First Report of Powdery Mildew Podoshaera tridactyla on Prunus hypoleuca in China

Prunus hypoleuca (≡ Maddenia hypoleuca), a native plant in China, grows in the Qinling Mountains that lie at the intersection of several forest regions in north, central, and southwest China. In October 2013, P. hypoleuca suffering from heavy powdery mildew infections was found with approximately 75% of the plants affected. The powdery mildew at first appeared as circular to irregular white patches, which subsequently showed abundant hyphal growth on both sides of leaves, leading to the withering of the leaves. A voucher specimen was maintained in the Mycological Herbarium of Northwest A & F University (Accession No. HMNWAFU-CF 2013166). Hyphal appressoria were nipple-shaped or nearly absent. Conidiophores were cylindrical, measured 83 to 110 × 10 to 12.5 μm, and produced two to five immature conidia in chains with a crenate outline. Foot-cells of conidiophores were straight, cylindrical, and 28 to 62 × 7 to 10 μm. Conidia were hyaline, ellipsoid to ovate, and measured 20 to 32 × 14 to 21 μm (length/width ratio 1.4:1.8). Chasmothecia were scattered or gregarious, depressed globose, and 65 to 112 μm in diameter. Appendages, arising from the upper half of the chasmothecia, usually had two to four dichotomous branches, and were one to three and a half times as long as the chasmothecial diameter. A single ascus in a chasmothecium was subglobose or broadly ellipsoid-ovoid, measured 66 to 86 × 47 to 76 μm and contained six to eight ascospores. The ascospores were ellipsoid-ovoid and 15 to 27 × 12 to 18 μm. The fungus was identified as Podosphaera tridactyla based on its anamorph and teleomorph characteristics (1,2). To confirm the identification, 28S rDNA and the ITS region were amplified. The ITS5/P3 and then PM5/ITS4 primers were used to amplify the ITS region by nested PCR. The primers LSU1/LSU2 were used to amplify the 28S rDNA, and the cloned fragments were sequenced. The 28S rDNA and ITS region sequences were deposited in GenBank (Accession Nos. KJ879240 and KM213121). A GenBank BLAST search of two sequences revealed 99% identity with P. tridactyla infecting Prunus salicina Lindl. in Korea (3). Based on ITS and a 28S rDNA phylogenetic tree, the two sequences retrieved from the Chinese specimen clustered within a strongly supported clade (bootstrap value = 100%) with P. tridactyla (JQ517296 and AB022393, respectively). Cladistic trees were constructed using the neighbor-joining method with the Kimura two-parameter substitution model in MEGA 5.0. Branch robustness was assessed via bootstrap analysis with 1,000 replicates. Phylogenetic analysis data were in agreement with morphological characters (3). To our knowledge, this is the first report of powdery mildew caused by P. tridactyla on P. hypoleuca. While Koch's postulates have not been carried out because of the biotrophic nature of the pathogen, the present report serves as a novel resource in order to improve the understanding of the etiology and epidemiology of the powdery mildew (P. tridactyla) on P. hypoleuca. The occurrence of P. tridactyla, a common powdery mildew on Prunus s. lat., supports recently published results of phylogenetic analyses of the Prunus complex, indicating that Maddenia must be reduced to synonymy with Prunus (4). References: (1) U. Braun. Beih. Nova Hedwigia 89:1, 1987. (2) U. Braun and R. T. A. Cook. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No. 11. CBS, Utrecht, Netherlands, 2012. (3) S. C. Lee et al. Res. Plant Dis. 18:49, 2012. (4) J. Wen and W. T. Shi. PhytoKeys 17(2):39, 2012.

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First Report of Powdery Mildew Caused by Podosphaera xanthii on Cucurbita argyrosperma in Mexico

Plant Disease ◽

10.1094/pdis-11-21-2458-pdn ◽

2021 ◽

Author(s):

José Francisco Díaz-Nájera ◽

Sergio Ayvar-Serna ◽

Antonio Mena-Bahena ◽

Guadalupe Arlene Mora-Romero ◽

Karla Yeriana Leyva-Madrigal ◽

...

Keyword(s):

