First Report of Leaf Spot Disease Caused by Cercosporella pfaffiae on Brazilian Ginseng (Pfaffia glomerata) in Brazil

Pfaffia glomerata (Spreng) Pedersen (Amaranthaceae) and other species in this genus, popularly known as “Brazilian ginseng,” have been marketed and used for many years in folk medicine for the treatment of various diseases (1). In January 2012, samples of P. glomerata with leaf spots were collected in the city of Viçosa, state of Minas Gerais, Brazil. Two samples were deposited in the herbarium at the Universidade Federal de Viçosa (VIC31849 and VIC31851). The diseased leaves were examined using a stereomicroscope (75×). The fungal structures were scraped with a scalpel from the plant surface and mounted in lactophenol. Thirty measurements of all of the relevant morphological characters were obtained using light microscopy for the identification of the species. To confirm the identification, fungal DNA from single-spore pure culture was isolated from the diseased leaves on PDA, and the DNA was amplified using primers ITS1 and ITS4 for the ITS region (GenBank Accession No. JQ990331) and LR0R and LR5 for partial 28S rDNA (Accession No. JQ990330). Sequencing was performed by Macrogen, Korea. The symptoms observed were leaf spots, subcircular, usually up to 6 mm diameter, initially yellowish becoming brown to reddish, margin indefinite, with the formation of fungal structures, hypophyllous, white, scattered, or grouped. Conidiophores were very numerous in dense subsynnematal fascicles, moderately brown at the base but for most of the length subhyaline, 42.5 to 350 × 2.5 to 3.5 μm, showing conidial scars. Conidia formed singly, 22.5 to 77.5 × 5 to 6 μm, hyaline, hilum slightly thickened, and refractive. These characteristics show that the fungus found on P. glomerata matched well with the description of Cercosporella pfaffiae (2). Koch's postulates were fulfilled by inoculation of 6-mm-diameter PDA plugs with the isolate mycelia on leaves of P. glomerata. Six plants were inoculated with the isolate and six plants were inoculated with an isolate-free agar plug. Inoculated plants were maintained in a moist chamber for 24 hours and subsequently in a greenhouse at 26°C. Leaf spot was observed in inoculated plants 15 days after inoculation, and symptoms were similar to those in the field. All non-inoculated plants remained healthy. A Megablast search of the NCBI GenBank nucleotide sequence database using the ITS sequence retrieved C. virgaureae as the closest match [GenBank GU214658; Identity = 458/476 (96%), Gaps = 2/476 (0%)]. To confirm the identification, Bayesian inference analyses were employed, and the tree was deposited in TreeBASE (Study S12680). The analysis placed our isolate in the same clade with the type species of Cercosporella. Molecular studies and morphological characteristics confirm our identification. C. pfaffiae has been previously reported in P. iresinoides (H.B.K.) Spreng. in Trinidad and Gomphrena glomerata L. in Argentina (2). To our knowledge, this is the first report of C. pfaffiae causing disease in P. glomerata in Brazil and it may become a serious problem for some medicinal plant growers, due to the severity of the disease and the lack of chemical products for this pathogen. References: (1) Neto et al. J. Ethnopharmacol. 96:87, 2005. (2) U. Braun. A Monograph of Cercosporella, Ramularia and Allied Genera (Phytopathogenic Hyphomycetes). Eching bei Müchen, IHW-Verlage. Vol. 1, p. 68, 1995.

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First Report of Alternaria Leaf Spot of Banana Caused by Alternaria alternata in the United States

Plant Disease ◽

10.1094/pdis-01-13-0007-pdn ◽

2013 ◽

Vol 97 (8) ◽

pp. 1116-1116 ◽

Cited By ~ 3

Author(s):

V. Parkunan ◽

S. Li ◽

E. G. Fonsah ◽

P. Ji

Keyword(s):

