First Report of Powdery Mildew Caused by Erysiphe euonymi-japonici on Euonymus japonicus in Central China

Euonymus japonicus Thunb. is a popular, woody, ornamental plant in China. From June to September 2010, severe outbreaks of powdery mildew occurred on all investigated E. japonicus plants used for hedges in Zhoukou and Shangqiu cities of Henan province in central China, which is the second largest province in terms of ornamental plant cultivation. A large amount of fungicide was used to prevent the fungal disease, which caused serious environmental pollution and was estimated to result in a 40 to 60% increase in preservation cost of E. japonicus hedges. Gray-white colonies of powdery mildew fungi occurred mainly on the leaves of E. japonicus, on average approximately 50% of the leaves of an individual plant were infected by the fungi. On severely infected leaves, mycelia were amphigenous, thick, forming irregular white patches, and effused to cover the whole surface. Subsequently, these leaves became chlorotic, curled, and withered. The fungus was identified as Erysiphe euonymi-japonici (Vienn.-Bourg.) U. Braun & S. Takam on the basis of the following data of microscopic morphology with scanning electron microscopy and molecular phylogenetic analysis of the internal transcribed spacer (ITS) region. The fungus had unbranched conidiophores with an average length of 57.3 μm and width of 8.8 μm, which was composed of a cylindrical foot cell, 15 to 40 × 6 to 10 μm and one to three shorter cells or cells of about the same length. Conidia were borne singly, cylindrical, or ellipsoid-cylindrical, with an average length of 27.7 μm and width of 10.4 μm. Chasmothecia were not observed in the collected samples during the whole outbreak period. PCR amplification and sequencing of the ITS region was amplified using the universal primers ITS1 and ITS4 (4). The obtained ITS sequence was assigned Accession No. HQ012432 in GenBank, which had a 99 and 98% nt similarity with the ITS sequences (ITS region including the 5.8S rDNA) of two Erysiphe euonymi-japonici isolates from Japan and Argentina in GenBank (Accession Nos. AB250228 and AB250229 (3), respectively). To our knowledge, Erysiphe euonymi-japonici has not been reported previously from central China, although synonymous species, Oidium euonymi-japonici and Microsphaera euonymi-japonici, were reported in southwestern (Sichuan Province) (1) and eastern (Shandong Province) (2) regions. Herbarium specimens are available at the Key Laboratory of Plant Genetics and Molecular Breeding, Zhoukou Normal University, Zhoukou, China. References: (1) H. Feng. J. Sichuan For. Sci. Technol. 13:57, 1992. (2) S. Z. Li et al. J. Shandong For. Sci. Technol. 46:40, 1995. (3) S. Limkaisang et al. Mycoscience 47:327, 2006. (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, CA, 1990.

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First Report of Powdery Mildew Caused by Erysiphe betae on Swiss Chard in China

Plant Disease ◽

10.1094/pdis-02-14-0166-pdn ◽

2014 ◽

Vol 98 (10) ◽

pp. 1429-1429 ◽

Cited By ~ 1

Author(s):

Y. Zhang ◽

F. L. Zhang ◽

P. Cao ◽

Y. Liu ◽

K. Liu ◽

...

Keyword(s):