Powdery Mildew ◽

Microscopic Examination ◽

Disease Incidence ◽

Phylogenetic Analyses ◽

Its Region ◽

Likelihood Method ◽

28S Rrna ◽

Podosphaera Xanthii ◽

Voucher Specimen ◽

First Report

Cucurbita argyrosperma, commonly named as winter or cushaw squash, is highly sought for its seeds, which have important uses in culinary arts. During the autumn 2021, powdery mildew-like signs and symptoms were observed on cushaw squash in several commercial fields located in Cocula, Guerrero, Mexico. Signs were initially appeared as whitish powdery patches on both sides of leaves and then covering entire leaves and causing premature senescence. The disease incidence was estimated to be 80% in about 1000 plants in two fields. The mycelium was amphigenous, persistent, white in color, and occurred in dense patches. A voucher specimen was deposited in the Herbarium of the Colegio Superior Agropecuario del Estado de Guerrero under the accession number CSAEG22. For the morphological characterization by light microscopy, fungal structures were mounted in a drop of lactic acid on a glass slide. Microscopic examination showed nipple-shaped hyphal appressoria. Conidiophores (n = 30) were straight, 100 to 190 × 10 to 12 μm and produced 2 to 6 conidia in chains. Foot-cells were cylindrical, 41 to 78 μm long, followed by 1 to 2 shorter cells. Conidia (n = 100) were ellipsoid-ovoid to barrel-shaped, 29.5 to 39.1 × 19.4 to 22.7 μm, and contained conspicuous fibrosin bodies. Germ tubes were produced from a lateral position on conidia. Chasmothecia were not observed during the growing season. The morphological characters were consistent with those of the anamorphic state of Podosphaera xanthii (Braun and Cook 2012). For further confirmation, total DNA was extracted from conidia and mycelia following the CTAB method (Doyle and Doyle 1990), and the internal transcribed spacer (ITS) region and part of the 28S gene were amplified by PCR, and sequenced. The ITS region of rDNA was amplified using the primers ITS5/ITS4 (White et al. 1990). For amplification of the 28S rRNA partial gene, a nested PCR was performed using the primer sets PM3 (Takamatsu and Kano 2001)/TW14 (Mori et al. 2000) and NL1/TW14 (Mori et al. 2000) for the first and second reactions, respectively. Phylogenetic analyses using the Maximum Likelihood method, including ITS and 28S sequences of isolates of Podosphaera spp. were performed and confirmed the results obtained in the morphological analysis. The isolate CSAEG22 grouped in a clade with isolates of Podosphaera xanthii. The ITS and 28S sequences were deposited in GenBank under accession numbers OL423329 and OL423343, respectively. Pathogenicity was confirmed by gently dusting conidia from infected leaves onto ten leaves of healthy C. argyrosperma plants. Five non-inoculated leaves served as controls. The plants were maintained in a greenhouse at 25 to 35 ºC, and relative humidity of 60 to 70%. All inoculated leaves developed similar signs to the original observation after 10 days, whereas control leaves remained symptomless. Microscopic examination of the fungus on inoculated leaves showed that it was morphologically identical to that originally observed on diseased plants, fulfilling Koch’s postulates. Podosphaera xanthii has been previously reported on C. maxima, C. moschata, and C. pepo in Mexico (Yañez-Morales et al. 2009; Farr and Rossman 2021). To our knowledge, this is the first report of P. xanthii causing powdery mildew on C. argyrosperma in Mexico. This pathogen is a serious threat to C. argyrosperma production in Mexico and disease management strategies should be developed.

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First Report of Powdery Mildew Caused by Erysiphe macleayae on Macleaya microcarpa in Poland

Plant Disease ◽

10.1094/pdis-03-12-0244-pdn ◽

2012 ◽

Vol 96 (9) ◽

pp. 1376-1376 ◽

Cited By ~ 3

Author(s):