United States ◽

Alternaria Alternata ◽

Leaf Spot ◽

Morphological Characteristics ◽

The United States ◽

Its Sequencing ◽

Single Spore ◽

First Report ◽

Alternaria Leaf Spot ◽

Leaf Spots

Research efforts were initiated in 2003 to identify and introduce banana (Musa spp.) cultivars suitable for production in Georgia (1). Selected cultivars have been evaluated since 2009 in Tifton Banana Garden, Tifton, GA, comprising of cold hardy, short cycle, and ornamental types. In spring and summer of 2012, 7 out of 13 cultivars (African Red, Blue Torres Island, Cacambou, Chinese Cavendish, Novaria, Raja Puri, and Veinte Cohol) showed tiny, oval (0.5 to 1.0 mm long and 0.3 to 0.9 mm wide), light to dark brown spots on the adaxial surface of the leaves. Spots were more concentrated along the midrib than the rest of the leaf and occurred on all except the newly emerged leaves. Leaf spots did not expand much in size, but the numbers approximately doubled during the season. Disease incidences on the seven cultivars ranged from 10 to 63% (10% on Blue Torres Island and 63% on Novaria), with an average of 35% when a total of 52 plants were evaluated. Six cultivars including Belle, Ice Cream, Dwarf Namwah, Kandarian, Praying Hands, and Saba did not show any spots. Tissue from infected leaves of the seven cultivars were surface sterilized with 0.5% NaOCl, plated onto potato dextrose agar (PDA) media and incubated at 25°C in the dark for 5 days. The plates were then incubated at room temperature (23 ± 2°C) under a 12-hour photoperiod for 3 days. Grayish black colonies developed from all the samples, which were further identified as Alternaria spp. based on the dark, brown, obclavate to obpyriform catenulate conidia with longitudinal and transverse septa tapering to a prominent beak attached in chains on a simple and short conidiophore (2). Conidia were 23 to 73 μm long and 15 to 35 μm wide, with a beak length of 5 to 10 μm, and had 3 to 6 transverse and 0 to 5 longitudinal septa. Single spore cultures of four isolates from four different cultivars were obtained and genomic DNA was extracted and the internal transcribed spacer (ITS1-5.8S-ITS2) regions of rDNA (562 bp) were amplified and sequenced with primers ITS1 and ITS4. MegaBLAST analysis of the four sequences showed that they were 100% identical to two Alternaria alternata isolates (GQ916545 and GQ169766). ITS sequence of a representative isolate VCT1FT1 from cv. Veinte Cohol was submitted to GenBank (JX985742). Pathogenicity assay was conducted using 1-month-old banana plants (cv. Veinte Cohol) grown in pots under greenhouse conditions (25 to 27°C). Three plants were spray inoculated with the isolate VCT1FT1 (100 ml suspension per plant containing 105 spores per ml) and incubated under 100% humidity for 2 days and then kept in the greenhouse. Three plants sprayed with water were used as a control. Leaf spots identical to those observed in the field were developed in a week on the inoculated plants but not on the non-inoculated control. The fungus was reisolated from the inoculated plants and the identity was confirmed by morphological characteristics and ITS sequencing. To our knowledge, this is the first report of Alternaria leaf spot caused by A. alternata on banana in the United States. Occurrence of the disease on some banana cultivars in Georgia provides useful information to potential producers, and the cultivars that were observed to be resistant to the disease may be more suitable for production. References: (1) E. G. Fonsah et al. J. Food Distrib. Res. 37:2, 2006. (2) E. G. Simmons. Alternaria: An identification manual. CBS Fungal Biodiversity Center, Utrecht, Netherlands, 2007.

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First Report of Leaf Spot Disease on Walnut Caused by Colletotrichum fioriniae in China

Plant Disease ◽

10.1094/pdis-09-14-0938-pdn ◽

2015 ◽

Vol 99 (2) ◽

pp. 289-289 ◽

Cited By ~ 9

Author(s):

Y. Z. Zhu ◽

W. J. Liao ◽

D. X. Zou ◽

Y. J. Wu ◽

Y. Zhou

Keyword(s):

Dna Sequences ◽

Leaf Spot ◽

Juglans Regia ◽

Morphological Characteristics ◽

Leaf Spot Disease ◽

Koch’S Postulates ◽

First Report ◽

Spot Disease ◽

Leaf Spots ◽

Koch's Postulates

In May 2014, a severe leaf spot disease was observed on walnut tree (Juglans regia L.) in Hechi, Guangxi, China. Leaf spots were circular to semicircular in shape, water-soaked, later becoming grayish white in the center with a dark brown margin and bordered by a tan halo. Necrotic lesions were approximately 3 to 4 mm in diameter. Diseased leaves were collected from 10 trees in each of five commercial orchards. The diseased leaves were cut into 5 × 5 mm slices, dipped in 75% ethanol for 30 s, washed three times in sterilized water, sterilized with 0.1% (w/v) HgCl2 for 3 min, and then rinsed five times with sterile distilled water. These slices were placed on potato dextrose agar (PDA), followed by incubating at 28°C for about 3 to 4 days. Fungal isolates were obtained from these diseased tissues, transferred onto PDA plates, and incubated at 28°C. These isolates produced gray aerial mycelium and then became pinkish gray with age. Moreover, the reverse of the colony was pink. The growth rate was 8.21 to 8.41 mm per day (average = 8.29 ± 0.11, n = 3) at 28°C. The colonies produced pale orange conidial masses and were fusiform with acute ends, hyaline, sometimes guttulate, 4.02 to 5.25 × 13.71 to 15.72 μm (average = 4.56 ± 0.31 × 14.87 ± 1.14 μm, n = 25). The morphological characteristics and measurements of this fungal isolate matched the previous descriptions of Colletotrichum fioriniae (Marcelino & Gouli) R.G. Shivas & Y.P. Tan (2). Meanwhile, these characterizations were further confirmed by analysis of the partial sequence of five genes: the internal transcribed spacer (ITS) of the ribosomal DNA, beta-tubulin (β-tub) gene, glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene, chitin synthase 3(CHS-1) gene, and actin (ACT) gene, with universal primers ITS4/ITS5, T1/βt2b, GDF1/GDR1, CHS1-79F/CHS1-354R, and ACT-512F/ACT-783R, respectively (1). BLAST of these DNA sequences using the nucleotide database of GenBank showed a high identify (ITS, 99%; β-tub, 99%; GAPDH, 99%; CHS-1, 99%; and ACT, 100%) with the previously deposited sequences of C. fioriniae (ITS, KF278459.1, NR111747.1; β-tub, AB744079.1, AB690809.1; GAPDH, KF944355.1, KF944354.1; CHS-1, JQ948987.1, JQ949005.1; and ACT, JQ949625.1, JQ949626.1). Koch's postulates were fulfilled by inoculating six healthy 1-year-old walnut trees in July 2014 with maximum and minimum temperatures of 33 and 26°C. The 6-mm mycelial plug, which was cut from the margin of a 5-day-old colony of the fungus on PDA, was placed onto each pin-wounded leaf, ensuring good contact between the mycelium and the wound. Non-colonized PDA plugs were placed onto pin-wounds as negative controls. Following inoculation, both inoculated and control plants were covered with plastic bags. Leaf spots, similar to those on naturally infected plants, were observed on the leaves inoculated with C. fioriniae within 5 days. No symptoms were observed on the negative control leaves. Finally, C. fioriniae was re-isolated from symptomatic leaves; in contrast, no fungus was isolated from the control, which confirmed Koch's postulates. To our knowledge, this is the first report of leaf disease on walnut caused by C. fioriniae. References: (1) L. Cai et al. Fungal Divers. 39:183, 2009. (2) R. G. Shivas and Y. P. Tan. Fungal Divers. 39:111, 2009.

