scholarly journals First Report of Gray Leaf Spot on Perennial Ryegrass in Indiana

Plant Disease ◽  
2000 ◽  
Vol 84 (4) ◽  
pp. 492-492 ◽  
Author(s):  
P. Harmon ◽  
K. Rane ◽  
G. Ruhl ◽  
R. Latin
Keyword(s):  
Perennial Ryegrass ◽  
Leaf Spot ◽  
Continuous Light ◽  
Gray Leaf Spot ◽  
Golf Course ◽  
Infected Leaf ◽  
Conidial Suspension ◽  
First Report ◽  
Saturated Atmosphere ◽  
Colony Surface

Pyricularia grisea, the causal agent of gray leaf spot on turfgrass, was isolated from symptomatic perennial ryegrass (Lolium perenne) leaves collected from a golf course in north-central Indiana in August 1999. Gray leaf spot is an emerging threat to stands of perennial ryegrass in the mid-Atlantic and Midwestern United States (1). Symptoms were first evident in taller (6 cm) mown, rough areas surrounding golf course fairways. Field symptoms included diffuse patches (1 to 4 m in diameter) of thin, yellow-tan turf. Within larger affected areas, some of the turf was dead and matted. Close inspection revealed the presence of typical tan-gray lesions with brown margins and fish hook-like distortion of infected leaf blade tips. Incubation of affected turf in a saturated environment at 23°C for 16 h resulted in production of numerous three-celled, pear-shaped conidia characteristic of those produced by P. grisea. A pure culture of the isolate was grown on V8-juice agar in darkness at 29°C. After 10 days, the culture was exposed to continuous light for 4 days at 23°C to induce sporulation. Conidia were washed from the colony surface with sterile distilled water. Two-week-old perennial ryegrass plants in 8-cm-diameter pots were inoculated with the conidial suspension. Typical gray leaf spot symptoms resulted after incubation of inoculated plants at 27°C for 72 h in a saturated atmosphere. Uninoculated control plants exposed to the same environmental conditions remained healthy. This is the first report of gray leaf spot on perennial ryegrass in Indiana. Reference: (1) P. J. Landschoot and B. F. Hoyland. Plant Dis. 76:1280, 1992.

scholarly journals First Report of Gray Leaf Spot Caused by Pyricularia grisea on Lolium perenne in Illinois

Plant Disease ◽  
2000 ◽  
Vol 84 (10) ◽  
pp. 1151-1151 ◽  
Author(s):  
D. K. Pedersen ◽  
R. T. Kane ◽  
H. T. Wilkinson
Keyword(s):  
Disease Severity ◽  
Lolium Perenne ◽  
Perennial Ryegrass ◽  
Leaf Spot ◽  
Gray Leaf Spot ◽  
Pyricularia Grisea ◽  
Conidial Suspension ◽  
First Report ◽  
Severity Rating ◽  
Plastic Bags

Each year from 1991 to 1999, a disease matching the description of gray leaf spot (1) was observed in the central and north central regions of Illinois. Disease severity was low (<10% blight) from 1991 to 1994 and 1999 and was severe (>50% blight in some areas) from 1995 to 1998. The disease was observed on Lolium perenne (perennial ryegrass) golf course fairways and sports fields. Isolations of Pyricularia grisea were made from L. perenne collected from golf courses in Bloomington, Decatur, Kankakee, Pekin, Urbana, and Moline, IL. All isolates were collected from surface-sterilized, symptomatic leaves. Cultures were maintained on one-fifth strength potato-dextrose agar (PDA) and induced to sporulate on full-strength oatmeal agar. All isolates in culture displayed vegetative and conidial characteristics similar to those previously described for P. grisea (1). Twenty-five different L. perenne germ plasms were inoculated with isolate WF9826 (Kankakee) using a suspension of 1 × 105 conidia per milliliter. The 4-week-old lawns (100 plants per 3-cm-diameter cone-tainer) of each ryegrass germ plasm were inoculated by spraying foliage with the conidial suspension until runoff. Inoculated and uninoculated lawns were enclosed in plastic bags and placed in an incubator (16 h light; 28°C) for 7 days. Disease severity was rated using a scale of 0 to 10 (10 = 100% blight). Each treatment was replicated three times, and all experiments were repeated four times. Small blue-gray, water-soaked lesions with dark brown borders were observed on leaves of all inoculated ryegrass germ plasms. Advanced symptoms included blighting of much of the leaves. The mean disease severity rating was 3.8 (range 2 to 7) for all experimental units and all 25 germ plasms. P. grisea was isolated from leaves that were inoculated with WF9826. This is the first report of gray leaf spot of perennial ryegrass caused by P. grisea in Illinois. Reference: (1) P. J. Landschoot et al. Plant Dis. 76:1280, 1992.

