First Report of Leaf Spot of Sweet Basil Caused by Cercospora guatemalensis in Korea

Sweet basil, Ocimum basilicum L., is a fragrant herb belonging to the family Lamiaceae. Originated in India 5,000 years ago, sweet basil plays a significant role in diverse cuisines across the world, especially in Asian and Italian cooking. In October 2008, hundreds of plants showing symptoms of leaf spot with nearly 100% incidence were found in polyethylene tunnels at an organic farm in Icheon, Korea. Leaf spots were circular to subcircular, water-soaked, dark brown with grayish center, and reached 10 mm or more in diameter. Diseased leaves defoliated prematurely. The damage purportedly due to this disease has reappeared every year with confirmation of the causal agent made again in 2011. A cercosporoid fungus was consistently associated with disease symptoms. Stromata were brown, consisting of brown cells, and 10 to 40 μm in width. Conidiophores were fasciculate (n = 2 to 10), olivaceous brown, paler upwards, straight to mildly curved, not geniculate in shorter ones or one to two times geniculate in longer ones, 40 to 200 μm long, occasionally reaching up to 350 μm long, 3.5 to 6 μm wide, and two- to six-septate. Conidia were hyaline, acicular to cylindric, straight in shorter ones, flexuous to curved in longer ones, truncate to obconically truncate at the base, three- to 16-septate, and 50 to 300 × 3.5 to 4.5 μm. Morphological characteristics of the fungus were consistent with the previous reports of Cercospora guatemalensis A.S. Mull. & Chupp (1,3). Voucher specimens were housed at Korea University herbarium (KUS). An isolate from KUS-F23757 was deposited in the Korean Agricultural Culture Collection (Accession No. KACC43980). Fungal DNA was extracted with DNeasy Plant Mini DNA Extraction Kits (Qiagen Inc., Valencia, CA). The complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced. The resulting sequence of 548 bp was deposited in GenBank (Accession No. JQ995781). This showed >99% similarity with sequences of many Cercospora species, indicating their close phylogenetic relationship. Isolate of KACC43980 was used in the pathogenicity tests. Hyphal suspensions were prepared by grinding 3-week-old colonies grown on PDA with distilled water using a mortar and pestle. Five plants were inoculated with hyphal suspensions and five plants were sprayed with sterile distilled water. The plants were covered with plastic bags to maintain a relative humidity of 100% for 24 h and then transferred to a 25 ± 2°C greenhouse with a 12-h photoperiod. Typical symptoms of necrotic spots appeared on the inoculated leaves 6 days after inoculation, and were identical to the ones observed in the field. C. guatemalensis was reisolated from symptomatic leaf tissues, confirming Koch's postulates. No symptoms were observed on control plants. Previously, the disease was reported in Malawi, India, China, and Japan (2,3), but not in Korea. To our knowledge, this is the first report of C. guatemalensis on sweet basil in Korea. Since farming of sweet basil has recently started on a commercial scale in Korea, the disease poses a serious threat to safe production of this herb, especially in organic farming. References: (1) C. Chupp. A Monograph of the Fungus Genus Cercospora. Ithaca, NY, 1953. (2) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology & Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , May 5, 2012. (3) J. Nishikawa et al. J. Gen. Plant Pathol. 68:46, 2002.

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First Report of Leaf Spot Caused by Cercospora fukushiana on New Guinea Impatiens in Korea

Plant Disease ◽

10.1094/pdis-04-14-0363-pdn ◽

2014 ◽

Vol 98 (9) ◽

pp. 1280-1280

Author(s):

B. S. Kim ◽

K. S. Baek ◽

C. H. Pak ◽

J. H. Park ◽

H. D. Shin

Keyword(s):