Powdery Mildew ◽

Its Region ◽

Central China ◽

Growth Chamber ◽

Universal Primers ◽

Academic Press ◽

First Report ◽

Swiss Chard ◽

Microscopic Evaluation ◽

Erysiphe Betae

Swiss chard (Beta vulgaris L. subsp. cicla) is a widely planted vegetable in China. From May to June 2013, an outbreak of powdery mildew on Swiss chard cultivar Fangzheng was observed in the commercial fields in Zhoukou city of Henan Province, located in central China. More than 80% of the plants exhibited symptoms of the disease. At the beginning of infection, circular, white, dust-like colonies of powdery mildew occurred mainly on adaxial surfaces of leaves. As the disease progressed, white mycelia covered the foliar parts of plant. No cleistothecia were found on or in collected samples. Upon microscopic evaluation, conidiophores were unbranched with the length of 63 to 126 and width of 7 to 10 μm (n = 50), produced conidia singly, and composed of a cylindrical foot cell followed by one to three short cells. Conidia were colorless, hyaline, ovoid, measured 29 to 40 × 12 to 18 μm (n = 100), lacked fibrosin bodies, and produced germ tubes on the ends of the conidia. The fungus was identified as Erysiphe betae according to the morphological features (1). To verify the identity, the internal transcribed spacer (ITS) region was amplified with the universal primers ITS1 and ITS4 (2) and sequenced. The ITS sequence obtained was assigned as Accession No. KF268348 in GenBank, which showed 100% homogeneity with two ITS sequences of E. betae isolates from UK (DQ164432 and DQ164436). Koch's postulates were conducted by inoculating 15 healthy 5-week-old plants (cv. Fangzheng) with detached infected leaves, which grew in a growth chamber under 22/16°C (day/night), 50% relative humidity, 120 μmol/m2/s light and a 16-h photoperiod. Fifteen non-inoculated plants grew in another growth chamber with the same conditions as control. Symptoms consistent with the infected field plants were observed on the inoculated plants, while no symptoms were found on the control plants. Microscopic observation revealed that the pathogen growing on the inoculated plants was consistent with the morphology of the original fungus. To our knowledge, this is the first report of E. betae infection on Swiss chard in China (3). References: (1) S. Francis. Mol. Plant Pathol. 3:119, 2002. (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, CA, 1990. (3) R. Y. Zheng et al. Page 63 in: Flora Fungorum Sinicorum, Vol. 1, Erysiphales. Science Press, Beijing, 1987.

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First Report of Powdery Mildew Caused by Erysiphe heraclei on Carrot in Central China

Plant Disease ◽

10.1094/pdis-04-13-0439-pdn ◽

2014 ◽

Vol 98 (2) ◽

pp. 277-277 ◽

Cited By ~ 1

Author(s):

Y. Wang ◽

K.-D. Xu ◽

Y. Zhang ◽

K. Liu ◽

F.-L. Zhang ◽

...

Keyword(s):

Powdery Mildew ◽

Its Region ◽

The United States ◽

Henan Province ◽

Central China ◽

Control Treatment ◽

Universal Primers ◽

Post Inoculation ◽

First Report ◽

Major Region

Carrot (Daucus carota) is an important root vegetable crop in China, which accounted for 46% of global production in 2011. Carrot was grown in Henan Province on >20,000 ha/year, which ranks first in China for area of carrots harvested. In October 2012, a powdery mildew outbreak was observed in 16 investigated carrot production fields in Zhoukou, Henan Province, in central China. White colonies typical of powdery mildew were seen on leaves of affected plants. The colonies enlarged and finally coalesced. Small, scattered fruiting bodies found on the adaxial and abaxial leaf surfaces were determined microscopically to be chasmothecia. Examining the pathogen morphologically revealed that appressoria were lobed, conidiophores were straight and bore single conidia, and cylindrical foot cells were followed by one to three shorter cells in the conidiophores. Conidiophores were subhyaline and 54.1 to 66.1 × 6.1 to 8.1 μm. Conidia were barrel-cylindrical and 28.8 to 38.6 × 11.4 to 14.8 μm. Chasmothecia were subspherical, dark brown to black, formed hyphoid appendages, and 110 to 122 μm in diameter. Appendages typically had one to five branches, which were nearly dichotomous or irregular, flexuous or almost straight, and 30 to 165 μm long. Each chasmothecium contained multiple asci that were saccate, multiguttulate, short-stipitate or not, 62.5 to 63.8 × 43.2 to 45.9 μm, and each contained two to six ascospores. Ascospores were subhyaline, ovoid to ellipsoid, and 16.5 to 17.7 × 11.2 to 12.7 μm. Based on characteristics of the anamorphic and teleomorphic stages, the fungus was identified as Erysiphe heraclei (2,4). To verify the identity, the internal transcribed spacer (ITS) region of ribosomal DNA was amplified with universal primers ITS1 and ITS4, and sequenced. The ITS sequence was assigned GenBank Accession No. KC480605, and showed 100% similarity to ITS sequences of E. heraclei on carrot in GenBank (EU371725 and GU252368). Koch's postulates were completed by using detached infected leaves from 10-week-old carrot plants growing in a field to inoculate 10 healthy, 5-week-old plants of the carrot cultivar Dinghong, growing in a growth chamber under 22/16°C (day/night) cycle at 50% relative humidity with 120 μmol/m2/s light and a 14-h photoperiod. Ten non-inoculated plants served as replicates of a control treatment. Symptoms consistent with those in the field were observed on inoculated plants 20 days post-inoculation. No symptoms were observed on the control plants. Microscopic observation of the pathogen growing on the inoculated plants revealed that it was the same as the original fungus. Powdery mildew on carrot has been observed in many countries including Australia (1), Mexico (3), and the United States (2). To our knowledge, this is the first report of E. heraclei infection on carrot in central China, a major region of carrot production, although the disease has previously been observed in northwestern China (4). Further research should help to reduce losses in carrot crops caused by E. heraclei in central China. References: (1) J. H. Cunnington et al. Australas. Plant Dis. Notes 3:38, 2008. (2) D. A. Glawe et al. Plant Health Progress doi: 10.1094/PHP-2005-0114-01-HN, 2005. (3) G. Rodríguez-Alvarado et al. Plant Dis. 94:483, 2010. (4) R. Zheng and G. Chen. Pp. 97-99 in: Flora Fungorum Sinicorum Vol. 1. Erysiphales. R. Zheng et al., eds. Science Press, Beijing, 1987.

