scholarly journals First Report of Downy Mildew Caused by Plasmopara halstedii on Black-eyed Susan (Rudbeckia fulgida cv. ‘Goldsturm’) in Maryland

Plant Disease ◽  
2014 ◽  
Vol 98 (7) ◽  
pp. 1005-1005 ◽  
Author(s):  
Y. Rivera ◽  
K. Rane ◽  
J. A. Crouch
Keyword(s):  
Downy Mildew ◽  
Leaf Surface ◽  
Control Plant ◽  
Morphological Data ◽  
Economic Losses ◽  
Morphological Identification ◽  
Post Inoculation ◽  
Disease Symptoms ◽  
Plasmopara Halstedii ◽  
First Report

The North American perennial black-eyed Susan (Rudbeckia fulgida cv. Goldsturm) is an important nursery crop, prized by gardeners and landscapers for its persistent bloom and ease of cultivation. In September 2013, disease symptoms characteristic of downy mildew were observed from multiple R. fulgida plants at two commercial nurseries in the Maryland counties of Howard and Anne Arundel. Over 100 R. fulgida were affected by this disease in both nurseries, rendering the plants unmarketable and causing a substantial financial loss. Plants exhibited dark necrotic lesions on the adaxial leaf surface, and sporulating masses of white mycelium on the abaxial leaf surface and on the adaxial in extreme infections. Plants were stunted with a reduced number of blooms. Microscopic visualization showed coenocytic mycelium, hyaline sporangiophores (length 261 to 904 μm; [Formula: see text] = 557 μm; n = 20) that were straight and monopodially branched at right angles with several terminal branchlets. Sporangia were hyaline, ovoid to elliptical with smooth surfaces ([Formula: see text] = 31 × 28 μm; n = 50). Based on morphological data, the organism was identified as Plasmopara halstedii (Farl.) Berl. & De Toni in Sacc (2). Voucher specimens were deposited in the U.S. National Fungus Collections (BPI 892792 to 892794). Molecular identification was conducted by extracting genomic DNA from sporangiophores and mycelium tweezed from the surface of three infected plants, with extractions performed using the QIAGEN Plant DNA kit (QIAGEN, Gaithersburg, MD). The large subunit of the nuclear rDNA was amplified by PCR using primers LROR and LR7 (3) and sequenced bidirectionally. BLASTn searches of NCBI GenBank showed that the resultant rDNA sequences (accessions KF927152 to KF927154) shared 99% nucleotide identity with curated P. halstedii sequences, consistent with morphological identification. To confirm pathogenicity, three 3.78-liter (1 gallon) containerized R. fulgida cv. Goldsturm plants were inoculated with a sporangial suspension of 2.4 × 104 sporangia/ml and sprayed until both the upper and lower surface of the leaves were completely covered. One negative control plant was sprayed with deionized water. Plants were placed in clear plastic bags in a growth chamber (20°C, 12-h photoperiod). Disease symptoms were observed 3 days post inoculation on all plants. The control plant was symptomless. Morphological features of the pathogen on the surface of inoculated plants were identical to those observed from the original infected plants. Although P. halstedii on R. fulgida cv. Goldsturm has been previously reported in Virginia in 2006 and Florida in 2004, to our knowledge, this is the first report on R. fulgida cv. Goldsturm in Maryland (1). Black-eyed Susans are widely distributed throughout Maryland's landscape and are a staple plant for gardeners, nurserymen and landscape professionals. Given the destructive nature of this disease, downy mildew has the potential to cause considerable economic losses to the state's ornamental crop industry. References: (1) D. F. Farr and A. Y. Rossman. Fungal Databases, Syst. Mycol. Microbiol. Lab., ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , November 18, 2013. (2) P. A. Saccardo. Syllogue Fungorum 7:242, 1888. (3) R. Vilgalys and M. Hester. J. Bacteriol. 172:4238, 1990.

scholarly journals First Report of Pseudoperonospora cubensis Causing Downy Mildew on Momordica balsamina and M. charantia in North Carolina

Plant Disease ◽  
2014 ◽  
Vol 98 (9) ◽  
pp. 1279-1279 ◽  
Author(s):  
E. Wallace ◽  
M. Adams ◽  
K. Ivors ◽  
P. S. Ojiambo ◽  
L. M. Quesada-Ocampo
Keyword(s):  
United States ◽  
North Carolina ◽  
Downy Mildew ◽  
Leaf Surface ◽  
The United States ◽  
Pseudoperonospora Cubensis ◽  
Post Inoculation ◽  
Bitter Melon ◽  
First Report ◽  
C Cycle