Leaf Spot ◽

Morphological Characteristics ◽

Its Region ◽

New Guinea ◽

Culture Collection ◽

Distilled Water ◽

First Report ◽

Leaf Spots ◽

Plastic Bags ◽

New Guinea Impatiens

New Guinea impatiens, Impatiens hawkeri W. Bull, is widely cultivated as a potted plant and garden plant. In July 2013, hundreds of young plants (cv. Fanfare) showing symptoms of leaf spot with approximately 50% incidence were found in polyethylene tunnels in Yongin City, Korea. Leaf spots were circular to oblong, reaching 6 mm or more in diameter. The spots were initially uniformly brown to reddish brown, turning gray with reddish brown margin. Diseased plants defoliated prematurely and were abandoned without marketing due to signs of discoloration and yellowing on leaves. A cercosporoid fungus was consistently observed in association with disease symptoms. Stromata were brown, small, and composed of a few swollen hyphal cells. Conidiophores were emerging through the cuticle, fasciculate (n = 2 to 20), olivaceous to brown, paler toward the apex, straight to mildly curved, geniculate, 30 to 260 μm long, 3.5 to 5 μm wide, 1- to 6-septate, and with conspicuous conidial scars. Conidia were hyaline and acicular. Smaller conidia were straight and longer conidia were mildly curved. Conidia were subacute to obtuse at the apex, truncate to obconically truncate at the base, 2- to 18-septate, 30 to 320 × 3.5 to 5.5 μm, and with thickened, darkened hila at the base. Morphological characteristics of the fungus were consistent with the previous reports of Cercospora fukushiana (Matsuura) W. Yamam. (1). Voucher specimens were housed in the Korea University herbarium (KUS). An isolate from KUS-F27438 was deposited in the Korean Agricultural Culture Collection (Accession No. KACC47640). Fungal DNA was extracted with DNeasy Plant Mini Kits (Qiagen Inc., Valencia, CA). The complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 (4) and sequenced. The resulting sequence of 497 bp was deposited in GenBank (Accession No. KJ620981). This showed >99% similarity with sequence of C. fukushiana (EF600954) on I. balsamina from Korea. Isolate of KACC47640 was used in the pathogenicity tests. Hyphal suspensions were prepared by grinding 3-week-old colonies grown on PDA with distilled water using a mortar and pestle. Five plants were inoculated with hyphal suspensions and five plants were sprayed with sterile distilled water. The plants were covered with plastic bags to maintain a relative humidity of 100% for 24 h and then transferred to a 25 ± 2°C greenhouse with a 12-h photoperiod. Typical symptoms of necrotic spots appeared on the inoculated leaves 10 days after inoculation, and were identical to the symptoms observed in the field. C. fukushiana was re-isolated from symptomatic leaf tissues, confirming Koch's postulates. No symptoms were observed on water-inoculated control plants. Previously, leaf spots of Impatiens spp. associated with C. apii, C. balsaminae, and C. fukushiana have been reported (1,2,3). To our knowledge, this is the first report of C. fukushiana on I. hawkeri in Korea. Our observations in the nurseries of I. hawkeri suggest that low humidity with good ventilation as well as plant hygiene in greenhouses might be main strategies for preventing this disease. References: (1) C. Chupp. A Monograph of the Fungus Genus Cercospora. Ithaca, NY, 1953. (2) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab., online publication, ARS, USDA, retrieved March 25, 2014. (3) J. M. Soares et al. Plant Dis. 93:1214, 2009. (4) 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 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 of Weigela florida Caused by Epicoccum layuense in China

Plant Disease ◽

10.1094/pdis-07-20-1498-pdn ◽

2021 ◽

Author(s):

Yue Tian ◽

Yingying Zhang ◽

Chaodong Qiu ◽

Zhenyu Liu

Keyword(s):