M. J. Park ◽

S. E. Cho ◽

M. Piątek ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Sequence Similarity ◽

Signs And Symptoms ◽

Its Region ◽

Botanical Garden ◽

Central China ◽

Perennial Herb ◽

Width Ratio ◽

First Report ◽

Potted Plants

Macleaya microcarpa (Maxim.) Fedde, also known as smallfruit plume poppy, is a perennial herb belonging to the family Papaveraceae. The plant, together with the better-known species M. cordata (Willd.) R. Br., is native to central China and is now planted worldwide for medicinal purposes. In October 2008 and August 2009, dozens of smallfruit plume poppy planted in the Kraków Botanical Garden, Poland, were found to be severely infected with a powdery mildew. White colonies with abundant sporulation developed on both sides of leaves and young stems, forming circular to irregular patches. Infections caused leaf yellowing and premature defoliation. The damage has been observed every year since 2009. Representative voucher specimens were deposited in the fungal herbarium of the W. Szafer Institute of Botany of the Polish Academy of Sciences (KRAM) and the Korea University herbarium (KUS). Appressoria on the mycelia were lobed, often in pairs. Conidiophores composed of three to four cells arose from the upper part of creeping hyphae, 65 to 120 × 7 to 10 μm, attenuated toward the base, sub-straight or slightly flexuous in foot-cells, and produced conidia singly. Conidia were hyaline, oblong-elliptical to doliiform, 25 to 38 × 12 to 18 μm with a length/width ratio of 1.8 to 2.6; lacked fibrosin bodies; and produced germ tubes on the subterminal position with club-shaped or lobed appressoria. The conidial surface was wrinkled to irregularly reticulate. No chasmothecia were found. The structures described above match well with the anamorph of Erysiphe macleayae R.Y. Zheng & G.Q. Chen (3). To confirm the identity of the causal fungus, the internal transcribed spacer (ITS) region of rDNA from KUS-F24459 was amplified using primers ITS5 and P3 (4) and directly sequenced. The resulting sequence of 553 bp was deposited in GenBank (Accession No. JQ681217). A GenBank BLAST search using the present data revealed >99% sequence similarity of the isolate with E. macleayae on M. cordata from Japan (AB016048). Pathogenicity was confirmed through inoculation by gently pressing diseased leaves onto leaves of three healthy potted plants. Three noninoculated plants served as controls. Plants were maintained in a greenhouse at 25°C. Inoculated plants developed signs and symptoms after 7 days, whereas the control plants remained healthy. The fungus present on the inoculated plants was morphologically identical to that originally observed on diseased plants. The powdery mildew infections of M. cordata associated with E. macleayae have been recorded in China and Japan (2), and more recently in Germany (1,3). To our knowledge, this is the first report of E. macleayae on M. microcarpa globally as well as in Poland. This mildew species was described in China and is endemic to Asia, where chasmothecia of the fungus were found. Only recently have powdery mildews been found on M. cordata in Germany (1,3) and now on M. microcarpa in Poland, indicating the fungus is spreading in Europe. References: (1) N. Ale-Agha et al. Schlechtendalia 17:39, 2008. (2) D. F. Farr and A. Y. Rossman. Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , February 7, 2012. (3) A. Schmidt and M. Scholler. Mycotaxon 115:287, 2011. (4) S. Takamatsu et al. Mycol. Res. 113:117, 2009.

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

Plant Disease ◽

10.1094/pdis-02-21-0349-pdn ◽

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.

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First Report of Powdery Mildew Caused by Podosphaera spiraeae on Japanese Spiraea in China

Plant Disease ◽

10.1094/pdis-09-13-0944-pdn ◽

2014 ◽

Vol 98 (4) ◽

pp. 571-571 ◽

Cited By ~ 1

Author(s):

H. H. Xing ◽

C. Liang ◽

S. E. Cho ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Width Ratio ◽

Pathogenicity Test ◽

Voucher Specimen ◽

First Report ◽

Powdery Mildews ◽

White Spots ◽

Length Width ◽

Qingdao City ◽

Leaf Distortion

Japanese spiraea (Spiraea japonica L.f.), belonging to Rosaceae, is widely planted for its ornamental value in China. Since July 2011, powdery mildew infections on leaves and stems of Japanese spiraea have been noticed in some parks and gardens of Chengyang District in Qingdao City, China (GPS coordinates 36°31′04.22″ N, 120°39′41.92″ E). Symptoms first appeared as white spots covered with mycelium on both side of the leaves and young stems. As the disease progressed, abundant mycelial growth covered the whole shoots and caused growth reduction and leaf distortion with or without reddening. A voucher specimen was deposited in the herbarium of Qingdao Agricultural University (Accession No. HMQAU13013). Hyphae were flexuous to straight, branched, septate, 5 to 7 μm wide, and had nipple-shaped appressoria. Conidiophores arising from the upper surface of hyphal cells produced 2 to 5 immature conidia in chains with a crenate outline. Foot-cells of conidiophores were straight, 60 to 125 × 7 to 9 μm, and followed by 1 to 2 shorter cells. Conidia were ellipsoid-ovoid to doliiform, measured 25 to 32 × 12 to 15 μm with a length/width ratio of 1.8 to 2.6, and had distinct fibrosin bodies. Chasmothecia were not found. The structures and measurements were compatible with the anamorphic state of Podosphaera spiraeae (Sawada) U. Braun & S. Takam. as described before (1). The identity of HMQAU13013 was further confirmed by analysis of nucleotide sequences of the internal transcribed spacer (ITS) regions amplified using the primers ITS1/ITS4 (4). The resulting 564-bp sequence was deposited in GenBank (Accession No. KF500426). A GenBank BLAST search of complete ITS sequence showed 100% identity with that of P. spiraeae on S. cantoniensis (AB525940). A pathogenicity test was conducted through inoculation by gently pressing a diseased leaf onto five healthy leaves of a potted Japanese spiraea. Five non-inoculated leaves served as controls. The plants were maintained in a greenhouse at 22°C. Inoculated leaves developed typical symptoms of powdery mildew after 5 days, but the non-inoculated leaves remained symptomless. The fungus presented on the inoculated plant was morphologically identical to that originally observed on diseased plants, fulfilling Koch's postulates. Powdery mildew of S. japonica caused by P. spiraeae has been recorded in Japan, Poland, and Switzerland (2,3). To our knowledge, this is the first report of powdery mildew caused by P. spiraeae on Japanese spiraea in China. References: (1) U. Braun and R. T. A. Cook. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No.11. CBS, Utrecht, 2012. (2) D. F. Farr and A. Y. Rossman. Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ September 10, 2013. (3) T. Kobayashi. Index of Fungi Inhabiting Woody Plants in Japan. Host, Distribution and Literature. Zenkoku-Noson-Kyoiku Kyokai Publishing Co. Ltd., Tokyo, 2007. (4) S. Matsuda and S. Takamatsu. Mol. Phylogenet. Evol. 27:314, 2003.