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First Report of Powdery Mildew (Podosphaera pannosa) of Roses in Sinaloa, Mexico

Plant Disease ◽

10.1094/pdis-06-14-0605-pdn ◽

2014 ◽

Vol 98 (10) ◽

pp. 1442-1442 ◽

Cited By ~ 4

Author(s):

R. Félix-Gastélum ◽

G. Herrera-Rodríguez ◽

C. Martínez-Valenzuela ◽

I. E. Maldonado-Mendoza ◽

F. R. Quiroz-Figueroa ◽

...

Keyword(s):

Phylogenetic Analysis ◽

Powdery Mildew ◽

Average Length ◽

Scientific Evidence ◽

Its Region ◽

Outer Wall ◽

Future Research ◽

Flower Bud ◽

Morphological Studies ◽

Sphaerotheca Pannosa

Rose (Rosa spp.) is the most important ornamental plant cultivated in greenhouse and open fields in Mexico but its quality has been limited by powdery mildew (PM). High incidence and disease damage is common during winter in Sinaloa, Mexico (temperature range 18 to 25°C and prolonged episodes of relative humidity ≥90%). The fungus attacks leaves and flowers and grows abundantly on the pedicels, sepals, and receptacles, especially when the flower bud is unopened (2). Field advisors in Mexico have referred to Sphaerotheca pannosa (Wallr. ex Fr.) Lév. as a causal agent of the disease. However, there has not been solid scientific evidence to support this statement. Morphometric and molecular analysis were conducted to elucidate the identity of the fungal isolates collected from 2012 through 2013 in northern Sinaloa. PM specimens included eight different rose varieties. Conidiophores and conidia were observed under a compound microscope. The mycelium had a mean diameter of 4.7 to 6.0 μm; conidiophores (Euoidium type) 2 to 5 celled, occasionally 6 celled emerged from the superficial mycelium; conidiophores were unbranched with conidia produced in chains from the apex. The average length of the conidiophores was 54.9 to 98.0 μm; the foot cell of the conidiophores was straight and was 24.9 to 53.6 μm long with a diameter from 8.2 to 9.8 μm across its medium part. Conidia originated from unswollen conidiogenous cells, with fibrosin bodies, formed in long chains, and were cylindrical to ovoid, 25.8 to 30.4 μm long and 13.9 to 17.3 μm wide. The outline of the conidial chains was crenate. Conidia exhibited a slight constriction at one end. The germ tubes emerged from a shoulder of the conidia. The outer wall of partially collapsed conidia showed longitudinal and transversal wrinkling and slight constrictions at the ends; the terminal end of the conidia was concentrically ridged. For molecular characterization, the ITS region of the specimens was amplified with primers ITS1F and ITS4. Phylogenetic analysis was performed with MEGA 6.0 (bootstrap = 1,000) using Kimura 2 parameter (K2P) substitution model. The resulting phylogeny grouped our specimens (GenBank KM001665 to 69) within a clade of Podosphaera pannosa (Wall.: Fr.) de Bary (formerly known as Sphaerotheca pannosa) sequences (e.g., AB525938; bootstrap (1,000) = 98). Phylogenetic and morphometric data are in agreement with descriptions of the anamorphic P. pannosa (1,3). Morphological studies indicate that P. macularis (previously known as S. humuli) and P. pannosa are not indistinctly different (2). Phylogenetic analysis showed relationship to P. pannosa, but not to P. macularis. Typical symptoms caused by P. pannosa were observed. Morphological studies (4) reported the anamorph of P. pannosa on Rosa spp. in central Mexico. To date, no report exists on the molecular identification of P. pannosa associated to roses in northern Sinaloa, Mexico. Future research directions should focus on finding the teleomorph of the fungus to support its identity, and to explore disease management tools such as effective fungicides and developing resistant rose cultivars. References: (1) U. Braun et al. Page 13 in: The Powdery Mildews: A Comprehensive Treatise. APS Press, St. Paul, MN, 2002. (2) R. K. Horst. Compendium of Rose Diseases. APS Press, St. Paul, MN, 1983. (3) L. Leus et al. J. Phytopathol. 154:23, 2006. (4) Yañez-Morales et al. Some new reports and new species of powdery mildew from Mexico. Schlechtendalia 19:46, 2009.

