scholarly journals First Report of Dimethachlon Resistance in Field Isolates of Sclerotinia sclerotiorum on Oilseed Rape in Shaanxi Province of Northwestern China

Plant Disease ◽  
2014 ◽  
Vol 98 (4) ◽  
pp. 568-568 ◽  
Author(s):  
F. Zhou ◽  
F. X. Zhu ◽  
X. L. Zhang ◽  
A. S. Zhang
Keyword(s):  
Oilseed Rape ◽  
Sclerotinia Sclerotiorum ◽  
The United States ◽  
Northwestern China ◽  
Shaanxi Province ◽  
Resistant Isolate ◽  
Economic Losses ◽  
First Report ◽  
Field Isolates ◽  
Wide Range

Sclerotinia sclerotiorum (Lib.) de Bary is a necrotrophic fungal pathogen causing diseases in a wide range of plants, including oilseed rape (3). Substantial economic losses caused by S. sclerotiorum have been reported in the United States, Canada, Brazil, South Africa, Hungary, India, Nepal, and Japan (1). Application of fungicides is the principal tool for controlling S. sclerotiorum because of lack of high level of host resistance. Dicarboximide fungicides such as dimethachlon have been widely used to control S. sclerotiorum in recent years in China and field isolates with reduced sensitivity to dimethachlon have been reported in Jiangsu Province of eastern China (2). In order to understand the current status of dimethachlon resistance in S. sclerotiorum isolates of northwestern China, 196 and 344 isolates of S. sclerotiorum collected from oilseed rape fields in 10 counties throughout Shaanxi Province in 2011 and 2012, respectively, were assayed for sensitivity to dimethachlon using 5 μg ml–1 dimethachlon as a discriminatory dose. Mycelial plugs (6 mm in diameter) cut from the margin of a 48-h-old colony were placed in the center of petri dishes containing potato dextrose agar (PDA) amended with 5 μg ml–1 dimethachlon; PDA without fungicide served as the control. Cultures were incubated at 26°C and colony growth was measured after 72 h of incubation. Isolates that showed growth on PDA amended with fungicide were tentatively considered resistant to dimethachlon, whereas the completely inhibited isolates were considered sensitive. Results showed that 1.02% or 2 isolates of the 196 isolates collected in 2011 and 3.78% or 13 isolates of the 344 isolates collected in 2012 were resistant to dimethachlon. For all the isolates considered resistant and 42 randomly selected sensitive isolates, 50% effective concentrations (EC50) were determined on PDA amended with a series of dimethachlon concentrations. The average EC50 value of dimethachlon for sensitive isolates was 0.29 ± 0.02 μg ml–1 Resistance ratios (EC50 of resistant isolate / average EC50 of sensitive isolates) for the two resistant isolates detected in 2011 were 10.28 and 23.83, respectively, whereas resistance ratios for the 13 resistant isolates detected in 2012 ranged from 24.90 to 101.97. The average EC50 value of dimethachlon for the 13 resistant isolates detected in 2012 was 19.05 μg ml–1, and EC50 values for the two resistant isolates detected in 2011 were 2.98 and 6.91 μg ml–1, respectively. These results indicated that both resistance frequency and resistance level increased from 2011 to 2012. Bioassay results of three resistant isolates indicated that there was positive cross-resistance between dimethachlon and other dicarboximide fungicides such as iprodione and procymidone. To our knowledge, this is the first report of dimethachlon resistance in S. sclerotiorum in Shaanxi Province of northwestern China. The molecular mechanism of dimethachlon resistance in field isolates of S. sclerotiorum remains to be studied. Although resistance frequency is low at present, dimethachlon resistance should be kept in mind and fungicide resistance management tactics such as use of biological control agents, fungicide tank-mixing, or alternating dimethachlon with other fungicides having different modes of action is recommended in controlling S. sclerotiorum. References: (1) M. D. Bolton et al. Mol Plant Pathol. 7:1, 2006. (2) H. X. Ma et al. Plant Dis. 93:36, 2009. (3) L. H. Prudy. Phytopathology 69:875, 1979.