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First Report of Powdery Mildew of Platanus occidentalis Caused by Erysiphe platani in Korea

Plant Disease ◽

10.1094/pdis-10-12-0982-pdn ◽

2013 ◽

Vol 97 (6) ◽

pp. 843-843 ◽

Cited By ~ 2

Author(s):

Y. J. La ◽

S. E. Cho ◽

H. D. Shin

Keyword(s):

North America ◽

Powdery Mildew ◽

Its Region ◽

The United States ◽

Control Measures ◽

Base Substitution ◽

Width Ratio ◽

First Report ◽

Platanus Occidentalis ◽

Young Leaves

Platanus occidentalis L., called American sycamore or American plane, is native to North America. The trees are commonly planted throughout the world on the sides of roads and in parks. In June 2012, diseased leaves exhibiting signs of powdery mildew from a park in Daegu City of Korea were sent to Plant Clinic of Seoul National University for diagnosis. Our observations in Daegu City during September and October 2012 showed that nearly 99% of the approximately 1,000 trees surveyed were infected with a powdery mildew. Voucher specimens (n = 6) were deposited at the Korea University Herbarium (KUS). Symptoms were characterized by chlorosis, distortion, or cupping of young leaves. White superficial colonies developed amphigenously on leaves. Hyphae were flexuous to straight, branched, septate, 4 to 7 μm wide, and had lobed appressoria. Conidiophores were 120 to 350 × 5 to 7.5 μm and produced conidia singly. Foot-cells of conidiophores were straight, cylindric, and 115 to 200 μm long. Conidia were hyaline, ellipsoid-ovoid, measured 33 to 47.5 × 17.5 to 29 μm with a length/width ratio of 1.5 to 2.0, lacked distinct fibrosin bodies, and showed reticulate wrinkling of the outer walls. Germ tubes were produced on the subterminal position of conidia. No chasmothecia were observed. The structures and measurements were compatible with those of the anamorphic state of Erysiphe platani (Howe) U. Braun & S. Takam. (1). To confirm the identification, the complete internal transcribed spacer (ITS) region of the rDNA from isolate KUS-F26959 was amplified with nested PCR and sequenced. The resulting sequence of 625 bp was deposited in GenBank (Accession No. JX997805). A GenBank BLAST search of this sequence showed only one base substitution with the four sequences (JQ365940 to JQ365943) of E. platani on Platanus spp. Pathogenicity was confirmed through inoculation tests by gently pressing diseased leaves onto young leaves of three 2-year-old disease-free seedlings. Three non-inoculated plants were used as control. Plants were maintained in a greenhouse at 24 to 30°C. Inoculated leaves developed symptoms after 7 days, whereas the control plants remained symptomless. The fungus present on the inoculated leaves was morphologically identical to that observed on the original diseased leaves, fulfilling Koch's postulates. Since E. platani first was recorded in the United States in 1874, it has been regarded as endemic in North America. From the second half of the 20th century, introduction and expansion of the range of this fungus to South America, South Africa, Australia and New Zealand, Europe, and Asia have been reported (1,2). To our knowledge, this is the first report of E. platani infections of P. occidentalis in Korea. This species was recorded on P.× hispanica from Japan in 1999 (4) and on P. orientalis from China in 2006 (3), suggesting invasive spread of the sycamore powdery mildew in East Asia. Since American sycamores are widely planted in Korea, control measures should be made to prevent further spread of the disease. References: (1) U. Braun and R. T. A. Cook. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No.11. CBS, Utrecht, 2012. (2) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab., Online publication, ARS, USDA, Retrieved October 22, 2012. (3) C. Liang et al. Plant Pathol. 57:375, 2008. (4) S, Tanda. J. Agric. Sci., Tokyo Univ. Agric. 43:253, 1999.

