First Report of Powdery Mildew Caused by Blumeria graminis f. sp. bromi on Bromus catharticus in China

Bromus catharticus, rescuegrass, is a brome grass that has been cultivated for herbage production, and been widely naturalized in many provinces of China, including Henan province. During April and May 2020, powdery mildew was found on leaves of Br. catharticus on the campus of Henan Normal University, Xinxiang city (35.3°N; 113.9°E), Henan Province, China. Abundant white or grayish irregular or coalesced circular powdery colonies were scattered on the adaxial surface of leaves and 70% of the leaf areas were affected. Some of the infected leaves either were chlorotic or senescent. About 60% of the observed plants showed powdery mildew symptoms. Conidiophores (n = 25) were 32 to 45 μm × 7 to 15 μm and composed of foot cells and conidia (mostly 6 conidia) in chains. Conidia (n = 50) were 25 to 35 μm × 10 to 15 μm, on average 30 × 13 μm, with a length/width ratio of 2.3. Chasmothecia were not found. Based on these morphologic characteristics, the pathogen was initially identified as Blumeria graminis f. sp. bromi (Braun and Cook 2012; Troch et al. 2014). B. graminis mycelia and conidia were collected, and total genomic DNA was extracted (Zhu et al. 2019). The rDNA internal transcribed spacer (ITS) region was amplified with primer pairs ITS1/ITS4. The amplicon was cloned and sequenced. The sequence (574 bp) was deposited into GenBank under Accession No. MT892940. BLASTn analysis revealed that MT892940 was 100% identical to B. graminis f. sp. bromi on Br. catharticus (AB000935, 550 of 550 nucleotides) (Takamatsu et al. 1998). Phylogenetic analysis of MT892940 and ITS of other B. graminis ff. spp. clearly indicated least two phylogenetically distinct clades of B. graminis f. sp. bromi and that MT892940 clustered with the Takamatsu vouchers. Leaf surfaces of five healthy plants were fixed at the base of a settling tower and then inoculated by blowing conidia from diseased leaves using pressurized air. Five non-inoculated plants served as controls. The inoculated and non-inoculated plants were maintained separately in two growth chambers (humidity, 60%; light/dark, 16 h/8 h; temperature, 18℃). Thirteen- to fifteen-days after inoculation, B. graminis signs and symptoms were visible on inoculated leaves, whereas control plants remained asymptomatic. The pathogenicity assays were repeated twice with the same results. The observed signs and symptoms were morphologically identical to those of the originally infected leaves. Accordingly, the causal organism of the powdery mildew was confirmed as B. graminis f. sp. bromi by morphological characteristics and ITS sequence data. B. graminis has been reported on Br. catharticus in the United States (Klingeman et al. 2018), Japan (Inuma et al. 2007) and Argentina (Delhey et al. 2003). To our best knowledge, this is the first report of B. graminis on Br. catharticus in China. Since hybridization of B. graminis ff. spp. is a mechanism of adaptation to new hosts, Br. catharticus may serve as a primary inoculum reservoir of B. graminis to infect other species (Menardo et al. 2016). This report provides fundamental information for the powdery mildew that can be used to develop control management of the disease in Br. catharticus herbage production.

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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 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 Golovinomyces cichoracearum Causing Powdery Mildew on Zinnia elegans in China

Plant Disease ◽

10.1094/pdis-11-20-2333-pdn ◽

2020 ◽

Author(s):

Mo Zhu ◽

Jie Ji ◽

Xiao Duan ◽

YongFang Li

Keyword(s):