First Report of Gray Leaf Spot on Perennial Ryegrass in Indiana

2000 ◽  
Vol 1 (1) ◽  
pp. 27
Author(s):  
P. Harmon ◽  
K. Rane ◽  
G. Ruhl ◽  
R. Latin
Keyword(s):  
United States ◽  
Lolium Perenne ◽  
Perennial Ryegrass ◽  
Leaf Spot ◽  
Gray Leaf Spot ◽  
Causal Agent ◽  
Golf Course ◽  
Pyricularia Grisea ◽  
North Central ◽  
First Report

Pyricularia grisea, the causal agent of gray leaf spot on turfgrass, was isolated from symptomatic perennial ryegrass (Lolium perenne) leaves collected from a golf course in north-central Indiana in August 1999. Gray leaf spot is an emerging threat to stands of perennial ryegrass in the mid-Atlantic and Midwestern United States. Posted 7 June 2000.

scholarly journals First Report of Gray Leaf Spot on St. Augustinegrass in Italy

Plant Disease ◽  
2003 ◽  
Vol 87 (12) ◽  
pp. 1536-1536 ◽  
Author(s):  
G. Polizzi ◽  
I. Castello ◽  
A. M. Picco ◽  
D. Rodino
Keyword(s):  
Leaf Spot ◽  
Magnaporthe Grisea ◽  
Fungal Spore ◽  
Gray Leaf Spot ◽  
Blast Disease ◽  
Leaf Spot Disease ◽  
High Humidity ◽  
Conidial Suspension ◽  
First Report ◽  
Pathogenicity Tests

St. Augustinegrass (Stenotaphrum secundatum (Walt.) Kuntze) is used for lawns in southern Italy because it is much more resistant to biotic and abiotic adversities than other turfgrass species. Because few seeds are viable, this species is established by vegetative propagation. A new disease was noticed during the spring of 2002 and 2003 on cuttings of St. Augustinegrass growing in three greenhouses in eastern Sicily. The disease affected leaves and culms and caused a progressive drying of the plants. The infection was first seen on leaves as gray, necrotic spots that enlarged in high-humidity conditions to form oval, and later, spindle-shaped lesions. In association with the lesions, it was possible to observe fungal spore development and sunken areas with blue-gray centers and slightly irregular, brown margins with yellow halos. Spots were concentrated without specific arrangement along longitudinal veins and the midrib and at the base, tip, and margins of the leaf blade. Symptoms on the culms consisted of brown-to-black blotches that sometimes extended throughout the internodes. From these infected tissues, 20 explants taken from leaves and culms were cut, washed with sterile water, and placed on 1.5% water agar (WA). Later, conidia and conidiophores were obtained from colonies with a sterile glass needle and placed on 4% WA. From these plates, two monoconidial isolates were obtained and transferred to rice meal medium (1). The colonies were identified as Pyricularia grisea Cooke (Sacc.), anamorphic state of Magnaporthe grisea (Hebert) Yeagashi & Udagawa, the cause of rice blast disease and gray leaf spot disease of turfgrasses. The conidia were pyriform to obclavate, narrowed toward the tip, rounded at the base, 2-septate, 21 to 31 μm × 6 to 10 μm (average 25.7 ×8.2 μm). Pathogenicity tests were performed by inoculating leaves and culms of six St. Augustinegrass plants with a conidial suspension of the fungus (1.5 ×105 conidia per ml). The same number of noninoculated plants was used as controls. All plants were incubated in a moist chamber with high humidity at 25°C. After 6 days, all inoculated plants showed typical symptoms of the disease. Koch's postulates were fulfilled by isolating P. grisea from inoculated plants. Gray leaf spot caused by P. grisea has been a chronic problem on St. Augustinegrass since it was first reported in 1957 (2). To our knowledge, this is the first report of P. grisea on St. Augustinegrass in Italy. While it does not appear to be an important disease in the field at this time in Sicily, it could cause losses in greenhouses where vegetative material is propagated for field planting. A preliminary molecular analysis has shown a clear distinction between the tested strain and other strains isolated from rice seeds and plants in northern Italy. References: (1) E. Roumen et al. Eur. J. Plant Pathol. 103:363, 1997. (2) L. P. Tredway et al. Plant Dis. 87:435, 2003.

