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

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.

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First Report of Alternaria tenuissimain Causing Leaf Spot of Celery (Apium graveolens) in China

Plant Disease ◽

10.1094/pdis-09-20-2083-pdn ◽

2020 ◽

Author(s):

Jianqiang Zhang ◽

Kangli Wu ◽

Xiaomeng Zhang ◽

Jiajia Li ◽

Abdramane salah zene ◽

...

Keyword(s):

Dna Sequences ◽

Leaf Spot ◽

Leaf Age ◽

Apium Graveolens ◽

Control Group ◽

Sterile Water ◽

Internal Transcribed Spacer Region ◽

Data Set ◽

First Report ◽

Initial Symptoms

Celery (Apium graveolens) is one of the most widely grown vegetables in the world. A survey in Anding District of Gansu Province in 2019 showed that the incidence of celery leaf spot was 25%-45%. The disease mainly occurs in late June and July. The leaf spot is conducive to the onset at high temperature and humidity environment. The initial symptoms were many small light brown, irregular-shaped on the leaves. The lesions gradually enlarged in the later stage of the disease, and multiple lesions coalesced to form large irregular brown spots, eventually the whole leaves died. A 3~4mm leaf tissue was cut from the junction of the diseased leaf and the healthy area, the leaf tisse was surface-sterilized in 1.5% NaClO for 1 min and washed with sterile water. Then, it was incubated on potato dextrose agar (PDA) and obtained the pure culture (Q1). After 5 days of cultivation at 25°C, the fungal colonies were olivaceous to dark olive with white margins and abundant aerial mycelia. The conidia were obclavate or ellipsoid, pale brown, with 3~4 longitudinal septa and 2~7 transverse septa, and measured 20.0 to 50.0 × 3.5 to 14.0μm (n=50). Conidiophores were septate, arising singly, and measured 3.5 to 40.0 × 2.5 to 4.5 μm (n=50). Based on morphological characteristics, the fungus was preliminarily identified as A.tenuissima (Simmons 2007). To further confirm the identification, the internal transcribed spacer region (ITS), translation elongation factor 1-α gene (TEF), RNA polymerase II second largest subunit (RPB2), major allergen Alt a 1 gene (Alt a 1), endopolygalacturonase gene (endoPG), anonymous gene region (OPA10-2) and glyceraldehyde 3-phos-phatedehydrogenase (GAPDH) were amplified and sequenced using primers ITS1/ITS4 (Peever et al. 2004), EF1-728F/EF1-986R (Carbone et al. 1999), RPB2-5F2/RPB2-5R (Sung et al. 2007), Alt-for/Alt-rev (Hong et al. 2005), EPG-specific/EPG-3b (Peever et al. 2004), OPA10-2R/OPA10-2L (Peever et al. 2004) and Gpd1/Gpd2 (Berbee et al. 1999) (GenBank accession no.MN046364, MW016001, MW016002, MW016003, MW016004, MW016005, MW016006). DNA sequences of TEF, RPB2, endoPG, OPA10-2 and GAPDH were 100% identical to those of A. tenuissima (MN256108, MK605866, KP789503, JQ859829 and MK683802), but ITS and Alt a 1 were 100% similarity with A. tenuissima (MN615420, JQ282277) and A. alternate (MT626589, KP123847). The ITS and Alt a 1 sequence did not distinguish A. tenuissima from the A. alternate complex. Maximum likelihood phylogenetic analyses were performed for the combined data set with TEF, RPB2, and endoPG using MEGA6 under the Tamura-Nei model (Kumar et al. 2016). The isolate Q1 clustered with type strain A. tenuissima CBS 918.96. The 20 celery plants of 4-7 leaf age were used test the pathogenicity of Q1, the ten plants were sprayed with 20ml of spore suspension (1×105 spores/ml), the control was sprayed with 20mL sterile water, which were placed in a growth chamber (25℃, a 14h light and 10h dark period, RH > 80%). Eight days after inoculation, 40% of the leaves formed lesions, which were consistent with the field observation，the control group was asymptomatic. The pathogen was reisolated from infected leaves to fulfill Koch’s postulates. To our knowledge, this is the first report of A. tenuissima causing leaf spot on celery in China.