Powdery Mildew ◽

Morphological Characteristics ◽

Signs And Symptoms ◽

Its Region ◽

Zinnia Elegans ◽

Width Ratio ◽

Post Inoculation ◽

First Report ◽

Golovinomyces Cichoracearum ◽

Length Width

Zinnia elegans, common zinnia, is an annual plant with highly ornamental values. It is widely planted in many nurseries, city parks, universities and home gardens in China. From August to October 2020, powdery mildew-like signs and symptoms were observed on leaves of Z. elegans growing on the campus of Henan Normal University, Henan Province, China. White powdery colonies in circular- or irregularly shaped-lesions were abundant on both surfaces of leaves and covered up to 95 % of the leaf area. Any infected leaves were chlorotic, deformed or senescence. More than 70 % of the monitored Z. elegans plants showed these signs and symptoms. Conidiophores (n = 20) were 100 to 200 × 9 to 13 μm and composed of foot cells, followed by straight cells and conidia. Mycelial appressoria were single and nipple-shaped. The oval-shaped conidia (n = 30) were 22 to 36 × 12 to 18 μm, with a length/width ratio of 1.4 to 2.7, and produced germ tubes from the polar ends of the spore. No chasmothecia were found. Based on these morphological characteristics, the pathogen was initially identified morphologically as Golovinomyces cichoracearum (Braun and Cook 2012). Structures of the pathogen were scraped from infected leaves and total genomic DNA was isolated using the method previously described by Zhu et al. (2019). The internal transcribed spacer (ITS) region of rDNA was amplified by PCR using the primers ITS1/ITS4 (White et al. 1990) and the amplicon was sequenced by Invitrogen (Shanghai, China). The sequence for the fungus was deposited into GenBank under Accession No. MW029904 and was 99.83 % identical (595/596 bp) to G. cichoracearum on Symphyotrichum novi-belgii (HM769725)(Mørk et al. 2011). To perform pathogenicity analysis, leaf surfaces of five healthy plants were fixed in a settling tower and then inoculated by blowing fungal conidia from mildew-infested leaves using pressurized air. Five non-inoculated plants served as a control. The inoculated and non-inoculated plants were separately maintained in two growth chambers (humidity, 60 %; light/dark, 16 h/8 h; temperature, 18 ℃). Eleven- to twelve-days post-inoculation, powdery mildew signs were conspicuous on inoculated plants, while control plants remained healthy. Similar results were obtained by conducting two repeated pathogenicity assays. Thus, based on the morphological characteristics and molecular analysis, the pathogen was identified and confirmed as G. cichoracearum. This pathogen has been reported on Z. elegans in India, Israel, Jordan, Korea, Nepal, Sri Lanka, Switzerland, and Turkey (Farr and Rossman 2020). To our best knowledge, this is the first report of G. cichoracearum on Z. elegans in China. The sudden outbreak of powdery mildew caused by G. cichoracearum on Z. elegans may adversely impact the plant health and ornamental value in China. Therefore, the confirmation of G. cichoracearum infecting Z. elegans expands the understanding of this pathogen and provides the fundamental knowledge for future powdery mildew control.

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

Plant Disease ◽

10.1094/pdis-02-14-0195-pdn ◽

2014 ◽

Vol 98 (8) ◽

pp. 1159-1159 ◽

Cited By ~ 2

Author(s):

S. E. Cho ◽

J. H. Park ◽

S. H. Hong ◽

B. S. Kim ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Morphological Characteristics ◽

Signs And Symptoms ◽

Its Region ◽

Lateral Position ◽

Jeju Island ◽

Width Ratio ◽

Indigenous Plants ◽

Poor Growth ◽

First Report

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 × 11 to 12.5 μm 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 μm long, and constricted at the very base of branching point from the hypha. Conidia were hyaline, ellipsoid to ovate, measured 28 to 38 × 18.5 to 22 μm (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.× 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.

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First Report of Powdery Mildew Caused by Blumeria graminis on Festuca arundinacea in China

Plant Disease ◽

10.1094/pdis-06-14-0567-pdn ◽

2014 ◽

Vol 98 (11) ◽

pp. 1585-1585 ◽

Cited By ~ 1

Author(s):

F.-L. Zhang ◽

Y. Zhang ◽

J. Zhang ◽

K.-D. Xu ◽

K. Liu ◽

...