scholarly journals First Report of Pyricularia grisea (Gray Leaf Spot) on Perennial Ryegrass (Lolium perenne) in Nevada

Plant Disease ◽  
2006 ◽  
Vol 90 (5) ◽  
pp. 683-683 ◽  
Author(s):  
F. P. Wong ◽  
K. A. de la Cerda
Keyword(s):  
Perennial Ryegrass ◽  
Leaf Spot ◽  
Gray Leaf Spot ◽  
Tween 20 ◽  
Pyricularia Grisea ◽  
Petroleum Jelly ◽  
First Report ◽  
Petri Dishes ◽  
Paper Towels ◽  
Plastic Containers

In August of 2005, a golf course in Las Vegas, NV reported turf loss from an unknown disease on perennial ryegrass fairways. Samples from this course were examined, and diseased plants were found covered with lesions and sporulation typical of gray leaf spot as caused by Pyricularia grisea (Cooke) Sacc. With petroleum jelly, sporulating leaves were attached to the inside top surface of 100-mm petri dishes filled with 15 ml of 1.5% water agar. Conidia were allowed to drop onto the agar surface and 24 h later, individual germinating pyriform conidia were transferred to petri dishes containing one-quarter-strength potato dextrose agar (¼-PDA) with the aid of a fine needle and stereomicroscope. Isolates of the fungus were maintained at 28°C with constant fluorescent light. Isolates were examined 7 to 10 days later, and morphology and conidia production were consistent with that described previously for P. grisea (1). Koch's postulates were performed using a single isolate (SSGC-1.1) grown for 14 days on ¼-PDA. The petri dish was flooded with 15 ml of sterile distilled water plus 0.05% Tween 20 and conidia dislodged into the solution with a rubber policeman to obtain a solution of approximately 5 × 103 conidia per ml. Using a modified thin-layer chromatography plate sprayer, the solution was misted onto six pots of 6-week-old perennial ryegrass (a mixture of approximately 33% each of varieties ‘Kokomo’, ‘Cabo’ and ‘Secretaria’), seeded at a density of 2 kg per 93 m2 grown in 4- × 4-cm plastic pots filled with University of California soil mix. As a control treatment, six pots of perennial ryegrass (grown as previously described) were treated with water plus 0.05% Tween 20 only. Pots of plants were placed into closed, translucent, plastic containers lined with wet paper towels to provide a moist environment and held at 30°C for 48 h. Pots of plants were transferred to an incubator set at 30°C and 80% relative humidity with 12 h of alternating light and dark cycles. Four days after inoculation, plants misted with conidia developed symptoms typical of gray leaf spot. Plants were again placed into closed plastic containers lined with wet paper towels for 24 h, at which time, lesions on symptomatic plants developed abundant conidia characteristic of P. grisea. Water-only treated plants did not show any symptoms or signs of disease. P. grisea was reisolated from sporulating leaves as described above. The disease has been spreading in the midwestern and northeastern United States since first reported in 1991 on perennial ryegrass in Pennsylvania. It has only recently been found on turfgrass in California (2), and to our knowledge, this is the first report of this pathogen on perennial ryegrass in Nevada. References: (1) M. B. Ellis. Dematiaceous Hyphomycetes. CMI, Kew, Surrey, UK, 1971. (2) W. Uddin et al. Plant Dis. 86:75, 2002.

