First Report of Powdery Mildew Caused by Erysiphe cruciferarum on Indian Mustard (Brassica juncea) in Korea

Indian mustard (Brassica juncea (L.) Czern.) belongs in the Brassicaceae and is widely cultivated in Korea for the edible leaves. In May 2011, Indian mustard plants of cv. Cheong-Kyeoja, growing in polyethylene-film-covered greenhouses in Hwaseong, Korea, were observed to be affected by a powdery mildew. Symptoms appeared as circular to irregular white colonies, which subsequently showed abundant hyphal growth on both leaf surfaces. Severely infected plants were unmarketable due to leaf discoloration, and most were not harvested. Voucher specimens have been deposited in the Korea University Herbarium (KUS). Appressoria on the mycelium were well developed, lobed, solitary, or in opposite pairs. Conidiophores were cylindrical, 70 to 115 × 8 to 10 μm, and composed of 3 to 4 cells. Foot-cells of conidiophores were straight to substraight, cylindrical, and relatively short (20 to 30 μm long). Singly-produced conidia were oblong to cylindrical or oval, 27.5 to 50 × 14 to 17.5 μm with a length/width ratio of 1.8 to 3.6, with angular/rectangular wrinkling of outer walls, and lacked distinct fibrosin bodies. Germ tubes were produced in the perihilar position of conidia. No chasmothecia were found. These structures are typical of the powdery mildew Pseudoidium anamorph of the genus Erysiphe. The specific measurements and characteristics were consistent with previous records of Erysiphe cruciferarum Opiz ex L. Junell (1). To confirm the identification, the complete internal transcribed spacer (ITS) region of rDNA of KUS-F24819 was amplified with primers ITS5 and P3 (4), and sequenced directly. The resulting 462-bp sequence was deposited in GenBank (Accession No. KC862331). A GenBank BLAST search of the ITS sequence showed 100% identity (462/462 bp) with those of isolates of E. cruciferarum from B. oleracea var. acephala, B. rapa, and Arabidopsis thaliana (GU721075, EU140958, and FJ548627, respectively). Pathogenicity was confirmed through inoculation by gently dusting conidia onto leaves of five healthy, potted Indian mustard plants of the cv. Cheong-Kyeoja. Five non-inoculated plants served as a control treatment. Inoculated plants were isolated from non-inoculated plants in separate rooms in a greenhouse at 18 to 24°C. Inoculated plants developed 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 the diseased plants, fulfilling Koch's postulates. There are records of E. cruciferarum infecting B. juncea in Europe (Finland, Romania, Sweden, Switzerland), the former Soviet Union, Australia, South Africa, and Asia (India, Japan, and China) (2,3). To our knowledge, this is the first report of powdery mildew caused by E. cruciferarum on B. juncea in Korea. Occurrence of powdery mildew is a threat to quality and marketability of this crop, 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. USDA ARS. Retrieved 20 March 2013. (3) P. Kaur et al. Plant Dis. 92:650, 2008. (4) S. Takamatsu et al. Mycol. Res. 113:117, 2009.

Download Full-text

First Report of Powdery Mildew Caused by Erysiphe cruciferarum on Brassica juncea in Australia

Plant Disease ◽

10.1094/pdis-92-4-0650c ◽

2008 ◽

Vol 92 (4) ◽

pp. 650-650 ◽

Cited By ~ 6

Author(s):

P. Kaur ◽

C. X. Li ◽

M. J. Barbetti ◽

M. P. You ◽

H. Li ◽

...