Momordica balsamina (balsam apple) and M. charantia L. (bitter melon/bitter gourd/balsam pear) commonly grow in the wild in Africa and Asia; bitter melon is also cultivated for food and medicinal purposes in Asia (1). In the United States, these cucurbits grow as weeds or ornamentals. Both species are found in southern states and bitter melon is also found in Pennsylvania and Connecticut (3). Cucurbit downy mildew (CDM), caused by the oomycete Pseudoperonospora cubensis, was observed on bitter melon and balsam apple between August and October of 2013 in six North Carolina sentinel plots belonging to the CDM ipmPIPE program (2). Plots were located at research stations in Johnston, Sampson, Lenoir, Henderson, Rowan, and Haywood counties, and contained six different commercial cucurbit species including cucumbers, melons, and squashes in addition to the Momordica spp. Leaves with symptoms typical of CDM were collected from the Momordica spp. and symptoms varied from irregular chlorotic lesions to circular lesions with chlorotic halos on the adaxial leaf surface. Sporulation on the abaxial side of the leaves was observed and a compound microscope revealed sporangiophores (180 to 200 μm height) bearing lemon-shaped, dark sporangia (20 to 35 × 10 to 20 μm diameter) with papilla on one end. Genomic DNA was extracted from lesions and regions of the NADH dehydrogynase subunit 1 (Nad1), NADH dehydrogynase subunit 5 (Nad5), and internal transcribed spacer (ITS) ribosomal RNA genes were amplified and sequenced (4). BLAST analysis revealed 100% identity to P. cubensis Nad1 (HQ636552.1, HQ636551.1), Nad5 (HQ636556.1), and ITS (HQ636491.1) sequences in GenBank. Sequences from a downy mildew isolate from each Momordica spp. were deposited in GenBank as accession nos. KJ496339 through 44. To further confirm host susceptibility, vein junctions on the abaxial leaf surface of five detached leaves of lab-grown balsam apple and bitter melon were either inoculated with a sporangia suspension (10 μl, 104 sporangia/ml) of a P. cubensis isolate from Cucumis sativus (‘Vlaspik' cucumber), or with water as a control. Inoculated leaves were placed in humidity chambers to promote infection and incubated using a 12-h light (21°C) and dark (18°C) cycle. Seven days post inoculation, CDM symptoms and sporulation were observed on inoculated balsam apple and bitter melon leaves. P. cubensis has been reported as a pathogen of both hosts in Iowa (5). To our knowledge, this is the first report of P. cubensis infecting these Momordica spp. in NC in the field. Identifying these Momordica spp. as hosts for P. cubensis is important since these cucurbits may serve as a source of CDM inoculum and potentially an overwintering mechanism for P. cubensis. Further research is needed to establish the role of non-commercial cucurbits in the yearly CDM epidemic, which will aid the efforts of the CDM ipmPIPE to predict disease outbreaks. References: (1) L. K. Bharathi and K. J. John. Momordica Genus in Asia-An Overview. Springer, New Delhi, India, 2013. (2) P. S. Ojiambo et al. Plant Health Prog. doi:10.1094/PHP-2011-0411-01-RV, 2011. (3) PLANTS Database. Natural Resources Conservation Service, USDA. Retrieved from http://plants.usda.gov/ , 7 February 2014. (4) L. M. Quesada-Ocampo et al. Plant Dis. 96:1459, 2012. (5) USDA. Index of Plant Disease in the United States. Agricultural Handbook 165, 1960.

scholarly journals First Report of Downy Mildew Caused by Plasmopara halstedii on Gerbera jamesonii in Brazil

Plant Disease ◽  
2013 ◽  
Vol 97 (10) ◽  
pp. 1382-1382
Author(s):  
L. L. Duarte ◽  
Y. J. Choi ◽  
R. W. Barreto
Keyword(s):  
Downy Mildew ◽  
Sequence Similarity ◽  
The United States ◽  
Plant Diseases ◽  
Morphological Data ◽  
Gerbera Jamesonii ◽  
High Sequence Similarity ◽  
Important Species ◽  
Plasmopara Halstedii ◽  
First Report

