scholarly journals First Report of Target Leaf Spot Caused by Corynespora cassiicola on Cowpea in China

Plant Disease ◽  
2014 ◽  
Vol 98 (10) ◽  
pp. 1427-1427
Author(s):  
J.-T. Li ◽  
S.-X. Mo ◽  
H.-B. Fu
Keyword(s):  
Leaf Spot ◽  
Its Region ◽  
American Samoa ◽  
Control Measures ◽  
Corynespora Cassiicola ◽  
Sterile Water ◽  
First Report ◽  
Humidity Chamber ◽  
Causal Pathogen ◽  
Its1 And Its2

Cowpea (Vigna unguiculata L.) is an important economic vegetable and is widely planted in China. During a survey of diseases in May 2009, a new leaf disease incited by the fungus Corynespora cassiicola was observed on cowpea growing in greenhouses in Shouguang city, Shandong Province, China. Circular lesions of different sizes were present on approximately 40% of the plants. Lesions were round with grayish brown centers surrounded by brownish concentric rings and ranged from 1 to 13 mm in diameter. Leaves with many lesions resulted in chlorosis, wilt, and defoliation. Yellow disk was observed on lesion edges of partly infected leaves. Abundant conidia and conidiophores appeared on the abaxial surface of leaves. To identify the causal pathogen, pieces of tissue from the leading border of lesions were sterilized in 75% ethanol for 1 min, rinsed in sterile water, transferred to potato dextrose agar (PDA), and then incubated at 28°C in an incubator. Colonies grew to 60 mm and were gray in color after 7 days. Conidiophores were straight and unbranched, pale or dark brown, and 63 to 211 × 4 to 8 μm. Conidia were born singly or in chains, obclavate or cylindrical, brown or olivaceous, 33 to 97 × 5 to 11 μm. Based on the above characteristics, the fungus was similar to C. cassiicola (Berk. & M.A. Curtis.) C.T. Wei (2). The internal transcribed spacer (ITS) region of rDNA was amplified using primers ITS1 and ITS2 and deposited in GenBank (Accession No. KC894915). A BLAST search in GenBank indicated precise match for a sequence of C. cassiicola from cowpea in American Samoa (1). To satisfy Koch's postulates, 20 one-month-old seedlings of cowpea were sprayed with a spore suspension (1 × 105 spores/ml) of one isolate of C. cassiicola until runoff. Another 20 seedlings, sprayed with sterile water, served as non-inoculated controls. Plants were placed in a humidity chamber at 28°C for 12 h and then transferred to a growth chamber at 28°C. Symptoms similar to those described above appeared after 7 days on inoculated plants; however, no symptoms were observed on non-inoculated controls. C. cassiicola was re-isolated from inoculated plants. The pathogen can cause diseases on a number of plants and lead to losses. In China, this pathogen has previously been recorded on about 20 genera of plants. It also included V. sinensis (3), a close plant with V. unguiculata. However, to our knowledge, this is the first report of target leaf spot caused by C. cassiicola on cowpea (V. unguiculata) in China. Control measures may be needed to manage the disease. References: (1) L. J. Dixon et al. Phytopathology 99:1015, 2009. (2) M. B. Ellis. CMI Mycol. Pap. No. 65, 1957. (3) F. L. Tai. Sylloge Fungorum Sinicorum. Science Press, Beijing, 1979.

scholarly journals First Report of Target Leaf Spot Caused by Corynespora cassiicola on Balsam Pear in China

Plant Disease ◽  
2010 ◽  
Vol 94 (1) ◽  
pp. 127-127 ◽  
Author(s):  
B.-J. Li ◽  
Y.-J. Zhao ◽  
W. Gao ◽  
Y.-X. Shi ◽  
X.-W. Xie
Keyword(s):  
Leaf Spot ◽  
Its Region ◽  
Potato Dextrose Agar ◽  
Corynespora Cassiicola ◽  
Sterile Water ◽  
Exact Match ◽  
First Report ◽  
Humidity Chamber ◽  
Plant Pathol ◽  
Dark Green