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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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Outbreak of Powdery Mildew Caused by Erysiphe cruciferarum on Spider Flower (Cleome hassleriana) in Italy

Plant Disease ◽

10.1094/pdis-93-9-0963c ◽

2009 ◽

Vol 93 (9) ◽

pp. 963-963 ◽

Cited By ~ 2

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

M. L. Gullino

Keyword(s):

Powdery Mildew ◽

Its Region ◽

Herbarium Specimens ◽

Pathogenicity Test ◽

Public Park ◽

Potted Plants ◽

Powdery Mildews ◽

Erysiphe Cruciferarum ◽

Average Size ◽

Germ Tubes

Spider flower (Cleome hassleriana L. [synonym = C. spinosa]) is used as a tall border in parks and gardens worldwide. During July 2008, severe outbreaks of a powdery mildew were observed in a public park in Torino (northern Italy). Leaves were covered with dense, white hyphae and conidia, especially on the adaxial surface. Hyphae were also present on petioles and fruits, but not on petals and stems. As the disease progressed, infected leaves turned chlorotic, curled, and wilted. Conidia were hyaline, cylindrical, single, and measured 31.1 to 48.2 × 12.9 to 17.6 μm (average 37.1 × 15.6 μm). Germ tubes terminating in a moderately lobed appressorium were produced terminally. The cylindrical foot cells of the erect condiophores were 19.2 to 27.8 × 6.5 to 8.6 μm (average 23.3 × 7.7 μm). Fibrosin bodies were absent. Chasmothecia were observed mostly on the lower surfaces of leaves. At maturity, they were dark amber and spherical with a diameter of 92.9 to 151.0 μm (average 121.4 μm). Each chasmothecium contained six stalked asci (average size 63.7 × 35.9 μm). Each ascus contained four ellipsoid ascospores that measured 17.3 to 26.4 × 10.9 to 15.6 μm (average 23.3 × 12.8 μm). The internal transcribed spacer (ITS) region of rDNA was amplified using primers ITS4/ITS6 and sequenced (1). The 602-bp sequence was deposited in GenBank under the Accession No. GQ149478 and was 99% similar to that of Erysiphe cruciferarum (Accession No. EU140958). As proof of pathogenicity, diseased leaves of C. hassleriana were pressed against leaves of three healthy 4-month-old potted plants of the same species for 10 min. Three noninoculated plants served as controls. Inoculated and noninoculated plants were maintained in a greenhouse at 22 to 25°C in isolation. After 11 days, typical powdery mildew colonies developed on inoculated plants. Noninoculated plants did not develop symptoms. The pathogenicity test was repeated once. Powdery mildew on C. hassleriana caused by E. cruciferarum was reported in Italy (2) but the pathogen was not characterized. Herbarium specimens are deposited at AGROINNOVA Collection, University of Torino, Italy. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) U. Braun. The Powdery Mildews (Erysiphales) of Europe. Gustav Fischer Verlag, Jena, Germany, 1995.