Leaf Spot ◽

Large Subunit ◽

Morphological Characteristics ◽

Likelihood Method ◽

Pathogenicity Test ◽

Distilled Water ◽

Beta Tubulin ◽

First Report ◽

Leaf Spots ◽

Weigela Florida

Weigela florida (Bunge) A. DC. is a dense, rounded, deciduous shrub commonly planted in landscapes. It is also used in Chinese medicine to treat sore throat, erysipelas, cold, and fever (Zheng et al. 2019). In May 2019, leaf spots were observed on approximately 50% of W. florida plants grown in the Wisdom Plaza Park of Anhui Agricultural University in Hefei, Anhui Province, China. Leaf spots begun as small light brown and irregular lesions, enlarged, turned reddish brown, coalesced to form large blighted areas, and eventually covered the entire leaf surface. Five pieces of tissues were removed from the lesion margins of each diseased leaf (five leaves from five different plants), chopped into several 3-4 mm2 pieces, disinfected with 1.5% NaOCl for 2 min, rinsed 3 times with sterile distilled water for 1 min, plated onto Potato Dextrose Agar (PDA) medium containing 50 μg/ml of ampicillin and kanamycin, and incubated at 25°C with a 12-hour photoperiod for 5 days. One segment of the fungal growth from the growing edge of the colony was transferred onto a fresh PDA plate for purification and incubated under the same conditions for another 5 days. The colony morphology of one representative isolate (AAU0519) was characterized by a pale orange cushion in the center surrounded by irregular pink margin, diffusing red orange pigments into the PDA medium. Isolate AAU0519 was cultured on PDA medium for 7 days at 25°C in the dark to induce sporulation. The produced conidia were globose, subglobose to pyriform, golden brown to brown, and with a diameter of 7.7 - 23.8 μm. Both cultural and morphological characteristics suggested that isolate AAU0519 was an Epicoccum species, according to the description by Chen et al. 2017. Amplification and sequencing of the internal transcribed spacer (ITS), beta-tubulin, and 28S large subunit ribosomal RNA (LSU) gene fragments from the extracted genomic DNA of AAU0519 were performed using primer sets ITS1/ITS4 (White et al. 1990), Bt2a/Bt2b (Glass and Donaldson 1995), and LSU1Fd/LR5 (Crous et al. 2009; Vilgalys and Hester 1990), respectively. A phylogenetic tree was constructed by the maximum-likelihood method with 1,000 bootstrapping replications based on the concatenated ITS, beta-tubulin, and LSU sequences from isolate AAU0519 and representative strains of 22 species of the genus Epicoccum (Chen et al. 2017). Isolate AAU0519 clustered with ex-holotype CGMCC 3.18362 of Epicoccum layuense Qian Chen, Crous & L. Cai (Chen et al. 2017). All obtained sequences were deposited into GenBank under accession numbers MK983497 (ITS), MN328723 (beta-tubulin), and MN328724 (LSU). A pathogenicity test was conducted on leaves of five 3-year-old W. florida cultivar “Red Prince” planted in the field (five leaves for each treatment and control per plant) by spraying 30 ml of a spore suspension (106 spores/ml) of isolate AAU0519 as treatment or sterilized distilled water as control. Before the inoculation, the leaves were disinfected with 70% ethanol. After inoculation, the leaves were wrapped with a plastic bag to keep high relative humidity. The average air temperature was about 28°C during the period of pathogenicity test. The experiment was repeated once. Ten days after inoculation, the fungal-inoculated leaves developed light brown lesions resembling those of naturally infected leaves, control leaves did not develop any symptoms. E. layuense was recovered from leaf lesions and its identity was confirmed by morphological and sequence analyses as described above. To our knowledge, E. layuense has been previously reported as a pathogen of Perilla sp. (Chen et al. 2017), oat (Avena sativa) (Chen et al. 2019), and tea (Camellia sinensis) plants (Chen et al. 2020), but this is the first report of E. layuense causing leaf spot on W. florida in China. This pathogen could pose a threat to the ornamental value of W. florida plants. Thus, it is necessary to adopt effective management strategies against leaf spot on W. florida.

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First Confirmed Report of Cercospora Blight of Asparagus Caused by Cercospora asparagi in Korea

Plant Disease ◽

10.1094/pdis-10-12-0984-pdn ◽

2013 ◽

Vol 97 (3) ◽

pp. 428-428 ◽

Cited By ~ 4

Author(s):

K. S. Han ◽

B. S. Kim ◽

J. H. Park ◽

H. D. Shin

Keyword(s):