Keyword(s):

Powdery Mildew ◽

Festuca Arundinacea ◽

Poa Pratensis ◽

Perennial Grass ◽

Morphological Characteristics ◽

The United States ◽

Blumeria Graminis ◽

Its Sequence ◽

Adaxial Surface ◽

First Report

Tall fescue (Festuca arundinacea Schreb), a predominant cool-season perennial grass, is widely used as forage and turf grasses in China. In July 2013, powdery mildew was observed on 10 F. arundinacea lawns (about 0.5 ha in total) in Urumchi, Xinjiang Province, China, with 20 to 30% of the area being infected. Signs of the disease initially appeared as irregular white mycelial colonies on the adaxial surface of infected leaves. As the disease progressed, the colonies covered the whole adaxial surface and white patches appeared on the abaxial surface of infected leaves. Conidiophores were unbranched and cylindrical with swollen bases, measuring 13.3 to 15 × 16.7 to 20 μm, and borne vertically on hyphae. Each conidiophore produced 10 to 18 conidia in a chain. The conidia were oval, one-celled, and colorless, measuring 8.1 to 9.8 × 26 to 29.7 μm. Cleistothecia were black, spherical, and 164.3 to 207.3 μm in diameter, each of which contained 9 to 26 asci. Asci were oblong or ovate, measuring 32.1 to 40 × 85.7 to 96.4 μm. Asci were petiolate, containing eight ascospores. Ascospores were round to oval, colorless, one-celled, measuring 19.1 to 22.5 × 11.7 to 13.6 μm. Based on morphological characteristics of the anamorph and the teleomorph, the fungus was identified as Blumeria graminis (DC.) Speer. Additionally, the internal transcribed spacer (ITS) of 563 bp was amplified from DNA of conidia using ITS1 and ITS4 primers (4). The ITS sequence was deposited in GenBank (Accession No. KF545644). The ITS sequence showed 100% homogeneity with those of B. graminis on Poa pratensis in Swizerland (AB273540) and on P. bulbosa in Iran (AB273551) (1), which further confirmed the identification. Ten 3-week-old healthy plants were inoculated by spraying a spore suspension (1 × 105 conidia ml−1) made from conidia brushed from infected plants, and 10 plants sprayed with sterile distilled water were served as controls. All the plants were placed in the same growth chamber at 20°C, 80% humidity, and 16-h photoperiod. Twenty days after inoculation, typical signs and symptoms of powdery mildew were observed on all the inoculated plants, whereas no symptoms were observed on the controls. Microscopic and ITS analysis showed that the fungus on the inoculated plants is identical to that on diseased field plants. B. graminis on F. arundinacea has been observed in a few European countries (1), Israel (3), and the United States (2). To our knowledge, this is the first report of powdery mildew caused by B. graminis on F. arundinacea in China, which will increase the difficulty to prevent powdery mildew on grasses including cereals. References: (1) U. Braun. The Powdery Mildews (Erysiphales) of Europe. Gustav Fischer Verlag, Jena-Stuttgart-New York, 1995. (2) F. M. Dugan and G. Newcombe. Pacific Northwest Fungi. 2:1-5, 2007. (3) S. O. Voytyuk et al. Biodiversity of the Powdery Mildew Fungi (Erysiphales, Ascomycota) of Israel Vol. 7. Biodiversity of Cyanoprocaryotes, Algae and Fungi of Israel. Koeltz Scientific Books, 2009. (4) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, San Diego, 1990.