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First Report of Erysiphe quercicola Causing Powdery Mildew on Ubame Oak in Korea

Plant Disease ◽

10.1094/pdis-05-10-0396 ◽

2011 ◽

Vol 95 (1) ◽

pp. 77-77 ◽

Cited By ~ 5

Author(s):

H. B. Lee ◽

C. J. Kim ◽

H. Y. Mun ◽

K. -H. Lee

Keyword(s):

Powdery Mildew ◽

Sequence Data ◽

Width Ratio ◽

Microbiology Laboratory ◽

Voucher Specimen ◽

First Report ◽

Erysiphe Quercicola ◽

Powdery Mildews ◽

Quercus Species ◽

National University

Ubame oak (Quercus phillyraeoides A. Gray) is native to eastern Asia, including China, Korea, and Japan. In 2009 and 2010, a powdery mildew on Q. phillyraeoides growing in clusters and singly was observed in three locations on the campus of Chonnam National University, Gwangju, Korea. White superficial conidia of the powdery mildew fungus occurred on adaxial and abaxial surfaces. However, the white powdery growth was more abundant on the adaxial surface. Leaf symptoms commonly appeared white from May to October. Along with the typical white powdery mildew, spot and/or necrotic symptoms with irregular violet-to-wine red surfaces were also frequently observed on overwintered leaves. A voucher specimen has been deposited in EML (Environmental Microbiology Laboratory) herbarium collection, Chonnam National University (EML-QUP1). Conidia were commonly formed singly but also occurred in chains. Primary conidia were obovoid to ellipsoid, with a rounded apex and subtruncate base. Secondary conidia were generally obovoid to ellipsoid or sometimes cylindrical but dolioform when mature. The size was 30.1 to 43.2 (average 37.7) × 14.1 to 21.1 (average 18.1) μm with length/width ratio of 1.8 to 2.4 (average 2.1). Conidiophores were erect and up to 102.2 μm long. No chasmothecia were found. From extracted genomic DNA, the internal transcribed spacer (ITS) region inclusive of 5.8S rDNA was amplified with ITS1F (5′-CTTGGT CATTTAGAGGAAGT-3′) and LR5F (5′-GCTATCCTGAGGGAAAC-3′) primers (4). Sequence analysis by BLASTN search indicated that EML-QUP1 (GenBank Accession No. HQ328834) was closest to E. quercicola (GenBank Accession No. AB292691) with >99% identity (478 of 480), forming a monophyletic quercicola clade in the resulting phylogenetic analysis. The causal fungus was determined to be Erysiphe quercicola on the basis of morphology and sequence data analysis. Major genera including Cystotheca, Erysiphe, Microsphaera, and Phyllactinia have been reported to cause powdery mildews on Quercus plants. Until now, 22 Erysiphe species including E. abbreviata, E. alphitoides, E. calocladophora, E. gracilis, E. polygoni, and E. quercicola have been reported to cause powdery mildews on Quercus spp. (1). Of these, four Erysiphe species including E. alphitoides, E. gracilis, E. quercicola, and an unidentified Erysiphe sp. have been found on Q. phillyraeoides from Japan (1–3). E. quercicola was reported to occur on five Quercus species: Q. crispula, Q. phillyraeoides, and Q. serrata in Japan, Q. robur in Australia, and Quercus sp. in Australia, Iran, and Thailand (1). To our knowledge, this is the first report of leaf powdery mildew caused by E. quercicola on Q. phillyraeoides in Korea. References: (1) D. F. Farr and A. Y. Rossman. Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved October 7, 2010, from http://nt.ars-grin.gov/fungaldatabases/ , 2010. (2) S. Limkaisang et al. Mycoscience 47:327, 2006. (3) S. Takamatsu et al. Mycol. Res. 111:809, 2007. (4) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.

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First Report of Sawadaea polyfida Causing Powdery Mildew of Acer palmatum in China

Plant Disease ◽

10.1094/pdis-07-21-1566-pdn ◽

2021 ◽

Author(s):

Yu Wan ◽

Yuan-Zhi Si ◽

Yang-Chun-Zi Liao ◽

Li-Hua Zhu

Keyword(s):