African daisy (Gerbera jamesonii Bolus ex Hook. f.) is an important species for both the cut flower and potted plant industries worldwide (4). Since the winter of 2009, plants showing severe downy mildew symptoms have been observed in a greenhouse located in an experimental area of the Universidade Federal de Viçosa (state of Minas Gerais, Brazil). The disease appeared as ill-delimited adaxial chlorosis of lamina; tissues became yellow and then brown with age with intense blighting of leaves of entire plants, leading to their death, when untreated. Dense, whitish sporulation was observed on the lower surfaces since early stages. A representative sample was dried in a plant press and deposited in the local herbarium under accession number VIC 32070. Slides were prepared with fungal structures mounted in lactofuchsin and observed under a light microscope (Olympus BX 51). Fungus morphology: Sporangiophores hypophyllous, emerging through stomata, cylindrical, up to 650 μm long and 5 to 10 μm wide, with slightly swollen base from 6.5 to 13 μm, hyaline, aseptate, straight, with up to 6 monopodial ramifications occurring mainly at right angles, the final branch ending in 3 or 4 ultimate branchlets; sporangia globose to ovoid, from 20 to 28 μm long and 13 to 18 μm wide, hyaline, smooth. Oospores were not observed. In order to further clarify the identity of the fungus on G. jamesonii, genomic DNA was extracted directly from the plant tissue and part of cytochrome c oxidase subunit 2 was amplified with the primers COX2 (3). The generated sequence was submitted to GenBank (Accession No. KC690148) and when compared with other entries revealed a high sequence similarity (99%) with Plasmopara halstedii (Farl.) Berl. & De Toni (EU743813) from Helianthus annuus L. This was also supported by the morphological data as compared with published descriptions (2) and it was then concluded that the chromistan fungus involved in downy mildew of African daisy was P. halstedii. Two different downy mildew genera, Bremia and Plasmopara, cause downy mildew disease on G. jamesoni. Bremia lactucae has been recorded in Argentina, Brazil, Germany, and Poland (4). There is only one record of a Plasmopara on this host in the United States (1), but this is an obscure report with no identification at the species level. Although P. halstedii has been commonly recorded on numerous hosts belonging to the Asteraceae worldwide, it has never been reported on G. jamesoni. To our knowledge, this is the first report of P. halstedii on G. jamesoni in Brazil. This disease has the potential to become important and cause significant losses because of a combination of the high severity to untreated plants and the increasing importance of African daisy in the flower market in Brazil. References: (1) S. A. Alfieri, Jr. et al. Bull. 11. Index of Plant Diseases in Florida (Revised). Florida Dep. Agric. Consumer Serv., Div. Plant Ind., 1984. (2) G. Hall. Plasmopara halstedii. CMI Descriptions of Pathogenic Fungi and Bacteria No 979. Mycopathologia 106:205, 1989. (3) D. S. S. Hudspeth et al. Mycologia 92:674, 2000. (4) S. M. Wolcan, Australas. Plant Dis. Notes 5:98, 2010.

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 Leaf Spot Disease Caused by Epicoccum nigrum on Lablab purpureus in India

Plant Disease ◽  
2014 ◽  
Vol 98 (2) ◽  
pp. 284-284 ◽  
Author(s):  
S. Mahadevakumar ◽  
K. M. Jayaramaiah ◽  
G. R. Janardhana
Keyword(s):  
Leaf Spot ◽  
Leaf Surface ◽  
Disease Incidence ◽  
Leaf Spot Disease ◽  
Post Inoculation ◽  
Conidial Suspension ◽  
Lablab Purpureus ◽  
First Report ◽  
Spot Disease ◽  
Epicoccum Nigrum