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First Report of Powdery Mildew Caused by Golovinomyces magnicellulatus var. magnicellulatus on Physalis alkekengi var. franchetii in China

Plant Disease ◽

10.1094/pdis-03-13-0328-pdn ◽

2013 ◽

Vol 97 (10) ◽

pp. 1382-1382 ◽

Cited By ~ 2

Author(s):

C. Liang ◽

H. H. Xing ◽

Z. Liu ◽

S. E. Cho ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Sequence Data ◽

Morphological Characteristics ◽

Its Region ◽

The United States ◽

Chinese Isolate ◽

Its Sequence ◽

Pathogenicity Test ◽

First Report ◽

Powdery Mildews

Physalis alkekengi var. franchetii (Mast.) Makino, known as Chinese lantern, belonging to Solanaceae, is cultivated for its fruits of medicinal value in East Asia (4). Since July 2010, a powdery mildew has been continuously observed on this plant in Shenyang City in northeastern China. More than 90% of the plants in a garden were affected. Symptoms first appeared as circular to irregular white patches, which progressed to abundant mycelial growth on both sides of leaves and young stems. In the middle of August, chasmothecia were formed abundantly, especially on the lower leaf surface. Voucher specimens were deposited in the herbarium of Qingdao Agricultural University (HMQAU10014, 12047, and 12144). Conidiophores produced 2 to 5 conidia in chains with a sinuate outline, followed by 2 to 3 cells. Foot-cells of conidiophores were straight and 46 to 65 × 9 to 11 μm. Conidia were ellipsoid to barrel-shaped, 26 to 32 × 13 to 15.5 μm, lacked distinct fibrosin bodies, and produced germ tubes on the subterminal position. Chasmothecia were amphigenous, also cauligenous, 100 to 140 μm across, and contained 10 to 25 asci. Appendages were mycelioid, 0.5 to 4 times as long as the chasmothecial diameter, and 1- to 3-septate. Asci were short-stalked, 45 to 64 × 26 to 34 μm, and contained two ascospores of 18 to 25 × 12.5 to 15 μm. The internal transcribed spacer (ITS) region of rDNA was amplified (3) and sequenced. The resulting 600-bp sequence was deposited in GenBank (Accession No. KC488260). A GenBank BLAST search of complete ITS sequence showed 100% identity with that of Golovinomyces orontii on P. alkekengi var. franchetii (AB077647 ex Japan) and >99% similarity with those of G. magnicellulatus on Phlox paniculata (AB077621 ex Japan, AF011303 ex the United States, and GU945756 and GU945757 ex Korea). G. orontii is currently confined to the Golovinomyces isolates on Cichorioideae (1). On the basis of the morphological characteristics and ITS sequence data, the fungus was identified as G. magnicellulatus var. magnicellulatus (U. Braun) V.P. Heluta (1). It was already noted that Golovinomyces isolates on Physalis and Phlox are phylogenetically close each other (3). A pathogenicity test was conducted by gently pressing a diseased leaf onto leaves of five healthy Chinese lanterns. Five non-inoculated plants served as controls. Inoculated plants developed symptoms after 8 days, whereas the control plants remained symptomless. The fungus present on the inoculated plants was morphologically identical to that originally observed on diseased plants, fulfilling Koch's postulates. Powdery mildews of Chinese lantern associated with Golovinomyces species have been known in Korea and Japan (2). A Korean material of Golovinomyces sp. on P. alkekengi var. franchetii was identified as G. magnicellulatus var. magnicellulatus based on morphological characteristics and 100% ITS sequence identity with a Chinese isolate (Shin, unpublished data). To our knowledge, this is the first report of powdery mildew caused by G. magnicellulatus var. magnicellulatus on Chinese lantern in China. References: (1) U. Braun and R. T. A. Cook. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No.11. CBS, Utrecht, 2012. (2) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab., Online publication, ARS, USDA, retrieved March 22, 2013. (3) S. Matsuda and S. Takamatsu. Mol. Phylogen. Evol. 27:314, 2003. (4) Y. Zheng et al. Phytochem. Anal. 23:337, 2012.