scholarly journals First Report of Oilseed Rape Stem Rot Caused by Sclerotinia sclerotiorum in Greece

Plant Disease ◽  
2008 ◽  
Vol 92 (10) ◽  
pp. 1473-1473 ◽  
Author(s):  
G. T. Tziros ◽  
G. A. Bardas ◽  
J. T. Tsialtas ◽  
G. S. Karaoglanidis
Keyword(s):  
Oilseed Rape ◽  
Sclerotinia Sclerotiorum ◽  
Morphological Characteristics ◽  
The United States ◽  
Stem Rot ◽  
Sclerotinia Stem Rot ◽  
Brassica Napus L ◽  
First Report ◽  
Plastic Bag ◽  
Pathogenicity Tests

Oilseed rape (Brassica napus L.) was recently introduced into Greece for the production of biofuels. During May of 2007, symptoms typical of stem rot were observed on oilseed rape plants in three commercial fields in the area of Galatades-Pella, Central Macedonia, Greece. Approximately 30% of the plants were affected. Symptoms began as a chlorotic wilt on the foliage and developed into necrosis of basal stems. In the advanced stages of the disease, stems and branches became bleached and eventually died. White, as well as black, mycelium and irregularly shaped sclerotia (2 to 5 mm in diameter) were produced abundantly on and inside the affected stems. To isolate the pathogen, 20 symptomatic 6-month-old plants were collected from each field. Sclerotia were dipped in 70% ethanol, surface sterilized in 1% sodium hypochlorite for 1 min, and rinsed in sterile water. Sclerotia placed on potato dextrose agar (PDA) were incubated in the dark at 25°C for 10 days. Sclerotinia sclerotiorum (Lib.) de Bary was identified on the basis of morphological characteristics (2). To conduct pathogenicity tests, 10 6-week-old oilseed rape plants (cv. Titan) were each inoculated with a 5-mm-diameter colonized PDA disk placed in wounds made in the basal stem with a sterile scalpel. Five control plants were treated similarly except that the agar disk did not contain mycelium. Plants were then covered with a plastic bag to maintain high humidity. After 72 h, the bags were removed and the plants were maintained in a growth chamber at 23 to 25°C with a 12-h photoperiod and 75% relative humidity. Pathogenicity tests were repeated three times. Symptoms identical to those observed in the field developed within 12 days after inoculation; control plants remained healthy. The fungus was reisolated from all inoculated plants, confirming Koch's postulates. S. sclerotiorum has been reported on oilseed rape in Argentina, Australia, Brazil, Canada, the United States, and New Zealand (1). To our knowledge, this is the first report of Sclerotinia stem rot of oilseed rape in Greece. References: (1) D. F. Farr et al. Fungal Databases. Systematic Botany and Mycology Laboratory. Online publication. ARS, USDA, 2008. (2) L. M. Kohn. Phytopathology 69:881, 1979.

Expansion of Groundnut ringspot virus Host and Geographic Ranges in Solanaceous Vegetables in Peninsular Florida

2011 ◽  
Vol 12 (1) ◽  
pp. 34 ◽  
Author(s):  
Craig G. Webster ◽  
William W. Turechek ◽  
H. Charles Mellinger ◽  
Galen Frantz ◽  
Nancy Roe ◽  
...  
Keyword(s):  
United States ◽  
The United States ◽  
Vegetable Production ◽  
Viral Pathogen ◽  
Geographic Ranges ◽  
First Report ◽  
Geographic Spread ◽  
Wide Range ◽  
Production Areas ◽  
Solanaceous Plants