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First Report of Leaf Spot Caused by Phyllosticta yuccae on Yucca filamentosa in Brazil

Plant Disease ◽

10.1094/pdis-04-13-0384-pdn ◽

2013 ◽

Vol 97 (9) ◽

pp. 1257-1257 ◽

Cited By ~ 1

Author(s):

A. D. A. Silva ◽

D. B. Pinho ◽

B. T. Hora Junior ◽

O. L. Pereira

Keyword(s):

Leaf Spot ◽

Its Region ◽

The United States ◽

Leaf Spot Disease ◽

Infected Leaf ◽

Single Spore ◽

First Report ◽

Leaf Spots ◽

Slime Layer ◽

Pure Cultures

Yucca filamentosa L. (Agavaceae), commonly known as Adam's needle, is known in Brazil as “agulha-de-adão.” It is an ornamental garden plant with medicinal properties (4). In 2010, 100% of Y. filamentosa seedlings and plants were observed with a severe leaf spot disease in two ornamental nurseries located in the municipality of Viçosa, Minas Gerais, Brazil. Initially, lesions were dark brown, elliptical, and scattered, and later became grayish at the center with a reddish brown margin, irregular and coalescent. Infected leaf samples were deposited in the herbarium at the Universidade Federal de Viçosa (Accession Nos. VIC32054 and VIC32055). A fungus was isolated from the leaf spots and single-spore pure cultures were obtained on potato dextrose agar (PDA). The sporulating single-spore cultures were deposited at the Coleção de Culturas de Fungos Fitopatogênicos “Prof. Maria Menezes” (CMM 1843 and CMM 1844). On the leaf, the fungus produced pycnidial conidiomata that were scattered or gregarious, usually epiphyllous, immersed, dark brown, unilocular, subglobose, and 95 to 158 × 108 to 175 μm, with a minute, subcircular ostiole. Conidiogenous cells were blastic, hyaline, conoidal, or short cylindrical. Conidia were aseptate, hyaline, smooth walled, coarsely granular, broadly ellipsoidal to subglobose or obovate, usually broadly rounded at both ends, occasionally truncate at the base or indented slightly at the apex, and 7.5 to 13.5 × 6 to 10 μm. Conidia were also surrounded by a slime layer, usually with a hyaline, flexuous, narrowly conoidal or cylindrical, mucilaginous apical appendage that was 10 to 16 μm long. Spermatia were hyaline, dumbbell shaped to cylindrical, both ends bluntly rounded, and 3 to 5 × 1 to 1.5 μm. These characteristics matched well with the description of Phyllosticta yuccae Bissett (1). To confirm this identification, DNA was extracted using a Wizard Genomic DNA Purification Kit and amplified using primers ITS1 and ITS4 (2) for the ITS region (GenBank Accession Nos. JX227945 and JX227946) and EF1-F and EF2-R (3) for the TEF-1α (JX227947 and JX227948). The sequencing was performed by Macrogen, South Korea. The ITS sequence matched sequence No. JN692541, P. yuccae, with 100% identity. To confirm Koch's postulates, four leaves of Y. filamentosa (five plants) were inoculated with 6-mm-diameter plugs from a 7-day-old culture growing on PDA. The leaves were covered with plastic sack and plants were maintained at 25°C. In a similar manner, fungus-free PDA plugs were placed on five control plants. Symptoms were consistently similar to those initially observed in the nurseries and all plants developed leaf spots by 15 days after inoculation. P. yuccae was successfully reisolated from the symptomatic tissue and control plants remained symptomless. P. yuccae has been previously reported in Canada, the Dominican Republic, Guatemala, Iran, and the United States of America. To our knowledge, this is the first report of P. yuccae causing disease in Y. filamentosa in Brazil and it may become a serious problem for the nurseries, due to the severity of the disease and the lack of chemical products to control this pathogen. References: (1) J. Bissett. Can. J. Bot. 64:1720, 1986. (2) M. A. Innis et al. PCR Protocols: A guide to methods and applications. Academic Press, 1990. (3) Jacobs et al. Mycol. Res. 108:411, 2004. (4) H. Lorenzi and H. M. Souza. Plantas Ornamentais no Brasil. Instituto Plantarum, 2001.

