scholarly journals First Report of Powdery Mildew Caused by Podosphaera xanthii on Salvia farinacea in Korea

Plant Disease ◽  
2021 ◽  
Author(s):  
In-Young Choi ◽  
Ho-Jong Ju ◽  
Kui-Jae Lee ◽  
Hyeon-Dong Shin
Keyword(s):  
Powdery Mildew ◽  
Large Subunit ◽  
Pcr Amplification ◽  
Echinacea Purpurea ◽  
The United States ◽  
Infected Leaf ◽  
Podosphaera Xanthii ◽  
Powdery Mildew Fungus ◽  
First Report ◽  
Perennial Plant

Salvia farinacea Benth. (Lamiaceae) is an herbaceous perennial plant, native to Mexico and southern parts of the United States. This plant is cultivated worldwide for its ornamental value. In November 2019, hundreds of S. farinacea ‘Blue Bedder” grown in a flower garden in Jeju (33°30'57"N 126°32'50"E), Korea have been found to be infected with a powdery mildew fungus. The disease severity was estimated to be 100%. Likewise in October 2020, a similar situation with this plant was also observed in a flower garden in Seoul (37°35'19"N 127°01'07"E), Korea. Leaves, stems and inflorescence of plants were covered by white, thin mycelial felt, bearing an abundance of conidiophores and conidia. Eventually, infected plants lose their ornamental value. Two voucher specimens have been deposited in the Korea University Herbarium (KUS-F31478 and F32164). Fresh materials were examined. Hyphal appressoria were nipple-shaped, but rarely found. Conidiophores (n = 30) were straight, 95 to 160 × 10 to 12 μm and produced 2 to 7 immature conidia in chains with a crenate outline. Foot-cells were cylindric and 36 to 60 μm long. Conidia (n = 30) were ellipsoid-ovoid to barrel-shaped, 32 to 38 × 18 to 24 μm, and contained conspicuous fibrosin bodies. Dark brown chasmothecia were found partly embedded in the mycelial felt on leaves, mostly hypophyllous, spherical, and 82 to 100 µm diameter, with a single ascus in each. Appendages were few, mycelioid, 1- to 4-septate, brown near the base when mature, but paler above. Asci were broadly ellipsoid to subglobose, 56 to 68 × 50 to 62 μm, sessile and 8-spored. Ascospores were colorless, oval to subglobose, and 14 to 18 × 12 to 15 µm. These characteristics were consistent with those of Podosphaera xanthii (Castagne) U. Braun & Shishkoff (Braun and Cook 2012). For further confirmation, genomic DNA was extracted from chasmothecia from KUS-F31478 and F32164. PCR amplification was performed using the primer pair ITS1F/PM6 for internal transcribed spacer (ITS) and PM3/TW14 for the large subunit (LSU) of the rDNA (Takamatsu and Kano 2001). Obtained sequences were deposited to the GenBank under the accession numbers MZ359847 and MZ359859 for ITS, MZ359858 and MZ359861 for LSU. For ITS regions 99.80-100% similarity was found with sequences MT131256 (Salvia farinacea), MT131254 (Mazus pumilus) and MT131252 (Erigeron bellioides) of P. xanthii, whereas it was 99.90% with sequences of this fungus on Echinacea purpurea (MT826247 and MT826245) for 28S rDNA gene. Pathogenicity tests were carried out by touching an infected leaf onto healthy leaves of disease-free 30 days old potted ‘Blue Bedder’ using replication of five plants, with five non-inoculated plants used as controls. The typical signs of powdery mildew started to develop on the inoculated leaves in 7 to 10 days, and microscopic examination revealed the morphological identity with the fungus observed from the field. All non-inoculated control plants remained symptomless. Hitherto Golovinomyces powdery mildews on Salvia spp. were reported globally (Farr and Rossman 2021). However, Podosphaera elsholtziae on Salvia sp. and P. xanthii on S. farinacea were reported from China and Taiwan (Zheng and Yu 1987, Yeh et al. 2021). To our knowledge, this is the first report of P. xanthii on S. farinacea in Korea. The occurrence of Podosphaera powdery mildew on S. farinacea could pose a serious threat to the beauty of this plant, causing premature senescence of young leaves and gray to purplish discoloration of the leaves.