Balsam pear (Momordica charantia L.) is an economically important vegetable in China with increasing interest as a medicinal plant. In December of 2006, a new foliar disease caused by Corynespora cassiicola was observed on balsam pear growing in greenhouses in Shouguang City, Shandong Province, China. The disease occurred on 35% or less of the plants. Leaves of affected plants developed off-white halos surrounding circular lesions that were 1 to 5 mm broad. The lesions became dark brown, necrotic with concentric rings, and up to 15 mm in diameter. Severely affected plants eventually wilted and defoliated. Pieces of tissue from the leading edges of lesions were disinfected in 1% NaOCl for 1 min, rinsed in sterile water, and plated on potato dextrose agar. Colonies of the fungus were gray to dark green. Conidiophores were erect and simple, pale brown to brown, and 100 to 450 μm long and 3 to 8 μm wide. Conidia were obclavate to cylindrical, pale olivaceous brown to dark brown, smooth, 35 to 100 × 8 to 12 μm, and were produced in chains. On the basis of these characteristics, the fungus was identified as Corynespora cassiicola (1). The internal transcribed spacer (ITS) region of rDNA was amplified with primers ITS1/ITS4 and deposited in GenBank (Accession No. GQ381292). It was an exact match for a sequence of C. cassiicola previously deposited (Accession No. EU364555). To confirm pathogenicity, 30 1-month-old healthy seedlings of balsam pear were inoculated by spraying a suspension of conidia (1 × 105 conidia per ml) of one isolate of C. cassiicola until runoff. Ten seedlings were sprayed with sterile water as controls. Plants were kept in a humidity chamber at 27°C overnight and then placed in a growth chamber at 27°C. After 7 days, symptoms identical to those described above were observed, while no symptoms developed on the control plants. The pathogen was reisolated from inoculated leaves. C. cassiicola causes foliar diseases on many plants, including tomato, eggplant, soybean, and cucumber (2). There is one report on balsam pear in Korea (3). To our knowledge, this is the first report of target leaf spot caused by C. cassiicola on balsam pear in China. References: (1) M. B. Ellis. CMI Mycol. Pap. No. 65, 1957. (2) M. B. Ellis et al. CMI Mycol. Pap. No. 303, 1971. (3) J. H. Kwon et al. Plant Pathol. J. 21:164, 2005.

scholarly journals First Report of Leaf Spot on Tibouchina semidecandra Caused by Beltrania rhombica in China

Plant Disease ◽  
2012 ◽  
Vol 96 (9) ◽  
pp. 1380-1380 ◽  
Author(s):  
Z. R. Shi ◽  
M. M. Xiang ◽  
Y. X. Zhang ◽  
J. H. Huang
Keyword(s):  
Leaf Spot ◽  
Its Region ◽  
Control Measures ◽  
Control Treatment ◽  
Sterile Water ◽  
Single Spore ◽  
First Report ◽  
Potted Plants ◽  
Detached Leaves

Tibouchina semidecandra Cogn. is a popular ornamental plant in tropical and subtropical areas (1). In August 2011, a leaf spot was observed on approximately 70% of 5,000 potted plants of T. semidecandra in a nursery in Zhongshan, Guangdong Province, China. Each leaf spot was round with a brown center surrounded by a reddish brown border, and ranged from 8 to 10 mm in diameter. A fungus was isolated consistently from the lesions by surface-sterilizing symptomatic leaf sections (each 3 cm2) with 75% alcohol for 8 s, washing the sections with sterile water, soaking the sections in 3% NaOCl for 15 s, rinsing the sections with sterile water three times, and then placing the sections on potato dextrose agar (PDA) at 28°C. Each of three single-spore isolates on PDA produced gray, floccose colonies that reached 70 mm in diameter after 5 days at 28°C. Setae were dark brown, straight, erect, distantly and inconspicuously septate, and 125 to 193 × 3.0 to 4.5 μm. Conidiophores were light brown, cylindrical, simple or sometimes branched at the base, and 105 to 202 × 3 to 5 μm. Separating cells were hyaline, oval, and 12 to 13 × 4 to 5 μm. Conidia were unequally biconic, unicellular, dark brown with a pale brown or subhyaline band just above the widest part, and 26 to 31 × 8.5 to 12 μm (mean 27.3 × 10.6 μm) with a conspicuous appendage at the apex that was 6 to 14 × 1 to 1.8 μm. These characteristics were consistent with the description of Beltrania rhombica Penz. (3). The internal transcribed spacer (ITS) region of the ribosomal DNA (rDNA) of one isolate (GenBank Accession No. JN853777) was amplified using primers ITS4 and ITS5 (4) and sequenced. A BLAST search in GenBank revealed 97% similarity to the ITS sequence of an isolate of B. rhombica (GU797390.1). To confirm pathogenicity of the isolate, ten detached leaves from 3-month-old plants of T. semidecandra ‘Purple Glorybush’ were inoculated in vitro with 5-mm diameter, colonized mycelial plugs from the periphery of 5-day-old cultures of the isolated fungus. The agar plugs were put on the leaf surface and secured with sterile, moist cotton. Sterile PDA plugs were similarly used as the control treatment on ten detached leaves. Leaves were placed in petri dishes and incubated in a growth chamber with 12 h of light/day at 28°C. Necrotic lesions appeared on leaves after 2 to 3 days of incubation, whereas control leaves inoculated with sterile PDA plugs remained asymptomatic. B. rhombica was consistently reisolated from the lesions using the same method described above, but was not reisolated from the control leaves. Although there are approximately 77 reported hosts of B. rhombica (2), to our knowledge, this is the first report of B. rhombica causing a leaf spot on T. semidecandra. Because the disease caused foliar damage and reduced the ornamental value of the nursery plants, control measures may need to be implemented for this species in nurseries. References: (1) M. Faravani and B. H. Bakar. J. Food Agric. Env. Pap. 5:234, 2007. (4) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , 30 Mar. 2012. (2) K. A. Pirozyski and S. D. Patil. Can. J. Bot. Pap. 48:567, 1970. (3) 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.