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First Report of Corynespora cassiicola Causing Leaf Spot of Cassava in China

Plant Disease ◽

10.1094/pdis-94-7-0916a ◽

2010 ◽

Vol 94 (7) ◽

pp. 916-916 ◽

Cited By ~ 1

Author(s):

X.-B. Liu ◽

T. Shi ◽

C.-P. Li ◽

J.-M. Cai ◽

G.-X. Huang

Keyword(s):

Leaf Spot ◽

Morphological Characteristics ◽

Its Region ◽

Pathogenic Fungi ◽

Commonwealth Mycological Institute ◽

Corynespora Cassiicola ◽

Single Spore ◽

First Report ◽

Leaf Spots ◽

Main Vein

Cassava (Manihot esculenta) is an important economic crop in the tropical area of China. During a survey of diseases in July and September of 2009, leaf spots were observed on cassava plants at three separate plantations in Guangxi (Yunfu and Wuming) and Hainan (Baisha) provinces. Circular or irregular-shaped leaf spots were present on more than one-third of the plants. Spots were dark brown or had white papery centers delimited by dark brown rims and surrounded by a yellow halo. Usually, the main vein or small veinlets adjacent to the spots were dark. Some defoliation of plants was evident at the Wuming location. A fungus was isolated from symptomatic leaves from each of the three locations and designated CCCGX01, CCCGX02, and CCCHN01. Single-spore cultures of these isolates were incubated on potato dextrose agar (PDA) for 7 days with a 12-h light/dark cycle at a temperature of 28 ± 1°C. Conidiophores were straight to slightly curved, unbranched, and pale to light brown. Conidia were formed singly or in chains, obclavate to cylindrical, straight or curved, subhyaline-to-pale olivaceous brown, 19.6 to 150.3 μm long and 5.5 to 10.7 μm wide at the base, with 4 to 13 pseudosepta. Morphological characteristics of the specimen and their conidia were similar to the descriptions for Corynespora cassiicola (2). The isolate CCCGX01 was selected as a representative for molecular identification. Genomic DNA was extracted by the cetyltrimethylammoniumbromide protocol (3) from mycelia and used as a template for amplification of the internal transcribed spacer (ITS) region of rDNA with primer pair ITS1/ITS4. The sequence (GenBank Accession No. GU138988) exactly matched several sequences (e.g., GenBank Accession Nos. FJ852715, EF198117, and AY238606) of C. cassiicola (1). Young, healthy, and fully expanded green leaves of cassava cv. SC205 were surface sterilized. Ten leaves were inoculated with 10-μl drops of 104 ml suspension of conidia and five leaves were inoculated with the same volume of sterile water to serve as controls. After inoculation, leaves were placed in a dew and dark chamber for 36 h at 25°C and subsequently transferred to the light for 5 days. All inoculated leaves with isolates showed symptoms similar to those observed in natural conditions, whereas the controls remained symptom free. The morphological characteristics of reisolated conidia that formed on the diseased parts were identical with the nature isolates. To our knowledge, this is the first report of leaf spot caused by C. cassiicola on cassava in China. References: (1) L. J. Dixon et al. Phytopathology 99:1015, 2009. (2) M. B. Ellis et al. Corynespora cassiicola. No. 303 in: CMI Description of Pathogenic Fungi and Bacteria. Commonwealth Mycological Institute, Kew, UK 1971. (3) J. R. Xu et al. Genetics 143:175, 1996.

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First Report of Pestalotiopsis microspora Causing Leaf Spot of Hidcote (Hypericum patulum) in Japan

Plant Disease ◽

10.1094/pdis-94-8-1064b ◽

2010 ◽

Vol 94 (8) ◽

pp. 1064-1064 ◽

Cited By ~ 3

Author(s):

M. Zhang ◽

H. Y. Wu ◽

T. Tsukiboshi ◽

I. Okabe

Keyword(s):