Keyword(s):

Powdery Mildew ◽

Brassica Juncea ◽

Oilseed Rape ◽

Western Australia ◽

Indian Mustard ◽

Pathogenic Fungi ◽

Research Centre ◽

Width Ratio ◽

Oilseed Crop ◽

Erysiphe Cruciferarum

In Australia, Brassica juncea (L.) Czern & Coss (Indian mustard) has the potential as a more drought-tolerant oilseed crop than the B. napus L., with the first canola-quality B. juncea varieties released in Australia in 2006 and first sown for commercial production in 2007. Increased production of B. juncea is expected to result in the appearance of diseases previously unreported in Australia. In the spring of 2007 at the University of Western Australia field plots at Crawley (31.99°S, 115.82°E), Western Australia, plants of B. juncea genotypes from Australia and China had extensive stem colonization by powdery mildew at the end of the flowering period, with whitish patches ranging in size from 3 mm to 3 cm long. These patches coalesced to form a dense, white, powdery layer as they expanded. Pathogenicity was demonstrated by gently pressing infected stems containing abundant sporulation onto leaves of potted B. juncea seedlings of variety JM-18, incubating the plants in a moist chamber for 48 h, and then maintaining the plants in a controlled-environment room at 18/13°C for day/night. Signs of powdery mildew appeared at 7 days after inoculation, and by 10 days, it was well developed. Uninoculated control plants did not have powdery mildew. When symptomatic plants were examined, abundant conidia were typical of Erysiphe cruciferarum Opiz ex Junell, with cylindrical conidia borne singly or in short chains as described previously (2). Mycelia were amphigenous, in patches, and often spreading to become effused. Conidiophores were straight, foot cells were cylindrical, and conidia were mostly produced singly and measured 21.2 to 35.4 (mean 26.7 μm) × 8.8 to 15.9 μm (mean 11.9 μm) from measurements of 100 conidia. The spore size that we measured approximated what was found for E. cruciferarum (2) (30 to 40 × 12 to 16 μm), since we found 35 and 50% of spores falling within this range in terms of length and width, respectively. Conidia were, however, generally smaller in size than that reported on broccoli raab in California (1) (35 to 50 × 12 to 21 μm). We confirmed a length-to-width ratio greater than 2 as was found previously (1,2). Infected leaves showed signs of early senescence. While powdery mildew caused by E. cruciferarum is an important disease of B. juncea in India where yield losses as much as 17% have been reported (4), its potential impact in Australia is yet to be determined. To our knowledge, this is the first record of E. cruciferarum on B. juncea in Australia. In Western Australia, E. cruciferarum has been recorded on B. napus (oilseed rape) since 1986 and on B. napus L. var. napobrassica (L.) Reichenb. (swede) since 1971 (3). In other regions of Australia, it has been recorded on B. rapa in Queensland since 1913 and on B. napus (oilseed rape) in South Australia since 1973. References: (1) S. T. Koike and G. S. Saenz. Plant Dis. 81:1093, 1997. (2) T. J. Purnell and A. Sivanesan. No 251 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1970. (3) R. G. Shivas. J. R. Soc. West. Aust. 72:1, 1989. (4) A. K. Shukla et al. Manual on Management of Rapeseed-Mustard Diseases. National Research Centre on Rapeseed-Mustard, Bharatpur, India, 2003.

Download Full-text

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.

Download Full-text

First Report of Powdery Mildew Caused by Golovinomyces artemisiae on Artemisia annua in Korea

Plant Disease ◽

10.1094/pdis-01-14-0055-pdn ◽

2014 ◽

Vol 98 (7) ◽

pp. 1010-1010

Author(s):

