First Report of Powdery Mildew Caused by Podosphaera xanthii on Gynostemma pentaphyllum in Korea.
83806965
First Report of Powdery Mildew Caused by Podosphaera xanthii on Gynostemma pentaphyllum in Korea
Sung-Eun Cho M J Park K S Han In Young Choi Hyeon-Dong Shin
214436629
First report of powdery mildew caused by Podosphaera xanthii on Cucurbita maxima in Korea
In Young Choi Young Joon Choi Hyeon-Dong Shin
92490852
First Report of Powdery Mildew Caused by Podosphaera xanthii on Ixeridium dentatum in Korea
Ixeridium dentatum (Thunb. ex Mori) Tzvelev, known as toothed ixeridium, belonging to the family Asteraceae, is native to Korea and East Asia. In Korea, it has been used as a traditional herbal medicine for the treatment of hepatitis, indigestion, pneumonia, tumors, and hyperlipidemia. I. dentatum is commercially cultivated in some areas (over 100 ha) of Korea. In October 2017, symptoms of powdery mildew were observed on over 60% of the leaves and stems of I. dentatum plants in a garden at Chonnam National University located in Gwangju, Korea. Disease symptoms included white powdery colonies on the upper leaf surfaces and stems with or without necrosis. Appressoria of the fungus were indistinct to slightly nipple shaped. Conidiophores were cylindrical, 90.3 to 190.5 x 10.5 to 12.5 mm. Foot cells of conidiophores were 45.2 to 65.1 x 10.4 to 12.5 mm, cylindrical, or slightly constricted at the base, followed by zero to three shorter cells, forming conidia in chains. Conidia were ellipsoid to oval, 28.8 to 38.4 x 16.5 to 21.3 mm. Chasmothecia were not observed. Morphologically, the isolate was consistent with the description of Podosphaera xanthii (Castagne) U. Braun N. Shishkoff (Braun and Cook 2012; Lee 2013; Meeboon and Takamatsu 2015) Genomic DNA was extracted directly from the mycelia and conidia using a gDNA prep kit (Solgent, Daejeon, Korea) The internal transcribed spacer (ITS) region of the rDNA of two isolates was amplified using the primers ITS1 and ITS4 as described by Lee (2015) A BLASTn search of the ITS sequences against the NCBI database indicated that the isolates EML IDPW1726 and EML IDPW1727 (GenBank accession nos. MG719995 and MG719996, respectively) matched P. xanthii (GenBank accession no. KY388505) with 100% (444/444 bp) sequence homology. Phylogenetic analyses based on the ITS rDNA indicated that EML IDPW1726 and EML IDPW1727 isolates were identical to P. xanthii. Therefore, the causal pathogen was identified as P. xanthii based on the morphology of its imperfect stage and molecular analyses. The pathogenicity of the biotrophic fungus was demonstrated by gently pressing the infected leaves onto healthy leaves of I. dentatum (Lee 2013) Plants were maintained in a greenhouse at 23 2degC. Seven days after inoculation, symptoms similar to those observed under natural conditions developed on the inoculated leaves of I. dentatum plants. The fungus on inoculated leaves was morphologically identical to that first observed. Powdery mildew of I. dentatum caused by Golovinomyces cichoracearum and P. fuliginea has also been reported previously from Japan (Farr and Rossman 2017) P. xanthii (synonyms: P. fusca, Sphaerotheca fuliginea, and S. fusca) has been reported to cause powdery mildew on Ixeridium spp. (synonyms: Ixeris, Paraixeris, Youngia, Chondrilla, Prenanthes, and Lactuca [The Plant List 2013] under the name of Sphaerotheca humuli var. fuliginea. To our knowledge, this is the first record of powdery mildew caused by P. xanthii on I. dentatum in Korea. The occurrence of powdery mildew on I. dentatum could pose a serious threat to the health of this plant, resulting in death and severe yield reduction.