scholarly journals First Report of Leaf Spot caused by Bipolaris oryzae on Switchgrass in Tennessee

Plant Disease ◽  
2013 ◽  
Vol 97 (12) ◽  
pp. 1654-1654 ◽  
Author(s):  
A. L. Vu ◽  
M. M. Dee ◽  
J. Zale ◽  
K. D. Gwinn ◽  
B. H. Ownley
Keyword(s):  
Leaf Spot ◽  
Panicum Virgatum ◽  
Morphological Characteristics ◽  
Its Region ◽  
Spore Production ◽  
Post Inoculation ◽  
Sterile Water ◽  
Bipolaris Oryzae ◽  
First Report ◽  
Symptomatic Leaf

Knowledge of pathogens in switchgrass, a potential biofuels crop, is limited. In December 2007, dark brown to black irregularly shaped foliar spots were observed on ‘Alamo’ switchgrass (Panicum virgatum L.) on the campus of the University of Tennessee. Symptomatic leaf samples were surface-sterilized (95% ethanol, 1 min; 20% commercial bleach, 3 min; 95% ethanol, 1 min), rinsed in sterile water, air-dried, and plated on 2% water agar amended with 3.45 mg fenpropathrin/liter (Danitol 2.4 EC, Valent Chemical, Walnut Creek, CA) and 10 mg/liter rifampicin (Sigma-Aldrich, St. Louis, MO). A sparsely sporulating, dematiaceous mitosporic fungus was observed. Fungal plugs were transferred to surface-sterilized detached ‘Alamo’ leaves on sterile filter paper in a moist chamber to increase spore production. Conidia were ovate, oblong, mostly straight to slightly curved, and light to olive-brown with 3 to 10 septa. Conidial dimensions were 12.5 to 17 × 27.5 to 95 (average 14.5 × 72) μm. Conidiophores were light brown, single, multiseptate, and geniculate. Conidial production was polytretic. Morphological characteristics and disease symptoms were similar to those described for Bipolaris oryzae (Breda de Haan) Shoemaker (2). Disease assays were done with 6-week-old ‘Alamo’ switchgrass grown from seed scarified with 60% sulfuric acid and surface-sterilized in 50% bleach. Nine 9 × 9-cm square pots with approximately 20 plants per pot were inoculated with a mycelial slurry (due to low spore production) prepared from cultures grown on potato dextrose agar for 7 days. Cultures were flooded with sterile water and rubbed gently to loosen mycelium. Two additional pots were inoculated with sterile water and subjected to the same conditions to serve as controls. Plants were exposed to high humidity by enclosure in a plastic bag for 72 h. Bags were removed, and plants were incubated at 25/20°C with 50 to 60% relative humidity. During the disease assay, plants were kept in a growth chamber with a 12-h photoperiod of fluorescent and incandescent lighting. Foliar leaf spot symptoms appeared 5 to 14 days post-inoculation for eight of nine replicates. Control plants had no symptoms. Symptomatic leaf tissue was processed and plated as described above. The original fungal isolate and the pathogen recovered in the disease assay were identified using internal transcribed spacer (ITS) region sequences. The ITS region of rDNA was amplified with PCR and primer pairs ITS4 and ITS5 (4). PCR amplicons of 553 bp were sequenced, and sequences from the original isolate and the reisolated pathogen were identical (GenBank Accession No. JQ237248). The sequence had 100% nucleotide identity to B. oryzae from switchgrass in Mississippi (GU222690, GU222691, GU222692, and GU222693) and New York (JF693908). Leaf spot caused by B. oryzae on switchgrass has also been described in North Dakota (1) and was seedborne in Mississippi (3). To our knowledge, this is the first report of B. oryzae from switchgrass in Tennessee. References: (1) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/, 28 June 2012. (2) J. M. Krupinsky et al. Can. J. Plant Pathol. 26:371, 2004. (3) M. Tomaso-Peterson and C. J. Balbalian. Plant Dis. 94:643, 2010. (4) T. J. White et al. Pages 315-322 in: PCR Protocols: a Guide to Methods and Applications. M. A. Innis et al. (eds), Acad. Press, San Diego, 1990.