J. K. Choi ◽

B. S. Kim ◽

I. Y. Choi ◽

S. E. Cho ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Artemisia Annua ◽

Russian Far East ◽

Far East ◽

Its Region ◽

Hyphal Growth ◽

Width Ratio ◽

First Report ◽

Powdery Mildews ◽

Sweet Wormwood

Artemisia annua L., known as sweet wormwood or sweet annie, is native to temperate Asia, but is naturalized throughout the world. It produces artemisinin, a potent antimalarial drug that is also effective in treating other parasitic diseases (4). In August 2013, hundreds of plants showing typical symptoms of powdery mildew were found in Seoul (37°36′29.4″ N 127°02′38.3″ E), Korea. Powdery mildew colonies first appeared as thin white patches, which progressed to abundant hyphal growth on both sides of the leaves, stems, and inflorescence. As symptoms continued to develop, the leaves became distorted and turned purplish-gray. Severe infections caused leaf withering and premature senescence. The same symptoms were found on sweet wormwoods in Nonsan (36°09′55.3″ N 127°01′07.1″ E) and Chuncheon (37°52′27.4″ N 127°43′10.0″ E), Korea. Voucher specimens were deposited in the Korea University Herbarium (KUS). Appressoria on the mycelium were nipple-shaped or occasionally lobed. Conidiophores were cylindrical, measured 120 to 230 × 10 to 12.5 μm, and produced 2 to 4 immature conidia in chains with a sinuate outline, followed by 2 to 3 cells. Foot-cells of conidiophores were straight, cylindrical, and 54 to 100 μm long. Conidia were hyaline, ellipsoid to barrel-shaped, measured 30 to 40 × 15 to 20 μm (length/width ratio of 1.5 to 2.1), lacked distinct fibrosin bodies, and showed reticulate wrinkling of the outer walls. Germ tubes were produced on the perihilar position of conidia. Primary conidia were apically rounded, basally subtruncate, and generally smaller than the secondary conidia. No chasmothecia were observed. The structures described above were typical of the powdery mildew Euoidium anamorph of the genus Golovinomyces, and the fungus measurements were similar to those of G. artemisiae (Grev.) V.P. Heluta (3). The complete internal transcribed spacer (ITS) region of rDNA from KUS-F27763 was amplified with primers ITS1/ITS4 and sequenced. The resulting sequence of 624 bp was deposited in GenBank (Accession No. KJ136112). The obtained ITS sequence shared >99% similarity with G. artemisiae on A. princeps and A. montana from Japan (AB077659 and AB077649) and A. argyi from China (KF056818). 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 5 days, whereas the control plants remained symptomless. The fungus present on the inoculated plants was identical morphologically to that originally observed on diseased plants. Powdery mildews of A. annua caused by G. artemisiae have been reported in Japan, China, the Russian Far East, and Romania (1,2). To our knowledge, this is the first report of powdery mildew caused by G. artemisiae on A. annua in Korea. Since sweet wormwood production was only recently started on a commercial scale in Korea, powdery mildew infections pose a serious threat to the production of this plant, especially in organic farming where chemical control options are limited. References: (1) K. Amano. Host Range and Geographical Distribution of the Powdery Mildew Fungi. Japan Scientific Societies Press, Tokyo, 1986. (2) U. Braun. The Powdery Mildews (Erysiphales) of Europe. G. Fischer Verlag, Jena, 1995. (3) U. Braun and R. T. A. Cook. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No.11. CBS, Utrecht, 2012. (4) P. J. Weathers et al. Phytochem. Rev. 10:173, 2011.

Download Full-text

First Report of Powdery Mildew Caused by Erysiphe cruciferarum on Chinese Cabbage in China

Plant Disease ◽

10.1094/pdis-06-13-0648-pdn ◽

2014 ◽

Vol 98 (3) ◽

pp. 421-421 ◽

Cited By ~ 4

Author(s):

H. H. Zhao ◽

H. H. Xing ◽

C. Liang ◽

X. Y. Yang ◽

S. E. Cho ◽

...

Keyword(s):