Plant Disease
T T T Nguyen
91151517
First Report of Powdery Mildew Caused by Podosphaera xanthii on Hydrocleys nymphoides in Korea
In October 2013, Hydrocleys nymphoides (Willd. Buchenau, known as waterpoppy, was found infected with a powdery mildew and lost its ornamental value with 100% infection. The waterpoppy was grown in a pot and placed in the window side of a building in Seoul, Korea. Powdery mildew colonies were circular to irregular or thinly effuse on adaxial side of the leaves. A voucher specimen was deposited in the Korea University Herbarium (KUS) Appressoria on the hyphae were nipple shaped or nearly absent. Conidiophores were straight, 115 to 180 x 10 to 12.5 mm and produced 2 to 5 immature conidia in chains with a crenate outline. Foot cells of conidiophores were cylindric and 40 to 60 mm long. Conidia were ellipsoid ovoid to barrel shaped, measured 30 to 40 x 19 to 23 mm with a length/width ratio of 1.3 to 1.9, and had distinct fibrosin bodies. Primary conidia were apically conical or rounded, mostly truncate at base, and generally smaller than secondary conidia. Dark brown chasmothecia were found partly embedded
Sung-Eun Cho K S Han In Young Choi Hyeon-Dong Shin
91065118
First Report of Powdery Mildew Caused by Podosphaera xanthii on Ricinus communis in Korea
Ricinus communis L. (Euphorbiaceae) known as castor bean, is widely planted in the tropical and warm temperate areas. The seed is a source of castor oil, which has plenty of applications in medicine and as a motor lubricant (Worbs et al. 2011) In September 2016, powdery mildew symptoms were observed on several castor bean plants grown as a leafy vegetable in a private garden in Gimcheon (36deg07'09''N, 128deg07'46''E) Korea. White patches consisting of hyphae, conidiophores, and conidia were distributed on both sides of leaves. Infections were weak and did not cause early defoliation or leaf distortion. A representative specimen was deposited in Korea University Herbarium (KUS F29541) Hyphal appressoria were nipple shaped. Conidiophores were erect, 110 to 230 x 10 to 12 mm, and produced two to five immature conidia in chains. Foot cells of conidiophores were cylindrical, 40 to 70 mm, and somewhat constricted at the basal parts. Conidia were ellipsoid to ovoid, 28 to 35 x 16 to 19 mm with a length/width ratio of 1.6 to 2.2, and contained distinct fibrosin bodies. Germ tubes produced from the lateral position of conidia were simple to forked. Primary conidia were apically conical or rounded, mostly subtruncate at the base, and generally smaller than secondary conidia. No chasmothecia were observed during the growing season. These structures are typical of the powdery mildew Fibroidium anamorph of the genus Podosphaera (Braun and Cook 2012) The internal transcribed spacer (ITS) regions of the specimen KUS F29541 were amplified and sequenced with primers PMITS1/PMITS2 (Cunnington et al. 2003) The ITS sequence was deposited in GenBank (accession no. MG462908) It showed over 99% similarity with Podosphaera xanthii sequences obtained from Cucurbita pepo (KJ698669) Calendula officinalis (AB525914) and Verbena brasiliensis (KJ472787) Based on the morphological characteristics and molecular data, the fungus on R. communis was identified as P. xanthii (Castagne) U. Braun Shishkoff (Braun and Cook 2012) Inoculation tests were conducted by pressing infected leaves onto 12 healthy leaves of three castor bean plants. Three noninoculated plants were used as controls. These plants were kept in a greenhouse at 24 to 30degC without artificial illumination. Typical powdery mildew symptoms developed on the inoculated plants after 5 days; however, the controls remained symptomless. The morphological characteristics of the pathogen on inoculated plants were in agreement with those on the diseased plants observed originally. There have been many records of powdery mildews belonging to Golovinomyces, Leveillula, Oidium, and Ovulariopsis on R. communis (Farr and Rossman 2017) However, no previous record of Podosphaera on R. communis has been found. To our knowledge, this is the first report of P. xanthii on R. communis globally as well as in Korea. Although identified from one locality, the natural occurrence of powdery mildew would be a new threat to this economically important crop in Korea.
Ting-ting Zhao Sung-Eun Cho In Young Choi Min-Kyung Choi Hyeon-Dong Shin
87915822
First report of powdery mildew caused by podosphaera xanthii on ramie in Korea
Sung-Eun Cho Ting-ting Zhao In Young Choi Young Joon Choi Hyeon-Dong Shin
73411486
First Report of Powdery Mildew Caused by Podosphaera xanthii on Sechium edule in Korea.
