First Report of Powdery Mildew Caused by Podosphaera xanthii on Papaya in Korea

In March 2013, papaya (Carica papaya L. cv. Sunrise) plants growing in polyethylene-film-covered greenhouses in Agricultural Research Center for Climate Change located in Jeju City, Korea, were observed severely affected by a powdery mildew. Symptoms appeared as circular to irregular white patches on both sides of the leaves. As the disease progressed, the plants were covered with dense masses of the spores, eventually causing senescence and withering of leaves. Voucher specimens were deposited in the Korea University Herbarium (KUS). Hyphae were flexuous to straight, branched, septate, and 5 to 8 μm wide. Conidiophores were 110 to 250 × 10 to 12.5 μm and produced 2 to 5 immature conidia in chains with a crenate outline followed by 2 to 3 cells. Foot-cells of conidiophores were straight, cylindric, slightly constricted at the basal septum, and 55 to 110 μm long. Conidia were hyaline, ellipsoid-ovoid, measured 22 to 38 × 18 to 21 μm with a length/width ratio of 1.2 to 1.8, and had distinct fibrosin bodies. Chasmothecia were scattered or partly clustered, dark brown, spherical, 80 to 100 μm in diameter, and each contained a single ascus. Appendages were mycelioid, 1- to 5-septate, brown at the base and becoming paler. Asci were sessile, 72 to 87 × 52 to 68 μm, had a terminal oculus of 17 to 23 μm wide, and contained 8 ascospores, each 17 to 23 × 12.5 to 15 μm. The morphological characteristics and measurements were consistent with those of Podosphaera xanthii (Castagne) U. Braun & Shishkoff (1). To confirm the identification, the complete internal transcribed spacer (ITS) region of rDNA of KUS-F27269 was amplified with the primers ITS5/P3 and sequenced (3). The resulting 443 bp sequence was deposited in GenBank (Accession No. KF111806). The Korean isolate showed >99% similarity with those of many P. xanthii isolates including an isolate on papaya from Taiwan (GU358450). Pathogenicity was confirmed through inoculation tests by gently pressing a diseased leaf onto young leaves of three asymptomatic, potted seedlings (cv. Sunrise). Three non-inoculated seedlings were used as control. Inoculated plants were isolated from non-inoculated plants in separate rooms in a greenhouse at 26 to 30°C. Inoculated leaves developed symptoms after 7 days, whereas the control plants remained symptomless. The fungus present on the inoculated leaves was identical morphologically to that observed on the original diseased leaves, fulfilling Koch's postulates. Powdery mildews of papaya caused by Podosphaera species including P. caricae-papayae have been reported in North America, South America, Hawaii, Africa, Ukraine, Australia, New Zealand, the Cook Islands, India, Thailand, Taiwan, and Japan (2,4). P. caricae-papayae is currently reduced to synonymy with P. xanthii (1). To our knowledge, this is the first report of powdery mildew caused by P. xanthii on papaya in Korea. Though papaya is a minor crop in Korea, producing about 300 M/T annually in greenhouses, powdery mildew disease is a threat to safe production of the fruits. 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 April 9, 2013. (3) S. Takamatsu et al. Mycol. Res. 113:117, 2009. (4) J. G. Tsay et al. Plant Dis. 95:1188, 2011.

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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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First Report of Powdery Mildew Caused by Erysiphe heraclei on Chervil in Korea

Plant Disease ◽

10.1094/pdis-07-13-0797-pdn ◽

2014 ◽

Vol 98 (3) ◽

pp. 426-426

Author(s):