Lablab purpureus (L.) Sweet (Indian bean) is an important pulse crop grown in arid and semi-arid regions of India. It is one of the most widely cultivated legume species and has multiple uses. During a September 2010 survey, we recorded a new leaf spot disease on L. purpureus in and around Mysore district (Karnataka state) with 40 to 80% disease incidence in 130 ha of field crop studied, which accounted for 20 to 35% estimated yield loss. The symptoms appeared as small necrotic spots on the upper leaf surface. The leaf spots were persistent under mild infection throughout the season with production of conidia in clusters on abaxial leaf surface. A Dueteromyceteous fungus was isolated from affected leaf tissues that were surface sterilized with 2% NaOCl2 solution then washed thrice, dried, inoculated on potato dextrose agar (PDA) medium, and incubated at 28 ± 2°C at 12 h alternate light and dark period for 7 days. The fungal colony with aerial mycelia interspersed with dark cushion-shaped sporodochia consists of short, compact conidiophores bearing large isodiametric, solitary, muricate, brown, globular to pear shaped conidia (29.43 to 23.92 μm). Fungal isolate was identified as Epicoccum sp. based on micro-morphological and cultural features (1). Further authenticity of the fungus was confirmed by PCR amplification of the internal transcribed spacer (ITS) region using ITS1/ITS4 universal primer. The amplified PCR product was purified, sequenced directly, and BLASTn search revealed 100% homology to Epicoccum nigrum Link. (DQ093668.1 and JX914480.1). A representative sequence of E. nigrum was deposited in GenBank (Accession No. KC568289.1). The isolated fungus was further tested for its pathogenicity on 30-day-old healthy L. purpureus plants under greenhouse conditions. A conidial suspension (106 conidia/ml) was applied as foliar spray (three replicates of 15 plants each) along with suitable controls. The plants were kept under high humidity (80%) for 5 days and at ambient temperature (28 ± 2°C). The appearance of leaf spot symptoms were observed after 25 days post inoculation. Further, the pathogen was re-isolated and confirmed by micro-morphological characteristics. E. nigrum has been reported to cause post-harvest decay of cantaloupe in Oklahoma (2). It has also been reported as an endophyte (3). Occurrence as a pathogen on lablab bean has not been previously reported. To our knowledge, this is the first report of the occurrence of E. nigrum on L. purpureus in India causing leaf spot disease. References: (1) H. L. Barnet and B. B. Hunter. Page 150 in: Illustrated Genera of Imperfect Fungi, 1972. (2) B. D. Bruten et al. Plant Dis. 77:1060, 1993. (3) L. C. Fávaro et al. PLoS One 7(6):e36826, 2012.

scholarly journals First Report of Downy Mildew on Gynura aurantiaca Caused by Plasmopara halstedii sensu lato in Florida

Plant Disease ◽  
2015 ◽  
Vol 99 (9) ◽  
pp. 1279-1279 ◽  
Author(s):  
A. J. Palmateer ◽  
R. A. Cating ◽  
P. Lopez
Keyword(s):  
Downy Mildew ◽  
Plasmopara Halstedii ◽  
First Report

scholarly journals First Report of Internal Black Rot Caused byNeoscytalidium dimidiatumonHylocereus undatus(Pitahaya) Fruit in Israel

Plant Disease ◽  
2013 ◽  
Vol 97 (11) ◽  
pp. 1513-1513 ◽  
Author(s):  
D. Ezra ◽  
O. Liarzi ◽  
T. Gat ◽  
M. Hershcovich ◽  
M. Dudai
Keyword(s):  
Its Region ◽  
Stem Canker ◽  
Brown Spot ◽  
Black Rot ◽  
Post Inoculation ◽  
Single Spore ◽  
Flower Opening ◽  
Disease Symptoms ◽  
First Report ◽  
Β Tubulin

