First Report of Powdery Mildew on Carrot Caused by Erysiphe heraclei in Michoacan, Mexico

Carrot (Daucus carota L. subsp. sativus (Hoffm.) Arcang.) is planted as a home-grown vegetable in the central region of Michoacan, Mexico. Powdery mildew was observed on carrot plants cv. Nantesa at several locations near Morelia, Michoacan during March 2009. Affected plants had abundant, white, superficial conidia and mycelium on leaves and stems. All plants at each of five locations surveyed had powdery mildew symptoms with percent foliage coverage ranging from 50 to 80%. Mycelial growth was amphigenous, mainly on the upper leaf surface, covering the whole leaf and with irregular patches on inflorescences and stems. Hyphae were ectophytic with lobed appressoria. Conidiophores presented foot cells 22.5 to 35 (30) × 5.75 to 7 (6.3) μm followed by two cells, one shorter and one longer than the foot cell. Conidia were produced singly, most subcylindric to cylindric, lacked fibrosin bodies, and measured 31.2 to 42 (36.2) × 8.7 to 11.2 (10.5) μm. The teleomorph was not observed. Genomic DNA was extracted from infected leaves; sequences of the internal transcribed spacers (ITS) inclusive of 5.8S rDNA were amplified using previously described primers specific for Erysiphales (3). The ITS sequences shared 100% homology to Erysiphe heraclei specimen VPRI41227 from carrot in Australia (GenBank Accession No. EU371725). On the basis of the morphological characteristics observed and the ITS rDNA sequences, the pathogen was identified as E. heraclei DC. The ITS sequence was deposited in NCBI as Accession No. GU252368. Pathogenicity tests were conducted twice on a total of 10 healthy 8-week-old carrot plants cv. Nantesa. Infected plants were placed in close proximity to healthy plants and maintained in a greenhouse at 27 ± 5°C. Initial signs and symptoms were observed 3 weeks after inoculation and appeared as small, white colonies, which later coalesced and covered most of the foliage. Microscopic examination of the conidia and mycelial morphology matched the originally described pathogen, E. heraclei. Powdery mildew caused by this pathogen has been extensively reported on diverse species and genera of the Apiaceae in Europe and remains one of the most important diseases of carrot (2). The appearance of E. heraclei in diverse regions on a variety of umbelliferous crops indicates that formae speciales have spread, infecting different and specific hosts (1–3). Recently, E. heraclei has been reported on parsley in Puebla, Mexico (4). To our knowledge, this is the first report of E. heraclei causing powdery mildew on carrot in Michoacan, Mexico. This pathogen should be considered as a threat to commercial carrot crops in Mexico. Other crops in the Apiaceae may not be at risk in this area if this powdery mildew is specific for carrots. References: (1) B. J. Aegerter. Page 22 in: Compendium of Umbelliferous Crop Diseases. The American Phytopathological Society, St. Paul, MN, 2002. (2) U. Braun. The Powdery Mildew (Erysiphales) of Europe. Gustav Fischer-Verlag. Jena, Germany, 1995. (3) J. H. Cunnington et al. Australas. Plant Pathol. 32:421, 2003. (4) M. J. Yáñez-Morales et al. Schlechtendalia 19:47, 2009.

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First Report of Powdery Mildew on Trident Maple Caused by Sawadaea nankinensis in Korea

Plant Disease ◽

10.1094/pdis-93-12-1348c ◽

2009 ◽

Vol 93 (12) ◽

pp. 1348-1348

Author(s):

H. B. Lee ◽

C. J. Kim ◽

H. Y. Mun ◽

J. P. Hong ◽

D. A. Glawe

Keyword(s):