scholarly journals First Report of Corynespora Leaf Spot on Patchouli Caused by Corynespora cassiicola in China

Plant Disease ◽  
2010 ◽  
Vol 94 (12) ◽  
pp. 1508-1508 ◽  
Author(s):  
X. Y. Chen ◽  
C. Sui ◽  
B. C. Gan ◽  
J. H. Wei ◽  
Y. K. Zhou
Keyword(s):  
Leaf Spot ◽  
Control Measures ◽  
Economic Losses ◽  
Leaf Spot Disease ◽  
Commonwealth Mycological Institute ◽  
Corynespora Cassiicola ◽  
Manihot Esculenta Crantz ◽  
First Report ◽  
Spot Disease ◽  
Potted Plants

Patchouli (Pogostemon cablin (Blanco) Benth.) is mainly cultivated in Southeast Asia as a medicinal shrub and a source of patchouli oil used in perfumery. In 2008, a leaf spot disease was observed on patchouli plants grown on most farms (some farms had 99% incidence) in Wanning, the predominant cultivation location in the Hainan Province of China. The disease usually began at the tip of leaves, the main veins, or small veinlets. Severely irregular-shaped dark brown leaf spots expanded over 5 to 10 days, eventually causing infected leaves to abscise. The time from initial leaf lesions to abscission usually took 1 month. The disease was usually most severe in April and May, causing significant economic losses along with quality losses to patchouli oil extracted from leaves. To isolate the causal pathogen, diseased leaves were collected in August 2008 from a farm of the Hainan Branch Institute of Medicinal Plant Development in Wanning, surface sterilized in 75% ethanol for 1 min, transferred to potato dextrose agar (PDA), and incubated at 28°C for 14 days. Single-spore cultures of three isolates were obtained and identified as Corynespora cassiicola (Berk. & Curt.) Wei. on the basis of morphological and physiological features (1). Genomic DNA was extracted from all the cultures. The internal transcribed spacer (ITS) region of the rDNA was amplified using primers ITS1 (5′-TCCGATGGTGAACCTGCGG-3′) and ITS4 (5′-TCCTCCGCTTATTGATATGC-3′). Amplicons were 546 bp (GenBank Accession No. HM145960) and had 99% nucleotide identity with the corresponding sequence (GenBank Accession No. GU138988) of C. cassiicola isolated from cassava (Manihot esculenta Crantz). To satisfy Koch's postulates, 50-day-old potted plants in a tent were sprayed until runoff with a spore suspension (1 × 106 spores/ml) prepared from 10-day-old cultures. Using this spray method, one isolate was inoculated separately onto nine leaves of three potted plants. The potted plants were covered with plastic bags to maintain high humidity for 48 h and then placed outside under natural environmental conditions (temperature 20 to 28°C). Another nine leaves of three potted plants, sprayed only with sterile water, served as noninoculated control plants. Leaf spot symptoms similar to those on diseased field plants appeared after 7 days on all inoculated plants. C. cassiicola was reisolated from all inoculated test plants. No symptoms were observed on the control plants. To our knowledge, this is the first report of C. cassiicola causing a leaf spot disease on patchouli in China. Other previous reports of this disease were from Cuba (2). This pathogen has also been reported previously to be economically important on a number of other hosts. On patchouli plants, more attention should be given to prevention and control measures to help manage this disease. References: (1) M. B. Ellis. Dematiaceous Hyphomycetes. Commonwealth Mycological Institute: Kew, Surrey, England, 1971. (2) I. Sandoval et al. Cienc. Tec. Agric., Prot. Plant. 10:21, 1987.