scholarly journals First Report of Powdery Mildew Caused by Podosphaera xanthii on Cuphea hyssopifolia (Lythraceae) in Mainland China

Plant Disease ◽  
2021 ◽  
Author(s):  
Irum Mukhtar ◽  
Ruiting Li ◽  
IBATSAM KHOKHAR ◽  
Ruanni Chen ◽  
Yunying Cheng ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Disease Incidence ◽  
Large Subunit ◽  
Mainland China ◽  
Lsu Rdna ◽  
Podosphaera Xanthii ◽  
Powdery Mildew Fungus ◽  
Potential Threat ◽  
First Report ◽  
Plant Pathol

Cuphea hyssopifolia (Mexican heather) is a popular evergreen perennial shrub used for ornamental and medicinal purposes. Due to its high ornamental value, it is often used as a ground cover in parks and gardens in China. During February and March 2019 & 2020, powdery mildew was observed on C. hyssopifolia in the districts of Minhou and Jinshan of Fuzhou, China. Disease incidence was 70% but of low severity with only a few older leaves showing yellowing and wilting. Sparse irregular patches of white superficial powdery mildew observed on both sides of mature and young leaves. The powdery mildew fungal appressoria that occurred on epigenous hyphae, were indistinct to nipple-shaped, hyaline, and smooth. Conidiophores were erect, smooth, 80 to 210 × 10 to 12 µm, and produced two to eight crenate-shaped conidia in chains. Foot-cells of conidiophores were straight, cylindric, and 30 to 65 × 10 to12 µm. Conidia were hyaline, smooth, ellipsoid-ovoid to barrel-shaped, 25 to 38 × 16 to 20 µm with distinct fibrosin bodies. Germ tubes were simple to forked and produced from the lateral position of the germinating conidia. No chasmothecia were observed on the surface of infected leaves. Based on the morphology of the imperfect state, the powdery mildew fungus was identified as Podosphaera xanthii (Castagne) U. Braun & N. Shishkoff (Braun and Cook 2012). To confirm fungal identification, total DNA was extracted (Mukhtar et al., 2018) directly from epiphytic mycelia on infected leaves collected from both districts. Internal transcribed spacer (ITS) regions and the partial large subunit (LSU) rDNA were amplified using primers ITS1/ITS4 and LSU1/LSU2 (Scholin et al. 1994, White et al. 1990), respectively. The sequences were deposited in GenBank (ITS: MW692364, MW692365; LSU: MW699924, MW699925). The ITS and LSU sequences were 99 to 100 % identical to those of P. xanthii in GenBank, (ITS: MT568609, MT472035, MT250855, and AB462800; LSU: AB936276, JX896687, AB936277, and AB936274). Koch’s postulates were completed by gently pressing diseased leaves onto leaves of five healthy potted C. hyssopifolia plants that were held in a greenhouse at 24 to 30°C without humidity control. Five non-inoculated plants served as controls. Inoculated plants developed symptoms after 6 to 10 days, whereas the controls remained symptomless. The morphology of the fungus on the inoculated leaves was identical to that observed on the originally diseased leaves. Previously, Podosphaera sp. has been reported on C. rosea in the United Kingdom (Beales & Cook 2008) and P. xanthii on C. hyssopifolia in Taiwan (Yeh et al. 2021). To our knowledge, this is the first report of powdery mildew caused by P. xanthii on C. hyssopifolia in mainland China. Our field observations suggest that the P. xanthii infections would be a potential threat to the health of C. hyssopifolia in China. References: Beales, P. A., and Cook, R. T. A. 2008. Plant Pathol. 57:778. Braun, U., Cook, R. T. A. 2012. The Taxonomic Manual of the Erysiphales (Powdery Mildews). CBS Biodiversity Series 11: CBS. Utrecht, The Netherlands. Mukhtar, I., et al. 2018. Sydowia.70:155. Scholin, C. A., et al. 1994. J. Phycol. 30:999. White, T. J., et al. 1990. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA. Yeh, Y. W., et al. 2021. Trop. Plant Pathol. 46:44.

scholarly journals First Report of Powdery Mildew Caused by Golovinomyces ambrosiae on Verbena bonariensis in Korea