To the best of our knowledge, this is the first report of GRSV infecting tomatillo and eggplant, and it is the first report of GRSV infecting pepper in the United States. This first identification of GRSV-infected crop plants in commercial fields in Palm Beach and Manatee Counties demonstrates the continuing geographic spread of the virus into additional vegetable production areas of Florida. This information indicates that a wide range of solanaceous plants is likely to be infected by this emerging viral pathogen in Florida and beyond. Accepted for publication 27 June 2011. Published 25 July 2011.

scholarly journals First Report of Impatiens Downy Mildew Outbreaks Caused by Plasmopara obducens Throughout the Hawai'ian Islands

Plant Disease ◽  
2014 ◽  
Vol 98 (5) ◽  
pp. 696-696 ◽  
Author(s):  
J. A. Crouch ◽  
M. P. Ko ◽  
J. M. McKemy
Keyword(s):  
United States ◽  
Downy Mildew ◽  
The United States ◽  
Molecular Data ◽  
Economic Losses ◽  
Voucher Specimen ◽  
First Report ◽  
Plastic Bags ◽  
Leaf Surfaces ◽  
Impatiens Walleriana

Downy mildew of impatiens (Impatiens walleriana Hook.f.) was first reported from the continental United States in 2004. In 2011 to 2012, severe and widespread outbreaks were documented across the United States mainland, resulting in considerable economic losses. On May 5, 2013, downy mildew disease symptoms were observed from I. walleriana ‘Super Elfin’ at a retail nursery in Mililani, on the Hawai'ian island of Oahu. Throughout May and June 2013, additional sightings of the disease were documented from the islands of Oahu, Kauai, Maui, and Hawai'i from nurseries, home gardens, and botanical park and landscape plantings. Symptoms of infected plants initially showed downward leaf curl, followed by a stippled chlorotic appearance on the adaxial leaf surfaces. Abaxial leaf surfaces were covered with a layer of white mycelia. Affected plants exhibited defoliation, flower drop, and stem rot as the disease progressed. Based on morphological and molecular data, the organism was identified as Plasmopara obducens (J. Schröt.) J. Schröt. Microscopic observation disclosed coenocytic mycelium and hyaline, thin-walled, tree-like (monopodial branches), straight, 94.0 to 300.0 × 3.2 to 10.8 μm sporangiophores. Ovoid, hyaline sporangia measuring 11.0 to 14.6 × 12.2 to 16.2 (average 13.2 × 14.7) μm were borne on sterigma tips of rigid branchlets (8.0 to 15.0 μm) at right angle to the main axis of the sporangiophores (1,3). Molecular identification of the pathogen was conducted by removing hyphae from the surface of three heavily infected leaves using sterile tweezers, then extracting DNA using the QIAGEN Plant DNA kit (QIAGEN, Gaithersburg, MD). The nuclear rDNA internal transcribed spacer was sequenced from each of the three samples bidirectionally from Illustra EXOStar (GE Healthcare, Piscataway, NJ) purified amplicon generated from primers ITS1-O and LR-0R (4). Resultant sequences (GenBank KF366378 to 80) shared 99 to 100% nucleotide identity with P. obducens accession DQ665666 (4). A voucher specimen (BPI892676) was deposited in the U.S. National Fungus Collections, Beltsville, MD. Pathogenicity tests were performed by spraying 6-week-old impatiens plants (I. walleriana var. Super Elfin) grown singly in 4-inch pots with a suspension of 1 × 104 P. obducens sporangia/ml until runoff using a handheld atomizer. Control plants were sprayed with distilled water. The plants were kept in high humidity by covering with black plastic bags for 48 h at 20°C, and then maintained in the greenhouse (night/day temperature of 20/24°C). The first symptoms (downward curling and chlorotic stippling of leaves) and sporulation of the pathogen on under-leaf surfaces of the inoculated plants appeared at 10 days and 21 days after inoculation, respectively. Control plants remained healthy. Morphological features and measurements matched those of the original inoculum, thus fulfilling Koch's postulates. To our knowledge, this is the first report of downy mildew on I. walleriana in Hawai'i (2). The disease appears to be widespread throughout the islands and is likely to cause considerable losses in Hawai'ian landscapes and production settings. References: (1) O. Constantinescu. Mycologia 83:473, 1991. (2) D. F. Farr and A. Y. Rossman. Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ July 16, 2013. (3) P. A. Saccardo. Syllogue Fungorum 7:242, 1888. (4) M. Thines. Fungal Genet Biol 44:199, 2007.