Pitahaya (Hylocereus undatus [Haw.] Britton & Rose) was introduced to Israel in 1994, and is grown throughout the country. In the summer of 2009, fruit with internal black rot was collected from a field in central Israel. Symptomatic tissue from the black rot was placed on potato dextrose agar (PDA) plates amended with 12 μg/ml tetracycline and incubated at 25°C for 3 days. A dark, gray to black, fast-growing fungus was isolated from all samples (10 fruits). For identification, single-spore cultures were grown on PDA at 25°C for 5 days, and colonies with gray to black, wooly mycelium were formed. The mycelia were branched and septate (4 to 8 μm wide). The arthroconidia were dark brown, thick-walled, and one-celled, 6.3 to 14.2 × 2.0 to 4.5 μm (n = 5), and ovate to rectangular. Based on these characteristics, the fungus was identified as Neoscytalidium dimidiatum (Penz.) Crous & Slippers (1). The internal transcribed spacer (ITS) region of rDNA and β-tubulin gene were amplified using ITS1 and ITS4, T121 (2), and Bt1b (3) primers, respectively, and then sequenced (GenBank Accessions KF000372 and KF020895, respectively). Both sequences were identical to sequences previously deposited in GenBank. The ITS (561 bp) and β-tubulin (488 bp) sequences exhibited 99% and 100% identity, and 100% and 84% coverage, respectively, to N. dimidiatum (JX524168 and FM211185, respectively). Thus, the results of the molecular identifications confirmed the morphological characterization. To establish fungal pathogenicity and the mechanism of infection, 60 flowers in a disease-free orchard were marked to form three different treatments (15 flowers per treatment): inoculations of the flower tube by inserting PDA plugs (0.5 × 0.5 cm) from a 5-day-old culture to the base of the flower, inoculations of the flower stigma by placing the fungus plug on intact, or pre-wounded flower stigma. The wounds were made by scratching the stigma with a sterile scalpel. For each treatment, five additional flowers were used as negative controls in which the PDA plugs did not contain any fungus. All flowers were hand-pollinated and left to grow for a month until the fruit had ripened. Only flowers inoculated by insertion of the fungus into the flower tube developed black rot in the fruit (8 of 15 fruit) 3 to 4 weeks post inoculation, suggesting involvement of the flower tube in the mechanism of infection. All other treatments and controls failed to develop any detectable disease symptoms. N. dimidiatum was reisolated from the rot, fulfilling Koch's postulates. Flowers with wounded stigma developed significantly smaller fruit. Interestingly, diseased fruit changed color about a week before ripening from the flower opening downwards, whereas healthy fruit changed color from the attachment point to the stem upwards. These results indicate that N. dimidiatum is the pathogen of pitahaya internal black rot disease. Recently, this pathogen was reported to cause brown spot disease and stem canker disease of pitahaya in China (4) and Taiwan (5), respectively. To date, the disease can be detected in all orchards in Israel, with up to 50% of the fruit being infected. Since the disease symptoms of the Israeli isolate are located in the fruit, the commercial loss due to pathogen attack is significant. To our knowledge, this is the first report of internal black rot caused by N. dimidiatum on pitahaya fruit in Israel.References: (1) P. W. Crous et al. Stud. Mycol. 55:235, 2006. (2) K. O'Donnell and E. Cigelnik. Mol. Phylo, Evol. 7:103, 1997. (3) N. L. Glass and G. C. Donaldson. Appl. Environ. Microiol. 61:1323, 1995. (4) G. B. Lan and Z. F. He. Plant Dis. 96:1702, 2012. (5) M. F. Chuang et al. Plant Dis. 96:906, 2012.

scholarly journals First Report of Meloidogyne graminicola on Rice in Henan Province, China

Plant Disease ◽  
2021 ◽  
Author(s):  
Mao-Yan Liu ◽  
Jing Liu ◽  
Wenkun Huang ◽  
Deliang Peng
Keyword(s):  
Oryza Sativa ◽  
Its Region ◽  
Henan Province ◽  
Morphological Data ◽  
Post Inoculation ◽  
Root Tips ◽  
Lateral Field ◽  
First Report ◽  
Meloidogyne Graminicola ◽  
Rice Plants