Plant Disease ◽  
2021 ◽  
Author(s):  
In-Young Choi ◽  
Ho-Jong Ju ◽  
Kui-Jae Lee ◽  
Hyeon-Dong Shin
Keyword(s):  
Powdery Mildew ◽  
Large Subunit ◽  
Morphological Characteristics ◽  
Morphological Characterization ◽  
Control Measures ◽  
Width Ratio ◽  
Infected Leaf ◽  
Voucher Specimen ◽  
First Report ◽  
Pcr Products

Verbena bonariensis L., named as purple-top vervain or Argentinian vervain, is native to tropical South America. It is cultivated worldwide as an ornamental plant. During summer and autumn of 2020, over 50% of the leaves of V. bonariensis were found infected with powdery mildew in a flower garden in Seoul (37°35'19"N 127°01'07"E), Korea. White, superficial mycelia developed initially on the leaves and subsequently covered surfaces of leaves and stems, are resulting in leaf discoloration, early defoliation, and shoots distortion. Heavily infected plants lost ornamental value. A representative voucher specimen was deposited in the Korea University herbarium (KUS-F32168). Morphological characterization and measurements of conidiophores and conidia were carried out using fresh samples. Microscopic observation showed that aAppressoria on the superficial hypha were nipple-shaped, but rarely found or nearly absent. Conidiophores (n = 30) were cylindrical, 110 to 220 × 10 to 12 µm, and produced 2 to 5 immature conidia in chains with a sinuate outline, followed by 2 to 3 short cells. Foot-cells of conidiophores were straight, cylindrical, and 46 to 90 μm long. Conidia (n = 30) were hyaline, ellipsoid to doliiform, 28 to 40 × 18 to 24 μm with a length/width ratio of 1.3 to 2.0, and contained small be like oil-like drops, but without distinct fibrosin bodies. Primary conidia were apically rounded and sub-truncate at the base. Germ tubes were produced at perihilar position of the conidia. Chasmothecia were not observed. These morphological characteristics were typical of the conidial stage of the genus Golovinomyces (Braun and Cook 2012, Qiu et al. 2020). To identify the fungus, rDNA was extracted from the voucher sample. PCR products were amplified using the primer pair ITS1F/PM6 for internal transcribed spacer (ITS), and PM3/TW14 for the large subunit (LSU) of the rDNA (Takamatsu and Kano 2001). The resulting sequences were registered to GenBank (MW599742 for ITS, and MW599743 for LSU). Using Blast’n search of GenBank, sequences showed 100% identity for ITS and LSU with G. ambrosiae (MT355557, KX987303, MH078047 for ITS, and AB769427, AB769426 for LSU), respectively. Thus, based on morphology and molecular analysis, the isolate on V. bonariensis in Korea was identified as G. ambrosiae (Schwein.) U. Braun & R.T.A. Cook. Pathogenicity tests were carried out by touching an infected leaf onto healthy leaves of disease-free pot-grown plants using a replication of five plants, with five non-inoculated plants used as controls. After 7 days, typical powdery mildew colonies started to appear on the inoculated leaves. The fungus on inoculated leaves was morphologically identical to that originally observed in the field. All non-inoculated control leaves remained symptomless. On different global Verbena species, tThere have been many reports of Golovinomyces powdery mildews including G. cichoracearum s.lat., G. longipes, G. monardae, G. orontii s.lat., and G. verbenae (Farr and Rossman 2021). In China, G. verbenae was recorded on V.erbena phlogiflora (Liu et al. 2006). Golovinomyces powdery mildew has not been reported on Verbena spp. in Korea. Powdery mildew has been reported on V. bonariensis in California, but identity of the causal agent had not been reported. To our knowledge, this is the first report on the identity of the powdery mildew caused by G. ambrosiae on V. bonariensis in Korea. Since heavily infected plants lost ornamental value, appropriate control measures should be developed.

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

Plant Disease ◽  
2004 ◽  
Vol 88 (10) ◽  
pp. 1163-1163 ◽  
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.

scholarly journals First Report of Powdery Mildew on Dollar-plant (Crassula ovata) Caused by an Oidium sp.