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First Report of Powdery Mildew Incited by Erysiphe heraclei on English Ivy (Hedera helix) in Italy

Plant Disease ◽

10.1094/pdis-92-2-0313a ◽

2008 ◽

Vol 92 (2) ◽

pp. 313-313 ◽

Cited By ~ 1

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

J. Rossi ◽

M. L. Gullino

Keyword(s):

Nucleotide Sequence ◽

Powdery Mildew ◽

Its Region ◽

The United States ◽

Tube Length ◽

Herbarium Specimens ◽

Pathogenicity Test ◽

Hedera Helix ◽

First Report ◽

Germ Tubes

Hedera helix L. (Araliaceae) is a common ornamental species that is able to grow in shaded areas and is often used in parks and gardens. During the fall of 2006, severe outbreaks of a previously unknown powdery mildew were observed in several gardens in Liguria (northern Italy). Both surfaces of young leaves of affected plants were covered with dense, white mycelia and conidia. As the disease progressed, infected leaves turned yellow and dropped. Mycelia and conidia were also observed on young stems. Conidia were hyaline, cylindrical, borne singly, and measured 38 to 51 × 12 to 18 (average 42 × 16) μm. Single germ tubes, moderately long (average 26 μm), developed at the end of conidia. Appressoria of germ tubes and hyphae were lobed (three to four lobes). Conidiophores, 68 to 82 × 7 to 8 (average75 × 8) μm, showed foot cells measuring 39 to 60 × 7 to 8 (average 52 × 8) μm, followed by one shorter cell measuring 19 to 28 × 8 to 9 (average 23 × 9) μm. Fibrosin bodies were absent. Chasmothecia were numerous, spherical, amber-colored then brown at maturity, with diameters ranging from 97 to 140 (average 120) μm, containing four asci shortly stalked, 57 to 72 × 32 to 51 (average 65 × 41 μm). Ascospores were ellipsoid and measured 24 to 34 × 15 to 20 (average 30 × 17) μm. The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS4/ITS6 and sequenced. BLASTn analysis (1) of the 613-bp fragment showed an E-value of 0.0 with Erysiphe heraclei. The nucleotide sequence has been assigned GenBank Accession No. EU 010381. In GenBank, our nucleotide sequence shows an E-value of 0.0 also with E. betae. However, the comparison of appressorium shape and germ tube length observed on our microorganism with those described for E. betae by Braun (2) suggests that the causal agent of the powdery mildew reported on ivy is E. heraclei. Furthermore, symptoms described on our host, appressorium shape and the length of conidiophores, are different from those of Oidium araliacearum described by Braun (2) on Araliaceae. Inoculations were made by gently pressing diseased leaves onto leaves of five healthy H. helix plants. Three noninoculated plants served as controls. Inoculated and noninoculated plants were maintained in a greenhouse at temperatures between 21 and 25°C. After 15 days, typical powdery mildew colonies developed on inoculated plants. Noninoculated plants did not show symptoms. The pathogenicity test was carried out twice. To our knowledge, this is the first report of the presence of powdery mildew on H. helix caused by E. heraclei in Italy. A powdery mildew caused by E. cichoracearum was previously reported on H. canariensis var. azorica in Italy (3), while a powdery mildew on H. helix caused by O. araliacearum and Golovinomyces orontii, respectively, were observed in the United States (4) and Germany. Herbarium specimens of this disease are available at AGROINNOVA Collection, University of Torino, Italy. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) U. Braun. A Monograph of the Erysiphaceae (Powdery Mildews). Cramer, Berlin, Germany, 1987. (3) C. Nali. Plant Dis. 83:198, 1999. (4) G. S. Saenz and S. T. Koike. Plant Dis. 82:127, 1998.

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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 Garlic Leaf Blight Caused by Botrytis porri in China

Plant Disease ◽

10.1094/pdis-93-11-1216b ◽

2009 ◽

Vol 93 (11) ◽

pp. 1216-1216 ◽

Cited By ~ 2

Author(s):

J. Zhang ◽

G. Q. Li ◽

D. H. Jiang

Keyword(s):