K. S. Han ◽

S. E. Cho ◽

J. H. Park ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Morphological Characteristics ◽

Signs And Symptoms ◽

Its Region ◽

The United States ◽

Control Treatment ◽

Width Ratio ◽

Anethum Graveolens ◽

First Report ◽

Powdery Mildews

Chervil (Anthriscus cerefolium (L.) Hoffm.), belonging to the family Apiaceae, is an aromatic annual herb that is native to the Caucasus. It is widely used as a flavoring agent for culinary purposes. This herb was recently introduced in Korea. In April 2013, plants showing typical symptoms of powdery mildew disease were observed in a polyethylene film-covered greenhouse in Seoul, Korea. White mycelium bearing conidia formed irregular patches on leaves and stems. Mycelial growth was amphigenous. Severe infections caused leaf withering and premature senescence. Voucher specimens were deposited in the Korea University Herbarium (KUS). Hyphae were septate, branched, with moderately lobed appressoria. Conidiophores presented 3 to 4 cells and measured 85 to 148 × 7 to 9 μm. Foot-cells of conidiophores were 37 to 50 μm long. Conidia were produced singly, oblong-elliptical to oblong, measured 30 to 50 × 13 to 18 μm with a length/width ratio of 2.0 to 3.3, lacked conspicuous fibrosin bodies, and with angular/rectangular wrinkling of the outer walls. Germ tubes were produced in the subterminal position of conidia. Chasmothecia were not found. These structures are typical of the powdery mildew Pseudoidium anamorph of the genus Erysiphe. The specific measurements and morphological characteristics were consistent with those of E. heraclei DC. (1). To confirm identity of the causal fungus, the complete internal transcribed spacer (ITS) region of rDNA of KUS-F27279 was amplified with primers ITS5 and P3 (4) and sequenced directly. The resulting 561-bp sequence was deposited in GenBank (Accession No. KF111807). A GenBank BLAST search of this sequence showed >99% similarity with those of many E. heraclei isolates, e.g., Pimpinella affinis (AB104513), Anethum graveolens (JN603995), and Daucus carota (EU371725). Pathogenicity was confirmed through inoculation by gently pressing a diseased leaf onto leaves of five healthy potted chervil plants. Five non-inoculated plants served as a control treatment. 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 identical morphologically to that originally observed on diseased plants. Chervil powdery mildews caused by E. heraclei have been reported in Europe (Bulgaria, France, Germany, Hungary, Italy, Romania, Switzerland, and the former Soviet Union) and the United States (2,3). To our knowledge, this is the first report of powdery mildew caused by E. heraclei on chervil in Asia as well as in Korea. The plant is cultivated in commercial farms for its edible leaves in Korea. Occurrence of powdery mildew is a threat to quality and marketability of this herb, especially those grown in organic farming where chemical control options are limited. 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 July 29, 2013. (3) S. T. Koike and G. S. Saenz. Plant Dis. 88:1163, 2004. (4) S. Takamatsu et al. Mycol. Res. 113:117, 2009.

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First Report of Powdery Mildew Caused by Erysiphe heraclei on Peucedanum japonicum in Korea

Plant Disease ◽

10.1094/pdis-09-14-0895-pdn ◽

2015 ◽

Vol 99 (1) ◽

pp. 161-161 ◽

Cited By ~ 1

Author(s):