Rice (Oryza sativa) is an important food crop in China and root-knot nematode Meloidogyne graminicola has been one of the most important diseases on rice in recently five years (Ju et al. 2020). In August 2020, rice plants were found to be maldeveloped, yellow leaves and hooked root tips in an irrigated paddy field of Yuanyang County, Xinxiang City, Henan Province. Fifty rice plants were randomly collected and 84.0 percent plants were infected with root-knot nematodes, with root-gall index of 56.0. Then nematodes from rice roots were isolated with 100-μm and 25-μm sieves. A large number of females, some third-stage juveniles (J3s), and a small number of males of Meloidogyne spp. were found in root galls of all samples after dissected, and then were identified and measured under the microscope. In females (n = 20), the perineal pattern was dorsoventrally oval with low and round dorsal arch, and the lateral field was not obvious or absent, striae are usually smooth, with occasional short and irregular striatal fragmentation. The morphological data of females are as follows: body length (BL) = 516.9 ± 72.5 μm (424.2 to 611.6 μm), body width (BW)= 328.4 ± 80.7 μm (232.1 to 437.4 μm), stylet length = 11.2 ± 1.3 μm (7.7 to 13.9 μm), dorsal pharyngeal gland orifice to stylet base (DGO) = 3.9 ± 0.5 μm (3.2 to 4.5 μm), vulval slit length = 24.3 ± 4.6 μm (15.2 to 31.4 μm), vulval slit to anus distance = 16.2 ± 2.5 μm (10.1 to 20.2 μm). Males are long cylindrical, wormlike, with a short round tail. Morphological measurements of males (n = 20) were BL = 1,218.0 ± 150.7μm (1,085.7 to 1,692.2 μm), BW = 34.2 ± 4.6 μm (28.5 to 39.7 μm), stylet = 17.4 ± 0.7 μm (15.9 to 19.3 μm), DGO = 3.6 ± 0.7 μm (2.5 to 4.5 μm), tail = 10.8 ± 2.1 μm (8.0 to 14.8 μm), spicule = 30.3 ± 2.6 μm (24.7 to 36.3 μm). The egg masses from the females were incubated at 28℃ for 48 hours. Measurements of J2s (n = 20) were BL = 444.2 ± 37.8 μm (315.7 to 547.5 μm), BW = 21.2 ± 2.7 μm (16.7 to 26.4 μm), stylet = 14.2 ± 0.3 μm (13.6 to 14.8 μm), DGO = 3.5 ± 0.5 μm (2.7 to 4.5 μm), tail = 70.8 ± 5.1 μm (61.3 to 80.8 μm), hyaline tail length = 21.0 ± 2.5 μm (16.3 to 26.1 μm). These morphological features are consistent with the original description by Golden and Birchfield (1965). DNA of a single female from each sample was extracted for molecular identification. Primer pairs D2A/D3B (5´-ACAAGTACCGTGAGGGAAAGTTG-3´/ 5´-TCGGAAGGAACCAGCTACTA-3´) (De Ley et al. 1999) and the species-specific primers Mg-F3/Mg-R2 (5′-TTATCGCATCATTTTATTTG-3′/ 5′-CGCTTTGTTAGAAAATGACCCT-3′) (Htay et al. 2016) were used to amplify D2/D3 region of 28S RNA and the internal transcribed spacer (ITS) region, respectively. The amplified sequences of D2/D3 region (GenBank MW490724, 766 bp) shared 99.9% and 99.7% homology with the sequences of M. graminicola (MN647592, MT576694) isolated from Guangxi and Anhui Province (Ju et al. 2020), respectively, while ITS region sequences (MW487239, 369 bp) shared 100% and 99.7% homology to M. graminicola isolate GXL3 (MN636702) and FQJJ01 (MT159690), respectively. In order to verify the pathogenicity of nematodes, about 300 J2s were inoculated on ten 14-week-old rice (Oryza sativa cv. Nipponbare) planted in pots with sterilized sandy soil, respcectively, and maintained in a greenhouse at 28°C/26°C with a 16h/8h light/dark photoperiod and 75% relative humidity. At 14 days post inoculation, obvious symptoms of hook galls were observed on roots in all inoculated rice plants, and females and males in the same shape as the collected samples were found in the root galls under the stereoscopic microscope. No symptoms were observed on non-inoculated rice plants. After 28 days, the growth of the inoculated rice plants was significantly worse than that of uninoculated ones, with yellow leaves and short plants. These results confirmed the pathogenicity of M. graminicola on rice and it indicated that M. graminicola was already spread from the main rice-producing areas to the wheat and rice rotation areas. To our knowledge, this is the first report of M. graminicola in the Henan Province of China.

scholarly journals First Report of Downy Mildew Caused by Plasmopara halstedii on Ageratum houstonianum in the United States

Plant Disease ◽  
2019 ◽  
Vol 103 (11) ◽  
pp. 2968-2968
Author(s):  
C. Pisani ◽  
P. C. Patel ◽  
E. N. Rosskopf ◽  
M. Abbasi ◽  
M. C. Aime
Keyword(s):  
United States ◽  
Downy Mildew ◽  
The United States ◽  
Plasmopara Halstedii ◽  
First Report

Ultrastructure of Plasmopara halstedii containing virus-like particles

1991 ◽  
Vol 49 ◽  
pp. 216-217
Author(s):  
Thomas Freeman ◽  
Thomas Gulya
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Helianthus Annuus ◽  
Downy Mildew ◽  
Systemic Disease ◽  
Disease Symptoms ◽  
Plasmopara Halstedii ◽  
Transmission Electron ◽  
Race 2 ◽  
Standard Techniques