scholarly journals First Report of Leaf Spot Caused by Corynespora cassiicola on Baphicacanthus cusia in China

Plant Disease ◽  
2013 ◽  
Vol 97 (5) ◽  
pp. 690-690
Author(s):  
Q.-L. Li ◽  
S.-P. Huang ◽  
T.-X. Guo ◽  
Z.-B. Pan ◽  
J.-Y. Mo ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Ipomoea Batatas ◽  
Its Region ◽  
Tween 20 ◽  
Herbaceous Plant ◽  
Commonwealth Mycological Institute ◽  
Corynespora Cassiicola ◽  
Single Spore ◽  
First Report ◽  
Perennial Herbaceous Plant

Baphicacanthus cusia is a perennial herbaceous plant in the family Acanthaceae that is native to China, where it grows in warm temperate mountainous or hilly regions. It is commonly used as a Chinese herbal medicine. In March 2012, symptoms of leaf spot were observed on leaves of B. cusia in Long'an County, Guangxi, China, where this plant is extensively cultivated. Symptoms were initially small brown dots which developed into irregular to circular leaf spots. These spots enlarged and overlapped, extending until the 7- to 9-cm-long and 3- to 4-cm-wide leaves withered entirely, mostly within 2 months. On potato dextrose agar (PDA), the same fungus was cultured from 92% of 75 symptomatic leaf samples that had been surface sterilized in a 45-second dip in 0.1% mercuric chloride. Fungal structures were observed on diseased leaves: conidiophores (85 to 460 × 4 to 8 μm) were erect, brown, single or in clusters, and conidia (36 to 90 × 5 to 16 μm) were single or in chains of two to four, brown, cylindrical or obclavate, straight or slightly curved, with 3 to 18 pseudosepta and a conspicuous hilum. Three single-spore isolates were identified as Corynespora cassiicola (Berk & Curt.) Wei based on morphological and cultural characteristics (1). The rDNA internal transcribed spacer (ITS) region of one isolate, ZY-1, was sequenced (GenBank Accession No. JX908713), and it showed 100% identity to C. cassiicola, GenBank FJ852716, an isolate from Micronesia cultured from Ipomoea batatas (2). Pathogenicity tests were performed with each of the three isolates by spraying conidial suspensions (5 × 104 conidia/ml) containing 0.1% Tween 20 onto the surfaces of leaves of 60-day-old, 20-cm tall 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, dark brown 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 C. cassiicola from diseased leaves. To our knowledge, this is the first report of C. cassiicola infecting B. cusia worldwide. References: (1) M. B. Ellis. Dematiaceous Hyphomycetes. Commonwealth Mycological Institute: Kew, Surrey, England, 1971. (2) L. J. Dixon et al. Phytopathology 99:1015, 2009.

scholarly journals First Report of Leaf Spot on Gerbera jamesonii Caused by Corynespora cassiicola in China

Plant Disease ◽  
2012 ◽  
Vol 96 (6) ◽  
pp. 915-915
Author(s):  
Z. R. Shi ◽  
M. M. Xiang ◽  
Y. X. Zhang ◽  
J. H. Huang
Keyword(s):  
Leaf Spot ◽  
Control Measures ◽  
Control Treatment ◽  
Leaf Spot Disease ◽  
Corynespora Cassiicola ◽  
Gerbera Jamesonii ◽  
Cut Flower ◽  
Single Spore ◽  
Internal Transcribed Spacer Region ◽  
First Report