Morphological Characteristics ◽

Its Region ◽

Culture Collection ◽

Asparagus Officinalis ◽

Organic Farm ◽

Plastic Bags ◽

Japanese Workers ◽

Close Phylogenetic Relationship ◽

Voucher Specimens ◽

Pathogenicity Tests

In September 2011, hundreds of asparagus (Asparagus officinalis L.) showing symptoms of blight with nearly 100% incidence (percentage of plants affected) were found in polyethylene tunnels at an organic farm in Gangneung City of Korea. Lesions on needles and branches of the ferns were small, elliptic to subcircular, pale tan to brown with reddish brown borders, and became gray and cottony due to heavy sporulation under continuous high humidity. Infection caused premature defoliation and weakened plant vigor. The damage purportedly due to this disease has reappeared with confirmation of the causal agent made again in 2012. A cercosporoid fungus was consistently associated with disease symptoms. Stromata were well developed, consisting of brown cells, and were 10 to 30 μm wide. Conidiophores were fasciculate (n = 2 to 12), olivaceous brown, paler upwards, straight to mildly curved, not geniculate in shorter ones, or 1 to 2 times geniculate in longer ones, 40 to 260 μm long, 3.5 to 5.5 μm wide, and 1- to 6-septate. Conidia were hyaline, cylindric to acicular, straight in shorter ones, curved in longer ones, truncate to obconically truncate at the base with darkened hila, guttulate, 2- to 12-septate, and 40 to 220 × 3 to 5 μm. Morphological characteristics of the fungus were consistent with the previous reports of Cercospora asparagi Sacc. (1). Voucher specimens were housed at the Korea University herbarium (KUS). An isolate from KUS-F26046 was deposited in the Korean Agricultural Culture Collection (Accession No. KACC46400). The complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced. The resulting sequence of 497 bp was deposited in GenBank (Accession No. JX964995). This showed >99% similarity with sequences of many Cercospora species, indicating their close phylogenetic relationship. For pathogenicity tests, conidial suspensions (105 conidia/ml) were prepared by culturing the fungus on V8 juice agar (2) for 3 weeks. Five plants were inoculated with conidial suspensions and five plants were sprayed with sterile distilled water. The plants were covered with plastic bags to maintain 100% RH for 24 h and then transferred to a greenhouse. Typical symptoms of necrotic lesions appeared on the inoculated plants 6 days after treatment, and were identical to the ones observed in the field. C. asparagi was reisolated from symptomatic tissues, confirming Koch's postulates. No symptoms were observed on control plants. The disease has been reported through the regions of the world where asparagus is grown (3). In Korea, the disease was recorded in 1928 by Japanese workers under Cercosporina asparagicola Speg. (regarded as synonymous with Cercospora asparagi) with brief notes (4). Though one sample of asparagus was sent to the author (KSH) for diagnosis in 2009 summer and determined to be infected with C. asparagi (unpublished data), there has been no additional finding of the disease in Korea for the last 82 years. To our knowledge, this is the first confirmed report of Cercospora blight of asparagus caused by C. asparagi in Korea. References: (1) C. Chupp. A Monograph of the Fungus Genus Cercospora. Ithaca, NY, 1953. (2) C. J. Cooperman and S. F. Jenkins. Phytopathology 76:617, 1986. (3) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab., Online publication, ARS, USDA, Retrieved October 20, 2012. (4) K. Nakata and S. Takimoto. Bull. Agric. Exp. Stat. Korea 15:1, 1928.

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First Report of Bipolaris peregianensis Causing Leaf Spot of Cynodon dactylon in China

Plant Disease ◽

10.1094/pdis-12-11-1066-pdn ◽

2012 ◽

Vol 96 (6) ◽

pp. 917-917 ◽

Cited By ~ 2

Author(s):

Z. Y. Wang ◽

S. N. Xie ◽

Y. Wang ◽

H. Y. Wu ◽

M. Zhang

Keyword(s):