Plant Disease ◽  
1999 ◽  
Vol 83 (2) ◽  
pp. 199-199 ◽  
Author(s):  
L. Kiss
Keyword(s):  
Powdery Mildew ◽  
The United States ◽  
Diseased Plant ◽  
Powdery Mildew Fungus ◽  
History Museum ◽  
First Report ◽  
Powdery Mildews ◽  
Leaf Surfaces ◽  
Hungarian Natural History Museum ◽  
Germ Tubes

Dollar-plant (Crassula ovata) is a perennial, succulent ornamental grown worldwide. In 1998, powdery mildew colonies were observed on the adaxial leaf surfaces of a 4-year-old specimen maintained outdoors. Symptoms included necrosis of the infected tissues and defoliation 2 months after the appearance of the first colonies. Conidia were produced in chains on unbranched conidiophores. Hyphal appressoria were lobed to multi-lobed, mostly opposite or spread. Conidia were ellipsoid to cylindrical, measured 34 to 48 μm × 17 to 26 μm, and contained no fibrosin bodies. On water agar, conidia produced a single germ tube from the end of the conidium. Germ tubes were either very short with lobed appressoria, or were two to three times longer than conidia, and terminated in lobed or unlobed appressoria. Cleistothecia were not produced. The pathogen was identified as an Oidium sp. belonging to the genus Erysiphe sect. Galeopsidis (1). To confirm pathogenicity, small, potted C. ovata plants were placed near the diseased plant in the laboratory. After 2 weeks, powdery mildew appeared on the small plants, and the pathogen was morphologically identical to the original fungus. This is the first report of a powdery mildew fungus on C. ovata, and it is different from both species of the Erysiphaceae identified on other Crassula spp. (1,2). Infected C. ovata leaves were deposited at the Department of Botany of the Hungarian Natural History Museum in Budapest under the accession number BP 91732. References: (1) U. Braun. 1995. The Powdery Mildews (Erysiphales) of Europe. Gustav Fischer Verlag, Jena. (2) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN.

scholarly journals First Report of the Powdery Mildews Leveillula taurica and Podosphaera pannosa on Rose Periwinkle in the United States

Plant Disease ◽  
2014 ◽  
Vol 98 (6) ◽  
pp. 848-848 ◽  
Author(s):  
M. K. Romberg ◽  
A. H. Kennedy ◽  
M. Ko
Keyword(s):  
United States ◽  
Powdery Mildew ◽  
Consensus Sequence ◽  
The United States ◽  
Infected Leaf ◽  
Adaxial Side ◽  
First Report ◽  
Leveillula Taurica ◽  
Powdery Mildews ◽  
External Hyphae

In April 2013, unthrifty rose periwinkle (Catharanthus roseus (L.) G. Don) from a residential garden in Mililani, HI, was sent to the Hawaii Department of Agriculture. Symptoms, present on all plants, included leaf chlorosis, defoliation, and premature flower drop with necrotic spots on the adaxial side of leaves corresponding to patches of grayish mildew-like growth on the abaxial side. Samples were collected and sent to USDA PPQ National Identification Services (NIS) for confirmation. At NIS, stereoscope examination of the plants revealed two distinct powdery mildews. One, on the stems and leaves, had dimorphic conidia, with lanceolate primary (54 to 72 × 14 to 22 μm) and cylindrical secondary conidia (49 to 75 × 11 to 21 μm) (n = 25 for each), both with a reticulate surface. This fungus was identified morphologically as Leveillula taurica (Lév.) G. Arnaud (1). The second powdery mildew appeared confined to the sepals and petals. The external hyphae of this fungus produced upright chains of cylindrical to ovoid conidia (up to eight per chain), which contained fibrosin bodies and measured 22 × 12 μm (n = 50) with straight foot cells averaging 43 μm long, placing this fungus in the genus Podosphaera Kunze (1). Plants containing both fungi were accessioned as BPI892677 in the US National Fungal Collection. For molecular characterization, genomic DNA of the Podosphaera was obtained by scraping conidia from a petal and extracting with Thermo Scientific's Lyse and Go PCR Reagent. DNA of the Leveillula was extracted from 5 mm2 of infected leaf using Qiagen's Plant mini kit. The ITS region of each fungus was amplified and sequenced directly with primers ITS1F and ITS4. Each consensus sequence was created from manually edited chromatograms, searched against NCBI's GenBank using MegaBLAST and phylogenetically analyzed in MEGA5.2 under maximum parsimony (MP) in context with most similar hits and representatives from phylogenetic studies (2,3). Sequences from types of these fungi are not available for comparison. The resulting Podosphaera phylogeny grouped the Podosphaera suspect (GenBank KF703448) within a clade of P. pannosa (e.g., AB525938; bootstrap = 90). The Leveillula phylogeny grouped the Leveillula suspect (KF703447) within a clade (bootstrap = 88) of L. taurica (e.g., AB044346), L. chrozophorae (AB044346), and L. elaeagni (AB048350). Although the ITS sequences of these taxa are phylogenetically indistinguishable, morphological characters differentiate each species and the suspect as L. taurica (1). L. taurica has been recorded on C. roseus in India and Korea (1). This is the first report of L. taurica on C. roseus in the United States. This is the first report of P. pannosa on C. roseus worldwide. P. pannosa is commonly known as a powdery mildew of Rosaceae hosts, and has also been reported on hosts in the Anacardaciae and Oleaceae (1). P. pannosa represents the second Podosphaera species reported on any member of the Apocynaceae, with P. sparsa reported on other Apocynaceae genera (1). The presence of two powdery mildew genera on different parts of the same plant could cause multiple forms of damage and impact the production of this popular landscape ornamental plant. References: (1) U. Braun and R. T. A. Cook. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No. 11. CBS, Utrecht, Netherlands, 2012. (2) S. A. Khodoparast et al. Mycol. Res. 105:909, 2001. (3) S. Takamatsu et al. Persoonia 24:38, 2010.