I. Y. Choi ◽

S. H. Hong ◽

S. E. Cho ◽

J. H. Park ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Organic Farming ◽

Disease Incidence ◽

Morphological Characteristics ◽

Its Region ◽

Petroselinum Crispum ◽

Width Ratio ◽

First Report ◽

Potted Plants ◽

Powdery Mildews

Peucedanum japonicum Thunb., belonging to the family Apiaceae, is distributed in many Asian countries, including Korea. This plant was recently developed as an edible green and is cultivated under organic farming in Korea. In June 2013, plants showing typical symptoms of powdery mildew were found with approximately 50% disease incidence in polyethylene-film-covered greenhouses in Iksan City, Korea. Symptoms first appeared as circular white colonies, which subsequently showed abundant mycelial growth on the leaves, often covering the whole surface. Infected plants were unmarketable mainly due to signs of white fungal growths and reddish discoloration on the leaves. The same symptoms were found on P. japonicum in poly-tunnels in Iksan City and Jinan County of Korea in 2014. Voucher specimens (n = 3) were deposited in the Korea University Herbarium (KUS). Appressoria were lobed, and solitary or in opposite pairs. Conidiophores were cylindrical, 80 to 145 × 8 to 10 μm, and composed of three to four cells. Foot-cells of conidiophores were straight to substraight, cylindrical, and 25 to 63 μm long. Singly produced conidia were oblong-elliptical to oblong, occasionally ovate, 35 to 50 × 13 to 16 μm with a length/width ratio of 2.3:3.1, with angular/rectangular wrinkling of outer walls, and lacked distinct fibrosin bodies. Germ tubes were produced on the perihilar position of conidia. Primary conidia were apically conical, basally truncate, and generally smaller than the secondary conidia. No chasmothecia were found. These structures are typical of the powdery mildew Pseudoidium anamorph of the genus Erysiphe. The specific measurements and morphological characteristics were consistent with those of E. heraclei DC. (2). To confirm the identification, the complete internal transcribed spacer (ITS) region of rDNA from KUS-F27872 was amplified with primers ITS1/ITS4 and sequenced. The resulting 560-bp sequence was deposited in GenBank (Accession No. KM491178). The obtained ITS sequence shared >99% similarity with those of E. heraclei from apiaceous hosts, e.g., Daucus carota (KC480605), Pimpinella affinis (AB104513), and Petroselinum crispum (KF931139). Pathogenicity was confirmed through inoculation by gently dusting conidia onto leaves of five healthy potted plants. Five non-inoculated plants served as controls. Inoculated plants developed symptoms after 6 days, whereas the control plants remained symptomless. The fungus present on the inoculated plants was identical in morphology to those observed in the field. Powdery mildew of P. japonicum caused by E. heraclei has been reported in Japan (4), and numerous reports of E. heraclei on various species of Peucedanum plants have been made in most part of Europe and East Asia (Japan and far eastern Russia) (1,3). However, this is the first report of powdery mildew caused by E. heraclei on P. japonicum in Korea. Occurrence of powdery mildews is a threat to the quality and marketability of this plant, especially in organic farming. 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 August 18, 2014. (4) S. Tanda and C. Nakashima. J. Agric. Sci., Tokyo Univ. Agric. 47:54, 2002.

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First Report of Powdery Mildew Caused by Podosphaera xanthii on Hibiscus mutabilis in Korea

Plant Disease ◽

10.1094/pdis-01-13-0065-pdn ◽

2013 ◽

Vol 97 (8) ◽

pp. 1118-1118

Author(s):

S. E. Cho ◽

J. H. Park ◽

S. K. Lee ◽

C. H. Shin ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Natural Habitat ◽

Morphological Characteristics ◽

Its Region ◽

Width Ratio ◽

Korean Isolate ◽

First Report ◽

Public Garden ◽

Young Leaves ◽

Length Width

Hibiscus mutabilis L., known as cotton rose, is a deciduous shrub native to China. Horticultural varieties of the species are widely planted throughout the world (4). In September 2012, typical powdery mildew symptoms on the cotton rose were observed in a public garden of Jeju City, Korea. Powdery mildew colonies were circular to irregular white patches on both sides of the leaves and also on young stems and sepals. As the disease progressed, white mycelial growth covered the entire shoot portion, causing leaf distortion. In the middle of November, numerous chasmothecia were formed on the lesions. Voucher specimens (n = 4) were deposited in the Korea University Herbarium (KUS). Hyphal appressoria were only swollen part of hyphae or occasionally nipple-shaped. Conidiophores were 140 to 275 × 10 to 11.5 μm and produced 2 to 8 immature conidia in chains with a crenate outline. Foot-cells of conidiophores were straight, 30 to 65 μm long, and cylindric. Conidia were hyaline, ellipsoid-ovoid, and measured 27 to 42 × 17.5 to 21 μm with a length/width ratio of 1.5 to 2.4, and had distinct fibrosin bodies. Chasmothecia were amphigenous, cauligenous, 85 to 110 μm in diameter, and contained one ascus each. Peridium cells of chasmothecia were irregularly polygonal, large, and 15 to 38 μm wide. Appendages were mycelioid, 1- to 6-septate, brown at the base, and becoming paler. Asci were sessile, oval to broadly fusiform, with terminal oculus of 15 to 20 μm wide. Ascospores numbered eight per ascus were ellipsoidal, 19 to 25 × 14 to 16 μm. The morphological characteristics were consistent with previous records of P. xanthii (Castagne) U. Braun & Shishkoff (1). To confirm the identification, the complete internal transcribed spacer (ITS) region of rDNA from isolate KUS-F27134 was amplified with the primers ITS5 and P3 and sequenced (3). The resulting sequence of 477 bp was deposited in GenBank (Accession No. KC460208). The Korean isolate showed >99% similarity with dozens of sequences of P. xanthii ex cucurbitaceous hosts (e.g., JQ912061, JQ409565, HM070403, etc.) as well as Podosphaera sp. ex H. mutabilis from Japan (AB040308). Pathogenicity was confirmed through inoculation tests by gently pressing diseased leaves onto young leaves of three asymptomatic, potted 2-year-old seedlings. Three non-inoculated seedlings were used as controls. 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. Powdery mildew infections of H. mutabilis associated with P. xanthii (including P. fuliginea in broad sense) have been known in China, Japan, and Taiwan (1,2). To our knowledge, this is the first report of powdery mildew caused by P. xanthii on H. mutabilis in Korea. Since Jeju, the southmost island of Korea, is the only habitat of cotton rose in Korea and is the northmost natural habitat in Asia, powdery mildew is a new threat to the health of wild populations of cotton rose. 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 January 18, 2013. (3) S. Takamatsu et al. Mycol. Res. 113:117, 2009. (4) D. A. Wise. J. Hered. 64:285, 1973.