scholarly journals First Report of Sclerotinia sclerotiorum on Campanula carpatica and Schizanthus × wisetonensis in Italy

Plant Disease ◽  
2002 ◽  
Vol 86 (1) ◽  
pp. 71-71
Author(s):  
A. Garibaldi ◽  
A. Minuto ◽  
M. L. Gullino
Keyword(s):  
United States ◽  
Sclerotinia Sclerotiorum ◽  
Ornamental Plants ◽  
Soil Surface ◽  
The United States ◽  
First Report ◽  
Potted Plants ◽  
Initial Symptoms ◽  
Stem Necrosis ◽  
Campanula Carpatica

The production of potted ornamental plants is very important in the Albenga Region of northern Italy, where plants are grown for export to central and northern Europe. During fall 2000 and spring 2001, sudden wilt of tussock bellflower (Campanula carpatica Jacq.) and butterfly flower (Schizanthus × wisetonensis Hort.) was observed on potted plants in a commercial greenhouse. Initial symptoms included stem necrosis at the soil line and yellowing and tan discoloration of the lower leaves. As stem necrosis progressed, infected plants growing in a peat, bark compost, and clay mixture (70-20-10) wilted and died. Necrotic tissues were covered with whitish mycelia that produced dark, spherical (2 to 6 mm diameter) sclerotia. Sclerotinia sclerotiorum was consistently recovered from symptomatic stem pieces of both plants disinfested for 1 min in 1% NaOCl and plated on potato dextrose agar amended with streptomycin sulphate at 100 ppm. Pathogenicity of three isolates obtained from each crop was confirmed by inoculating 45- to 60-day-old C. carpatica and Schizanthus × wisetonensis plants grown in containers (14 cm diameter). Inoculum that consisted of wheat kernels infested with mycelia and sclerotia of each isolate was placed on the soil surface around the base of previously artificially wounded or nonwounded plants. Noninoculated plants served as controls. All plants were maintained outdoors where temperatures ranged between 8 and 15°C. Inoculated plants developed symptoms of leaf yellowing, followed by wilt, within 7 to 10 days, while control plants remained symptomless. White mycelia and sclerotia developed on infected tissues and S. sclerotiorum was reisolated from inoculated plants. To our knowledge, this is the first report of stem blight of C. carpatica and Schizanthus × wisetonensis caused by S. sclerotiorum in Italy. The disease was previously observed on C. carpatica in Great Britain (2) and on Schizanthus sp. in the United States (1). References: (1) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN, 1989. (2) J. Rees. Welsh J. Agric. 1:188, 1925.

scholarly journals First Report of White Mold Caused by Sclerotinia sclerotiorum on Oreganum vulgare and Taraxacum officinale in Italy

Plant Disease ◽  
2007 ◽  
Vol 91 (10) ◽  
pp. 1360-1360
Author(s):  
A. Garibaldi ◽  
A. Minuto ◽  
M. L. Gullino
Keyword(s):  
Sclerotinia Sclerotiorum ◽  
Soil Surface ◽  
Taraxacum Officinale ◽  
White Mold ◽  
Economic Losses ◽  
Medicinal Uses ◽  
First Report ◽  
Potted Plants ◽  
Mycelial Plug ◽  
Commercial Farms