scholarly journals Erysiphe trifolii Causing Powdery Mildew of Lentil (Lens culinaris)

Plant Disease ◽  
2009 ◽  
Vol 93 (8) ◽  
pp. 797-803 ◽  
Author(s):  
Renuka N. Attanayake ◽  
Dean A. Glawe ◽  
Frank M. Dugan ◽  
Weidong Chen
Keyword(s):  
Powdery Mildew ◽  
Pacific Northwest ◽  
The United States ◽  
Morphological Characters ◽  
Grain Legumes ◽  
Its Sequences ◽  
Powdery Mildew Fungus ◽  
The Pacific ◽  
Soybean Genotypes ◽  
Erysiphe Trifolii

The taxonomy of the powdery mildew fungus infecting lentil in the Pacific Northwest (PNW) of the United States was investigated on the basis of morphology and rDNA internal transcribed spacer (ITS) sequences. Anamorphic characters were in close agreement with descriptions of Erysiphe trifolii. However, teleomorphs formed chasmothecial appendages with highly branched apices, whereas E. trifolii has been described as producing flexuous or sometimes loosely branched appendages. Branched appendages have been described in Erysiphe diffusa, a fungus reported from species of Lens, Glycine, and Sophora, raising the possibility that the PNW fungus could be E. diffusa. Examination of morphological characters of an authentic specimen of E. trifolii from Austria determined that it included chasmothecial appendages resembling those seen in PNW specimens. Furthermore, ITS sequences from five powdery mildew samples collected from lentils in PNW greenhouses and fields from 2006 to 2008 were identical to one another, and exhibited higher similarity to sequences of E. trifolii (99%) than to those of any other Erysiphe spp. available in GenBank. Parsimony analysis grouped the lentil powdery mildew into a clade with Erysiphe baeumleri, E. trifolii, and E. trifolii–like Oidium sp., but indicated a more distant relationship to E. diffusa. In greenhouse inoculation studies, the lentil powdery mildew fungus did not infect soybean genotypes known to be susceptible to E. diffusa. The pathogenicity of E. trifolii on lentil was confirmed using modified Koch's postulates. This is the first report of E. trifolii infecting lentil. E. diffusa and E. trifolii have different host ranges, so the discovery of E. trifolii on lentil has implications both for determining species of powdery mildews on cool-season grain legumes, and in disease management.

scholarly journals First Report of Powdery Mildew, Caused by Erysiphe cichoracearum, on Coneflowers

Plant Disease ◽  
1999 ◽  
Vol 83 (7) ◽  
pp. 694-694 ◽  
Author(s):  
P. L. Sholberg ◽  
J. H. Ginns ◽  
T. S. C. Li
Keyword(s):  
Powdery Mildew ◽  
Ornamental Plants ◽  
Echinacea Purpurea ◽  
The United States ◽  
Plant Diseases ◽  
Conidial Suspension ◽  
Decay Fungi ◽  
Erysiphe Cichoracearum ◽  
Epidermal Surface ◽  
Medicinal Properties