Powdery Mildew ◽

Its Region ◽

Agricultural Science ◽

Morphological Data ◽

First Report ◽

5.8S Rdna ◽

Rdna Sequences ◽

National University ◽

Causal Fungus ◽

Pathogenicity Tests

Trident maple (Acer buergerianum Miq.) is widely grown in Korea as an ornamental tree as well as for the art of bonsai. During 2008 and 2009, a powdery mildew was observed on trident maple plants at the campus of Chonnam National University, Gwangju, Korea. Further surveys revealed the disease to be widespread on this species in other areas including Jeonbuk and Chungnam provinces in Korea. White, superficial mycelia were observed on young shoots and leaves early in spring. Both macroconidia and microconidia were produced beginning in May and conidial production continued through the summer into September and October. Production of chasmothecia was observed starting in September and continued into October. Macroconidia were produced in chains that were sinuate in outline. Individual macroconidia were barrel shaped and 23.4 to 30.0 (26.6) × 15.6 to 21.1 (18.1) μm. Foot cells of macroconidial conidiophores were 26.7 to 110.7 (48) × 7.1 to 11.2 (8.8) μm with one to five following cells. Microconidia were broadly ellipsoidal to subglobose and 8.9 to 12.5 (10.5) × 4.3 to 5.8 (5.1) μm. Chasmothecia typically were formed on adaxial leaf surfaces and 193.2 to 238.1 (216.8) μm in diameter. Appendages bore uncinate to circinate apices and were 176.8 to 267.7 (211.5) × 4.3 to 8.0 (6.2) μm. From extracted genomic DNA, internal transcribed spacer (ITS) region inclusive of 5.8S rDNA was amplified with ITS1F (5′-CTTGGTCATTTAGAGGAAGT-3′) and LR5F (5′-GCTATCCTGAGGGAAAC-3′) primers. The causal fungus was determined to be Sawadaea nankinensis (F.L. Tai) S. Takam. & U. Braun (2) on the basis of morphological data and ITS rDNA sequences. A BLAST search of GenBank with an ITS sequence from this fungus determined that the five sequences exhibiting the highest max score values (1,811 to 2,004) were from S. nankinensis; these sequences produced max ident values from 94% to 99%. In contrast, max score and max ident values from sequences of other Sawadaea spp. were lower, including scores of 1,063 and 98% similarity for S. polyfida var. japonica, 915 and 97% for S. tulasnei, and 913 and 97% for S. bicornis. Pathogenicity tests were conducted on field-grown plants in two replicates. These plants were inoculated with a paintbrush to apply conidia (~5 × 106/ml) collected from powdery-mildew-infected leaves. Inoculated plants developed powdery mildew symptoms within 5 days of inoculation and resembled those observed on naturally infected plants. S. nankinensis (synonym Uncinula nankinensis) was first reported on A. buergerianum from China in 1930 (2). Recently, S. nankinensis (F.L. Tai) S. Takam & U. Braun was reported to occur on A. buergerianum in Japan (3). Until now, three Sawadaea spp. (S. bicornis (Wallr.) Homma, S. negundinis Homma, and S. tulasnei (Fuckel) Homma) have been reported to cause powdery mildew on A. ginnala, but only S. bicornis (= U. circinata Cooke & Peck) has been reported to cause powdery mildew on A. ginnala in Korea (1). However, no Sawadaea sp. previously was reported to cause powdery mildew on A. buergerianum. To our knowledge, this is the first report of powdery mildew on trident maple (A. buergerianum) caused by S. nankinensis in Korea. References: (1) H. D. Shin. Erysiphaceae of Korea. National Institute of Agricultural Science and Technology, 2000. (2) F. L. Tai. Page 1517 in: Sylloge Fungorum Sinicorum. Science Press, Academia Sinica, Peking, 1979. (3) S. Takamatsu et al. Mycoscience 49:161, 2008.