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First Report of Cochliobolus sativus Causing Leaf Spot on Paper Mulberry in China

Plant Disease ◽

10.1094/pdis-04-11-0319 ◽

2011 ◽

Vol 95 (12) ◽

pp. 1586-1586 ◽

Cited By ~ 1

Author(s):

P. S. Wu ◽

K. Chen ◽

H. Z. Du ◽

J. Yan ◽

Q. E. Zhang

Keyword(s):

Leaf Spot ◽

Leaf Tissue ◽

Pathogenic Fungi ◽

Bipolaris Sorokiniana ◽

Causal Agent ◽

Cochliobolus Sativus ◽

Conidial Suspension ◽

Sterile Water ◽

First Report ◽

Forest Park

Paper mulberry, Broussonetia papyrifera (L.) Vent., is a highly adaptable, fast-growing tree that is native to eastern Asia. Its ability to absorb pollutants makes it ideal for ornamental landscapes, especially in industrial and mining areas. During the summer of 2010, brown lesions were observed on leaves of paper mulberry in Baiwangshan Forest Park, Beijing, China. These lesions were ovoid to fusiform and 4 to 9 × 2 to 4 mm with dark brown centers and light brown irregular edges. Spots on severely infected leaves sometimes coalesced to form long stripes with gray centers. To isolate the causal agent of the lesions, 4-mm2 pieces of diseased leaf tissue from 12 leaves were collected at the lesion margins and surface disinfected in 0.5% NaOCl for 3 min, rinsed three times with sterile water, plated on water agar, and incubated at 25°C with a 12-h photoperiod. After 5 days, the cultures, which became dark brown to black, were observed. Conidiophores (120 to 220 × 4 to 7 μm) were solitary or in groups of two to five, straight or flexuous with swollen bases, and light or dark brown. Conidia were dark olive brown, spindle- or oval-shaped with truncated ends (60 to 120 × 15 to 30 μm), slightly curved, and containing 3 to 12 distoseptate (mostly 6 to 10). Pseudothecia, produced after 14 days in culture, were dark brown to black and flask shaped (420 to 530 μm in diameter with 85 to 100 × 75 to 90 μm ostiolar beaks). Asci were cylindrical (100 to 220 × 30 to 40 μm) and contained eight ascospores. Ascospores were filiform, (150 to 360 × 6 to 9 μm), hyaline, with 6 to 11 septations. Isolates were identified as Cochliobolus sativus (Ito & Kurib.) Drechsler & Dastur (anamorph Bipolaris sorokiniana (Sacc. & Sorok.) Shoem.) on the basis of culture color and dimensions and colors of pseudothecia, asci, ascospores, conidiophores, and conidia (2,3). The identity of one isolate was confirmed by ITS1-5.8S-ITS2 rDNA sequence (GenBank Accession No. HQ 654781) analysis that showed 100% homology to C. sativus listed in Berbee et al. (1). Koch's postulates were performed with six potted 3-month-old paper mulberry plants. An isolate was grown on potato dextrose agar for 14 days to obtain conidia for a conidial suspension (3 × 104 conidia/ml). Three of the potted plants were sprayed with the conidial suspension and three were sprayed with sterile water as controls. Each plant was covered with a plastic bag for 24 h to maintain high humidity and incubated at 25°C with a 12-h photoperiod. After 7 days, the inoculated plants showed leaf symptoms identical to those previously observed on paper mulberry trees in the Baiwangshan Forest Park, while control trees remained symptom free. Reisolation of the fungus from the inoculated plants confirmed that the causal agent was C. sativus. C. sativus is widely distributed worldwide causing a variety of cereal diseases. Wheat and barley are the most economically important hosts. To our knowledge, this is the first report of C. sativus as a pathogen causing leaf spot of paper mulberry in China. References: (1) M. L. Berbee et al. Mycologia 91:964, 1999. (2) M. B. Ellis. Dematiaceous Hyphomycetes. CABI, Oxon, UK, 1971. (3) A. Sivanesan et al. No.701 in: Descriptions of Pathogenic Fungi and Bacteria. CAB, Kew, Surrey, U.K., 1981.