Leaf Spot ◽

Cynodon Dactylon ◽

Control Strategies ◽

Tap Water ◽

Morphological Characteristics ◽

Its Region ◽

Basal Cells ◽

First Report ◽

Leaf Spots ◽

Plastic Bags

Cynodon dactylon is widely cultivated as a sod crop in warm climates worldwide. In early September 2009, heavy leaf spot infection was observed on C. dactylon from Zhengzhou, Henan, China. Early symptoms appeared as small, elliptical, pale brown lesions on the leaves. Lesions later expanded to 5 to 10 mm long and 1 to 2 mm wide, becoming brown to dark brown. A fungus was consistently isolated from leaf spots on potato dextrose agar (PDA), but with poor sporulation. Morphological characteristics were observed from single-conidium cultures on tap water agar + wheat straw (TWA+W) after 5 to 7 days. Conidiophores were light to medium brown, cylindrical, solitary or clustered, unbranched, usually with basal cells enlarged, and 94.5 to 147.0 × 4.0 to 9.0 μm. Conidia were fusoid, strongly curved, end cells broadly hemiellipsoidal, brown, 58.5 to 84.5 × 13.5 to 18.5 μm, with 6 to 10 septa. These morphological characteristics are similar to those of Bipolaris peregianensis (2). The identity of our fungus was confirmed to be B. peregianensis by DNA sequencing of the internal transcribed spacer (ITS) region (GenBank Accession No. JQ316121), which was 99% homologous to those of other B. peregianensis isolates (= Cochliobolus peregianensis; Accession Nos AF071328 and AF158111) (1). Koch's postulates were performed with the leaves of three pots of C. dactylon. Leaves were sprayed with 1 × 105 conidia/ml of B. peregianensis; an equal number of leaves in the pots of the same plant sprayed with sterile distilled water served as the control. All test plants were covered with plastic bags for 24 h to maintain high relative humidity at 23 to 25°C. After 7 days, more than 50% of inoculated leaves showed symptoms identical to those observed in natural condition, whereas controls remained symptom free. Reisolation of the fungus from lesions on inoculated leaves confirmed that the causal agent was B. peregianensis. To our knowledge, this is the first report of leaf spots caused by B. peregianensis on C. dactylon in China. The disease cycle and the control strategies in the regions are being further studied. References: (1) M. L. Berbee et al. Mycologia 91:964, 1999. (2) A. Sivanesan. Mycol. Pap. 158:1, 1987.

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First Report of Corynespora Leaf Spot Caused by Corynespora cassiicola on Gynura in China

Plant Disease ◽

10.1094/pdis-12-13-1284-pdn ◽

2014 ◽

Vol 98 (7) ◽

pp. 1007-1007 ◽

Cited By ~ 1

Author(s):

B. J. Li ◽

J. X. Chuan ◽

M. Yang ◽

G. F. Du

Keyword(s):

Leaf Spot ◽

Disease Incidence ◽

Morphological Characteristics ◽

Its Region ◽

Leaf Spot Disease ◽

Herbaceous Plant ◽

Distilled Water ◽

Corynespora Cassiicola ◽

Single Spore ◽

First Report

Gynura (Gynura bicolor DC.) is a perennial herbaceous plant in the family Compositae. It is an important Chinese vegetable, and is commonly used as a Chinese herbal medicine. In 2010, a severe leaf spot disease was observed on gynura grown in the main production areas in Tong Nan County, Chongqing City, China. Some farms experienced 60% disease incidence. Symptoms usually began on the lower leaves, as circular to elliptical or irregular spots with concentric rings. Individual spots were dark brown with grayish centers, sometimes coalescing and leading to extensive necrosis. The fungus associated with lesions was characterized as follows: Conidiophores were single or in clusters, straight or flexuous, unbranched, percurrent, cylindrical, pale to dark brown, 87.5 to 375.0 μm long and 5.0 to 10.5 μm wide. Conidia were solitary or catenate, straight to slightly curved, obclavate to cylindrical, 3 to 14 pseudoseptate, 82.8 to 237.5 μm long and 7.0 to 7.8 μm wide, and pale brown. The morphological characteristics of the conidia and conidiophores agreed with the descriptions for Corynespora cassiicola (1). To isolate the causal pathogen, surface-sterilized tissue at the margin of lesions was immersed in 75% ethanol for 30 s, rinsed in sterile water, dried in a laminar flow bench, transferred to PDA, and incubated at 28°C. Four single-spore cultures of the isolates were obtained and named from ZBTK10110637 to ZBTK10110640. All strains were identified as C. cassiicola. The isolate ZBTK10110637 was selected as representative for molecular identification. Genomic DNA was extracted by CTAB (2). The internal transcribed spacer (ITS) region of the rDNA was amplified using primers with ITS1 (5′-TCCGATGGTGAACCTGCGG-3′) and ITS4 (5′-TCCTCCGCTTATTGATATGC-3′). Amplicons were 433 bp (GenBank Accession No. JX867272) and shared 100% similarity with that of C. cassiicola (NRC2-1 No. AB539285.1). To confirm pathogenicity, four isolates were used to inoculate 12 gynura plants (6 weeks old) by mist spray-inoculation with 108 spores/ml suspension in sterile distilled water on the leaves. Control plants were misted with sterile distilled water. After inoculation, all plants were incubated in a greenhouse maintained at 20 to 28°C with relative humidity of 80 to 85%. Five days after inoculation, dark brown spots with a grayish center typical of field symptoms were observed on all inoculated plants. No symptoms were seen on water-treated control plants. The fungus was re-isolated from inoculated plants. The morphological characteristics of isolates were identical with the pathogen recovered originally. This is the first report of C. cassiicola on gynura. References: (1) M. B. Ellis. CMI Mycological Papers 65(9):1-15, 1957. (2) 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 a Leaf Spot on Pepper Caused by Cladosporium oxysporum in China