Leaf Spot ◽

Morphological Characteristics ◽

Its Region ◽

Basal Cells ◽

Single Spore ◽

Management Options ◽

First Report ◽

Leaf Spots ◽

Plastic Bags ◽

Pestalotiopsis Microspora

Hidcote, Hypericum patulum Thunb. ex Murray, is a deciduous shrub that is cultivated as an ornamental in landscape gardens and courtyards in Japan. In early August 2008, severe leaf spotting was observed on plants growing in a courtyard in Nasushiobara, Tochigi, Japan. More than 30% of the leaves on five shrubs exhibited leaf spot symptoms. Small, round, pale brown lesions were initially observed. Later, they expanded to 5 to 12 mm in diameter, round to irregular-shaped with pale brown centers and dark brown margins. Under continuously wet or humid conditions, black acervuli developed on the leaf lesions. Conidia were straight or slightly curved, fusiform to clavate, and five-celled with constrictions at the septa. Conidia ranged from 17 to 21 × 5 to 8 μm with hyaline apical and basal cells. Fifteen percent of apical cells had two and the rest had three appendages (setulae) ranging from 10 to 21 μm long. The basal hyaline cell tapered into a 2 to 4 μm pedicel. The three median cells ranged from light or dark brown to olive green. These morphological characteristics matched those of Pestalotiopsis microspora (Speg.) G.C. Zhao & N. Li (1,2). The identity of the fungus was confirmed by DNA sequencing of the internal transcribed spacer (ITS) region (GenBank Accession No. GU908473) from single-spore isolates, which revealed 100% homology with those of other P. microspora isolates (e.g., GenBank Accession Nos. FJ459950 and DQ456865). Koch's postulates were confirmed using leaves of three detached branches of a field-grown asymptomatic plant of H. patulum. Thirty leaves of each branch were inoculated by placing mycelial plugs obtained from the periphery of 7-day-old single-spore cultures on the leaf surface. Potato dextrose agar plugs without mycelium served as controls. Leaves on branches were covered with plastic bags for 24 h to maintain high relative humidity in a greenhouse (approximately 24 to 28°C). After 5 days, all inoculated leaves showed symptoms identical to those described above, whereas control leaves remained symptom free. Reisolation of the fungus from lesions on inoculated leaves confirmed that the causal agent was P. microspora. To our knowledge, this is the first report of leaf spots on H. patulum caused by P. microspora in Japan. Management options may have to be developed and implemented to protect Hidcote plants in areas where leaf spot cannot be tolerated. References: (1) P. A. Saccardo. Sylloge Fungorum III:789, 1884. (2) G. C. Zhao and N. Li. J. Northeast For. Univ. 23(4):21, 1995.

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First Report of a Leaf Spot on Hazel Leaves Caused by Phyllosticta coryli in Liaoning Province of China

Plant Disease ◽

10.1094/pdis-02-13-0213-pdn ◽

2013 ◽

Vol 97 (9) ◽

pp. 1254-1254 ◽

Cited By ~ 10

Author(s):

J. Sun ◽

D.-M. Wang ◽

X.-Y. Huang ◽

Z.-H. Liu

Keyword(s):

Leaf Spot ◽

Control Strategies ◽

Morphological Characteristics ◽

Leaf Tissue ◽

Its Region ◽

Liaoning Province ◽

Single Spore ◽

First Report ◽

Leaf Spots ◽

Microscopic Morphology

Hazel (Corylus heterophylla Fischl) is an important nut tree grown in China, especially in Liaoning Province, and is rich in nutritional and medicinal values. In August 2011, leaf spotting was observed on hybrid hazel (Dawei) leaves in Paotai Town, Wafangdian County of Liaoning Province. By August 2012, the disease had spread to Zhangdang Town, Fushun County. Symptoms initially appeared on both sides of leaves as pinpoint brown spots, which enlarged and developed into regular, dark brown lesions, 3 to 9 mm in diameter. The lesions were lighter in color in the center compared to the margin. To identify the pathogen, leaf pieces (3 to 5 mm) taken from the margins, including both symptomatic and healthy portions of leaf tissue, were surface-disinfected first in 75% ethanol for 5 s, next in 0.1% aqueous mercuric chloride for 50 s, and then rinsed with sterilized water three times. Leaf pieces were incubated on potato dextrose agar (PDA) at 25°C for 14 days in darkness. Single spore isolates were obtained from individual conidia. For studies of microscopic morphology, isolates were grown on synthetic nutrient agar (SNA) in slide cultures. Colonies grew up to 45 to 48 mm in diameter on PDA after 14 days. Pycnidia appeared on the colonies after 12 days. Conidiophores were short. Pycnidia were dark brown, subglobose, and 150 to 205 μm in diameter. Conidia were unicellular, colorless, ovoid to oval, and from 2.4 to 4.5 × 1.6 to 2.4 μm. On the basis of these morphological characteristics, the isolates were tentatively identified as Phyllosticta coryli Westend (2). The rDNA internal transcribed spacer (ITS) region was amplified using primers ITS1 and ITS4 and sequenced (GenBank Accession No. KC196068). The 490-bp amplicons had 100% identity to an undescribed Phyllosticta species isolated from Cornus macrophylla in Gansu, Tianshui, China (AB470897). On the basis of morphological characteristics and nucleotide homology, the isolate was tentatively identified as P. coryli. Koch's postulates were fulfilled in the growth chamber on hazelnut leaves inoculated with P. coryli conidial suspensions (107 conidia ml–1). Eight inoculated 1-year-old seedlings (Dawei) were incubated under moist conditions for 8 to 10 days at 25°C. All leaf spots that developed on inoculated leaves were similar in appearance to those observed on diseased hazel leaves in the field. P. coryli was recovered from lesions and its identity was confirmed by morphological characteristics. P. coryli was first reported as a pathogen of hazel leaves in Bull of Belgium (2). In China, P. coryli was first reported on Corylus heterophylla Fisch. in Jilin Province (1). To our knowledge, this is the first report of P. coryli causing leaf spot on hybrid hazel in Liaoning Province of China. The outbreak and spread of this disease may decrease the yield of hazelnut in northern regions of China. More studies are needed on control strategies, including the possible resistance of hazel cultivars to P. coryli. References: (1) Y. Li et al. J. Shenyang Agric. Univ. 25:153, 1994. (2) P. A. Saccardo. Sylloge Fungorum Vol. III, page 31, 1884.