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First Report of Leaf Spot Caused by Colletotrichum fructicola on Myrica rubra in China

Plant Disease ◽

10.1094/pdis-10-21-2138-pdn ◽

2021 ◽

Author(s):

Shucheng Li ◽

Liuhua Xiao ◽

Fan Wu ◽

Yinbao Wang ◽

Mingshu Jia ◽

...

Keyword(s):

Leaf Spot ◽

Juglans Regia ◽

Morphological Characteristics ◽

Effective Control ◽

Bootstrap Support ◽

Sterile Water ◽

First Report ◽

Myrica Rubra ◽

Initial Symptoms ◽

Colletotrichum Fructicola

Myrica rubra is an important fruit tree with high nutritional and economic value, which is widely cultivated in multiple regions of China. In January 2021, an unknown disease which caused leaf spot with approximately 20% (n=100 investigated plants) of incidence was discovered on the leaves of M.rubra in Jiujiang City of Jiangxi Province (29.71° N, 115.97° E). The initial symptoms were small pale brown spots (1 to 2 mm diameter) on the leaves, which gradually expanded into round or irregular dark brown spots with the occurrence of the disease, and the lesion developed necrotic tissues in the center at later stages, eventually leading the leaves to chlorotic and wilted. Ten diseased leaves with typical symptoms were collected and the leaf tissue (5 × 5 mm) at junction of diseased and healthy portion were cut. The surfaces were disinfected with 75% ethanol for 45 s, 1% sodium hypochlorite for 1 min, and rinsed in sterile water for 3 times then transferred to potato dextrose agar (PDA) at 28 ± 1 ℃ for 3 days. Five fungal single isolates with similar morphology were purified from single spores. On PDA medium, the colonies initially appeared white with numerous aerial hyphae, and the center of the colony turned gray at later stages, less sporulation. While on modified czapek-dox medium (Peptone 3g, K2HPO4 1g, MgSO4·7H2O 0.5g, KCl 0.5g, FeSO4 0.01g, Maltose 30g, Agar 15g, Distilled water 1000 mL, pH=7.0), the mycelia of the colony were sparse and produced a large number of small bright orange particles (conidial masses). Conidia were single-celled, transparent, smooth-walled, 1-2 oil globule, cylindrical with slightly blunt rounded ends, 14.45-18.44 × 5.54-6.98 μm (av=16.27 μm × 6.19 μm, n=50) in size. These morphological characteristics of the pathogen were similar to the descriptions of Colletotrichum fructicola (Ruan et al, 2017; Yang et al, 2021). To further confirm the identity of the pathogen, genomic DNA from a representative isolate was extracted with DNA Extraction Kit (Yeasen, Shanghai, China), and the internal transcribed spacer (ITS), glyceraldehyde-3-phosphatedehydrogenase (GAPDH), calmodulin gene (CAL), actin (ACT) and chitin synthase 1 (CHS 1) were amplified by using the primers ITS1/ITS4 (Gardes et al, 1993), GDF/GDR (Templeton et al, 1992), CL1C/CL2C (Weir et al, 2012), ACT-512F/ACT-783R and CHS-79F/CHS-345R (Carbone et al, 1999), respectively. The PCR amplified sequences were submitted to GenBank (GenBank Accession No. ITS, MW740334; GAPDH, MW759805; CAL, MW759804; ACT, MW812384; CHS-1, MW759803) and aligned with GenBank showed 100% identity with C. fructicola (GenBank Accession No. ITS, MT355821.1 (546/546 bp); GAPDH, MT374664.1 (255/255 bp); CAL, MK681354.1 (741/741 bp); ACT, MT364655.1 (262/262 bp); CHS, MT374618.1 (271/271 bp)). Phylogenetic tree using the maximum likelihood methods with Kimura 2-parameter model and combined ITS-ACT-GAPDH-CHS-CAL concatenated sequences, bootstrap nodal support for 1000 replicates in MEGA7.0, revealed that the isolate was assigned to C. fructicola strain (ICMP 18581 and CBS 125397) (Yang et al. 2021) with 98% bootstrap support. Pathogenicities of were tested on fifteen healthy M. rubra plants (five for wounded inoculation, five for nonwounded inoculation, and five for controls) in the orchard. Twenty leaves were marked from each plant, and disinfected the surface with 75% ethanol. Ten μL spore suspension (1.0 × 106 conidia/ml) of each isolate from 7-day-old culture were inoculated on the surface of 20 needle-wounded and 20 nonwounded leaves, respectively. Healthy leaves were inoculated with sterile water as controls by the same method. All inoculated leaves were sprayed with sterile water and covered with plastic film to remained humidification. After 5 days, all the wounded leaves which were inoculated with C. fructicola showed similar symptoms to those observed on the original leaves. Symptoms of nonwounded leaves were milder than the wounded inoculated leaves, while control leaves remained healthy. Finally, the C. fructicola was re-isolated from the inoculated leaves. C. fructicola has been reported on Juglans regia, Peucedanum praeruptorum, Paris polyphylla var. Chinensis in China (Wang et al, 2017; Ma et al, 2020; Zhou et al, 2020). As far as we know, this is the first report of C. fructicola causing leaf spot on M.rubra in China. This result contributes to better understand the pathogens causing diseases of M.rubra in this region of China and develop effective control strategies.