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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 Phytophthora hydropathica Causing Wilting and Shoot Dieback on Viburnum in Italy

Plant Disease ◽

10.1094/pdis-03-14-0308-pdn ◽

2014 ◽

Vol 98 (11) ◽

pp. 1582-1582 ◽

Cited By ~ 5

Author(s):

S. Vitale ◽

L. Luongo ◽

M. Galli ◽

A. Belisario

Keyword(s):

Natural Infection ◽

Morphological Characteristics ◽

Leaf Tissue ◽

The United States ◽

Selective Medium ◽

Phytophthora Species ◽

Phytophthora Ramorum ◽

Width Ratio ◽

Morphological Identification ◽

First Report

The genus Viburnum comprises over 150 species of shrubs and small trees such as Laurustinus (Viburnum tinus L.), which is one of the most widely used ornamental plants in private and public gardens. Furthermore, it commonly forms stands of natural woodland in the Mediterranean area. In autumn 2012, a survey was conducted to determine the presence of Phytophthora ramorum on Viburnum in commercial nurseries in the Latium region where wilting, dieback, and death of twigs were observed on 30% of the Laurustinus plants. A Phytophthora species was consistently recovered from soil rich in feeder roots from potted Laurustinus plants showing symptoms. Soil samples were baited with rhododendron leaves. Small pieces of leaf tissue cut from the margin of lesions were plated on P5ARPH selective medium (4). Pure cultures, obtained by single-hypha transfers on potato dextrose agar (PDA), were petaloid. Sporangia formation was induced on pepper seeds (3). Sporangia were almost spherical, ovoid or obpyriform, non-papillate and non-caducous, measuring 36.6 to 71.4 × 33.4 to 48.3 μm (average 53.3 × 37.4 μm) with a length/width ratio of 1.4. Chlamydospores were terminal and 25.2 to 37.9 μm in diameter. Isolates were considered heterothallic because they did not produce gametangia in culture or on the host. All isolates examined had 30 to 35°C as optimum temperatures. Based on these morphological characteristics, the isolates were identified as Phytophthora hydropathica (2). Morphological identification was confirmed by internal transcribed spacer (ITS), and mitochondrial partial cytochrome oxidase subunit 2 (CoxII) with BLAST analysis in the NCBI database revealing 99% identity with ITS and 100% identity with CoxII. The sequences of the three isolates AB234, AB235, and AB236 were deposited in European Nucleotide Archive (ENA) with the accession nos. HG934148, HG934149, and HG934150 for ITS and HG934151, HG934152, and HG934153 for CoxII, respectively. Pathogenicity tests were conducted in the greenhouse on a total of six 1-year-old shoots cut from V. tinus plants with two inoculation points each. Mycelial plugs cut from the margins of actively growing 8-day-old cultures on PDA were inserted through the epidermis into the phloem. Controls were treated as described above except that sterile PDA plugs replaced the inoculum. Shoots were incubated in test tubes with sterile water in the dark at 24 ± 2°C. After 2 weeks, lesions were evident at the inoculation points and symptoms were similar to those caused by natural infection. P. hydropathica was consistently re-isolated from the margin of lesions, while controls remained symptomless. In the United States in 2008, P. hydropathica was described as spreading from irrigation water to Rhododendron catawbiense and Kalmia latifolia (2). This pathogen can also attack several other horticultural crops (1), but to our knowledge, this is the first report of P. hydropathica causing wilting and shoot dieback on V. tinus. References: (1) C. X. Hong et al. Plant Dis. 92:1201, 2008. (2) C. X. Hong et al. Plant Pathol. 59:913, 2010. (3) E. Ilieva et al. Eur. J. Plant Path. 101:623, 1995. (4) S. N. Jeffers and S. B. Martin. Plant Dis. 70:1038, 1986.