Powdery Mildew ◽

Chinese Cabbage ◽

Control Treatment ◽

Width Ratio ◽

Pathogenicity Test ◽

Potential Threat ◽

Voucher Specimen ◽

First Report ◽

Powdery Mildews ◽

Erysiphe Cruciferarum

Chinese cabbage, Brassica rapa ssp. pekinensis (syn. Brassica pekinensis (Lour.) Rupr.), in the Brassicaceae, is an important vegetable grown on about 3 million ha in China. Since 2012, a powdery mildew has been found infecting Chinese cabbage plants (cv. Qingyanchunbai No. 1) after bolting for seed production from autumn through spring 2013 in a greenhouse in Qingdao, China. Symptoms first appeared as circular to irregular white patches on both sides of the leaves, and on stems and pods, often thinly covering the whole surface. A voucher specimen was deposited in the herbarium of Qingdao Agricultural University (Accession No. HMQAU12216). Hyphae were thin-walled, smooth, hyaline, and 4 to 6 μm wide. Appressoria on the mycelia were well developed, lobed, solitary, or in pairs. Conidiophores were erect, cylindrical, 45 to 110 μm long, and comprised 3 to 4 cells. Foot-cells of conidiophores were straight, cylindrical, 16 to 28 μm long, and 7.6 to 10 μm wide. Singly-produced conidia were oblong to cylindrical or somewhat ellipsoid-doliiform, 32 to 56 × 12 to 18 μm, with a length/width ratio of 1.8 to 3.8, with angular/rectangular wrinkling of the outer wall surface, and lacked distinct fibrosin bodies. Germ tubes were produced in the perihilar position of conidia. No chasmothecia were found. These structures are typical of the powdery mildew Pseudoidium anamorph of Erysiphe (2). The specific measurements and characteristics (especially short foot-cells of conidiophores) were consistent with previous records of Erysiphe cruciferarum Opiz ex L. Junell (2,3). To confirm the identification, the complete internal transcribed spacer (ITS) region of rDNA of isolate HMQAU12216 was amplified (4) and sequenced directly. The resulting 649-bp sequence was deposited in GenBank (Accession No. KC878683). A GenBank BLAST search of ITS sequences showed an exact match with those of E. cruciferarum on B. oleracea var. acephala (GU721075) and Oidium sp. on B. pekinensis (AB522714). A pathogenicity test was conducted by gently pressing a symptomatic leaf loaded with conidia onto a leaf of each five, healthy, potted, 40-day-old plants (cv. Qingyanchunbai No. 1). Five non-inoculated plants served as a control treatment. Inoculated plants were isolated from non-inoculated plants in separate rooms in a greenhouse at 20 ± 2°C. Inoculated plants developed signs and symptoms after 10 days, whereas the control plants remained symptomless. The fungus present on the inoculated plants was identical morphologically to that originally observed on diseased plants, thus fulfilling Koch's postulates. Though many Brassica spp. have been known to be infected with E. cruciferarum throughout the world, powdery mildew of Chinese cabbage caused by E. cruciferarum has been reported only in Finland, Germany, and Korea (1,3). To our knowledge, this is the first report of powdery mildew caused by E. cruciferarum on Chinese cabbage in China. Though occurrence of the powdery mildew on Chinese cabbage was noticed in an experimental breeding plot, this finding poses a potential threat to production of this vegetable in China. References: (1) U. Braun. The Powdery Mildews (Erysiphales) of Europe. Gustav Fischer Verlag, Jena, Germany, 1995. (2) U. Braun and R. T. A. Cook. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No. 11. CBS, Utrecht, 2012. (3) H. J. Jee et al. Plant Pathol. 57:777, 2008. (4) S. Matsuda and S. Takamatsu. Mol. Phylogen. Evol. 27:314, 2003.

Download Full-text

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.

Download Full-text

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.

Download Full-text

First report of the cactus cyst nematode, Cactodera cacti, infecting Cereus jamacaru (Cactaceae) in Brazil

Plant Disease ◽

10.1094/pdis-09-21-1924-pdn ◽

2021 ◽

Author(s):

Francisco Bruno da Silva Café ◽

Rhannaldy Benício Rebouças ◽

Juvenil H. Cares ◽

Cristiano Souza Lima ◽

Francisco de Assis Câmara Rabelo Filho ◽

...