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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 Corynespora cassiicola Causing Leaf Spot on Akebia trifoliate

Plant Disease ◽

10.1094/pdis-04-13-0454-pdn ◽

2013 ◽

Vol 97 (12) ◽

pp. 1659-1659 ◽

Cited By ~ 2

Author(s):

Y. F. Ye ◽

N. Jiang ◽

G. Fu ◽

W. Liu ◽

F. Y. Hu ◽

...

Keyword(s):

Leaf Spot ◽

Sequence Similarity ◽

Yangtze River Basin ◽

Morphological Characteristics ◽

Colletotrichum Acutatum ◽

Leaf Spot Disease ◽

Corynespora Cassiicola ◽

High Sequence Similarity ◽

First Report ◽

Initial Symptoms

Akebia species have been used for centuries in medicinal practices in a few Asian countries such as China and Japan. The dried stems of Akebia trifoliata are known as mutong in the Chinese pharmacopoeia (4) and mokutsu in Kampo, the traditional Chinese medicine developed in Japan (2). In China, the plant is grown in the provinces of Shandong, Hebei, Shanxi, Henan, Gansu, and some provinces in the south of the Yangtze River basin. During the summer of 2012, a leaf spot disease was detected on A. trifoliata grown in Nanning, Guangxi, China. The disease occurred and spread rapidly in July under conditions of high temperature and high humidity. The symptoms appeared on three sites that we inspected; disease incidences were higher than 80%. Initial symptoms consisted of small (less than 5 mm in diameter), circular, purple-brown leaf spots. Spots later enlarged and became elliptical, circular, or irregular with gray-white centers and dark brown rims. The centers were slightly concave. The spots could coalesce with each other, resulting in leaf desiccation and wilting. A fungal isolate was obtained from symptomatic leaf tissue that taken from a field (22°50′N, 108°22′E) in Nanning, Guangxi, China. Single-spore culture of the isolate was incubated on potato dextrose agar (PDA) for 7 days in the dark at 28°C. Conidiophores were straight to slightly curved, unbranched, and pale brown. Conidia (19.0 to 140.5 μm long and 7.0 to 11.0 μm wide) were formed singly or in chains, obclavate to cylindrical, straight or curved, pale brown, with a rounded apex and truncate base, and 1 to 13 pseudosepta. Morphological characteristics of the isolate were similar to the descriptions of Corynespora cassiicola (Berk. & M.A. Curtis) C.T. Wei (1). Genomic DNA of the isolate was extracted and used for PCR amplification of rDNA-ITS (internal transcribed spacer) sequence with primers ITS1 and ITS4. The PCR products were purified and sequenced. The sequence (GenBank Accession No. KC977496) was used in BLAST searches to interrogate GenBank for sequence similarity. High sequence similarity of 100% was obtained with several C. cassiicola strains. Pathogenicity of the isolate was investigated to demonstrate Koch's postulate. Young, healthy, fully expanded green leaves of A. trifoliata were surface sterilized. Fifteen leaves were inoculated with 10-μl drops of conidia suspension (105 conidia per ml) and 10 leaves were inoculated with the same volume of sterile water to serve as controls. All the leaves were placed in a humid chamber for 5 days. Spots with similar symptoms to those observed in the field developed on all inoculated leaves. The pathogen was reisolated and identified as C. cassiicola. The controls remained symptomless. According to previous reports, A. trifoliata was infected by Alternaria tenuissima in China and by Colletotrichum acutatum in Japan (3). To our knowledge, this is the first report of C. cassiicola found on Akebia species worldwide. Furthermore, this new disease primarily affects plantations and reduces the quality and yield of the medicine. Some effective measures should be taken to control this disease. References: (1) M. B. Ellis and P. Holliday. CMI Description of Pathogenic Fungi and Bacteria, 303, 1971. (2) F. Kitaoka et al. J. Nat. Med. 63:374, 2009. (3) Y. Kobayshi et al. J. Gen. Plant Pathol. 70:295, 2004. (4) L. Li et al. HortScience 45:4, 2010.