scholarly journals First Report of Tomato Gray Leaf Spot Disease Caused by Stemphylium solani in Malaysia

Plant Disease ◽  
2012 ◽  
Vol 96 (8) ◽  
pp. 1226-1226
Author(s):  
A. Nasehi ◽  
J. B. Kadir ◽  
M. A. Zainal Abidin ◽  
M. Y. Wong ◽  
F. Mahmodi
Keyword(s):  
Leaf Spot ◽  
Disease Incidence ◽  
Gray Leaf Spot ◽  
Leaf Spot Disease ◽  
Conidial Suspension ◽  
Internal Transcribed Spacer Region ◽  
First Report ◽  
Spot Disease ◽  
Pcr Product ◽  
Morphological Criteria

In June 2011, tomatoes (Solanum lycopersicum) in major growing areas of the Cameron Highlands and the Johor state in Malaysia were affected by a leaf spot disease. Disease incidence exceeded 80% in some severely infected regions. Symptoms on 50 observed plants initially appeared on leaves as small, brownish black specks, which later became grayish brown, angular lesions surrounded by a yellow border. As the lesions matured, the affected leaves dried up and became brittle and later developed cracks in the center of the lesions. A survey was performed in these growing areas and 27 isolates of the pathogen were isolated from the tomato leaves on potato carrot agar (PCA). The isolates were purified by the single spore technique and were transferred onto PCA and V8 agar media for conidiophore and conidia production under alternating light (8 hours per day) and darkness (16 hours per day) (4). Colonies on PCA and V8 agar exhibited grey mycelium and numerous conidia were formed at the terminal end of conidiophores. The conidiophores were up to 240 μm long. Conidia were oblong with 2 to 11 transverse and 1 to 6 longitudinal septa and were 24 to 69.6 μm long × 9.6 to 14.4 μm wide. The pathogen was identified as Stemphylium solani on the basis of morphological criteria (2). In addition, DNA was extracted and the internal transcribed spacer region (ITS) was amplified by universal primers ITS5 and ITS4 (1). The PCR product was purified by the commercial PCR purification kit and the purified PCR product sequenced. The resulting sequences were 100% identical to published S. solani sequences (GenBank Accestion Nos. AF203451 and HQ840713). The amplified ITS region was deposited with NCBI GenBank under Accession No. JQ657726. A representative isolate of the pathogen was inoculated on detached 45-day-old tomato leaves of Malaysian cultivar 152177-A for pathogenicity testing. One wounded and two nonwounded leaflets per leaf were used in this experiment. The leaves were wounded by applying pressure to leaf blades with the serrated edge of a forceps. A 20-μl drop of conidial suspension containing 105 conidia/ml was used to inoculate these leaves (3). The inoculated leaves were placed on moist filter paper in petri dishes and incubated for 48 h at 25°C. Control leaves were inoculated with sterilized distilled water. After 7 days, typical symptoms for S. solani similar to those observed in the farmers' fields developed on both wounded and nonwounded inoculated leaves, but not on noninoculated controls, and S. solani was consistently reisolated. To our knowledge, this is the first report of S. solani causing gray leaf spot of tomato in Malaysia. References: (1) M. P. S. Camara et al. Mycologia 94:660, 2002. (2) B. S. Kim et al. Plant Pathol. J. 15:348, 1999. (3) B. M. Pryor and T. J. Michailides. Phytopathology 92:406, 2002. (4) E. G. Simmons. CBS Biodiversity Series 6:775, 2007.