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First Report of Powdery Mildew Caused by Golovinomyces biocellatus on Agastache rugosa in Korea

Plant Disease ◽

10.1094/pdis-03-14-0298-pdn ◽

2014 ◽

Vol 98 (9) ◽

pp. 1278-1278 ◽

Cited By ~ 1

Author(s):

S. E. Cho ◽

J. H. Park ◽

S. H. Hong ◽

I. Y. Choi ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Severe Disease ◽

Morphological Characteristics ◽

Control Measures ◽

Control Treatment ◽

Width Ratio ◽

Korean Isolate ◽

Pathogenicity Test ◽

Agastache Rugosa ◽

First Report

Agastache rugosa (Fisch. & C.A. Mey.) Kuntze, known as Korean mint, is an aromatic plant in the Lamiaceae. It is widely distributed in East Asian countries and is used as a Chinese traditional medicine. In Korea, fresh leaves are commonly added to fish soups and stews (3). In November 2008, several dozen Korean mints plants growing outdoors in Gimhae City, Korea, were found to be severely infected with a powdery mildew. The same symptoms had been observed in Korean mint plots in Busan and Miryang cities from 2008 to 2013. Symptoms first appeared as thin white colonies, which subsequently developed into abundant hyphal growth on stems and both sides of the leaves. Severe disease pressure caused withering and senescence of the leaves. Voucher specimens (n = 5) were deposited in the Korea University Herbarium (KUS). Appressoria on the mycelium were nipple-shaped or nearly absent. Conidiophores were 105 to 188 × 10 to 13 μm and produced 2 to 4 immature conidia in chains with a sinuate outline, followed by 2 to 3 cells. Foot-cells of the conidiophores were straight, cylindrical, slightly constricted at the base, and 37 to 58 μm long. Conidia were hyaline, ellipsoid to barrel-shaped, measured 25 to 40 × 15 to 23 μm (length/width ratio = 1.4 to 2.1), lacked distinct fibrosin bodies, and showed reticulate wrinkling of the outer walls. Primary conidia were obconically rounded at the apex and subtruncate at the base. Germ tubes were produced at the perihilar position of conidia. No chasmothecia were observed. The structures described above were typical of the Oidium subgenus Reticuloidium anamorph of the genus Golovinomyces. The measurements and morphological characteristics were compatible with those of G. biocellatus (Ehrenb.) V.P. Heluta (1). To confirm the identification, molecular analysis of the sequence of the internal transcribed spacer (ITS) region of ribosomal DNA (rDNA) of isolate KUS-F27200 was conducted. The complete ITS rDNA sequence was amplified using primers ITS5 and P3 (4). The resulting 514-bp sequence was deposited in GenBank (Accession No. KJ585415). A GenBank BLAST search of the Korean isolate sequence showed >99% similarity with the ITS sequence of many G. biocellatus isolates on plants in the Lamiaceae (e.g., Accession Nos. AB307669, AB769437, and JQ340358). Pathogenicity was confirmed by gently pressing diseased leaf onto leaves of five healthy, potted Korean mint plants. Five non-inoculated plants served as a control treatment. Inoculated plants developed symptoms after 7 days, whereas the control plants remained symptomless. The fungus present on inoculated plants was identical morphologically to that observed on the original diseased plants. The pathogenicity test was repeated with identical results. A powdery mildew on A. rugosa caused by G. biocellatus was reported from Romania (2). To our knowledge, this is the first report of powdery mildew caused by G. biocellatus on A. rugosa in Korea. The plant is mostly grown using organic farming methods with limited chemical control options. Therefore, alternative control measures should be considered. 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, USDA ARS, retrieved 17 February 2014. (3) T. H. Kim et al. J. Sci. Food Agric. 81:569, 2001. (4) S. Takamatsu et al. Mycol. Res. 113:117, 2009.