Average Length ◽

Morphological Characteristics ◽

Its Region ◽

Gray Mold ◽

Leaf Blight ◽

Lesion Length ◽

Width Ratio ◽

Its Sequence ◽

First Report ◽

5.8S Rdna

In the spring of each year from 2007 to 2009, a leaf blight of garlic (Allium sativum L.) was observed in more than 50 fields in Zhushan County of Hubei Province, China. Gray mold was observed on many of the blighted garlic leaves. The percentage of garlic plants with blight and gray mold symptoms ranged from 10 to 50% with one to three blighted leaves on each plant, which severely reduced the yield of young garlic plants (produced as a green vegetable). Ten strains of a Botrytis sp. were isolated from symptomatic garlic leaves collected from 10 different fields. These strains were inoculated onto potato dextrose agar (PDA) in petri dishes and incubated at 20°C for 3 to 15 days for observation of colony characteristics and morphology of sclerotia and conidia. All 10 Botrytis strains formed flat and “ropy” mycelia (mycelial strands) on PDA. Abundant sporulation with a gray powdery appearance was observed on the colonies after 6 days. Conidiophores were erect with alternate branches at the top and ranged from 907 to 1,256 μm high. Conidia were borne in botryose clusters on conidiophores, obovate, and 10.4 to 17.6 × 7.6 to 13.1 μm with an average length/width ratio of 1.36. Discrete sclerotia were produced on each colony after 15 days. Mature sclerotia were black, cerebriform and convoluted, and 1.9 to 9.1 × 1.6 to 6.5 mm. Morphological characteristics of the colonies, conidia, and sclerotia of these Botrytis strains were similar to Botrytis porri Buchwald (1,2). Strain GarlicBC-16 was selected as a representative for molecular identification. Genomic DNA was extracted from mycelia of this strain and used as a template for amplification of the internal transcribed spacer (ITS) region of rDNA using primer pair ITS1/ITS4. A 539-bp amplicon was obtained and sequenced (GenBank Accession No. EU519206). Excluding the flanking regions, the amplicon contained a 453-bp ITS sequence (ITS1 + 5.8S rDNA + ITS2) 100% identical to the ITS sequence of strain MUCL3234 of B. porri (GenBank Accession No. AJ716292). Pathogenicity of strain GarlicBC-16 was tested by inoculation of 10 young and fully expanded garlic leaves taken from 100-day-old garlic plants with mycelial agar plugs (three plugs per leaf and spaced by 5 cm). Ten garlic leaves inoculated with agar plugs of PDA alone served as controls. Inoculated garlic leaves were covered with a plastic film (0.1 mm thick; Gold Mine Plastic Industrial Ltd. Jiangmen, China) and incubated at 20°C with 12-h light/12-h dark. Control leaves remained healthy after 48 to 120 h, but gray, water-soaked lesions appeared on leaves inoculated with strain GarlicBC-16 after 48 h. The average lesion length reached 27.3 mm after 90 h and abundant sporulation was produced on necrotic leaf lesions after 120 h. Microscopic examination showed the shape and size of conidia that formed on garlic leaf lesions were similar to those formed by strain GarlicBC-16 on PDA. On the basis of the isolation, identification, and pathogenicity tests, B. porri was determined to be the causal agent of garlic leaf blight in Zhushan County. B. porri has been reported to cause neck rot of leek (A. porrum) (1) and clove rot of garlic (2), and has been isolated from asymptomatic foliage and seeds of A. cepa (3). To our knowledge, this is the first report of garlic leaf blight caused by B. porri in China. References: (1) S. K. Asiedu et al. Plant Dis. 70:259, 1986. (2) F. M. Dugan et al. J. Phytopathol. 155:437. 2007. (3) L. J. du Toit et al. Plant Dis. 86:1178, 2002.

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First Report of Oidium longipes as the Causal Agent of Petunia Powdery Mildew in the United Kingdom

Plant Disease ◽

10.1094/pdis-09-10-0680 ◽

2011 ◽

Vol 95 (3) ◽

pp. 361-361 ◽

Cited By ~ 1

Author(s):

L. Kiss ◽

Z. Bereczky

Keyword(s):