Oreganum vulgare (wild marjoram) and Taraxacum officinale (dandelion) plants with culinary and medicinal uses are grown in the field and as potted plants in Liguria in northern Italy. In the spring of 2006, extensive chlorosis was observed on both crops on commercial farms. Economic losses were low. Symptoms included foliar necrosis and a watery decay of the stem at the soil level. Necrotic tissues became covered with a whitish mycelium that produced dark sclerotia. Eventually, affected plants wilted and died. Samples of diseased stem tissue were surface sterilized for 1 min in 1% NaOCl and plated on potato dextrose agar (PDA) amended with 100 mg/l of streptomycin sulfate. Sclerotinia sclerotiorum (Lib.) de Bary (1) was consistently recovered from diseased stem pieces. Sclerotia from infected O. vulgare plants measured 1.8 to 3.4 × 1.8 to 6.1 (average 2.5 to 3.6) mm. Sclerotia from these isolates measured 1.3 to 4.7 × 1.6 to 6.1 (average 2.7 to 3.4) mm on PDA. Sclerotia from infected T. officinale plants measured 1.8 to 3.4 × 1.8 to 6.1 (average 2.5 to 3.6) mm. Sclerotia from these isolates measured 1.7 to 5.2 × 2.0 to 5.7 (average 3.3 to 3.8) mm on PDA. Pathogenicity of three isolates obtained from O. vulgare and three isolates from T. officinale was confirmed on each host. Inoculum consisted of 1 cm2 of mycelial plugs excised from a 10-day-old PDA culture of each isolate. Plants were inoculated by placing a mycelial plug on the soil surface around the base of each plant. Ten plants were inoculated per isolate and an equal number of noninoculated plants served as controls. Plants were incubated at 10 to 27°C (average 18°C) and watered as needed. Pathogenicity tests were repeated once. All inoculated plants developed chlorosis within 12 to 18 days, followed by the appearance of white mycelium and sclerotia, and eventually wilt. Control plants remained symptomless. S. sclerotiorum was reisolated from inoculated plants of both hosts. To our knowledge, this is the first report of white mold on O. vulgare in Italy as well as worldwide and the first report of white mold on T. officinale in Italy. S. sclerotiorum is a well known pathogen of T. officinale (2) and its use as a mycoherbicide has been proposed (3). References: (1) N. F. Buchwald. Page 75. Den. Kgl. Veterin.er-og Landbohojskoles Aarsskrift, 1949. (2) D. M. McLean. Plant Dis. Rep. 35:162, 1951 (3) G. E. Riddle et al. Weed Sci. 39:109, 1991.

scholarly journals First Report of Okra yellow mosaic Mexico virus in Okra in the United States

Plant Disease ◽  
2010 ◽  
Vol 94 (7) ◽  
pp. 924-924 ◽  
Author(s):  
C. Hernandez-Zepeda ◽  
T. Isakeit ◽  
A. Scott ◽  
J. K. Brown
Keyword(s):  
United States ◽  
The United States ◽  
Full Length ◽  
Bipartite Begomoviruses ◽  
Economic Losses ◽  
Growth Stages ◽  
First Report ◽  
Total Dna ◽  
Hidalgo County ◽  
Whitefly Vector