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First Report of Powdery Mildew Caused by Erysiphe diffusa, Oidium neolycopersici, and Podosphaera xanthii on Papaya in Taiwan

Plant Disease ◽

10.1094/pdis-05-11-0362 ◽

2011 ◽

Vol 95 (9) ◽

pp. 1188-1188 ◽

Cited By ~ 6

Author(s):

J.-G. Tsay ◽

R.-S. Chen ◽

H.-L. Wang ◽

W.-L. Wang ◽

B.-C. Weng

Keyword(s):

Powdery Mildew ◽

Morphological Characteristics ◽

Its Region ◽

Podosphaera Xanthii ◽

Oidium Neolycopersici ◽

First Report ◽

Plastic Bags ◽

The World ◽

Golovinomyces Cichoracearum ◽

Powdery Mildew Fungi

Powdery mildew can be found in most papaya (Carica papaya L.) fields during the winter and spring seasons in Taiwan. It usually causes severe yellowing of the leaf lamina and petiole and serious defoliation. Three types of powdery mildew fungi were isolated from papaya leaves in Chiayi City (23.28°N, 120.28°E) at the beginning of 2008. Conidia of the first one were single, globose, hyaline, and 24 to 36 × 14 to 18 μm (average 30.2 × 15.6 μm) without fibrosin bodies and with straight or occasionally flexuous conidiophores at the base. The second one had short pseudo-chains of two to four conidia which were ellipsoidal to ovoid, hyaline, and 24 to 40 × 12 to 16 μm (average 29.7 × 13.4 μm) without fibrosin bodies. The third type had chains of ellipsoidal conidia that were hyaline, 24 to 28 × 12 to 16 μm (average 26.3 × 14.4 μm) and contained fibrosin bodies. To confirm the identity of the three fungi, the internal transcribed spacer (ITS) region of rDNA was amplified using the primer pairs G1 (5′-TCC GTA GGT GAA CCT GCG GAA GGA T-3′)/Ed2 (5′-CGC GTA GAG CCC ACG TCG GA-3′), G1 (5′-TCC GTA GGT GAA CCT GCG GAA GGA T-3′)/On2 (5′-TGT GAT CCA TGT GAC TGG AA-3′), and S1 (5′-GGA TCA TTA CTG AGC GCG AGG CCC CG-3′)/S2 (5′-CGC CGC CCT GGC GCG AGA TAC A-3′). The alignment of obtained sequences (GenBank Accession Nos. GU358452, 507 bp; GU358451, 580 bp; and GU358450, 455 bp) showed a sequence identity of 100, 99, and 99% with the ITS sequences of Erysiphe diffusa, Oidium neolycopersici, and Podosphaera xanthii (GenBank Accession Nos. FJ378880, EU909694, and GQ927254), respectively. On the basis of morphological characteristics and ITS sequence similarities, these fungi were identified as E. diffusa (Cooke & Peck) U. Braun & S. Takam., O. neolycopersici L. Kiss, and P. xanthii (Castagne) U. Braun & S. Takam., respectively (1,3). Single colonies on papaya leaves infected with powdery mildew were identified in the laboratory and maintained on papaya leaves as inoculum. Pathogenicity was confirmed through inoculations by gently pressing a single colony of each fungus onto leaves of healthy papaya seedlings (cv. Horng-Fe). Five seedlings were inoculated for each fungus and then covered with plastic bags for 2 days. Five noninoculated seedlings served as control. After inoculation, treated plants were maintained separately from the control in different rooms of a greenhouse at 25°C under natural daylight conditions. Seven days after inoculation, typical symptoms of powdery mildew were observed on inoculated plants, but not on noninoculated plants. The same species from diseased lesions following artificial inoculation with each fungus were identified with light microscopy. Papaya was previously described as a host to O. caricae Noack in many tropical and subtropical areas of the world including Taiwan (2). However E. cruciferarum, Golovinomyces cichoracearum, Oidiopsis sicula, O. caricae, O. caricae-papayae, O. caricicola, O. indicum, O. papayae, Ovulariopsis papayae, P. caricae-papayae, P. macularis, P. xanthii, and Streptopodium caricae were reported to infect papaya (4). To our knowledge, this is the first report of papaya powdery mildew caused by E. diffusa and O. neolycopersici in the world and the first report of the three fungi found on papaya in Taiwan. References: (1) U. Braun and S. Takamatsu. Schlechtendalia 4:1, 2000. (2) H. S. Chien and H. L. Wang. J. Agric. Res. China 33:320, 1984. (3) L. Kiss et al. Mycol. Res. 105:684, 2001. (4) J. R. Liberato et al. Mycol. Res. 108:1185, 2004.

