First Report of Target Spot Disease Caused by Corynespora cassiicola on Vegetable Crops in Trinidad

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.

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First Report of Corynespora cassiicola Causing Leaf Spot Disease on Buxus sinica subsp. sinica var. parvifolia in China

Plant Disease ◽

10.1094/pdis-11-17-1797-pdn ◽

2018 ◽

Vol 102 (9) ◽

pp. 1856-1856

Author(s):

W. Gao ◽

H.-Y. Ben ◽

Y. Wang ◽

Y.-R. Yao

Keyword(s):

Leaf Spot ◽

Leaf Spot Disease ◽

Corynespora Cassiicola ◽

First Report ◽

Spot Disease

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First Report of Target Spot of Soybean Caused by Corynespora cassiicola in the Colombian Eastern Plains

Plant Disease ◽

10.1094/pdis-07-20-1586-pdn ◽

2020 ◽

pp. PDIS-07-20-1586

Author(s):

Nathali López-Cardona ◽

Alejandra Guevara-Castro ◽

Lederson Gañán

Keyword(s):

Corynespora Cassiicola ◽

First Report ◽

Target Spot

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First Report of Target Spot on Tomato Caused by Corynespora cassiicola in Mauritius

Plant Disease ◽

10.1094/pdis-05-20-1119-pdn ◽

2021 ◽

Vol 105 (1) ◽

pp. 226

Author(s):

N. Mamode Ally ◽

H. Neetoo ◽

M. Ranghoo-Sanmukhiya ◽

S. Hardowar ◽

V. Vally ◽

...

Keyword(s):

Corynespora Cassiicola ◽

First Report ◽

Target Spot

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First Report of Corynespora cassiicola-Incited Target Spot on Cotton in Alabama

Plant Disease ◽

10.1094/pdis-02-13-0133-pdn ◽

2013 ◽

Vol 97 (10) ◽

pp. 1379-1379 ◽

Cited By ~ 14

Author(s):

K. N. Conner ◽

A. K. Hagan ◽

L. Zhang

Keyword(s):

Sequence Data ◽

Disease Onset ◽

Original Description ◽

Rrna Gene ◽

Corynespora Cassiicola ◽

Internal Transcribed Spacer Region ◽

Nucleotide Sequence Data ◽

First Report ◽

Leaf Spots ◽

Target Spot

Target spot symptoms were first observed on dryland and irrigated cotton (Gossypium hirsutum L.) statewide in Alabama in 2011. Leaf spots first appeared in the lower canopy and spread upward through the canopy toward the shoot tips. Individual leaf spots were roughly circular, formed concentric rings of alternating light and dark brown bands, and were up to 10 mm in diameter. Leaves with multiple lesions senesced prematurely. In 2012, target spot symptoms were observed as early as 68 days after planting in Tallapoosa County, Alabama. The possible combination of early disease onset and frequent showers/irrigation triggered rapid premature defoliation in some fields in excess of 75% in susceptible cultivars (Phytogen 499). Estimated yield losses in select cultivars (Deltapine 1050 and Phytogen 499) exceeded 336 kg/ha seed cotton. In 2012, symptomatic leaves were obtained from two separate locations in Alabama (Baldwin and Tallapoosa counties). The fungus was isolated from lesions by single spores plated on antibiotic V8 agar (1) and incubated at 21°C for 2 weeks under 12-h light cycles. Conidiophores arising from the gray, flocculose colonies were simple, erect, cylindrical, brown or olivaceous, unbranched, with two to seven septa. Conidia were borne singly, ranging from subhyaline to olivaceous, obclavate to cylindrical, straight to slightly curved, contained 4 to 15 pseudosepta, and were 50 to 209 μm long and 7 to 15 μm wide. These characteristics were consistent with the original description of Corynespora cassiicola on cotton (2). The internal transcribed spacer region (ITS) of two isolates, one representing each location, was amplified using primers 2234c and 3126t targeting a 550-bp region of the ITS1, 5.8S rRNA gene, and ITS2 (3). Sequences revealed 99% similarity to C. cassiicola in NCBI (Accession Nos. AY238606 and JQ717069). In greenhouse pathogenicity tests, 10 cotton seedlings (Phytogen 499) were inoculated by spraying a fungal suspension (2 × 104 spores/ml) of each of the two isolates prepared from 2-week-old cultures until runoff. Controls were inoculated with sterile water. Cotton seedlings were incubated in a moist chamber at 21°C for 72 h. All plants inoculated with the fungus developed leaf spot symptoms in 6 days. The fungus was reisolated from five inoculated plants. DNA was extracted from each isolate, amplified using primer pair 2234c/3126t, and sequenced. Sequences (550-bp) from all isolates shared 99% similarity to other C. cassiicola sequences in GenBank (Accession Nos. AY238606 and JQ717069). Nucleotide sequence data reported are available in GenBank under Accession Nos. KC544017 to 23. This pathogen has been reported previously to be economically important on a number of other hosts. To our knowledge, this is the first report of C. cassiicola on cotton in Alabama. Given the increasing prevalence of this disease in Alabama, its confirmation is a significant step toward developing management recommendations for growers. References: (1) L. J. Dixon et al. Phytopathology 99:1015, 2009. (2) J. P. Jones. Phytopathology 51:305, 1961. (3) J. Sequerra et al. Mycol. Res. 101:465, 1997.

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First Report of Target Spot Caused by Corynespora cassiicola on Strawberry in North America

Plant Disease ◽

10.1094/pdis-01-19-0057-pdn ◽

2019 ◽

Vol 103 (6) ◽

pp. 1412-1412 ◽

Cited By ~ 1

Author(s):

R. B. Onofre ◽

C. S. Rebello ◽

J. C. Mertely ◽

N. A. Peres

Keyword(s):

North America ◽

Corynespora Cassiicola ◽

First Report ◽

Target Spot

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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 Spot Caused by Corynespora cassiicola on Cotton in Georgia

Plant Disease ◽

10.1094/pdis-01-12-0035-pdn ◽

2012 ◽

Vol 96 (7) ◽

pp. 1066-1066 ◽

Cited By ~ 14

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.

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