3) H. D. Shin and Y. J. La. Mycotaxon 46:445, 1993.

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