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First Report of Leaf Spot Disease Caused by Glomerella magna on Lobelia chinensis in China

Plant Disease ◽

10.1094/pdis-03-13-0346-pdn ◽

2013 ◽

Vol 97 (10) ◽

pp. 1383-1383 ◽

Cited By ~ 4

Author(s):

Q. L. Li ◽

J. Y. Mo ◽

S. P. Huang ◽

T. X. Guo ◽

Z. B. Pan ◽

...

Keyword(s):

Leaf Spot ◽

Morphological Characteristics ◽

Its Region ◽

Tween 20 ◽

Leaf Spot Disease ◽

Herbaceous Plant ◽

Single Spore ◽

First Report ◽

Small Water ◽

Perennial Herbaceous Plant

Lobelia chinensis is a perennial herbaceous plant in the family Campanulaceae that is native to China, where it grows well in moist to wet soils. It is commonly used as a Chinese herbal medicine. In May 2012, symptoms of leaf spot were observed on leaves of L. chinensis in Nanning, Guangxi Zhuang Autonomous Region, China. The leaf lesions began as small, water-soaked, pale greenish to grayish spots, which enlarged to gray to pale yellowish spots, 4 to 6 mm in diameter. At later stages, numerous acervuli appeared on the lesions. Acervuli were mostly epiphyllous, and 40 to 196 μm in diameter. On potato dextrose agar (PDA), a fungus was consistently recovered from symptomatic leaf samples, with a 93% isolation rate from 60 leaf pieces that were surface sterilized in 75% ethanol for 30 s and then in 0.1% mercuric chloride for 45 s. Three single-spore isolates were used to evaluate cultural and morphological characteristics of the pathogen. Setae were two to three septate, dark brown at the base, acicular, and up to 90 μm long. Conidia were long oblong-elliptical, guttulate, hyaline, and 11 to 20 × 4.1 to 6.3 μm (mean 15.2 × 5.1 μm). These morphological characteristics of the fungus were consistent with the description of Colletotrichum magna (teleomorph Glomerella magna Jenkins & Winstead) (1). The rDNA internal transcribed spacer (ITS) region of one isolate, LC-1, was sequenced (GenBank Accession No. KC815123), and it showed 100% identity to G. magna, GenBank HM163187.1, an isolate from Brazil cultured from papaya (2). Although KC815123 was identified as G. magna, it shows 99% identity to GenBank sequences from isolates of C. magna, and more research is needed to elucidate the relationships between these taxa, especially with consideration to host specificity. Pathogenicity tests were performed with each of the three isolates by spraying conidial suspensions (1 × 106 conidia/ml) containing 0.1% Tween 20 onto the surfaces of leaves of 30-day-old and 6- to 8-cm-high plants. For each isolate, 30 leaves from five replicate plants were treated. Control plants were treated with sterilized water containing 0.1% Tween 20. All plants were incubated for 36 h at 25°C and 90% relative humidity in an artificial climate chamber, and then moved into a greenhouse. Seven days after inoculation, gray spots typical of field symptoms were observed on all inoculated leaves, but no symptoms were seen on water-treated control plants. Koch's postulates were fulfilled by reisolation of G. magna from diseased leaves. To our knowledge, this is the first report of G. magna infecting L. chinensis worldwide. References: (1) M. Z. Du et al. Mycologia 97:641, 2005. (2) R. J. Nascimento et al. Plant Dis. 94:1506, 2010.

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First report of leaf spot disease caused by Corynespora cassiicola on American sweetgum (Liquidambar styraciflua L.) in China

Plant Disease ◽

10.1094/pdis-08-20-1842-pdn ◽

2021 ◽

Author(s):

Yun-fei Mao ◽

Xiang-rong Zheng ◽

Fengmao Chen

Keyword(s):