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First Report of Powdery Mildew Caused by Podosphaera xanthii (syn. P. fusca) on Cocklebur in Korea

Plant Disease ◽

10.1094/pdis-10-12-0951-pdn ◽

2013 ◽

Vol 97 (6) ◽

pp. 842-842 ◽

Cited By ~ 2

Author(s):

H. B. Lee

Keyword(s):

Powdery Mildew ◽

Natural Infection ◽

Morphological Characteristics ◽

Its Region ◽

Xanthium Strumarium ◽

Podosphaera Xanthii ◽

First Report ◽

Rdna Its ◽

Causal Fungus ◽

Powdery Mildew Pathogen

Cocklebur (Xanthium strumarium L., Asteraceae) is an annual broadleaf weed native to the Americas and eastern Asia. The plant is known as one of the worst competitive weeds in soybean fields and also is known to have some phytopharmacological or toxicological properties. In October 2011, a powdery mildew disease was observed on cocklebur growing in a natural landscape at Geomun Oreum located in Jeju Island, South Korea. Initial signs appeared as thin white colonies, which subsequently developed abundant growth on adaxial leaf surfaces. As the disease progressed, brown discoloration extended down infected leaves which withered. Conidia were formed singly and terminally on conidiophores. Primary conidia (20.3 to 28.6 [average 25.1] μm long × 11.1 to 15.2 [14.3] μm wide, n = 30) were ellipsoid with a round apex and truncate base. Conidiophores were straight or slightly curved and 60.1 to 101.7 (97.3) μm long × 8.2 to 13.2 (11.3) μm wide. Chasmothecia were not observed. No fibrosin bodies were observed in the conidia. Morphological characteristics were consistent with descriptions of Podosphaera xanthii (syn. P. fusca) (2,4). To confirm the identity of the causal fungus, the internal transcribed spacer (ITS) region inclusive of 5.8S and 28S rDNA was amplified from white patches consisting of mycelia and conidia on one leaf using ITS1 (5′-TCCGTAGGTGAACCTGCGG-3′) and LR5F (5′-GCTATCCTGAGGGAAAC-3′), and LROR (5′-ACCCGCTGAACTTAAGC-3′) and LR5F primer sets, respectively. The resulting sequences were deposited in GenBank (Accession Nos. JX502022 and JX964999). A NCBI BLASTn search revealed that the rDNA ITS (JX502022) and 28S (JX964999) homologies of isolate EML-XSPW1 represented 99.6% (512/514) and 100% (803/803) identity values with those of P. xanthii (AB040330 and AB462792, respectively). The rDNA ITS and 28S sequence analysis revealed that the causal fungus clustered with P. xanthii (syn. P. fusca), falling into the Xanthii/Fusca phylogenetic group (2,4). Pathogenicity was confirmed through inoculations made by gently pressing infected leaves onto mature leaves of healthy cocklebur plants in the field in August. The six inoculated leaves were sealed in sterilized vinyl bags to maintain humid conditions for 2 days. Seven days after inoculation, symptoms similar to those observed under natural infection were observed on the inoculated plant leaves. No symptoms developed on the uninoculated control plants. A fungal pathogen that was morphologically identical to the fungus originally observed on diseased plants was also observed on inoculated plants. Erysiphe cichoracearum, E. communis, Oidium asteris-punicei, O. xanthimi, P. xanthii, and P. fuliginea have all been reported to cause powdery mildew on cocklebur (1). P. xanthii was first reported on X. strumarium in Russia (3). To our knowledge, this is the first report of powdery mildew on cocklebur caused by P. xanthii in Korea. The powdery mildew pathogen may represent an option for biocontrol of the noxious weed in the near future. References: (1) D. F. Farr and A. Y. Rossman. Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases , December 11, 2012. (2) H. B. Lee. J. Microbiol. 51:1075, 2012. (3) V. A. Rusanov and T. S. Bulgakov. Mikol. Fitopatol. 42:314, 2008. (4) S. Takamatsu et al. Persoonia 24:38, 2010.