Gerbera (Gerbera jamesonii Bolus ex. Hook f.) is a popular cut flower and flowering potted plant. In August 2011, a new leaf spot disease was observed on double-type Gerbera growing in outdoor ground beds in Guangzhou, Guangdong Province, China. Approximately 30% of about 20,000 Gerbera plants in the Guangzhou ground beds were affected. Leaf spots were round or irregular with grayish centers surrounded by dark brown borders and ranged from 5 to 15 mm in diameter. Leaves with multiple lesions became blighted. A fungus was isolated from the lesions and single-spore isolates plated on potato dextrose agar (PDA) produced gray, floccose colonies, which reached 65 mm on PDA after 7 days at 28°C. Conidiophores were brown or olivaceous, cylindrical, straight and unbranched, two to seven septations, and 25 to 83 × 4 to 7 μm. Conidiogenous cells were olivaceous or brown, cylindrical, and 11 to 21 × 4 to 6 μm. Conidia were borne singly or in chains of two to five, brown, cylindrical, straight to slightly curved, two to eight pseudosepta, and 30 to 90 × 5.5 to 11.5 μm (mean 70.4 × 7.3 μm), with a conspicuous hilum. These characteristics were consistent with the description of Corynespora cassiicola (Berk. & M.A. Curtis.) C.T. Wei (1). The internal transcribed spacer region (ITS) of one isolate (GenBank Accession No. JN853778) was amplified using primers ITS4 and ITS5 (3) and sequenced. A BLAST search in GenBank revealed highest similarity (99%) to sequences of C. cassiicola (AY238606.1 and FJ852715.1). Pathogenicity tests were conducted on 10 potted double-type Gerbera plants. Five wounded and five unwounded leaves on each plant were inoculated with 5-mm mycelial plugs from the periphery of 5-day-old cultures of the isolated fungus. The plugs were put on the leaf surface and secured with sterile wet cotton. Sterile PDA plugs were used as the control treatment on different leaves of the same plants that were inoculated. Plants were covered with plastic bags and incubated in a growth chamber with 12 h of light at 28°C. Necrotic lesions appeared on wounded leaves after 2 to 3 days of incubation and on unwounded leaves 5 to 7 days after incubation. Symptoms on wounded and unwounded leaves were similar to those observed in the field, whereas control leaves inoculated with sterile PDA plugs remained symptomless. C. cassiicola was consistently reisolated from these lesions. Although there are approximately 644 reported hosts of C. cassiicola (2), to our knowledge, this is the first report of C. cassiicola leaf spot on G. jamesonii. Because the disease caused damage to the foliage and affected the flowering of the plants, control measures may need to be implemented for the production of Gerbera in cut flower nurseries. References: (1) M. B. Ellis. CMI Mycol. Pap. 65:15, 1957. (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/ , 21 November 2011. (3) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, San Diego, 1990.

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

Plant Disease ◽  
2010 ◽  
Vol 94 (7) ◽  
pp. 916-916 ◽  
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.

scholarly journals First Report of Target Spot Caused by Corynespora cassiicola on Cotton in Georgia

Plant Disease ◽  
2012 ◽  
Vol 96 (7) ◽  
pp. 1066-1066 ◽  
Author(s):  
A. M. Fulmer ◽  
J. T. Walls ◽  
B. Dutta ◽  
V. Parkunan ◽  
J. Brock ◽  
...  
Keyword(s):  
Dna Sequences ◽  
Leaf Spot ◽  
Pure Culture ◽  
Pathogenic Fungi ◽  
Fluorescent Light ◽  
Corynespora Cassiicola ◽  
Sterile Water ◽  
First Report ◽  
Target Spot ◽  
Initial Symptoms

In 2005, crop consultants in southwestern Georgia reported an unusual occurrence of leaf spot in cotton (Gossypium hirsutum L.). Initial symptoms first developed as brick red dots that led to the formation of irregular to circular lesions with tan-to-light brown centers. Lesions further enlarged and often demonstrated a targetlike appearance formed from concentric rings within the spot. Observations included estimates of premature defoliation up to 70%, abundant characteristic spots on the leaves and bracts, and losses of several hundred kg of lint/ha. When symptomatic leaves were submitted to the University of Georgia Tifton Plant Disease Clinic in Tifton, GA, for identification in 2008, the causal agent was tentatively diagnosed as Corynespora cassiicola (Berk. & M.A. Curtis) C.T. Wei on the basis of similar symptoms and signs previously reported on cotton (3). In September 2011, symptomatic leaves were obtained from diseased cotton within a field (var. DP 1048B2RF) near Attapulgus, GA. Symptomatic tissue from diseased leaves was surface disinfested in 0.5% sodium hypochlorite for 1 min and plated on potato dextrose agar (PDA). Ten isolates were incubated at 21.1°C for 2 weeks with a 12/12 h light/dark cycle using fluorescent light located approximately 70 cm above the cultures. After 1 week, two isolates were transferred to quarter strength PDA for enhanced sporulation and were grown under the same conditions. Conidiophores from the isolated fungus were simple, erect, intermittently branching and septate, and gave rise to single, subhyaline conidia. Conidia had 4 to 17 pseudosepta and were 50 to 197 μm long and 7 to 16 μm wide, straight to curved, and obclavate to cylindrical. Pathogenicity tests were conducted by spraying 10 cotton seedlings (DP 555BR and DP 1048B2RF, two to four true leaf stage) until runoff with a blended suspension from a 2-week-old pure culture of the fungus diluted with 100 mL of sterile water. Five plants were sprayed with sterile water as noninoculated controls. Cotton seedlings were then incubated in a moist chamber at 21.1°C for 48 h. Within 1 week, all inoculated plants showed symptoms similar to those of diseased field plants. Symptoms were not observed on noninoculated control plants. The fungus was reisolated five times from symptomatic leaves and grown in pure culture. Conidia and conidiophores were identical to the morphology of the original isolates, and were similar to descriptions of C. cassiicola (2). To confirm the identity of the pathogen, DNA was extracted from a week-old culture and amplified with specific primers for loci “ga4” and “rDNA ITS” (1). DNA sequences obtained with the Applied Biosystems 3730xl 96-capillary DNA Analyzer showed 99% identity to C. cassiicola from BLAST analysis in GenBank. The resulting sequence was deposited into GenBank (Accession No. JQ717069). To our knowledge, this is the first report of this pathogen in Georgia. Given the increasing prevalence of this disease in southwestern Georgia, its confirmation is a significant step toward management recommendations for growers. Because foliar diseases caused by C. cassiicola are commonly referred to as “target spot” in other crops (e.g., soybeans), it is proposed that Corynespora leaf spot of cotton be known as “target spot of cotton.” References: (1) L. J. Dixon et al. Phytopathology 99:1015, 2009. (2) M. B. Ellis and P. Holliday. CMI Description of Pathogenic Fungi and Bacteria, 303, 1971. (3) J. P. Jones. Phytopathology 51:305, 1961.