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First Report of Target Spot of Cotton Caused by Corynespora cassiicola in China

Plant Disease ◽

10.1094/pdis-12-13-1243-pdn ◽

2014 ◽

Vol 98 (7) ◽

pp. 1006-1006 ◽

Cited By ~ 9

Author(s):

Y.-X. Wei ◽

H. Zhang ◽

J.-J. Pu ◽

X.-M. Liu

Keyword(s):

Limiting Factors ◽

Control Treatment ◽

Pathogenicity Test ◽

Corynespora Cassiicola ◽

Single Spore ◽

Internal Transcribed Spacer Region ◽

First Report ◽

Leaf Spots ◽

Target Spot ◽

Initial Symptoms

Cotton (Gossypium hirsutum L.) is one of the most important economic crops in China and fungal diseases are the major limiting factors in its production. In September 2013, cotton plants infected with leaf spots were observed in Sanya, Hainan Province, China. Initial symptoms developed as brick-red dots that led to the formation of irregular to circular lesions with gray centers surrounded by brown borders. Individual leaf spots formed concentric rings of alternating light and dark brown bands. Leaf tissue segments collected from the border between symptomatic and healthy tissue were surface disinfested in 75% ethanol for 1 min, then rinsed three times in sterile water with streptomycin sulfate. Fungal isolates obtained from these segments were purified by the single spore technique on potato dextrose agar (PDA) at 28°C. The initial color of the colonies was olivaceous, turning dark brown after 5 days. Conidiophores were scattered or clustered, brown, straight to curved, unbranched, and glabrous. Conidia had 4 to 12 pseudosepta and were 56 to 230 μm long and 5 to 15 μm wide, brown, straight to slightly curved, obclavate to cylindrical, glabrous, and apex obtuse. These characteristics were consistent with the description of Corynespora cassiicola (Berk. & M.A. Curtis.) C.T. Wei (3). A pathogenicity test was conducted with the four isolates on detached young cotton leaves (two to four true leaf stage). For each isolate, three slightly wounded and three unwounded leaves were inoculated with 5.5-mm-diameter mycelial plugs. For the control treatment, wounded and unwounded leaves were mock inoculated with sterile PDA plugs of the same size. The inoculated leaves were placed in a moist chamber and incubated with a 12-h photoperiod at 28°C. Necrotic lesions appeared on wounded spots after 2 days of incubation and on unwounded leaves 3 days after incubation. All symptoms were similar to those observed in the field. Symptoms were not observed on control leaves. The same fungus was always re-isolated from the diseased tissue according to Koch's postulates. To confirm the identity of the pathogen, DNA was extracted from a 1-week-old culture grown on PDA and the internal transcribed spacer region (ITS) of one isolate (GenBank Accession No. KF924624) was amplified using primers ITS1 and ITS4 (4) and sequenced. BLAST search in GenBank revealed 100% homology with sequences of C. cassiicola (EU364535.1, EU364536.1, FJ852574.1, and FJ852575.1). Based on the symptoms, fungal morphology, ITS sequence comparison, and pathogenicity test, this fungus was identified as C. cassiicola. Target spot of cotton associated with C. cassiicola has been reported in Georgia (2) and Alabama (1). To our knowledge, this is the first report that C. cassiicola can infect cotton in China inducing target spot of cotton (2). This report will establish a foundation for further study of C. cassiicola to aid disease measurement and control. References: (1) K. N. Conner et al. Plant Dis. 97:1379, 2013. (2) A. M. Fulmer et al. Plant Dis. 96:1066, 2012. (3) J. Y. Lu. Page 407 in: Plant Pathogenic Mycology. China Agricultural Press, Beijing, 2000. (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 Target Leaf Spot Caused by Corynespora cassiicola on Balsam Pear in China