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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 heraclei on Parsley in Korea

Plant Disease ◽

10.1094/pdis-09-13-0972-pdn ◽

2014 ◽

Vol 98 (6) ◽

pp. 847-847

Author(s):

S. E. Cho ◽

M. J. Park ◽

J. H. Park ◽

J. Y. Kim ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Morphological Characteristics ◽

Its Region ◽

Petroselinum Crispum ◽

Width Ratio ◽

Anethum Graveolens ◽

First Report ◽

Organic Farm ◽

Length Width ◽

A Minor

Parsley, Petroselinum crispum (Mill.) Nyman, is a minor but important leaf crop in Korea. In June 2010, parsley plants (cv. Paramount) showing typical symptoms of powdery mildew were found with approximately 90% incidence (percentage of plants showing symptoms) in polyethylene-film-covered greenhouses in an organic farm in Icheon County of Korea. Symptoms first appeared as thin white colonies, which subsequently showed abundant growth on the leaves with chlorosis and crinkling. Most diseased plantings were unmarketable and shriveled without being harvested. The damage due to powdery mildew infections on parsley has reappeared in Icheon County and Gangneung City with confirmation of the causal agent made again in 2011 and 2012. Voucher specimens were deposited in the Korea University Herbarium (KUS). Appressoria on the mycelium were multilobed or moderately lobed. Conidiophores were cylindrical, 75 to 125 × 8 to 10 μm, straight in foot-cells, and produced conidia singly, followed by 2 to 3 cells. Conidia were oblong-elliptical to oblong, 32 to 55 × 14 to 20 μm with a length/width ratio of 1.7 to 2.9, lacked fibrosin bodies, and produced germ tubes on the perihilar position, with angular/rectangular wrinkling of the outer walls. First-formed conidia were apically conical, basally subtruncate to rounded, and generally smaller than the secondary conidia. Chasmothecia were not found. These structures are typical of the powdery mildew Pseudoidium anamorph of the genus Erysiphe. The specific measurements and morphological characteristics were consistent with those of E. heraclei DC. (1). To confirm the identity of the causal fungus, the complete ITS region of rDNA from isolate KUS-F25037 was amplified with primers ITS5 and P3 (3) and sequenced directly. The resulting 606-bp sequence was deposited in GenBank (Accession No. KF680162). A GenBank BLAST search of this sequence revealed 100% identity with that of E. heraclei on Anethum graveolens from Korea (JN603995) and >99% similarity with those of E. heraclei on Daucus carota from Mexico (GU252368), Pimpinella affinis from Iran (AB104513), Anthriscus cerefolium from Korea (KF111807), and many other parsley family (Apiaceae) plants. Pathogenicity was verified through inoculation by gently pressing diseased leaves onto leaves of five healthy potted parsley plants. Five non-inoculated plants served as negative controls. Inoculated plants developed symptoms after 7 days, whereas the control plants remained symptomless. The fungus present on the inoculated plants was morphologically identical to that originally observed on diseased plants. Parsley powdery mildew caused by E. heraclei has been known in Europe, North America, Brazil, and Japan (2,4). To our knowledge, this is the first report of powdery mildew infections by E. heraclei on parsley in Korea. Since cultivation of parsley was only recently started on a commercial scale in Korea, powdery mildew infections pose a serious threat to safe production of this herb, especially those grown in organic farming where chemical options are limited. 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 September 17, 2013. (3) S. Takamatsu et al. Mycol. Res. 113:117, 2009. (4) Y. Tsuzaki and K. Sogou. Proc. Assoc. Plant Prot. Shikoku 24:47, 1989.