Mycoviruses have been found in more than 100 species of fungi and it is estimated that they may occur in as many as 500 species (Buck, 1986; Hollings, 1978; and Lemke, 1981). Mycoviruses range in size from small, isometric particles (25 nm in diameter) to long, flexuous rods exceeding 2000 nm in length, with the majority being isometric particles ranging in size from 25-50 nm (Buck, 1986). Mycoviruses hae been reported in all groups of fungi, but have been least frequently observed in the Oomycetes.Sunflower (Helianthus annuus) seedlings were inoculated with a North Dakota isolate of race 2 Plasmopara halstedii, the causal agent of sunflower downy mildew. Systemic disease symptoms developed within 14 days and samples were prepared for transmission electron microscopy using standard techniques.

scholarly journals First Report of Brown Rot Caused by Monilinia fructicola on Nectarine in Serbia

Plant Disease ◽  
2013 ◽  
Vol 97 (1) ◽  
pp. 147-147 ◽  
Author(s):  
J. Hrustić ◽  
M. Mihajlović ◽  
B. Tanović ◽  
G. Delibašić ◽  
I. Stanković ◽  
...  
Keyword(s):  
Prunus Persica ◽  
Its Region ◽  
Fruit Rot ◽  
Economic Losses ◽  
Morphological Identification ◽  
Single Spore ◽  
Daily Growth ◽  
Causal Organism ◽  
First Report ◽  
Apple Fruits

In August 2011, nectarine (Prunus persica (L.) Batsch var. nucipersica (Suckow) C. K. Schneid) fruit originated from Oplenac region with symptoms of fruit rot was collected at a green market in Belgrade. Fruit had large, brown, sunken lesions covered with grayish brown tufts. Symptoms resembled those caused by species of Monilinia including M. laxa, M. fructigena, or M. fructicola (2). In order to isolate the causal organism, small superficial fragments of pericarp were superficially disinfected with commercial bleach and placed on potato dextrose agar (PDA). The majority (32 out of 33) isolates formed rosetted non-sporulating colonies with lobed margins resembling those of M. laxa. However, one isolate (Npgm) produced an abundant, grayish-white colony with even margins and concentric rings of sporogenous mycelium, resembling those described for M. fructicola (2). Conidia were one-celled, hyaline, ellipsoid to lemon shaped, 7.38 to 14.76 × 4.92 to 9.84 μm, and borne in branched monilioid chains. The average daily growth on PDA at 24°C was 10.9 mm. A single-spore isolate of Npgm was identified as M. fructicola based on the morphology of colony and conidia, temperature requirements, and growth rate (2). Morphological identification was confirmed by an amplified product of 535 bp using genomic DNA extracted from the mycelium of pure culture and species-specific PCR for the detection of M. fructicola (2). The ribosomal internal transcribed spacer (ITS) region of rDNA of Npgm was amplified and sequenced using primers ITS1/ITS4. Sequence analysis of ITS region revealed 100% nucleotide identity between the isolate Npgm (GenBank Accession No. JX127303) and 17 isolates of M. fructicola from different parts of the world, including four from Europe (FJ411109, FJ411110, GU967379, JN176564). Pathogenicity of the isolate Npgm was confirmed by inoculating five surface-disinfected mature nectarine and five apple fruits by placing a mycelial plug under the wounded skin of the fruit. Nectarine and apple fruits inoculated with sterile PDA plugs served as a negative controls. After a 3-day incubation at 22°C, inoculated sites developed brown lesions and the pathogen was succesfully reisolated. There were no symptoms on the control nectarine or apple fruits. M. fructicola is commonly present in Asia, North and South America, New Zealand, and Australia, while in the EPPO Region the pathogen is listed as an A2 quarantine organism (3). In Europe, the first discovery of M. fructicola was reported in France and since then, it has been found in Hungary, Switzerland, the Czech Republic, Spain, Slovenia, Italy, Austria, Poland, Romania, Germany, and Slovakia (1). Most recently, M. fructicola was found on stored apple fruits in Serbia (4). To our knowledge, this is the first report of M. fructicola decaying peach fruit in Serbia. These findings suggest that the pathogen is spreading on its principal host plants and causing substantial economic losses in the Serbian fruit production. References: (1) R. Baker et al. European Food Safety Authority. Online publication. www.efsa.europa.eu/efsajournal . EFSA J. 9:2119, 2011. (2) M. J. Côté. Plant Dis. 88:1219, 2004. (3) OEPP/EPPO. EPPO A2 list of pests recommended for regulation as quarantine pests. Version 2009-09. http://www.eppo.org/QUARANTINE/listA2.htm . (4). M. Vasic et al. Plant Dis. 96:456, 2012.

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