During the okra growing season from August to November of 2009, symptoms reminiscent of geminivirus infection were observed on 75% of ‘Green Emerald’ Abelmoschus esculentus (L.) Moench, plants in a 0.2-km2 field in Hidalgo County, TX. Visible symptoms consisted of irregular yellow patches on leaves, distinctive yellow borders on leaf edges, and chlorosis of subsequently developing leaves. The whitefly vector of begomoviruses, Bemisia tabaci (Genn.), infested okra plants in the early growth stages during late July 2009. Total DNA was isolated from the leaves of three symptomatic okra plant samples (1) and used as the PCR template to amplify a 575-bp fragment of the coat protein gene (CP) using the universal begomovirus primers AV494 and AC1048 (2). PCR products of the expected size were cloned into the pGEM-T Easy (Promega, Madison, WI) and sequenced using the universal M13F and M13 R primers. ClustalV alignment indicated 99 to 100% shared nucleotide (nt) identity, and BLAST analysis revealed that the closest relative was Okra yellow mosaic Mexico virus - Tetekalitla (OkYMMV) (GenBank Accession No. EF591631) at 98%. To amplify the full-length DNA-A and a possible cognate DNA-B component, one plant that was positive by CP-PCR and DNA sequencing was selected for further analysis. Total DNA from this plant was used as template for a second detection method that consisted of rolling circle amplification (RCA) using the TempliPhi 100 Amplification System (GE Healthcare). RCA is a non-sequence-specific approach that permits amplification of circular DNA. The RCA products were linearized to release unit length ~2.6 kb DNA-A and DNA-B components using BamHI, and EcoRI, respectively. These products were cloned into pGEM3zf+ (Promega) and sequenced using M13F and M13 R primers and then by primer walking (>300 base overlap). Full-length DNA-A and DNA-B components were obtained, respectively, at 2,613 bp (GenBank Accession No. HM035059) and 2,594 bp (GenBank Accession No HM035060). Alignment of the DNA-A component using ClustalV (MegAlign, DNASTAR, Madison, WI) with begomoviral sequences available in GenBank indicated that it was 99% identical to OkYMMV DNA-A (GenBank Accession No. DQ022611). The closest relative to the DNA-B component (ClustalV) was Sida golden mosaic virus (SiGMV) (GenBank Accession No. AJ250731) at 73%. The nt identity of the 172-nt ‘common region’ present in the DNA-A and DNA-B components was 99%, and the iterons (predicted Rep binding motif) were identical for the two components, indicating that they are a cognate pair. The genome organization was typical of other New World bipartite begomoviruses. The economic losses due to infection by this virus could not be determined because an early freeze killed the plants. Hidalgo County is adjacent to Tamaulipas, Mexico, where ~50 km2 of okra are grown and the whitefly vector is also present. The identification of OkYMMV based on two independent detection methods, and the presence of begomovirus-like symptoms together with the whitefly vector, provide robust evidence for the association of OkYMMV-TX with diseased okra plants. To our knowledge, this is the first report of OkYMMV-TX infecting okra crops in Texas and in the continental United States. References: (1) J. J. Doyle and J. L. Doyle. Focus 12:13, 1990. (2) S. Wyatt and J. K. Brown. Phytopathology 86:1288, 1996.

scholarly journals Overexpression of Brassica napus MPK4 Enhances Resistance to Sclerotinia sclerotiorum in Oilseed Rape

2009 ◽  
Vol 22 (3) ◽  
pp. 235-244 ◽  
Author(s):  
Zheng Wang ◽  
Han Mao ◽  
Caihua Dong ◽  
Ruiqin Ji ◽  
Li Cai ◽  
...  
Keyword(s):  
Brassica Napus ◽  
Transgenic Plants ◽  
Oilseed Rape ◽  
Sclerotinia Sclerotiorum ◽  
Mitogen Activated Protein Kinase ◽  
Economic Losses ◽  
Loss Of Function ◽  
Mitogen Activated Protein ◽  
Transgenic Oilseed Rape ◽  
Plant Pathogen Interactions

Sclerotinia sclerotiorum causes a highly destructive disease in oilseed rape (Brassica napus) resulting in significant economic losses. Studies on the Arabidopsis thaliana MPK4 loss-of-function mutant have implicated that AtMPK4 is involved in plant defense regulation, and its effect on disease resistance varies in different plant–pathogen interactions. In this study, we isolated a B. napus mitogen-activated protein kinase, BnMPK4, and found that BnMPK4 along with PDF1.2 are inducible in resistant line Zhongshuang9 but both are consistently suppressed in susceptible line 84039 after inoculation with S. sclerotiorum. Transgenic oilseed rape overexpressing BnMPK4 markedly enhances resistance to S. sclerotiorum and Botrytis cinerea. Further experiments showed that transgenic plants inhibited growth of S. sclerotiorum and constitutively activated PDF1.2 but decreased H2O2 production and constitutively suppressed PR-1 expression. Treatment of roots of the transgenic plants with H2O2 solution resulted in enhanced susceptibility to the two pathogens. Our results support the idea that MPK4 positively regulates jasmonic acid-mediated defense response, which might play an important role in resistance to S. sclerotiorum in oilseed rape.