scholarly journals First Report of Gray Leaf Spot on Pepper Caused by Stemphylium solani in Malaysia

Plant Disease ◽  
2012 ◽  
Vol 96 (8) ◽  
pp. 1227-1227 ◽  
Author(s):  
A. Nasehi ◽  
J. B. Kadir ◽  
M. A. Zainal Abidin ◽  
M. Y. Wong ◽  
F. Abed Ashtiani
Keyword(s):  
Leaf Spot ◽  
Disease Incidence ◽  
Leaf Tissue ◽  
Gray Leaf Spot ◽  
Universal Primers ◽  
Conidial Suspension ◽  
Internal Transcribed Spacer Region ◽  
First Report ◽  
Morphological Criteria ◽  
Pepper Leaves

Symptoms of gray leaf spot were first observed in June 2011 on pepper (Capsicum annuum) plants cultivated in the Cameron Highlands and Johor State, the two main regions of pepper production in Malaysia (about 1,000 ha). Disease incidence exceeded 70% in severely infected fields and greenhouses. Symptoms initially appeared as tiny (average 1.3 mm in diameter), round, orange-brown spots on the leaves, with the center of each spot turning gray to white as the disease developed, and the margin of each spot remaining dark brown. A fungus was isolated consistently from the lesions using sections of symptomatic leaf tissue surface-sterilized in 1% NaOCl for 2 min, rinsed in sterile water, dried, and plated onto PDA and V8 agar media (3). After 7 days, the fungal colonies were gray, dematiaceous conidia had formed at the end of long conidiophores (19.2 to 33.6 × 12.0 to 21.6 μm), and the conidia typically had two to six transverse and one to four longitudinal septa. Fifteen isolates were identified as Stemphylium solani on the basis of morphological criteria described by Kim et al. (3). The universal primers ITS5 and ITS4 were used to amplify the internal transcribed spacer region (ITS1, 5.8, and ITS2) of ribosomal DNA (rDNA) of a representative isolate (2). A 570 bp fragment was amplified, purified, sequenced, and identified as S. solani using a BLAST search with 100% identity to the published ITS sequence of an S. solani isolate in GenBank (1). The sequence was deposited in GenBank (Accession No. JQ736024). Pathogenicity of the fungal isolate was tested by inoculating healthy pepper leaves of cv. 152177-A. A 20-μl drop of conidial suspension (105 spores/ml) was used to inoculate each of four detached, 45-day-old pepper leaves placed on moist filter papers in petri dishes (4). Four control leaves were inoculated similarly with sterilized, distilled water. The leaves were incubated at 25°C at 95% relative humidity for 7 days. Gray leaf spot symptoms similar to those observed on the original pepper plants began to develop on leaves inoculated with the fungus after 3 days, and S. solani was consistently reisolated from the leaves. Control leaves did not develop symptoms and the fungus was not reisolated from these leaves. Pathogenicity testing was repeated with the same results. To our knowledge, this is the first report of S. solani causing gray leaf spot on pepper in Malaysia. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) M. P. S. Camara et al. Mycologia 94:660, 2002. (3) B. S. Kim et al. Plant Pathol. J. 15:348, 1999. (4) B. M. Pryor and T. J. Michailides. Phytopathology 92:406, 2002.

scholarly journals First Report of Pyricularia grisea Causing Gray Leaf Spot on Kikuyugrass (Pennisetum clandestinum) in the United States

Plant Disease ◽  
2005 ◽  
Vol 89 (4) ◽  
pp. 433-433 ◽  
Author(s):  
F. P. Wong ◽  
W. Gelernter ◽  
L. Stowell
Keyword(s):  
Perennial Ryegrass ◽  
Leaf Spot ◽  
Southern California ◽  
The United States ◽  
Gray Leaf Spot ◽  
Pyricularia Grisea ◽  
Commonwealth Mycological Institute ◽  
Single Spore ◽  
First Report ◽  
Pennisetum Clandestinum