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

Plant Disease ◽

10.1094/pdis-09-20-1983-pdn ◽

2020 ◽

Author(s):

Mo Zhu ◽

Jie Ji ◽

Xiao Duan ◽

Wenqi Shi ◽

YongFang Li

Keyword(s):

Powdery Mildew ◽

Sequence Data ◽

Morphological Characteristics ◽

Signs And Symptoms ◽

The United States ◽

Blumeria Graminis ◽

Henan Province ◽

Width Ratio ◽

Causal Organism ◽

First Report

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 Golovinomyces cichoracearum on Zinnia elegans in Turkey

Plant Disease ◽

10.1094/pdis-06-11-0519 ◽

2011 ◽

Vol 95 (10) ◽

pp. 1317-1317 ◽

Cited By ~ 1

Author(s):

S. Soylu ◽

S. E. Cho ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Molecular Analysis ◽

Sequence Similarity ◽

Morphological Characteristics ◽

Signs And Symptoms ◽

Current Data ◽

Zinnia Elegans ◽

Width Ratio ◽

Rdna Sequences ◽

Powdery Mildews

Powdery mildews are one of the most common diseases of plants growing in many nurseries, city parks, and home gardens in Turkey. Common zinnia (Zinnia elegans Jacq.) is widely cultivated in Turkey for ornamental purposes. In September 2010, zinnia plants grown in Hatay, Turkey were found to be heavily infected with a powdery mildew. Pathogen mycelia and sporulation were observed as circular to irregular, white patches on both sides of the leaves and on stems and flower petals. As the disease progressed, infected leaves turned yellow and died. Hyphae were straight to wavy and 4 to 7 μm wide. Conidiophores arose from the upper part of the hyphae, measured 120 to 190 × 10 to 13 μm, were simple, and produced two to six immature conidia in chains with a sinuate edge, followed by two to three straight cells. Conidia were hyaline, ellipsoid to barrel-shaped, measured 25 to 42 × 14 to 22 μm (length/width ratio = 1.3 to 2.5), lacked distinct fibrosin bodies, and produced germ tubes on the perihilar position, with reticulate wrinkling of the outer walls. No chasmothecia were observed. The structures described above were typical of the Oidium subgenus Reticuloidium, anamorph of the genus Golovinomyces, and the fungus measurements were compatible with those of G. cichoracearum (DC.) V.P. Heluta described previously (1,3). To confirm the tentative identification based on morphological characteristics, molecular analysis of internal transcribed spacer (ITS) rDNA sequences from a representative material (MKU-ZK311077, duplicate KUS-F25655) was conducted. The complete ITS regions of rDNA were amplified using primers ITS5 and P3 as described by S. Takamatsu (4) and sequenced. The resulting sequence of 508 bp from MKU-ZK311077 was deposited in GenBank (Accession No. JN051414). A GenBank BLAST search using the current data revealed an exact match for several sequences of G. cichoracearum, including Australian and Korean powdery mildews on zinnia plants, with a 100% sequence similarity. Pathogenicity was confirmed through inoculation by gently pressing diseased leaves onto leaves of three healthy, potted zinnia plants. Three noninoculated plants served as controls. Plants were maintained in a greenhouse at 25°C. Inoculated plants developed signs and symptoms after 10 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 Z. elegans associated with G. cichoracearum are nearly circumglobal, including Europe, North America, South America, Africa, Oceania, and Western Asian localities like India, Nepal, Jordan, and Israel (1,2). The current work confirmed the occurrence of G. cichoracearum infecting Z. elegans in Turkey using detailed morphological and molecular analysis. References: (1) U. Braun. Beih. Nova Hedw. 89:1, 1987. (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/ , May 24, 2011. (3) M. J. Park et al. Plant Pathol. J. 27:85, 2011. (4) S. Takamatsu et al. Mycol. Res. 113:117, 2009.