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First Report of Powdery Mildew Caused by Podosphaera xanthii on Sechium edule in Korea

Plant Disease ◽

10.1094/pdis-10-14-1011-pdn ◽

2015 ◽

Vol 99 (1) ◽

pp. 162-162 ◽

Cited By ~ 1

Author(s):

I. Y. Choi ◽

S. S. Cheong ◽

J. H. Joa ◽

S. E. Cho ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

The United States ◽

Soil Conditions ◽

Width Ratio ◽

Korean Isolate ◽

Pathogenicity Test ◽

First Report ◽

Powdery Mildews ◽

Sechium Edule ◽

Length Width

Sechium edule (Jacq.) Sw. (Cucurbitaceae, chayote, mirliton) is native to Mexico and Central America. Several trials have recently been conducted to determine the ability of chayote cultivars to grow under the climatic and soil conditions of South Korea. In April 2013, chayote plants were observed showing typical symptoms of powdery mildew in a glasshouse in Jeju City, Korea. Powdery mildew colonies were circular to irregular, forming white patches on both sides of the leaves. As the disease progressed, entire leaves were covered with white mycelium, followed by leaf withering and premature senescence. The same symptoms were also found on chayote plants in a polyethylene-film-covered greenhouse in Iksan City, Korea, in 2014. Voucher specimens were deposited in the Korea University Herbarium (KUS-F27289, F27422, F28186). Hyphae were flexuous to straight, branched, septate, and 5 to 7 μm wide. Appressoria on the mycelium were nipple-shaped or nearly absent. Conidiophores were straight, 150 to 240 × 10 to 12 μm and produced three to seven immature conidia in chains with a crenate outline. Foot-cells of conidiophores were straight, cylindric, and 52 to 85 μm long. Conidia were hyaline, ellipsoid-ovoid to barrel-shaped, measured 27 to 36 × 16 to 23 μm with a length/width ratio of 1.3 to 2.0, and had distinct fibrosin bodies. Simple to forked germ tubes were produced from the lateral position of conidia. No chasmothecia were found. These structures are typical of the powdery mildew Euoidium anamorph of the genus Podosphaera. Dimensions of foot-cells and conidia were within the ranges provided for P. xanthii (Castagne) U. Braun & Shishkoff, and the length/width ratio of conidia, appressorial characteristics, and conidial germination patterns also conformed to the standard description (2). To confirm the identification, the complete internal transcribed spacer (ITS) region of rDNA of isolate KUS-F27289 was amplified with primers ITS1 and ITS4 and sequenced directly. The resulting 473-bp sequence was deposited in GenBank (Accession No. KM657960). A GenBank BLAST search of the Korean isolate showed 99% similarity with P. xanthii isolates from cucurbitaceous hosts (e.g., AB774155 to AB774158, AB040321, JQ340082, etc.). Pathogenicity was confirmed through inoculation tests by gently pressing a diseased leaf onto young leaves of three asymptomatic, potted chayote plants. Three non-inoculated plants were used as controls. Plants were maintained in a greenhouse at 24 to 34°C. Inoculated leaves started to develop symptoms after 5 days, whereas the control plants remained symptomless. The pathogenicity test was carried out twice with similar results. Powdery mildews of chayote caused by Podosphaera species have been reported in Australia, South Africa, Portugal, India, China, and the United States (1,3,4). To our knowledge, this is the first report of powdery mildew caused by P. xanthii on chayote in Korea. Since chayote production was only recently started on a commercial scale in Korea, powdery mildew infections may pose a serious threat to the safe production of this vegetable. References: (1) P. Baiswar et al. Australas. Plant Dis. Notes 3:160, 2008. (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 October 4, 2014. (4) R. Singh et al. Plant Dis. 93:1348, 2009.

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