Purple coneflowers (Echinacea purpurea) are grown in North America and Europe for their medicinal properties and as ornamental plants. In September 1997 and again in 1998, a previously undescribed disease was noticed on fully grown coneflower plants in Summerland and Oliver, British Columbia. Mycelia were observed on stems, foliage, and flowers, and distinct dark red to black, round (approximately 5 mm in diameter) lesions were observed on the flower petals. The disease appeared similar to powdery mildews that have been reported on numerous genera of the Asteraceae. Samples of the diseased tissue were examined and the salient features of the fungus on two specimens were determined: cleistothecia infrequent, subglobose or flattened on the side next to the leaf surface, 121 to 209 μm in diameter; epidermal (surface) cells 20 μm in diameter; appendages hyphoid, 5 μm in diameter, up to 200 μm long; asci, 10 to 19 in each cleistothecium, broadly ellipsoid, 47 to 85 × 28 to 37 μm with a short stalk, about 8 to 13 μm long and 8 μm in diameter; ascospores, immature, two per ascus, ellipsoid to broadly ellipsoid, 17 to 25 × 11 to 13 μm, thin walled, hyaline, and smooth; conidia oblong with sides slightly convex and apices truncate, 27 to 40 × 14 to 20 μm, walls hyaline, thin, smooth. Based on the occurrence of asci that contained two ascospores and the hyphoid appendages on the cleistothecia we concluded that the fungus was Erysiphe cichoracearum DC. Damage due to this disease was minimal in 1997 and 1998 because it developed very late in the growing season and occurred sporadically within the plantings. In order to complete Koch's postulates, Echinacea purpurea plants grown in the greenhouse were inoculated with a conidial suspension (105 to 106 conidia per ml) from field-infected plants. Powdery mildew first appeared 3 months later, eventually infecting leaves and stems of 12 of 49 inoculated plants. It was distinctly white and in discrete patches on leaves, compared with coalescing dark brown areas on the stems. Microscopic examination of the conidia confirmed that they were E. cichoracearum. Although powdery mildew caused by E. cichoracearum has been widely reported on lettuce, safflower, and other cultivated and wild Compositae, we found no reference to it on Echinacea spp. in Canada (1,2), the U.S. (3), or elsewhere in the world (4). The specimens have been deposited in the National Mycological Herbarium of Canada (DAOM) with accession numbers 225933 and 225934 for Oliver and Summerland, B.C., respectively. References: (1) U. Braun. Beih. Nova Hedwigia 89:1, 1987. (2) I. L. Conners. 1967. An annotated index of plant diseases in Canada and fungi recorded on plants in Alaska, Canada, and Greenland. Canada Dept. of Agric. Pub. 1251. (3) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN. (4) J. Ginns. 1986. Compendium of plant disease and decay fungi in Canada, 1960-1980. Agriculture Canada Pub. 1813.

scholarly journals First Report of Soybean Rust Caused by Phakopsora pachyrhizi on Pachyrhizus erosus in the United States

Plant Disease ◽  
2011 ◽  
Vol 95 (8) ◽  
pp. 1034-1034
Author(s):  
M. A. Delaney ◽  
E. J. Sikora ◽  
D. P. Delaney ◽  
M. E. Palm ◽  
J. Roscoe ◽  
...  
Keyword(s):  
United States ◽  
Ribosomal Rna ◽  
Agricultural Research ◽  
The United States ◽  
University Teaching ◽  
Soybean Rust ◽  
Infected Leaf ◽  
Phakopsora Pachyrhizi ◽  
First Report ◽  
Pachyrhizus Erosus