Plant Disease ◽

10.1094/pdis-94-1-0127c ◽

2010 ◽

Vol 94 (1) ◽

pp. 127-127 ◽

Cited By ~ 1

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.

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First Report of Bacterial Leaf Spot on Snow Lotus Caused by Pseudomonas syringae in China

Plant Disease ◽

10.1094/pdis-93-2-0204a ◽

2009 ◽

Vol 93 (2) ◽

pp. 204-204 ◽

Cited By ~ 1

Author(s):

S. F. Zhao ◽

Y. N. Luo ◽

H. Y. Zhao ◽

J. Du ◽

X. Y. Fang

Keyword(s):

Pseudomonas Syringae ◽

Leaf Spot ◽

Unknown Etiology ◽

Leaf Spot Disease ◽

Sterile Water ◽

Bacterial Leaf Spot ◽

Saussurea Involucrata ◽

First Report ◽

Initial Symptoms ◽

Snow Lotus

Snow lotus (Saussurea involucrata (Kar. & Kir.) Sch. Bip.) is an economically important medicinal herb increasingly grown in China in recent years. During the summer and autumn of 2005, 2006, and 2007, a necrosis of unknown etiology was observed on leaves in commercial production areas in Xinjiang Province of China. Disease incidence was approximately 40 to 50% of the plants during the 2005 and 2007 growing seasons. Initial symptoms consisted of pronounced water-soaked, dark brown-to-black spots that were 1 to 2 mm in diameter on young, expanding leaves. Later, some leaf spots on older leaves enlarged and coalesced, causing leaf desiccation. Leaf samples were collected in 2005, 2006, and 2007 from the affected hosts. Bacterial streaming was evident from these samples, and 28 strains were isolated on nutrient agar or King's medium B (KMB). All strains were gram negative and fluoresced bluegreen under UV light after 48 h of growth at 28°C on KMB. On the basis of LOPAT tests, the strains were identified as Pseudomonas syringae (1). The identity of two strains was confirmed by sequencing the 16S rDNA gene, which revealed 98% similarity to P. syringae strains in NCBI (Accession Nos. FJ001817 and FJ001818 for XJSNL 111 and 107, respectively). Infiltration of tobacco leaves with bacterial suspensions resulted in typical hypersensitivity reactions within 24 h. Pathogenicity of the strains was confirmed by spray inoculating five snow lotus leaves of a six-leaf stage plant with 108 CFU ml–1 bacterial suspensions in sterile water and five plants sprayed with sterile distilled water served as controls. Inoculated and sterile water-sprayed controls were maintained in the growth chamber with 90% relative humidity for 15 days at 15 ± 2°C. Symptoms similar to the original symptoms were observed on inoculated plants after 2 weeks. No symptoms developed on controls. Bacteria reisolated from inoculated plants were identified as strains of P. syringae. Isolates were deposited at the Key Laboratory for Oasis Crop Disease Prevention and Cure, Shihezi University. Rust caused by Puccinia carthami and leaf spot disease caused by Alternaria carthami of snow lotus have been reported (2,3). To our knowledge, this is the first report of P. syringae as the cause of bacterial leaf spot on snow lotus in China. References: (1) A. Braun-Kiewnick and D. C. Sands. Pseudomonas. Page 84 in: Laboratory Guide for the Identification of Plant Pathogenic Bacteria. 3rd ed. N. W. Schaad et al., eds. The American Phytopathological Society, St. Paul, MN, 2001. (2) S. Zhao et al. Plant Dis. 91:772, 2007. (3) S. Zhao et al. Plant Dis. 92:318, 2008.