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

Plant Disease ◽

10.1094/pdis-07-21-1566-pdn ◽

2021 ◽

Author(s):

Yu Wan ◽

Yuan-Zhi Si ◽

Yang-Chun-Zi Liao ◽

Li-Hua Zhu

Keyword(s):

Powdery Mildew ◽

Phylogenetic Analyses ◽

Morphological Characteristics ◽

Signs And Symptoms ◽

Species Identity ◽

Internal Transcribed Spacer Region ◽

Voucher Specimen ◽

First Report ◽

Effective Strategies ◽

And Control

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

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

Plant Disease ◽

10.1094/pdis-03-12-0300-pdn ◽

2012 ◽

Vol 96 (7) ◽

pp. 1072-1072 ◽

Cited By ~ 3

Author(s):

M. J. Park ◽

S. E. Cho ◽

J. H. Park ◽

S. K. Lee ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Sequence Data ◽

Morphological Characteristics ◽

Signs And Symptoms ◽

Its Region ◽

Polyethylene Film ◽

Width Ratio ◽

First Report ◽

Close Phylogenetic Relationship ◽

Powdery Mildew Disease

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

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First Report of Buckeye Rot Caused by Phytophthora nicotianae in Tomato in New Mexico

Plant Disease ◽

10.1094/pdis-01-11-0049 ◽

2011 ◽

Vol 95 (8) ◽

pp. 1029-1029 ◽

Cited By ~ 1

Author(s):

J. M. French ◽

R. A. Stamler ◽

J. J. Randall ◽

N. P. Goldberg

Keyword(s):

New Mexico ◽

Dna Analysis ◽

Tomato Fruit ◽

Morphological Characteristics ◽

Negative Control ◽

Internal Transcribed Spacers ◽

Phytophthora Nicotianae ◽

Width Ratio ◽

First Report ◽

5.8S Rdna

Phytophthora nicotianae Breda de Haan was isolated from turning tomato fruit (Solanum lycopersicum L.) in August 2010 from a garden in central New Mexico. Symptoms typical of buckeye rot including brown, water-soaked, necrotic lesions with concentric rings were observed on three tomato fruit. Tissue from each fruit was surface sterilized and plated onto water agar and incubated at room temperature. After 72 h, colonies of Phytophthora (identified by the presence of coenocytic hyphae and papillate sporangia) were found and subcultured by hyphal tips to V8 agar amended with ampicillin (250 mg/liter), rifampicin (10 mg/liter), and pimaricin (0.2% wt/vol). The isolates of Phytophthora were identified as P. nicotianae based on morphological characteristics and DNA analysis. Sporangia were sharply papillate, noncaducous, and ovoid to spherical. The average sporangium size was 44.5 × 35.5 μm with a length-to-width ratio of 1.26. Chlamydospores, both terminal and intercalary, were spherical to ovoid and averaged 38.9 × 37.5 μm. PCR amplification and sequence analysis on three isolates from the infected tomato tissue was performed using primers ITS4 and ITS6 that amplify the 5.8S rDNA and ITSI and ITSII internal transcribed spacers (1,2). A band of approximately 890 bp was amplified and directly sequenced (GenBank Accession No. HQ711620). A BLAST search of the NCBI total nucleotide collection revealed a 100% similarity to multiple P. nicotianae isolates previously sequenced. Pathogenicity tests with sequenced P. nicotianae isolates were performed to confirm virulence on tomato fruit. Tomatoes were surface sterilized with 95% ethanol and 0.1 ml of a P. nicotianae zoospore suspension (10,000 zoospores/ml) or sterile water was pipetted onto the surface of the tomato fruit. After 5 days in a humidity chamber, all three inoculated tomatoes had expanding water-soaked, circular lesions and the negative control showed no disease symptoms. P. nicotianae was successfully reisolated from the inoculated tomato tissue and the ITS region was sequenced to confirm its identity. Although the disease has been reported in many other states since the early 1900s, to our knowledge, this is the first report of P. nicotianae causing disease on tomato in New Mexico. References: (1) D. E. L. Cooke and J. M. Duncan. Mycol. Res. 101:667, 1997. (2) 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 Erysiphe sedi on Kalanchoe blossfeldiana in Korea