Powdery Mildew ◽

Phylogenetic Analyses ◽

Morphological Characteristics ◽

Signs And Symptoms ◽

Species Identity ◽

Internal Transcribed Spacer Region ◽

Voucher Specimen ◽

First Report ◽

Effective Strategies ◽

And Control

Acer palmatum Thunb. is an important colorful leaf ornamental tree species widely distributed in Japan, Korea and China (Carlos et al. 2016). In October 2019, powdery mildew was observed on leaves of A. palmatum planted at Qixia Mountain Park and the campus of Nanjing Forestry University, Nanjing, Jiangsu, China. The powdery mildew infected and colonized leaves, covering both leaf surfaces with white mycelia, giving affected plants an unsightly appearance. Nearly 17.4% of the plants (87/501) exhibited these signs and symptoms. Fresh specimens were collected and examined for the identification of the pathogen. Photos were taken with a ZEISS Axio Imager A2m microscope and a scanning electronic microscope. Chasmothecia were scattered or aggregated on the upper and lower surfaces of the leaves, blackish brown, oblate, 157.5 to 238.1 × 152.3 to 217.8 μm (n=30), with numerous appendages (100 to 200). Appendages were often (1−) 2 to 3 times branched from the middle of the stalk, uncinate to circinate at the apex, hyaline, aseptate, 30.0 to 70.8 × 4.1 to 8.2 μm (n=30). Asci were 11 to 21 per chasmothecium (n=30), long oval, oval, oblong, with short stalk or sessile, 80.6 ± 8.6 × 40.3 ± 4.0 um (n=30) in length, 6 to 8 spored (n=30). Ascospores were ovoid, 18.2 ± 1.6 × 11.1 ± 1.2 μm (n=30). Microconidiophores were 25 to 50 × 4.0 to 5.5 μm, producing microconidia in chains. Microconidia were ellipsoidal, subglobose, 8.7 ± 0.6 × 7.2 ± 0.6 μm (n=30). Macroconidia were not observed. Based on the morphological characteristics, the fungus was identified as Sawadaea polyfida (C.T. Wei) R.Y. Zheng & G. Q. Chen (Zheng and Yu 1987). To confirm the causative species identity, a representative voucher specimen collected and deposited at Nanjing Forestry University was used for a molecular analysis. Mycelia and conidia were collected from diseased leaves and genomic DNA of the pathogen was extracted and the internal transcribed spacer region (ITS) was amplified with primers ITS1/ITS4 (White et al. 1990). The resulting sequence of 461 bp was deposited in GenBank (accession no. MW255383). BLAST result showed that this sequence fully agreed with a sequence of S. polyfida [AB193381.1 (ITS), identities = 461/461 (100%)]. A maximum likelihood phylogenetic analyses using IQtree v. 1.6.8 with the ITS sequence placed this fungus in the S. polyfida clade. Based on the morphology and phylogeny, the fungus was identified as S. polyfida (Hirose et al. 2005; Zheng and Yu 1987). Pathogenicity was tested through inoculation by gently pressing the naturally infected leaves onto healthy ones of three potted A. palmatum seedlings wih five leaves. Healthy leaves from three other seedlings served as control. Inoculated and control seedlings were placed in separate growth chambers maintained at 20 ± 2°C, 70% humidity, with a 16 h/8 h light/dark period. Symptoms developed 8 days after inoculation. The powdery mildew developing on the inoculated seedlings was sequenced and confirmed as S. polyfida. The control leaves did not develop powdery mildew. S. polyfida has been reported on Acer catalpifolium in China (Zheng and Chen 1980), A. amoenum, A. australe, A. japonicum, A. palmatum, A. shirasawanum, and A. sieboldianum in Japan (Hirose et al. 2005; Meeboonet al. 2015), as well as A. takesimense in Korea (Lee et al. 2011). To the best of our knowledge, this is the first report of powdery mildew caused by S. polyfida on A. palmatum in China. These results form the basis for developing effective strategies for monitoring and managing this disease.

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First Report of Powdery Mildew Caused by Oidium hortensiae on Mophead Hydrangea in Korea

Plant Disease ◽

10.1094/pdis-03-12-0300-pdn ◽

2012 ◽

Vol 96 (7) ◽

pp. 1072-1072 ◽

Cited By ~ 3

Author(s):