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

Plant Disease ◽

10.1094/pdis-11-13-1113-pdn ◽

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.

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First Report of Corynespora cassiicola Causing Target Spot on Soybean in Taiwan

Plant Disease ◽

10.1094/pdis-02-21-0277-pdn ◽

2021 ◽

Author(s):

Po Kuan Lu ◽

Hsuan-Hao Liu ◽

Hao-Xun Chang

Keyword(s):

Leaf Spot Disease ◽

Broad Host Range ◽

Distilled Water ◽

Conidial Suspension ◽

Corynespora Cassiicola ◽

Average Growth ◽

First Report ◽

Foliar Symptoms ◽

Target Spot ◽

Initial Symptoms

Soybean (Glycine max [L.] Merr.) is an important crop in Taiwan. In October 2020, an unknown leaf spot disease was counted (n = 100) to occur over 70% of soybean cultivar ‘Hualien No.1’ in the Shoufeng Township of Hualien County, eastern Taiwan. Initial symptoms on leaves as tiny lesions approximately 3 mm in diameter, which later enlarged and developed into round, irregular, and reddish-brown spots with concentric rings surrounded by a yellowish halo. The symptoms appeared on both young and old leaves, but rarely on the stem or pods. The lesions at the margin of healthy and infected tissues were surface-disinfested in 1% NaOCl for 30 seconds, washed twice in sterilized distilled water, dissected and plated on potato dextrose agar (PDA) to isolate the potential pathogen. Colonies on PDA exhibited light to dark brown color at 24°C with 12-hours light after 7-days incubation. The average growth rate was 3 mm per day. Conidia were light brown in color and obclavate to cylindrical in shape. The size of a conidium was measured with an average of 110.8 ± 28.2 μm in length and 15.2 ± 2.8 μm in width, typically with 3 to 18 septa (n = 50). To confirm the pathogenicity of this fungus, conidial suspension (104 conidia/mL) of two isolates, HL_GM-6 and HL_GM-7, were sprayed on the healthy leaves of 4-weeks-old soybean. Plants sprayed with sterile distilled water were used as a control. After inoculation, the plants were covered with plastic bags to maintain a high humidity for 24 hours before moving into a greenhouse with a condition of 20 to 25°C and relative humidity of 75 to 80%. After 7 days of inoculation, foliar symptoms began to appear and which were identical with the field observations. To complete the Koch’s postulates, pathogen isolation was attempted and the identical fungus was retrieved from the foliar spots of the inoculated leaves. The foliar symptoms as well as the morphology of the conidiophores and conidia suggested the pathogen to be Corynespora cassiicola (Ellis et al. 1971). Molecular characterization was performed using the sequences of internal transcribed spacer (ITS) region of rDNA, actin (act1), tubulin, and translation elongation factor 1 alpha (tef1) genes after a PCR with ITS1/ITS4 (White et al. 1990), ACT-512F/ACT-783R (Carbone and Kohn, 1999), BT2a/Bt2b (Udayanga et al. 2012), EF1-728F/EF1-986R (Udayanga et al. 2012), respectively. BLASTN sequence analyses of the ITS, act1, tubulin, and tef1 genomic regions of the isolate HL_GM-7 (GenBanK accessions MW548097 MW961420, MW961419 and MW961421) showed high similarity with the isolates of C. cassiicola including 99.58% with sequence KF810854 (Deon et al. 2014), 99.11% with FJ853005 (Dixon et al. 2009), 99.34% with MH763700 (Duan et al. 2019), and 99.33% with KY112719 (Zhang et al. 2018) respectively. Based on the morphology, pathogenicity, and sequence results, this study becomes the first report of C. cassiicola causing target spot on soybean in Taiwan. C. cassiicola is known to infect a broad host range (Dixon et al. 2009; Lopezet al. 2018), and it has been found to infect tomato, cucumber, papaya, and Salvia miltiorrhiza in Taiwan (Lu et al. 2019; Tsai et al. 2015). Therefore, the emergence of soybean target spot should be aware to avoid potential damage to soybean production in Taiwan.

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