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 mm wide. Appressoria on the mycelium were nipple shaped or nearly absent. Conidiophores were straight, 150 to 240 x 10 to 12 mm and produced three to seven immature conidia in chains with a crenate outline. Foot cells of conidiophores were straight, cylindric, and 52 to 85 mm long. Conidia were hyaline, ellipsoid ovoid to barrel shaped, measured 27 to 36 x 16 to 23 mm 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 34degC. 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.
Plant disease
In Young Choi S S Cheong Jae Ho Joa S E Cho H D Shin
73451755
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 mm wide. Conidiophores were 110 to 250 x 10 to 12.5 mm 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 mm long. Conidia were hyaline, ellipsoid ovoid, measured 22 to 38 x 18 to 21 mm 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 mm 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 x 52 to 68 mm, had a terminal oculus of 17 to 23 mm wide, and contained 8 ascospores, each 17 to 23 x 12.5 to 15 mm. 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 30degC. 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.
Plant disease
Jae Ho Joa Bong Nam Chung K S Han S E Cho H D Shin
73415016
First Report of Powdery Mildew Caused by Podosphaera xanthii on Verbena brasiliensis in Korea.
Verbena brasiliensis Vell. commonly known as Brazilian verbena, is native to South America and has been introduced into North America, coastal Europe, southern Africa, and Australasia. Though partly cultivated for garden use, it is invasive in riverine areas and also on roadsides, forest margins, pastures, and waste areas (4) In Korea, this plant was first reported in 1998 in Jeju Island and has become widely naturalized by replacing indigenous plants and disrupting native ecosystems in most of southern part of Korea (3) Since 2009, powdery mildew on Brazilian verbena has been consistently found in several locations of Busan City, Korea. Symptoms appeared as circular to irregular white patches, which subsequently showed abundant hyphal growth on both sides of the leaves and on stems. High disease severity caused poor growth of the plants, resulting in premature senescence and reduced flowering. Specimens (n 5) were deposited in the Korea University Herbarium (KUS) Appressoria on the mycelium were nipple shaped or nearly absent. Conidiophores were 140 to 190 x 11 to 12.5 mm and produced 2 to 7 immature conidia in chains with a crenate outline. Foot cells in conidiophores were straight, cylindric, relatively short, 50 to 65 mm long, and constricted at the very base of branching point from the hypha. Conidia were hyaline, ellipsoid to ovate, measured 28 to 38 x 18.5 to 22 mm (length/width ratio of 1.2 to 1.8) and contained distinct fibrosin bodies. Germ tubes were produced from the lateral position of conidia. No chasmothecia were observed. These structures are typical of the powdery mildew Euoidium anamorph of the genus Podosphaera. The morphological characteristics and measurements were consistent with those of P. xanthii (Castagne) U. Braun Shishkoff (1) To confirm the identity, the complete internal transcribed spacer (ITS) region of rDNA of the isolate KUS F27220 was amplified with primers ITS1/ITS4, and sequenced. The resulting 477 bp sequence was deposited in GenBank (Accession No. KJ472787) A GenBank BLAST search of this sequence revealed 100% identity with Podosphaera sp. on V. bonariensis and V.x hybrida from Japan (AB462804 and AB040347) The Podosphaera sp. isolates listed above are now placed in P. xanthii (1) Pathogenicity was confirmed through inoculation by gently pressing a diseased leaf onto leaves of three healthy, potted 2 month old Brazilian verbena plants. Three non inoculated plants served as controls. Inoculated plants developed signs and symptoms after 6 days, whereas the control plants remained symptomless. The fungus present on the inoculated leaves was identical morphologically to that originally observed on diseased plants. Powdery mildew of Verbena spp. associated with Podosphaera sp. (including Sphaerotheca sp. has been globally reported, but not on V. brasiliensis (1,2) To our knowledge, this is the first report of powdery mildew disease caused by P. xanthii on V. brasiliensis globally. Our field observations suggest that the powdery mildew could limit expansion of V. brasiliensis in Korea. 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 February 18, 2014. (3) C. G. Song and Y. H. Yang. The Naturalized Plants in Jeju Island. Nam Jeju County, Jeju, Korea, 2005. (4) P. F. Yao. Kew Bull. 45:101, 1990.
Plant disease
S E Cho J H Park S H Hong B S Kim H D Shin
87230874
First Report of Powdery Mildew Caused by Podosphaera xanthii on Coreopsis verticillata in Korea
Sung-Eun Cho Mi-Jeong Park K S Han Ting-ting Zhao Hyeon-Dong Shin