Leaf Spot ◽

Morphological Characteristics ◽

Liquidambar Styraciflua ◽

Bootstrap Support ◽

Leaf Spot Disease ◽

Pathogenicity Test ◽

Conidial Suspension ◽

Corynespora Cassiicola ◽

First Report ◽

Leaf Spots

American sweetgum (Liquidambar styraciflua L.) is a forest plant native to North America, which has been introduced into other countries due to its ornamental and medicinal values. In June 2019, symptoms of leaf spots on sweetgum were observed in a field (5 ha) located in Xuzhou, Jiangsu Province, China. On this field, approximately 45% of 1,000 trees showed the same symptoms. Symptoms were observed showing irregular or circular dark brown necrotic lesions approximately 5 to 15 mm in diameter with a yellowish margin on the leaves. To isolate the pathogen, diseased leaf sections (4×4mm) were excised from the margin of the lesion, surface-sterilized with 0.1% NaOCl for 90 s, rinsed 4 times in sterile distilled water, air dried and then transferred on potato dextrose agar (PDA) medium at 25°C in the dark. Pure cultures were obtained by monospore isolation after subculture. Ten purified isolates, named FXI to FXR, were transferred to fresh PDA and incubated as above to allow for morphological and molecular identification. After 7 days, the aerial mycelium was abundant, fluffy and exhibited white to greyish-green coloration. The conidia were dark brown or olive, solitary or produced in chains, obclavate, with 1 to 15 pseudosepta, and measured 45 to 200µm  10 to 18µm. Based on morphological features, these 10 isolates were identified as Corynespora cassiicola (Ellis et al. 1971). Genomic DNA of each isolate was extracted from mycelia using the cetyltrimethylammonium bromide (CTAB) method. The EF-1α gene and ITS region were amplified and sequenced with the primer pairs rDNA ITS primers (ITS4/ITS5) (White et al. 1990) and EF1-728F/EF-986R (Carbone et al.1999) respectively. The sequences were deposited in GenBank. BLAST analysis revealed that the ITS sequence had 99.66% similarity to C. cassiicola MH255527 and that the EF-1α sequence had 100% similarity to C. cassiicola KX429668A. maximum likelihood phylogenetic analysis based on EF-1α and ITS sequences using MEGA 7 revealed that ten isolates were placed in the same clade as C. cassiicola (Isolate: XQ3-1; accession numbers: MH572687 and MH569606, respectively) at 98% bootstrap support. Based on the morphological characteristics and phylogenetic analyses, all isolates were identified as C. cassiicola. For the pathogenicity test, a 10 µl conidial suspension (1×105 spores/ml) of each isolate was dripped onto healthy leaves of 2-year-old sweetgum potted seedlings respectively. Leaves inoculated with sterile water served as controls. Three plants (3 leaves per plant) were conducted for each treatment. The experiment was repeat twice. All seedlings were enclosed in plastic transparent incubators to maintain high relative humidity (90% to 100%) and incubated in a greenhouse at 25°C with a 12-h photoperiod. After 10 days, leaves inoculated with conidial suspension of each isolate showed symptoms of leaf spots, similar to those observed in the field. Control plants were remained healthy. In order to reisolate the pathogen, surface-sterilized and monosporic isolation was conducted as described above. The same fungus was reisolated from the lesions of symptomatic leaves, and its identity was confirmed by molecular and morphological approaches, thus fulfilling Koch’s postulates. Chlorothalonil and Boscalid can be used to effectively control Corynespora leaf spot (Chairin T et al.2017). To our knowledge, this is the first report of leaf spot caused by C. cassiicola on L. styraciflua in China.

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First Report of Myrothecium Leaf Spot of Hemionitis arifolia Caused by Myrothecium roridum in China

Plant Disease ◽

10.1094/pdis-02-11-0124 ◽

2011 ◽

Vol 95 (8) ◽

pp. 1030-1030 ◽

Cited By ~ 4

Author(s):

Y. X. Zhang ◽

J. H. Huang ◽

M. M. Xiang

Keyword(s):

Leaf Spot ◽

Ornamental Plants ◽

Morphological Characteristics ◽

Control Measures ◽

Control Treatment ◽

Chinese Isolate ◽

Single Spore ◽

First Report ◽

Leaf Spots ◽

Myrothecium Roridum

Hemionitis arifolia (Burm.) Moore. was grown commercially as an ornamental plant in China. In January 2010, a new foliar disease with typical leaf spot symptoms was observed on H. arifolia in Dongguan City, Guangdong Province. Approximately 10% of the plants in the Dongguan nursery were affected. Leaf spots were circular to subcircular, dark brown, with distinct concentric zones, and ranged from 10 to 20 mm in diameter. Lesions developed mostly on the lower leaves and black sporodochia with white mycelial tufts were produced mostly in older lesions under high humidity. Single-spore isolates from lesions plated on potato dextrose agar (PDA) produced white, floccose colonies and dark green-to-black sporodochia. Colonies reached 60 mm on PDA at 25°C after 14 days. Conidiophores branched repeatedly. Conidiogenous cells in whorls of two to six on ultimate branches were hyaline, cylindrical, and 13 to 20 × 1.2 to 1.8 μm. Conidia were hyaline, cylindrical, mostly with both rounded ends, occasionally one blunt end, and mean size was 6.1 (4.5 to 7.0) × 2.3 (1.8 to 3.0) μm. These characteristics were consistent with the descriptions of Myrothecium roridum Tode ex Fr. (2–4). The internal transcribed spacer regions including ITS1, ITS2, and the 5.8S rRNA of one isolate were PCR amplified and sequenced. A BLAST search in GenBank revealed highest similarity (99%) to M. roridum sequences from isolates collected from Germany (Accession Nos. AJ302001.1 and AJ301995.1). The M. roridum sequence from the Chinese isolate was submitted to GenBank (Accession No. JF343832). To confirm pathogenicity, five leaves on five H. arifolia plants were inoculated with 5-mm mycelial plugs from the periphery of 7-day-old cultures; sterile PDA plugs were used as the control treatment. Plants were covered with plastic bags and incubated in a growth chamber at 28°C. Necrotic lesions appeared 2 to 3 days after inoculation and the symptoms described above were observed after 7 days on all inoculated leaves, whereas sterile PDA plugs did not produce any leaf lesion. The pathogen was reisolated from the inoculated leaves and confirmed to be M. roridum on the basis of morphological characteristics. There are approximately 271 hosts of M. roridum (1), including many ornamental plants such as salvia (2) and garden hydrangea (3). To our knowledge, this is the first report of Myrothecium leaf spot on H. arifolia. Because the disease caused damage to the foliage and reduced the ornamental value of H. arifolia plants, control measures may need to be implemented for production of this species in ornamental nurseries. References: (1) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrived from http://nt.ars-grin.gov/fungaldatabases/ , 6 February 2011. (2) J. A. Mangandi et al. Plant Dis. 91:772, 2007. (3) M. T. Mmbaga et al. Plant Dis. 94:1266, 2010. (4) M. Tulloch. Mycol. Pap. No. 130. CMI, Wallingford, UK, 1972.