Plant Disease ◽

10.1094/pdis-06-12-0570-pdn ◽

2012 ◽

Vol 96 (11) ◽

pp. 1701-1701 ◽

Cited By ~ 5

Author(s):

S. E. Cho ◽

M. J. Park ◽

J. Y. Kim ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Morphological Characteristics ◽

Signs And Symptoms ◽

Its Region ◽

Economic Losses ◽

Representative Specimen ◽

First Report ◽

Kalanchoe Blossfeldiana ◽

Poor Ventilation ◽

Kalanchoë Blossfeldiana

Kalanchoe blossfeldiana Poelln., belonging to the Crassulaceae, is a common ornamental houseplant with many cultivars. In May 2010, powdery mildew was observed on about 50% of 3,000 potted kalanchoe ‘Rose Queen’ plants in plastic greenhouses located in Yongin city of central Korea. Farmers producing potted kalanchoes in Yongin region stated that powdery mildew on kalanchoes was mild without causing problems for the last several years. The disease became severe from April 2010 and caused economic losses. The economic and esthetic value was reduced by the unsightly appearance of infected plants with most being unmarketable. Damage due to powdery mildew infections on kalanchoes appeared every year. A representative specimen was deposited in the Korea University herbarium (Accession No. KUS-F24911). Mycelial colonies were white, conspicuous and epiphytic on leaves and stems. Hyphae were septate, branched, and 3 to 6 μm wide. Appressoria on the hyphae were well developed, lobed, and mostly positioned in pairs. Conidiophores were cylindrical, 70 to 145 × 7 to 11.5 μm, and composed of three to four cells. Foot-cells of conidiophores were straight, cylindrical, and 28 to 48 μm long. Conidia produced singly were variable in shape, oval to cylindrical, oval or oblong-elliptical, 30 to 55 × 14 to 24 μm, lacked distinct fibrosin bodies, and showed angular/rectangular wrinkling of outer walls. Germ tubes were produced on the perihilar position of conidia. No chasmothecia were found. The morphological characteristics were consistent with descriptions of Erysiphe sedi U. Braun (1). To confirm the identity of the causal fungus, the complete ITS region of rDNA from KUS-F24911 was amplified with primers ITS5 and P3 as described by Takamatsu et al. (4) and directly sequenced. The resulting sequence was deposited in GenBank (Accession No. JX173288). A GenBank BLAST search using the present data revealed that the ITS sequence shares 100% (552/552 bp) similarity with those of E. sedi on Sedum spp. (Accession Nos. JX173289, JX173290). Pathogenicity was confirmed through inoculation by gently pressing diseased leaves onto leaves of five healthy potted kalanchoe plants. Five non-inoculated plants served as controls. Plants were maintained in a greenhouse at 22 ± 2°C. Inoculated plants developed signs and symptoms after 7 days, whereas the control plants remained symptomless. The fungus present on the inoculated plants was morphologically identical to that originally observed on diseased plants, fulfilling Koch's postulates. E. sedi is also known to infect Kalanchoe pinnata (Lam.) Pers. (= Bryophyllum calycinum Salisb.) in Romania (1,2) and other crassulaceous plants including Sedum spectabile in North America (3). To our knowledge, this is the first report of E. sedi infections of K. blossfeldiana in Korea. This disease seems to be a serious threat to the commercial production of kalanchoe plants which are cultivated under plastic greenhouses of poor ventilation and low light levels 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, Systematic Mycology & Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , June 13, 2012. (3) L. Kiss and M. L. Daughtrey. Plant Dis. 85:1207, 2001. (4) S. Takamatsu et al. Mycol. Res. 113:117, 2009.