Plant Disease ◽

10.1094/pdis-04-12-0323-pdn ◽

2012 ◽

Vol 96 (7) ◽

pp. 1072-1072 ◽

Cited By ~ 2

Author(s):

X.-Y. Huang ◽

Z.-H. Liu ◽

J.-X. Hu ◽

S.-W. Wang ◽

Y. Zou ◽

...

Keyword(s):

Leaf Spot ◽

Morphological Characteristics ◽

Its Region ◽

Liaoning Province ◽

Morphological Description ◽

Hot Pepper ◽

Malt Extract ◽

First Report ◽

Leaf Spots ◽

Microscopic Morphology

Pepper (Capsicum annuum L.) is an important vegetable crop grown in Liaoning Province of China. In June 2009, leaf spotting was observed on hot pepper cv. 37-74 in Wafangdian County of Liaoning Province. By August 2011, the disease had spread to Pulandian and Donggang Counties. Symptoms initially appeared on both sides of leaves as pinpoint chlorotic spots that enlarged and developed into irregular, brown lesions, 1 to 8 mm in diameter. To identify the pathogen, leaf pieces (3 to 5 mm) taken at the edge of lesions with both infected and healthy portions were surface disinfected by placing them in 75% ethanol for 5 s, then transferred to a 0.1% aqueous mercuric chloride solution for 30 s and rinsed with sterilized water three times. The sections were placed on potato dextrose agar (PDA) at 25°C in the dark. Ten pure fungal cultures were obtained from single spores. For growth rate determination and morphological description of colonies, single conidial isolates were inoculated on PDA, malt extract agar (MEA), and oatmeal agar (OA), and incubated at 25°C for 14 days in darkness. For studies of microscopic morphology, isolates were grown on synthetic nutrient agar (SNA) in slide cultures. Colonies grew up to 77 to 80 mm in diameter on PDA, 62 to 66 mm on MEA, and 58 to 60 mm on OA after 14 days. Conidiophores were straight to slightly flexuous. Conidia ranged in shape from subglobose or ovoid to subcylindrical. Macronematous conidiophores measured 40 to 670 × 3 to 5.5 μm with swellings, micronematous conidiophores 15 to 137 × 1.5 to 3.5 μm, terminal conidia 2 to 4 × 2 to 3 μm, and intercalary conidia 4 to 10 × 2.5 to 4 μm. Ramoconidia were rarely observed. Secondary ramoconidia were zero- to one-septate and measured 5.2 to 14.8 × 2.4 to 4 μm. On the basis of these characteristics, the isolates were identified as Cladosporium oxysporum (1). The internal transcribed spacer (ITS) region from isolate W10-02 was amplified using primers ITS1 and ITS4 and sequenced (GenBank Accession No. JQ775499). The 525-bp amplicons had 99% identity to C. oxysporum (GenBank Accession No. EF029816). On the basis of morphological characteristics and nucleotide homology, the isolate was identified as C. oxysporum. Koch's postulates were fulfilled in the laboratory on pepper leaves inoculated with C. oxysporum conidial suspensions (107 conidia ml–1). Eight inoculated 4-week-old seedlings 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 pepper in the field. C. oxysporum was reisolated from lesions and its identity was confirmed by morphological characteristics. C. oxysporum was first reported as a pathogen of pepper in the Sultanate of Oman (2). To our knowledge, this is the first report of C. oxysporum causing leaf spot on pepper in China. The outbreak and spread of this disease may decrease the yield of pepper in the northern regions of China. More studies are needed on the management strategy including the resistance of pepper cultivars against C. oxysporum. References: (1) K. Bensch et al. 2010. Stud. Mycol. 67:1, 2010. (2) A. M. Hammouda. Plant Dis. 76:536, 1992.