Soybean rust, caused by the fungus Phakopsora pachyrhizi, was detected on jicama (Pachyrhizus erosus L. Urban) for the first time in the United States in November 2009. The pathogen was observed on leaves of a single, potted jicama plant grown outdoors in a residential area and on leaves of all plants in a 12-m2 demonstration plot located at the Auburn University Teaching Garden in Auburn, AL. Symptoms on the upper leaf surfaces were isolated chlorotic areas near the leaf edges in the lower part of the canopy. The abaxial surface was first observed to exhibit brown lesions and subsequently produced volcano-shaped uredinia. These symptoms are consistent with a rust previously described on jicama in Mexico (1). Representative symptomatic plant tissue was sent to the USDA National Identification Services (Mycology) Laboratory in Beltsville, MD for diagnostic confirmation at both the Urbana, IL lab and the USDA National Plant Germplasm and Biotechnology Laboratory for DNA testing. From an infected leaf, samples of approximately 5 mm2 were excised from a microscopically observed rust lesion and an apparently noninfected area. Total DNA was purified with the FastDNA Spin Kit (MP Biomedicals, Solon, OH) followed by the E.Z.N.A. MicroElute DNA Clean-Up Kit (Omega Bio-tek, Inc, Doraville, GA) per manufacturer's instructions. Detection of P. pachyrhizi and P. meibomiae DNA was achieved by quantitative PCR using the method of Frederick et al. (2) and a DNA standard of previously prepared P. pachyrhizi spores. The observed rust pustule was found to contain P. pachyrhizi DNA in excess of 28,000 genomes, while no P. pachyrhizi DNA was observed from the asymptomatic sample. Both samples were negative for P. meibomiae. The fungal structures present were confirmed to be Phakopsora spp. DNA was extracted from sori aseptically removed from leaves with a Qiagen (Valencia, CA) DNeasy Plant Mini Kit and amplified with primers Ppa1 and NL4. The resulting partial ITS2 and 28S ribosomal RNA sequences were 100% identical to GenBank entry DQ354537 P. pachyrhizi internal transcribed spacer 2 and 28S ribosomal RNA gene, partial sequence. Sequences from jicama from Alabama were deposited in GenBank. Voucher specimens were deposited in the USDA Agricultural Research Service, National Fungus Collection (BPI). To our knowledge, this is the first report of the disease on jicama in the United States. References: (1) A. Cárcamo Rodriguez et al. Plant Dis. 90:1260, 2006. (2) R. D. Frederick et al. Phytopathology 92:217, 2002.

scholarly journals First Report of Plum pox virus (Sharka Disease) in Prunus persica in the United States

Plant Disease ◽  
2000 ◽  
Vol 84 (2) ◽  
pp. 202-202 ◽  
Author(s):  
L. Levy ◽  
V. Damsteegt ◽  
R. Welliver
Keyword(s):  
Prunus Persica ◽  
Virus Disease ◽  
Sandwich Elisa ◽  
Pcr Amplification ◽  
The United States ◽  
Enzyme Linked Immunosorbent Assay ◽  
Plum Pox Virus ◽  
Rt Pcr ◽  
Peach Fruit ◽  
First Report

Plum pox (Sharka) is the most important virus disease of Prunus in Europe and the Mediterranean region and is caused by Plum pox potyvirus (PPV). In September 1999, PPV-like symptoms were observed in peach fruit culls in a packinghouse in Pennsylvania. All symptomatic fruit originated from a single block of peach (P. persica cv. Encore) in Adams County. Trees in the block exhibited ring pattern symptoms on their leaves. A potyvirus was detected in symptomatic fruit using the Poty-Group enzyme-linked immunosorbent assay (ELISA) test from Agdia (Elkhart, IN). Reactions for symptomatic peach fruit and leaves also were positive using triple-antibody sandwich ELISA with the PPV polyclonal antibody from Bioreba (Carrboro, NC) for coating, the Poty-Group monoclonal antibody (MAb; Agdia) as the intermediate antibody, and double-antibody sandwich ELISA with PPV detection kits from Sanofi (Sanofi Diagnostics Pasteur, Marnes-La-Coquette, France) and Agdia and the REAL PPV kit (Durviz, Valencia, Spain) containing universal (5B) and strain typing (4DG5 and AL) PPV MAbs (1). PPV also was identified by immunocapture-reverse transcription-polymerase chain reaction (IC-RT-PCR) amplification and subsequent sequencing of the 220-bp 3′ noncoding region (2) (>99% sequence homology to PPV) and by IC-RT-PCR amplification of a 243-bp product in the coat protein (CP) gene (1). The virus was identified as PPV strain D based on serological typing with strainspecific MAbs and on PCR-restriction fragment length polymorphism of the CP IC-RT-PCR product with Rsa1 and Alu1 (1). This is the first report of PPV in North America. References: (1) T. Candresse et al. Phytopathology 88:198, 1998. (2) L. Levy and A. Hadidi. EPPO Bull. 24:595, 1994.

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