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First Report of Stemphylium solani as the Causal Agent of a Leaf Spot on Greenhouse Cucumber

Plant Disease ◽

10.1094/pdis-08-12-0776-pdn ◽

2013 ◽

Vol 97 (2) ◽

pp. 287-287 ◽

Cited By ~ 5

Author(s):

D. J. Vakalounakis ◽

E. A. Markakis

Keyword(s):

Leaf Spot ◽

Natural Infection ◽

Apical Cell ◽

Morphological Characteristics ◽

Leaf Spot Disease ◽

Pathogenicity Test ◽

Conidial Suspension ◽

Single Spore ◽

Internal Transcribed Spacer Region ◽

First Report

During the 2011 to 2012 crop season, a severe leaf spot disease of cucumber (Cucumis sativus) cv. Cadiz was noticed on crops in some greenhouses in the Goudouras area, Lasithi, Crete, Greece. Symptoms appeared in late winter, mainly on the leaves of the middle and upper part of the plants. Initially, small necrotic pinpoint lesions with white centers, surrounded by chlorotic halos, 1 to 3 mm in diameter, appeared on the upper leaf surfaces, and these progressively enlarged to spots that could coalesce to form nearly circular lesions up to 2 cm or more in diameter. Stemphylium-like fructifications appeared on necrotic tissue of older lesions. Severely affected leaves became chlorotic and died. No other part of the plant was affected. Small tissue pieces from the edges of lesions were surface disinfected in 0.5% NaClO for 5 min, rinsed in sterile distilled water, plated on acidified potato dextrose agar and incubated at 22 ± 0.5°C with a 12-h photoperiod. Stemphylium sp. was consistently isolated from diseased samples. Colonies showed a typical septate mycelium with the young hyphae subhyaline and gradually became greyish green to dark brown with age. Conidiophores were subhyaline to light brown, 3- to 10-septate, up to 200 μm in length, and 4 to 7 μm in width, with apical cell slightly to distinctly swollen, bearing a single spore at the apex. Conidia were muriform, mostly oblong to ovoid, but occasionally nearly globose, subhyline to variant shades of brown, mostly constricted at the median septum, 22.6 ± 6.22 (11.9 to 36.9) μm in length, and 15.1 ± 2.85 (8.3 to 22.6) μm in width, with 1 to 8 transverse and 0 to 5 longitudinal septa. DNA from a representative single-spore isolate was extracted and the internal transcribed spacer region (ITS) of ribosomal DNA (rDNA) was amplified using the universal primers ITS5 and ITS4. The PCR product was sequenced and deposited in GenBank (Accession No. JX481911). On the basis of morphological characteristics (3) and a BLAST search with 100% identity to the published ITS sequence of a S. solani isolate in GenBank (EF0767501), the fungus was identified as S. solani. Pathogenicity tests were performed by spraying a conidial suspension (105 conidia ml–1) on healthy cucumber (cv. Knossos), melon (C. melo, cv. Galia), watermelon (Citrullus lanatus cv. Crimson sweet), pumpkin (Cucurbita pepo, cv. Rigas), and sponge gourd (Luffa aegyptiaca, local variety) plants, at the 5-true-leaf stage. Disease symptoms appeared on cucumber and melon only, which were similar to those observed under natural infection conditions on cucumber. S. solani was consistently reisolated from artificially infected cucumber and melon tissues, thus confirming Koch's postulates. The pathogenicity test was repeated with similar results. In 1918, a report of a Stemphylium leaf spot of cucumber in Indiana and Ohio was attributed to Stemphylium cucurbitacearum Osner (4), but that pathogen has since been reclassified as Leandria momordicae Rangel (2). That disease was later reported from Florida (1) and net spot was suggested as a common name for that disease. For the disease reported here, we suggest the name Stemphylium leaf spot. This is the first report of a disease of cucumber caused by a species of Stemphylium. References: (1) C. H. Blazquez. Plant Dis. 67:534, 1983. (2) P. Holliday. Page 243 in: A Dictionary of Plant Pathology. Cambridge University Press, Cambridge, UK, 1998. (3) B. S. Kim et al. Plant Pathol. J. 15:348, 1999. (4) G. A. Osner. J. Agric. Res. 13:295, 1918.

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