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

Plant Disease ◽

10.1094/pdis-07-13-0797-pdn ◽

2014 ◽

Vol 98 (3) ◽

pp. 426-426

Author(s):

K. S. Han ◽

S. E. Cho ◽

J. H. Park ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Morphological Characteristics ◽

Signs And Symptoms ◽

Its Region ◽

The United States ◽

Control Treatment ◽

Width Ratio ◽

Anethum Graveolens ◽

First Report ◽

Powdery Mildews

Chervil (Anthriscus cerefolium (L.) Hoffm.), belonging to the family Apiaceae, is an aromatic annual herb that is native to the Caucasus. It is widely used as a flavoring agent for culinary purposes. This herb was recently introduced in Korea. In April 2013, plants showing typical symptoms of powdery mildew disease were observed in a polyethylene film-covered greenhouse in Seoul, Korea. White mycelium bearing conidia formed irregular patches on leaves and stems. Mycelial growth was amphigenous. Severe infections caused leaf withering and premature senescence. Voucher specimens were deposited in the Korea University Herbarium (KUS). Hyphae were septate, branched, with moderately lobed appressoria. Conidiophores presented 3 to 4 cells and measured 85 to 148 × 7 to 9 μm. Foot-cells of conidiophores were 37 to 50 μm long. Conidia were produced singly, oblong-elliptical to oblong, measured 30 to 50 × 13 to 18 μm with a length/width ratio of 2.0 to 3.3, lacked conspicuous fibrosin bodies, and with angular/rectangular wrinkling of the outer walls. Germ tubes were produced in the subterminal position of conidia. Chasmothecia were not found. These structures are typical of the powdery mildew Pseudoidium anamorph of the genus Erysiphe. The specific measurements and morphological characteristics were consistent with those of E. heraclei DC. (1). To confirm identity of the causal fungus, the complete internal transcribed spacer (ITS) region of rDNA of KUS-F27279 was amplified with primers ITS5 and P3 (4) and sequenced directly. The resulting 561-bp sequence was deposited in GenBank (Accession No. KF111807). A GenBank BLAST search of this sequence showed >99% similarity with those of many E. heraclei isolates, e.g., Pimpinella affinis (AB104513), Anethum graveolens (JN603995), and Daucus carota (EU371725). Pathogenicity was confirmed through inoculation by gently pressing a diseased leaf onto leaves of five healthy potted chervil plants. Five non-inoculated plants served as a control treatment. Plants were maintained in a greenhouse at 22 ± 2°C. Inoculated plants developed signs and symptoms after 6 days, whereas the control plants remained healthy. The fungus present on the inoculated plants was identical morphologically to that originally observed on diseased plants. Chervil powdery mildews caused by E. heraclei have been reported in Europe (Bulgaria, France, Germany, Hungary, Italy, Romania, Switzerland, and the former Soviet Union) and the United States (2,3). To our knowledge, this is the first report of powdery mildew caused by E. heraclei on chervil in Asia as well as in Korea. The plant is cultivated in commercial farms for its edible leaves in Korea. Occurrence of powdery mildew is a threat to quality and marketability of this herb, especially those grown in organic farming where chemical control options are limited. References: (1) U. Braun and R. T. A. Cook. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No. 11, CBS, Utrecht, 2012. (2) D. F. Farr and A. Y. Rossman. Fungal Databases, Syst. Mycol. Microbiol. Lab., Online publication. ARS, USDA. Retrieved July 29, 2013. (3) S. T. Koike and G. S. Saenz. Plant Dis. 88:1163, 2004. (4) S. Takamatsu et al. Mycol. Res. 113:117, 2009.