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First Report of Leaf Spot Caused by Pseudocercospora subsessilis on Melia azedarach in Korea

Plant Disease ◽

10.1094/pdis-10-12-1004-pdn ◽

2013 ◽

Vol 97 (7) ◽

pp. 993-993

Author(s):

S. T. Seo ◽

C. H. Shin ◽

J. H. Park ◽

H. D. Shin

Keyword(s):

Leaf Spot ◽

Morphological Characteristics ◽

Its Region ◽

The United States ◽

Melia Azedarach ◽

Leaf Spot Disease ◽

Limiting Factor ◽

First Report ◽

Leaf Spots ◽

White Leaf

Melia azedarach L., called chinaberry, is native to Southeast Asia and Australia. The trees are commonly planted as ornamentals in the southern part of Korea. In October 2010, a leaf spot disease was observed on trees for the first time in Wando, Korea. Further surveys conducted from 2010 to 2012 showed that the disease occurs on trees in Jeju, Seogwipo, and Tongyeong cities as well as Wando county with nearly 100% incidence. Leaf spots were circular to semicircular, later becoming angular, small, pale brown in the center with a dark brown margin, and later becoming milky white. Leaf spots sometimes coalesced to blight the entire leaf and were capable of rapidly defoliating whole trees in late September. Fruiting was amphigenous, but mostly hypogenous. Stromata were substomatal, globular, dark brown, and 25 to 70 μm in diameter. Conidiophores were densely fasciculate, pale olivaceous to pale brown, substraight to mildly curved, not geniculate, 10 to 30 μm long, 2.5 to 4.5 μm wide, and aseptate or uniseptate. Conidia were pale olivaceous, generally darker than conidiophores, cylindric to obclavate, substraight in shorter ones, curved to mildly sinuous in longer ones, obconically truncate at the base, obtuse at the apex, 2- to 14-septate, 16 to 120 × 3 to 5 μm, guttulate, and had inconspicuous hila. Morphological characteristics of the fungus were consistent with the previous descriptions of Pseudocercospora subsessilis (Syd. & P. Syd.) Deighton (2). Voucher specimens (n = 6) were deposited in the Korea University Herbarium (KUS). An isolate from KUS-F25395 was deposited in the Korean Agricultural Culture Collection (KACC45688). The complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 (3) and sequenced. The resulting sequence of 517 bp was deposited in GenBank (Accession No. JX993904). A BLAST search in GenBank revealed that the sequence shows >99% similarity (1 bp substitution) with a sequence of P. subsessilis ex M. azedarach from Cuba (GU269815). For pathogenicity tests, hyphal suspensions were prepared by grinding 3-week-old colonies grown on potato dextrose agar with distilled water using a mortar and pestle. Five 3-year-old chinaberry trees were inoculated with hyphal suspensions using a fine haired paint brush. Three healthy trees of the same age, serving as controls, were sprayed with sterile water. The plants were covered with plastic bags to maintain 100% relative humidity for 24 h and then transferred to a greenhouse. Typical symptoms of necrotic spots that appeared on the inoculated leaves 10 days after inoculation were identical to the ones observed in the field. P. subsessilis was reisolated from symptomatic leaf tissues, confirming Koch's postulates. No symptoms were observed on control plants. The disease has been reported in several Asian countries as well as in Cuba and the United States (1). To our knowledge, this is the first report of leaf spot on chinaberry caused by P. subsessilis in Korea. The observed high incidence and severity suggest that this disease can be a limiting factor in utilizing this tree species as ornamentals in public areas. References: (1) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab., Online publication, ARS, USDA, Retrieved October 22, 2012. (2) Y. L. Guo and W. H. Hsieh. The genus Pseudocercospora in China. International Academic Publishers, Beijing, China, 1995. (3) T. J. White et al. PCR Protocols. Academic Press, San Diego, CA, 1990.

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