United Kingdom ◽

Powdery Mildew ◽

Its Region ◽

Its Sequences ◽

Nuclear Ribosomal Dna ◽

Herbarium Specimens ◽

First Report ◽

The United Kingdom ◽

The Uk ◽

Solanaceous Plants

In autumn 2009, during a survey of powdery mildews of solanaceous plants in the United Kingdom, petunia (Petunia × hybrida) plants showing typical symptoms of powdery mildew infections were repeatedly collected in East Malling, Rochester, and Sandringham, UK. Leaves, stems, and petals of the collected plants, grown as outdoor ornamentals, were covered by dense, sporulating, white mycelium. Conidia were ellipsoid-cylindrical, measured 20 to 30 × 10 to 15 μm, and were produced in chains. Germ tubes arose from the ends of conidia and terminated in simple, unlobed apices. Some of the conidiophores were extremely long, up to 250 μm, because the second or third cell, or sometimes the foot cell, was up to 105 to 170 μm long. Other conidiophores were shorter, with no exceptionally long cells, but all of them exhibited a few characteristics in common: their width increased from base to top, sometimes enlarging considerably at a particular point of the foot cell, and basal septa were usually located 7 to 30 μm from the point of branching. Hyphal appressoria were nipple shaped. The teleomorph stage was not found. On the basis of these characteristics, the fungus was identified as Oidium longipes, a recently described (4) and little known pathogen of petunia and other solanaceous plants (1,3). To support the identification of this fungus, DNA was extracted from conidia collected with sterile brushes from single leaves collected in Sandringham, East Malling, and Rochester with a Qiagen DNeasy Plant Kit (Qiagen, Hilden, Germany), and the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA was amplified and determined as described in Jankovics et al. (2). The three identical ITS sequences, deposited in GenBank under Accession Nos. HM156495, HM156496, and HM156497, were identical to several ITS sequences of O. longipes, such as AF250777, EU327324, and EU327325. This has also supported that the disease was caused by this species. Herbarium specimens were deposited under the Accession Nos. HAL 2373F, HAL 2374F, and HAL 2375F at the Herbarium of Martin Luther University, Halle, Germany. To our knowledge, this is the first report of O. longipes in the UK. References: (1) A. Bolay. Cryptogam. Helv. 20:1, 2005. (2) T. Jankovics et al. Phytopathology 98:529, 2008. (3) L. Kiss et al. Plant Disease 92:818, 2008. (4) M. E. Noordeloos and W. M. Loerakker. Persoonia 14:51, 1989.

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First Report of Powdery Mildew Caused by Erysiphe pulchra on Cornus florida in Italy

Plant Disease ◽

10.1094/pdis-93-3-0320c ◽

2009 ◽

Vol 93 (3) ◽

pp. 320-320 ◽

Cited By ~ 2

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

M. L. Gullino

Keyword(s):

Powdery Mildew ◽

Its Region ◽

The United States ◽

Deciduous Tree ◽

Herbarium Specimens ◽

Pathogenicity Test ◽

Cornus Florida ◽

First Report ◽

Flowering Dogwood ◽

Young Leaves

Cornus florida L. (Cornaceae), flowering dogwood, is a small deciduous tree whose showy inflorescences, clusters of bright red fruits and red and purple leaves in autumn, make it a much appreciated ornamental. During the summer of 2008, severe outbreaks of a previously unknown powdery mildew were observed in several gardens and nurseries in Piedmont (northern Italy). Young leaves were covered with dense, white mycelia and conidia, especially on the adaxial surface. As the disease progressed, infected leaves turned red. Conidia were hyaline, elliptical, borne singly, and measured 32 to 46 × 15 to 20 (average 38 × 17) μm. Conidiophores measured 68 to 77 × 8 to 9 (average 73 × 8) μm, with a cylindrical foot cell measuring 26 to 37 × 8 to 10 (average 31 × 9) μm, followed by two shorter cells. Fibrosin bodies were absent. No chasmothecia were observed. The ITS region (internal transcribed spacer) of rDNA was amplified using primers ITS4/ITS6 and sequenced. The 627-bp sequence (Accession No. EU FJ436989 in GenBank) has 99% identity with Erysiphe pulchra. As proof of pathogenicity, diseased leaves were pressed against leaves of three healthy 3-year-old plants. Three noninoculated plants served as controls. Inoculated and noninoculated plants were maintained outdoors at 13 to 21°C. After 15 days, typical powdery mildew colonies developed on inoculated plants. Noninoculated plants did not show symptoms. The pathogenicity test was carried out twice. To our knowledge, this is the first report of the presence of powdery mildew on C. florida caused by E. pulchra in Italy. Powdery mildew of dogwood, caused by Microsphaera (Erysiphe) pulchra, has been reported in the United States (3) and Japan (1). In Italy, a powdery mildew caused by an Oidium sp. has been reported on C. sanguinea (2). Herbarium specimens of this disease are available at AGROINNOVA Collection, University of Torino, Italy. References: (1) T. Kobayashi. Index of Fungi Inhabiting Woody Plants in Japan. Host, Distribution, and Literature. Zenkoku-Noson-Kyoikai Publishing Co., Ltd., Tokyo, 2007. (2) G. Sicoli et al. Inf. Agrario 56/48:84, 2000. (3) V. L. Smith. Plant Dis. 83:782, 1999.

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