scholarly journals First Report of Gray Leaf Spot of Maize Caused by Cercospora zeina in China

Plant Disease ◽  
2013 ◽  
Vol 97 (12) ◽  
pp. 1656-1656 ◽  
Author(s):  
K.-J. Liu ◽  
X.-D. Xu
Keyword(s):  
Leaf Spot ◽  
Its Region ◽  
Gray Leaf Spot ◽  
Molecular Characteristics ◽  
Maturity Stage ◽  
Sterile Water ◽  
Causal Organism ◽  
First Report ◽  
Single Well ◽  
Species Specific

Gray leaf spot of maize (Zea mays L.) is an important foliar disease in many parts of China. The causal organism of gray leaf spot in China is generally regarded as Cercospora zeae-maydis (3). In October 2011, symptoms similar to gray leaf spot were observed on 77% of maize plants in 25 locations (about 3,000 ha.) of Yunnan Province, China, and the disease could cause yield losses of 35 to 50%. The symptoms of leaf spot were different from those caused by C. zeae-maydis. The lesions on leaves were oblong, pale gray to pale brown, 2 to 3 × 5 to 40 mm, and confined by leaf veins that eventually coalesced. To identify the pathogen, 75 leaf samples were collected from 25 fields (three leaf samples for each field) at the kernel maturity stage. Single, well-separated lesions were excised and surface-sterilized by placing them in 75% ethanol for 5 s, then disinfested in 2% sodium hypochlorite for 5 min and rinsed with sterilized water. The lesions were incubated on water agar (WA) at 24°C for 48 to 72 h to allow sporulation. Seventy-five single-conidial isolates were obtained and cultured as described in Crous (1). Morphology of the isolates was determined on plates containing maize leaf powder agar (MLPA). After 5 days, isolates produced pale brown mycelia that consisted of 3- to 4-μm-wide, septate, branched hyphae. Conidiophores were 5 to 7 × 55 to 100 μm, straight to slightly flexuous, and usually 1- to 5-septate. Conidia were average 7.5 × 68 μm, fusiform, apex subobtuse, base subtruncate, and 3- to 6-septate. These characteristics are similar to C. zeina (2). The internal transcribed spacer (ITS) region of rDNA was amplified from each of the 75 isolates using primers ITS1/ITS4 and sequenced. The same sequences were obtained and the sequence of isolate YNGLS was submitted to GenBank (Accession No. KC878692). BLAST analysis of the sequence showed 100% confirmation to C. zeina (DQ185081). Additionally, a PCR-based diagnostic test using species-specific primers (2) confirmed the identification of the 75 isolates as C. zeina. The pathogenicity of the isolates was tested on greenhouse grown maize variety Huidan 4. The test was performed on 40 plants and replicated three times. The plants were inoculated at the 10 leaf stage by injecting 2 ml of conidial suspensions (2,500 conidia ml–1) into leaf whorl using a hypodermic syringe, and control plants were injected with sterile water. Conidia were collected from 5-day-old cultures grown on MLPA and suspended in sterile water. Forty days after inoculation, all inoculated plants showed characteristic lesions on leaves, but control plants remained asymptomatic. C. zeina was reisolated from the lesions, and the identity of the reisolates was confirmed by the morphological and molecular characteristics as stated above. C. zeina was previously reported as the causal agent of maize gray leaf spot (2). To our knowledge, this is the first report of C. zeina causing gray leaf spot of maize in China. References: (1) P. W. Crous. Mycologia Memoir. 21:1, 1998. (2) P. W. Crous et al. Stud. Mycol. 55:189, 2006. (3) C. H. Lu et al. J. Southwest China Normal Univ. 37:51, 2012.