M. J. Park ◽

S. E. Cho ◽

J. H. Park ◽

S. K. Lee ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Sequence Data ◽

Morphological Characteristics ◽

Signs And Symptoms ◽

Its Region ◽

Polyethylene Film ◽

Width Ratio ◽

First Report ◽

Close Phylogenetic Relationship ◽

Powdery Mildew Disease

Hydrangea macrophylla (Thunb.) Ser., known as mophead hydrangea, is native to Japan and is used as a potted ornamental or is planted for landscaping in gardens worldwide. In May 2011, powdery mildew occurred on potted mophead hydrangea cv. Emerald plants in polyethylene-film-covered greenhouses in Icheon, Korea. Heavily infected plantings were unmarketable, mainly due to purplish red discoloration and crinkling of leaves. Such powdery mildew symptoms on mophead hydrangea in gardens had been often found in Korea since 2001, and the collections (n = 10) were deposited in the Korea University herbarium (KUS). In all cases, there was no trace of chasmothecia formation. Mycelium was effuse on both sides of leaves, young stems, and flower petals. Appressoria were well developed, lobed, and solitary or in opposite pairs. Conidiophores were cylindrical, 70 to 145 × 7.5 to 10 μm, and composed of three to four cells. Foot-cells of conidiophores were straight to sub-straight, cylindric, short, and mostly less than 30 μm long. Conidia produced singly were ellipsoid to oval, 32 to 50 × 14 to 22 μm with a length/width ratio of 1.7 to 2.8, lacked fibrosin bodies, and showed angular/rectangular wrinkling of outer walls. Germ tubes were produced on the perihilar position of conidia. Primary conidia were apically conical, basally rounded to subtruncate, 32 to 42 × 14 to 18 μm, and thus generally smaller than the secondary conidia. The morphological characteristics are consistent with previous descriptions of Oidium hortensiae Jørst. (3,4). To confirm the identification, the complete internal transcribed spacer (ITS) region of rDNA from KUS-F25514 was amplified with primers ITS5 and P3 and directly sequenced. The resulting sequence of 694 bp was deposited in GenBank (Accession No. JQ669944). There was no ITS sequence data known from powdery mildews on Hydrangea. Therefore, this is the first sequence of O. hortensiae submitted to GenBank. Nevertheless, a GenBank BLAST search of this sequence showed >99% similarity with those of Oidium spp. recorded on crassulacean hosts (e.g. GenBank Accession Nos. EU185641 ex Sedum, EU185636 ex Echeveria, and EU185639 ex Dudleya) (2), suggesting their close phylogenetic relationship. Pathogenicity was confirmed through inoculation by gently pressing diseased leaves onto leaves of five healthy potted mophead hydrangea cv. Emerald plants. Five noninoculated plants of the same cultivar served as controls. Plants were maintained in a greenhouse at 22 ± 2°C. Inoculated plants developed signs and symptoms after 6 days, whereas the control plants remained healthy. The fungus present on the inoculated plants was morphologically identical to that originally observed on diseased plants, fulfilling Koch's postulates. Occurrence of powdery mildew disease on mophead hydrangea is circumglobal (1). To our knowledge, this is the first report of powdery mildew disease caused by O. hortensiae on mophead hydrangea in Korea. Powdery mildew infections in Korea pose a serious threat to the continued production of quality potted mophead hydrangea in polyethylene-film-covered greenhouses. References: (1) D. F. Farr and A. Y. Rossman. Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved March 19, 2012, from http://nt.ars-grin.gov/fungaldatabases/ . (2) B. Henricot. Plant Pathol. 57:779, 2008. (3) A. Schmidt and M. Scholler. Mycotaxon 115:287, 2011. (4) S. Tanda. J. Agric. Sci. Tokyo Univ. Agric. 43:253, 1999.

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First Report of Powdery Mildew Caused by Erysiphe buhrii on Gypsophila paniculata in Korea

Plant Disease ◽

10.1094/pdis-03-14-0237-pdn ◽

2014 ◽

Vol 98 (7) ◽

pp. 1013-1013 ◽

Cited By ~ 4

Author(s):

I. Y. Choi ◽

B. S. Kim ◽

S. E. Cho ◽

J. H. Park ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Host Range ◽

Disease Incidence ◽

Width Ratio ◽

Korean Isolate ◽

Pathogenicity Test ◽

Cut Flower ◽

Voucher Specimen ◽

First Report ◽

Gypsophila Paniculata

Gypsophila paniculata L. (baby's breath, family Caryophyllaceae), native to Central and Eastern Europe, is commonly cultivated as a commercial cut flower crop in greenhouses in Korea. Since 2011, baby's breath cv. Cassiopeia has been observed affected by a powdery mildew with nearly 100% disease incidence at the stage of harvesting in Iksan City. Powdery mildew colonies first appeared as thin white patches on stems and both sides of the leaves. As disease progressed, plants were covered with dense masses of spores, followed by senescence and reduction of quality of cut flowers. A voucher specimen was deposited in the Korea University Herbarium (Accession KUS-F27313). Appressoria were well-developed, multilobed or moderately lobed, and single or opposite in pairs. Conidiophores were straight, 95 to 150 × 7 to 10 μm, and composed of 3 to 4 cells. Foot-cells were cylindric or slightly sinuous at the base and 37 to 53 μm long. Singly produced conidia were cylindrical to oblong-elliptical, 35 to 56 × 12.5 to 18 μm with a length/width ratio of 2.1 to 3.6, devoid of fibrosin bodies, and with angular/rectangular wrinkling of outer walls. Germ tubes were in the perihilar position on conidia, and ended with lobed appressoria. No chasmothecia were found. These structures are typical of the Pseudoidium anamorph of the genus Erysiphe. Specific measurements and host range were consistent with those of E. buhrii U. Braun (2). To confirm identification, the complete internal transcribed spacer (ITS) region of rDNA of isolate KUS-F27313 was amplified with primers ITS1/ITS4, and sequenced directly. The resulting 725-bp sequence was deposited in GenBank (KJ530705). A GenBank BLAST search of the Korean isolate showed 99% similarity with E. buhrii on Acanthophyllum sp. (Caryophyllaceae) from Iran (AB128924). Pathogenicity was confirmed through inoculation by gently dusting conidia onto leaves of five healthy, potted baby's breath cv. Cassiopeia. Five non-inoculated plants served as controls. Inoculated plants were isolated from non-inoculated plants in separate rooms in a greenhouse at 25 ± 2°C. Inoculated plants developed signs and symptoms after 7 days, whereas the control plants remained symptomless. The fungus present on the inoculated plants was identical morphologically to that originally observed on diseased plants. Pathogenicity test was repeated twice. The powdery mildew disease caused by E. buhrii on baby's breath has been recorded in the former Soviet Union (Armenia, Kazakhstan, Ukraine), Romania, Turkey, Iran, Mongolia, and Argentina (1,3). Also, a fungus occurring on baby's breath was recorded as Oidium sp. from Japan (4). To our knowledge, this is the first report of powdery mildew caused by E. buhrii on baby's breath in Korea. Powdery mildew infections pose a serious threat to production of this cut flower crop. References: (1) K. Amano. Host Range and Geographical Distribution of the Powdery Mildew Fungi. Japan Scientific Societies Press, Tokyo, 1986. (2) U. Braun and R. T. A. Cook. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No. 11. CBS, Utrecht, 2012. (3) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab., Online publication, ARS, USDA, Retrieved February 18, 2014. (4) M. Satou et al. Ann. Phytopathol. Soc. Jpn. 62:541, 1996.