Keyword(s):

Body Length ◽

Morphological Characteristics ◽

Its Region ◽

The Body ◽

Control Treatment ◽

Molecular Characteristics ◽

Width Ratio ◽

Morphometric Characteristics ◽

First Report ◽

Second Stage

During a survey in 2018 for plant nematodes associated with roots and soil in cactus cultivation areas in Ceará State (3°44'48"S, 38°34'29"W), cysts were found on roots of mandacaru, Cereus jamacaru DC. This cactus is native to Brazil, can grow to 6-10 meters in height, and is widely distributed in the Northeast region (Romeiro-Brito et al. 2016) where it is used in construction, in disease remedies, as forage, and as an ornamental (Sales et al. 2014). Several cysts, second-stage juveniles (J2) and eggs extracted from the soil and roots, using sucrose centrifugation, were examined by scanning electron microscopy (SEM) and light microscopy (LM) to determine morphological and morphometric characteristics. Molecular characteristics were determined by DNA extraction from J2 and embryonated eggs using a protocol specific for Heteroderidae (Subbotin et al., 2018). The internal transcribed spacer sequence (ITS) region of the rDNA and D2-D3 regions of the 28S rDNA were amplified using the universal primers TW81 (5′-GTTTCCGTAGGTGAACCTGC-3′) and AB28 (5′-ATATGCTTAAGTTCAGCGGGT-3′), D2A(5′-ACAAGTACCGTGAGGGAAAGTTG-3′) and D3B(5′-TCGGAAGGAACCAGCTACTA-3′), respectively. To confirm that mandacaru is a host for C. cacti, six plantlets of mandacaru were inoculated with 1,800 eggs of the nematode, and kept in a greenhouse at 31 ± 3 ºC and irrigated daily. Six non inoculated mandacaru plantlets served as control treatment. Morphometric characteristics of cysts (n=35) were body length, excluding neck, 555.8 ± 87.8 (354,9 - 727,6) μm, body width 392.1 ± 63.4 (297.9 - 553.7) μm, neck length 63.5 ± 25.8 (49.8-105.0) μm, length to width ratio 1.4 ± 0.2 (1.0-1.8) μm and vulval cone length 48.4 ± 15.2 (40.7 –53.6) μm. Cysts had a rough surface, were lemon-shaped to rounded and had a zigzag cuticular pattern with a protruding vulval cone. They were circumfenestrate without underbridge and bullae, but with the presence of vulval denticles. Measurements of second-stage juveniles (n = 13) included the body length 511.2 ± 33.7 (452.7 - 551.5) μm, stylet length 28.0 ± 2.8 (25.4 - 34.0) μm, tail length 50.7 ± 5.1 (40.6 - 57.4) μm, tail hyaline region 22.7 ± 2.2 (18.9 – 27.1), with a = 20.9 ± 2.2 (17.7-24.3) μm, b = 5.4 ± 0.4 (5.1-5.8) μm, b'= 3.4 ± 0.4 (3.1-3.9) μm, c = 10.2 ± 1.3 (8.9-13.3) μm and c' = 3.8 ± 0.4 (3.0-4.5) μm. The observations of essential morphological characteristics for identification indicated that the species found on C. jamacaru was Cactodera cacti (Filipjev & Schuurmans-Stekhoven, 1941) Krall & Krall, 1978. The sequences of the studied rDNA regions were submitted to GenBank (ITS: MW562829 and D2–D3 regions of 28S: MW562830). The samples used for molecular analysis showed a high degree of sequence identity (99.59%) with C. cacti, from China, Iran and USA for the ITS region. The identity of the D2-D3 regions of 28S sequence was 99.54% with C. cacti isolates from Germany and 99.41% with isolates from USA. Phylogenetic analyses were performed using Maximum likelihood (ML) method for both individual loci, confirming the species as Cactodera cacti. All inoculated mandacaru plantlets showed C. cacti cysts on the roots after 60 days, confirming that mandacaru is a host for C. cacti. This species was reported in São Paulo State, in 2001, associated with ornamental cactus cultivated in pots, but plant species were not identified (Santos et al., 2001). The second report in Brazil was to Schlumbergera sp., an ornamental plant (Oliveira et al. 2007). In both studies, the nematode was not morphologically nor molecularly characterized. Cactodera cacti has been commonly associated with cactus worldwide (Esser, 1992). It has been reported in association with C. jamacaru was first reported in 2011 in China (Duan et al. 2012). This is the first report of the occurrence of C. cacti on C. jamacaru in field conditions in Brazil, and its presence in cactus cultivation areas with agricultural importance represents a threat to cactus production in the country.