scholarly journals An Outbreak of Leaf Spot Caused by Corynespora cassiicola on Korean Raspberry in Korea

Plant Disease ◽  
2012 ◽  
Vol 96 (5) ◽  
pp. 762-762 ◽  
Author(s):  
J.-H. Kwon ◽  
D.-W. Kang ◽  
Y.-S. Kwak ◽  
J. Kim
Keyword(s):  
New York ◽  
Leaf Spot ◽  
Disease Incidence ◽  
Morphological Characteristics ◽  
Its Region ◽  
Pathogenic Fungi ◽  
Corynespora Cassiicola ◽  
Leaf Spots ◽  
Causal Pathogen ◽  
Recent Occurrence

In September and October 2010, leaf spots were observed on Korean raspberry (Rubus crataegifolius Bunge) plants in farmers' fields in Hapcheon, Gyeongnam Province, South Korea. Disease incidence ranged from 50 to 80% among fields. Circular- to irregular-shaped spots surrounded by yellow halos occurred frequently on the leaves of Korean raspberry plants. Brown spots became dark with wavy borders and ranged from 20 to 300 mm in diameter. Infected leaves became chlorotic, blighted, and eventually died. Fungal hyphae covered the lesions with abundant conidia and conidiophores. Fresh leaf specimens were collected from infected plants and the putative causal pathogen was isolated onto potato dextrose agar (PDA). A total of 30 isolates of the fungus were collected from diseased plants collected in the field. Fungal colonies were gray to brown on PDA. Colonies formed conidia, 38 to 210 × 8 to 20 μm, which were solitary or catenary, obclavate to cylindrical, smooth, straight or curved, and subhyaline to pale brown or brown. Conidiophores, 98 to 840 × 4 to 12 μm, were slightly or conspicuously swollen at apex, single, simple, straight or slightly flexuous, pale to midbrown, smooth, septate, thick, monotretic, and determinate or in tufts. Morphological characteristics of the fungal specimens were similar to descriptions of Corynespora cassiicola (1). A representative isolate of the pathogen was used to inoculate leaves of Korean raspberry plants for pathogenicity testing. Five leaves of a 3-month-old potted plant were sprayed with a suspension of conidia in water. Conidia were harvested from PDA cultures and adjusted to 2 × 104 conidia/ml with a hemocytometer. Five leaves sprayed with sterile distilled water served as controls. Inoculated plants were placed in a humid chamber with 100% relative humidity at 30°C for 24 h and then moved to a greenhouse. Symptoms similar to those observed in the farmers' fields developed on the inoculated leaves within 12 days, whereas the controls remained asymptomatic. The causal fungus was reisolated from the lesions of inoculated plants to satisfy Koch's postulates. To confirm the identity of the fungus, the complete internal transcribed spacer (ITS) rDNA region was amplified and sequenced (3). Amplification of the ITS region generated a 559-bp sequence (GenBank Accession No. JQ340026) with 100% similarity to sequences of C. cassiicola in GenBank (Accession No. GU138988) causing leaf spot on cassava (2). Based on the symptoms, morphological characteristics, pathogenicity, and molecular identification, this fungus was identified as C. cassiicola (1). To our knowledge, this is the first report of leaf spot caused by C. cassiicola on Korean raspberry. The recent occurrence of leaf spot on Korean raspberry suggests that C. cassiicola is spreading widely and posing a serious threat to these plants in Korea. References: (1) M. B. Ellis et al. No. 303 in: CMI Descriptions of Pathogenic Fungi and Bacteria. Surrey, Kew, UK, 1971. (2) X.-B. Liu et al. Plant Dis. 94:916, 2010. (3) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, Inc., New York, 1990.

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