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First Report of Powdery Mildew (Pseudoidium neolycopersici) on Croton (Codiaeum variegatum var. pictum) in China

Plant Disease ◽

10.1094/pdis-09-14-0892-pdn ◽

2015 ◽

Vol 99 (2) ◽

pp. 288-288 ◽

Cited By ~ 3

Author(s):

X.-M. Liu ◽

Y.-X. Wei ◽

H. Zhang ◽

F.-X. Zhou ◽

J.-J. Pu

Keyword(s):

Powdery Mildew ◽

Southern China ◽

Disease Incidence ◽

Morphological Characteristics ◽

Oidium Neolycopersici ◽

Tomato Plants ◽

First Report ◽

Pseudoidium Neolycopersici ◽

Codiaeum Variegatum ◽

Pathogenicity Tests

Croton (Codiaeum variegatum (Linn.) var. pictum (Lodd.)) is an ornamental plant commonly grown in southern China. In March 2014, severe powdery mildew infections were observed on crotons in gardens of Hainan University (20.1°N and 110.3°E), Haikou, Hainan province. Disease incidence was estimated in a random batch of 100 plants in three replicates, with the average value approaching 80%. Symptoms first appeared as white circular patches on the adaxial surface and expanded to the abaxial surface, petioles, and stems. The top leaves were the most affected. Upper surfaces of the infected leaves were covered by white, dense mycelia. As the disease progressed, infected leaves turned purple on the lower surfaces and curly before becoming necrotic and abscising from the plant. Powdery mildew was more severe in shaded environments, especially during rainy or foggy weather in early spring. Two hundred conidiophores and conidia were observed microscopically. The conidiophores were straight or occasionally flexuous, 62.3 to 127.6 × 6.2 to 10.2 μm, consisting of two to three straight cells. Conidia were born in solitary on the top of conidiophores. Conidia were hyaline, ellipsoidal, 26.4 to 42.2 × 11.7 to 23.4 μm (average 32.5 × 16.5 μm), contained no distinct fibrosin bodies, and produced a subterminal germ tube. The wrinkling pattern of the outer walls of older conidia was angular or reticulated. Appressoria were single and multilobed. Cleistothecia were not observed. Based on morphological characteristics, the fungus was identified as Oidium neolycopersici (2), which was recently renamed Pseudoidium neolycopersici (L. Kiss) (3). The identity was confirmed by sequence analysis. Genomic DNA was extracted from the foliar powdery mildew colonies using Chelex-100 (Bio-Rad, Shanghai, China). The rDNA internal transcribed spacer (ITS) region was amplified with primers ITS1 and ITS4 (5). The ITS sequence of the representative isolates C01 (GenBank Accession No. KJ890378.1) and four other powdery mildew samples collected from crotons in Hainan University was 100% identical to that of P. neolycopersici isolates from tomato plants such as JQ972700 and AB163927. Inoculations were made by gently pressing diseased leaves onto leaves of five healthy plants of croton and tomato (‘Money maker’). Five non-inoculated croton and tomato plants served as controls. Inoculated and non-inoculated plants were maintained in an incubator at 25°C with a 12-h photoperiod. After eight days, typical powdery mildew symptoms developed on 93% of the inoculated plants, while no symptom developed on the non-inoculated plants. The pathogenicity tests were repeated three times. The same fungus was always re-isolated from the diseased tissue according to Koch's postulates. The pathogenicity tests further confirmed that the pathogen from crotons is P. neolycopersici (Basionym. Oidium neolycopersici (KJ890378.1)), which is commonly known as the tomato powdery mildew. P. neolycopersici is also a pathogen of Normania triphylla (1) and papaya (4). To our knowledge, this is the first report of P. neolycopersici infecting croton. The avenue of this pathogen entering gardens of Hainan University remains unknown. The gardens are located far away from tomato farms. Also no symptom of powdery mildew on croton was observed during surveys in other locations in Haikou. The origin of the pathogen warrants additional research. References: (1) D. Delmail et al. Mycotaxon 113:269, 2010. (2) L. Kiss et al. Mycol. Res. 105:684, 2001. (3) L. Kiss et al. Mycol. Res. 115:612, 2011. (4) J. G. Tsay et al. Plant Dis. 95:1188, 2011. (5) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA, 1990.

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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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