Download Full-text

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.

Download Full-text

First Report of Powdery Mildew Caused by Podosphaera leucotricha on Photinia serrulata in China

Plant Disease ◽

10.1094/pdis-05-12-0473-pdn ◽

2012 ◽

Vol 96 (11) ◽

pp. 1695-1695 ◽

Cited By ~ 3

Author(s):

C. Liang ◽

H. H. Xing ◽

S. E. Cho ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Its Region ◽

The United States ◽

The Philippines ◽

Control Treatment ◽

Width Ratio ◽

Podosphaera Leucotricha ◽

Potential Threat ◽

Young Leaves ◽

Qingdao City

Photinia serrulata Franch. & Sav. (syn. P. serratifolia (Desf.) Kalkman), called Chinese photinia, is native to China, Taiwan, Japan, Indonesia, the Philippines, and India. The plants are evergreen shrubs to small trees belonging in the Rosaceae, and are widely cultivated throughout the world for ornamental purposes. Since 2005, severe powdery mildew infection has been observed on this plant in the Chengyang District of Qingdao City in Shandong Province, China. Powdery mildew colonies were circular to irregular white patches on both sides of the leaves and on young stems. As the disease progressed, white mycelial growth covered the entire shoot portion, causing leaf distortion. Voucher specimens (n= 7) were deposited in the herbarium of Qingdao Agricultural University, China. Hyphae were flexuous to straight, branched, septate, 4 to 6 μm wide, and had nipple-shaped appressoria. Conidiophores arising from the upper part of the hyphae were 110 to 185 × 9 to 12 μm and produced two to six immature conidia in chains with a crenate outline. Foot cells of conidiophores were straight, 30 to 40 μm long, and cylindric to somewhat attenuated toward the base. Conidia were hyaline, ellipsoid-ovoid, 22 to 32 × 13.5 to 20 μm (length/width ratio = 1.5 to 1.9), and had distinct fibrosin bodies. No chasmothecia were observed. The structures and measurements were compatible with those of the anamorphic state of Podosphaera leucotricha (Ellis & Everh.) E.S. Salmon as described by Braun (2). To confirm the identification, the complete internal transcribed spacer (ITS) region of the rDNA was amplified with nested PCR (4) and sequenced. The resulting sequence of 562 bp was deposited in GenBank (Accession No. JQ999954). A GenBank BLAST search of this sequence revealed 100% identity with that of seven isolates of P. leucotricha on rosaceous plants. Pathogenicity was confirmed through inoculation tests by gently pressing diseased leaves onto young leaves of three asymptomatic, potted 3-year-old photinia plants. Three non-inoculated plants were used for a control treatment. Plants were maintained in a greenhouse at 22 ± 2°C. Inoculated leaves developed symptoms after 5 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. The powdery mildew infections of P. serrulata associated with P. leucotricha have been recorded in New Zealand, Ukraine, Italy, and the United States (1,3). To our knowledge, P. leucotricha on P. serrulata has not been reported in Asia except for a record of a Podosphaera sp. on P. serratifolia in Japan (3). Since this ornamental shrub is native to China and nearby countries, occurrence of powdery mildew in China poses a potential threat to the health of photinia in other places. References: (1) E. Baldacci. Rev. Appl. Mycol. 16:358, 1937. (2) U. Braun. Beih. Nova Hedw. 89:1, 1987. (3) D. F. Farr and A. Y. Rossman. Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from , May 14, 2012. (4) Y. Matsuda et al. Phytopathology 95:1137, 2005.

Download Full-text

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.

Download Full-text