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

Plant Disease ◽  
2013 ◽  
Vol 97 (8) ◽  
pp. 1117-1117 ◽  
Author(s):  
S. E. Cho ◽  
J. H. Park ◽  
S. H. Hong ◽  
H. D. Shin
Keyword(s):  
Its Region ◽  
The United States ◽  
Infected Leaf ◽  
Invasive Weed ◽  
Voucher Specimen ◽  
First Report ◽  
Leaf Spots ◽  
Initial Symptoms ◽  
Wide Range ◽  
Humulus Japonicus

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

scholarly journals First Report of Sclerotinia sclerotiorum on Common Ragweed (Ambrosia artemisiifolia) in Europe

Plant Disease ◽  
1999 ◽  
Vol 83 (3) ◽  
pp. 302-302 ◽  
Author(s):  
Gy. Bohár ◽  
L. Kiss
Keyword(s):  
Sclerotinia Sclerotiorum ◽  
Aerial Mycelium ◽  
The United States ◽  
Ambrosia Artemisiifolia ◽  
American Phytopathological Society ◽  
Common Ragweed ◽  
First Report ◽  
Sclerotinia Rot ◽  
Stem Lesions ◽  
Test Plants

Common ragweed (Ambrosia artemisiifolia L.) is reported as a host of Sclerotinia sclerotiorum (Lib.) de Bary in North America (2,4), but not in Europe. A Hungarian survey of fungal diseases of ragweed in 1994 did not find sclerotinia rot of common ragweed (A. artemisiifolia var. elatior (L.) Descourt.) (1). In autumn 1998, mature ragweed plants, 1 to 1.5 m tall, were collected from the borders of four sunflower (Helianthus annuus L.) fields in which sclerotinia rot of sunflower was frequently observed during the season, and also from six other roadside sites in Hungary. Ragweed plants exhibiting symptoms characteristic of sclerotinia rot, i.e., wilting foliage and light brown, dry lesions on the stems, were found only near two sunflower fields. Black, round to irregular or oblong sclerotia were also observed on the infected ragweed plants both externally on the stem lesions and internally, in the pith cavity. Sclerotia measured up to 5 mm in diameter and were 5 to 14 mm long. After isolation on potato dextrose agar, the pathogen produced abundant aerial mycelium and large sclerotia characteristic of S. sclerotiorum. To confirm pathogenicity, potted seedlings and mature plants of ragweed were inoculated in the greenhouse with autoclaved wheat grains colonized with mycelia of S. sclerotiorum placed 0.5 to 1 cm from the collar of the test plants. Seedlings were killed in 2 to 3 days while mature plants wilted after 5 to 6 days. In a field test, six mature plants were inoculated by attaching mycelial disks to their stems with Parafilm. These plants wilted 12 to 14 days after inoculation. The pathogen was reisolated from all diseased plants. This is the first report of S. sclerotiorum on common ragweed in Europe. Nonsclerotial mutants of the fungus (3) are being produced to be tested as potential biocontrol agents of common ragweed, which has become not only the most widespread, but also the most important allergenic plant species in Hungary since the early 1990s. References: (1) Gy. Bohár and L. Vajna. Nōvényvédelem 32:527, 1996. (2) G. J. Boland and R. Hall. Can. J. Plant Pathol. 16:93, 1994. (3) G. J. Boland and E. A. Smith. Phytopathology 81:766, 1991.(4) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN.

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