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First Report of Powdery Mildew Caused by Golovinomyces sonchicola on Ixeris chinensis in Korea

Plant Disease ◽

10.1094/pdis-11-13-1132-pdn ◽

2014 ◽

Vol 98 (7) ◽

pp. 999-999 ◽

Cited By ~ 2

Author(s):

J. K. Choi ◽

B. S. Kim ◽

S. H. Hong ◽

S. E. Cho ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Sequence Similarity ◽

Folk Medicine ◽

Morphological Characteristics ◽

Its Region ◽

Width Ratio ◽

Lateral Part ◽

Potential Threat ◽

First Report ◽

Powdery Mildews

Ixeris chinensis (Thunb.) Nakai, known as Chinese ixeris, is distributed from Siberia to Japan, including Korea, Taiwan, and China. The whole plant has been used in folk medicine in Asia (4). In Korea, the plants of Chinese ixeris have been gathered and used as a wild root vegetable. During summer to autumn of 2011, Chinese ixeris leaves were found to be heavily infected with a powdery mildew in several locations of Korea. Symptoms first appeared as thin white colonies, which subsequently developed into abundant hyphal growth on both sides of the leaves, leading to drying of the leaves. The same symptoms on Chinese ixeris leaves were continuously observed in 2012 and 2013. Voucher specimens (n = 10) were deposited at Korea University Herbarium (KUS). Hyphal appressoria were moderately lobed or nipple-shaped. Conidiophores arose from the lateral part of the hyphae, measured 100 to 270 × 10 to 12.5 μm, and produced 2 to 6 immature conidia in chains with a sinuate outline. Basal parts of foot-cells in conidiophores were curved. Conidia were barrel-shaped to ellipsoid, measured 26 to 36 × 13 to 19 μm (length/width ratio = 1.7 to 2.4), lacked fibrosin bodies, and showed reticulate wrinkling of the outer walls. Primary conidia were ovate with conical-obtuse apex and subtruncate base. Germ tubes were produced on the perihilar position of conidia. Chasmothecia were not observed. The morphological characteristics were typical of the Euoidium type anamorph of the genus Golovinomyces, and the fungus measurements and structures were consistent with those of G. sonchicola U. Braun & R.T.A. Cook (1). To confirm the identification, internal transcribed spacer (ITS) region of rDNA sequences from a representative material (KUS-F26212) was amplified using primers ITS5/P3 and sequenced (3). The resulting 416-bp sequence was deposited in GenBank (Accession No. KF819857). A GenBank BLAST search revealed that the isolate showed >99% sequence similarity with those of G. cichoracearum from Sonchus spp. (e.g., AB453762, AF011296, JQ010848, etc.). G. sonchicola is currently confined to G. cichoracearum s. lat. on Sonchus spp., based on molecular sequence analyses (1). Pathogenicity was confirmed through inoculation by gently pressing a diseased leaf onto leaves of five healthy potted Chinese ixeris. Five non-inoculated plants served as controls. Inoculated plants developed symptoms after 6 days, whereas the controls remained symptomless. The fungus present on the inoculated plants was identical morphologically to that originally observed on diseased plants. Powdery mildew infections of I. chinensis associated with Golovinomyces have been known in China (2). To our knowledge, this is the first report of powdery mildew disease caused by G. sonchicola on I. chinensis in Korea. Farming of Chinese ixeris has recently started on a commercial scale in Korea. Though no statistical data are available, we postulate the cultivation area in Korea to be approximately 200 ha, mostly growing without chemical controls. Occurrence of powdery mildews poses a potential threat to safe production of this vegetable, especially in organic farming. References: (1) U. Braun and R. T. A. Cook. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No.11. CBS, Utrecht, 2012. (2) F. L. Tai. Bull. Chinese Bot. Sci. 2:16, 1936. (3) S. Takamatsu et al. Mycol. Res. 113:117, 2009. (4) S. J. Zhang et al. J. Nat. Prod. 69:1425, 2006.

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