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Occurrence of Powdery Mildew Caused by Blumeria graminis f. sp. poae on Poa pratensis in China

Plant Disease ◽

10.1094/pdis-09-20-2051-pdn ◽

2020 ◽

Author(s):

Mo Zhu ◽

Jie Ji ◽

Wenqi Shi ◽

YongFang Li

Keyword(s):

Powdery Mildew ◽

Germ Tube ◽

Poa Pratensis ◽

Perennial Grass ◽

Morphological Characteristics ◽

Signs And Symptoms ◽

Its Region ◽

Width Ratio ◽

Leaf Surfaces ◽

Length Width

Poa pratensis, known as bluegrass, is a perennial grass and one of the best varieties with highly valued pasture and turf grass uses. It is widely grown on golf courses and used for lawns in squares and parks (Luo et al. 2020). During April and May 2020, powdery mildew-like signs and symptoms were observed on leaves of P. pratensis in Muye Park, Xinxiang city (35.3°N; 113.9°E), Henan Province, China. White or grayish powdery masses in spots- or coalesced lesions were abundant on the adaxial surfaces of leaves and covered up to 90 % of the leaf area. Some of the mildew-infested leaves appeared chlorotic or began senescence. Mildew-infested leaves were collected to microscopically observe the morphological characteristics of this pathogen. Conidiophores were composed of foot cells, followed by one or two cells, and conidia. The ellipsoid- shaped conidia (n = 50) were 25 - 36 × 10 - 15 μm (length × width), on average 30 × 13 μm, with a length/width ratio of 2.3. Foot-cells (n = 15) were 30 - 44 μm long and 7 - 15 μm wide. On leaf surfaces, germinated conidia produced a short primary germ tube and then a long secondary germ tube that finally differentiated into a hooked appressorium. Chasmothecia were not found. Based on these morphological characteristics, the pathogen was initially identified as B. graminis f. sp. poae, the known forma specialis (f. sp.) of B. graminis on P. pratensis (Braun and Cook 2012; Troch et al. 2014). Mycelia of the pathogen were scraped from infected leaves and total genomic DNA was isolated using the method described previously (Zhu et al. 2019). The rDNA internal transcribed spacer (ITS) region was amplified applying primer pairs ITS1/ITS4 (White et al. 1990). The amplicon was cloned and sequenced by Invitrogen (Shanghai, China). The obtained sequence for the pathogen was deposited into GenBank under Accession No. MT892956 and was 100 % identical (549/549 bp) to B. graminis on P. pratensis (AB273530) (Inuma et al. 2007). In addition, the phylogenetic analysis clearly showed that the identified fungus and B. graminis f. sp. poae were clustered in the same branch. To perform pathogenicity analysis, leaf surfaces of eight healthy plants were inoculated by dusting fungal conidia from diseased leaves. Eight non-inoculated plants served as a control. The non-inoculated and inoculated plants were separately maintained in two growth chambers (humidity, 60 %; light/dark, 16 h/8 h; temperature, 18 ℃). Twelve to fourteen days after inoculation, B. graminis signs were visible on inoculated leaves, while control plants remained healthy. The pathogenicity assays were repeated twice and showed same results. Therefore, based on the morphological characteristics and molecular analysis, the pathogen was identified and confirmed as B. graminis f. sp. poae. This pathogen has been reported on P. pratensis in Switzerland and Japan (Inuma et al. 2007). This is, to our best knowledge, the first disease note reporting B. graminis on P. pratensis in China. Because the hybridization of B. graminis formae speciales (ff. spp.). allow the pathogens to adapt to new hosts, P. pratensis may serve as a primary inoculum reservoir of B. graminis to threaten other species, including cereal crops (Klingeman et al. 2018; Menardo et al. 2016). In addition, powdery mildew may negatively affect the yield and quality of grasses. Our report expands the knowledge of B. graminis f. sp. poae and provides the fundamental information for future powdery mildew control.

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

Plant Disease ◽

10.1094/pdis-03-12-0244-pdn ◽

2012 ◽

Vol 96 (9) ◽

pp. 1376-1376 ◽

Cited By ~ 3

Author(s):

M. J. Park ◽

S. E. Cho ◽

M. Piątek ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Sequence Similarity ◽

Signs And Symptoms ◽

Its Region ◽

Botanical Garden ◽

Central China ◽

Perennial Herb ◽

Width Ratio ◽

First Report ◽

Potted Plants

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

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