Kikuyugrass (Pennisetum clandestinum) is a warm-season turfgrass that has been adopted for use in fairways and roughs in a number of subtropical areas including southern California, Mexico, Australia, and South Africa. During August 2003, a foliar disease of Kikuyugrass was reported from a number of golf courses in southern California. Examination of diseased plants showed the presence of dark, olive green-to-brown lesions on the foliage. Incubation of these plants in a moist chamber for 12 h led to the production of numerous pyriform conidia from these lesions that were characteristic of Pyricularia grisea. Single-spore isolates of the fungus were obtained from infected kikuyugrass samples by transferring conidia to acidified 1.5% water agar and then transferring single, germinated conidia to one-quarter-strength potato dextrose agar. Colony morphology and conidia production were consistent with that described for P. grisea (1). Koch's postulates were performed separately for two single-spore isolates (OSGC-1 and CCCC-1) obtained from infected kikuyugrass. For each isolate, 2-week-old, glasshouse-grown seedlings of kikuyugrass (cv. ‘AZ-1’) and perennial ryegrass (Lolium perenne) grown in 75-mm pots in soilless media were inoculated with conidia from either OSGC-1 or CCCC-1. For each test, six pots of both kikuyugrass and ryegrass were inoculated, and the tests were conducted three times for each isolate. Conidia were obtained from isolates grown on clarified V8 agar in 100-mm petri plates for 14 days at 25°C. Suspensions were made by adding 10 ml of sterile distilled H2O (sdH2O) to the plates, scraping the surface of the media to dislodge the conidia, filtering the suspension through cheesecloth, and then adjusting the final concentration to 1 × 106 conidia/ml with sdH2O. Seedlings were inoculated with the conidial suspensions with an aerosol applicator, placed in plastic boxes lined with wet paper towels, and sealed to provide adequate moisture for infection. Boxes were incubated at 28°C for 48 h after which time the covers were removed and the plants maintained in ambient glasshouse conditions at approximately 28°C. In all three replicated experiments, kikuyugrass seedlings inoculated with OSGC-1 or CCCC-1 developed symptoms of disease approximately 5 days after inoculation, while inoculated perennial ryegrass did not, even 14 days after inoculation. Symptomatic kikuyugrass leaves were taken randomly from plants from each of the three replicated tests, surface disinfested in 0.3% sodium hypochlorite for 30 s, rinsed with sdH2O, blotted dry, and placed onto acidified water agar in petri plates. Twenty-four hours later, abundant sporulation was observed from symptomatic tissue with conidiophores bearing conidia typical of P. grisea. To our knowledge, this is the first report of gray leaf spot being caused by P. grisea on Pennisetum clandestinum in North America. Reference: (1) M. B. Ellis. Dematiaceous Hyphomycetes. Commonwealth Mycological Institute, Kew, Surrey, UK, 1971.

scholarly journals First Report of Gray Leaf Spot of Mango (Mangifera indica) Caused by Pestalotiopsis mangiferae in Taiwan

Plant Disease ◽  
2007 ◽  
Vol 91 (12) ◽  
pp. 1684-1684 ◽  
Author(s):  
Y. Ko ◽  
K. S. Yao ◽  
C. Y. Chen ◽  
C. H. Lin
Keyword(s):  
Leaf Spot ◽  
Mangifera Indica ◽  
Gray Leaf Spot ◽  
Leaf Spot Disease ◽  
Continuous Exposure ◽  
Conidial Suspension ◽  
Tropical Fruit ◽  
First Report ◽  
Spot Disease ◽  
Initial Symptoms

Mango (Mangifera indica L.; family Anacardiaceae) is one of the world's most important fruit crops and is widely grown in tropical and subtropical regions. Since 2001, a leaf spot disease was found in mango orchards of Taiwan. Now, the disease was observed throughout (approximately 21,000 ha) Taiwan in moderate to severe form, thus affecting the general health of mango trees and orchards. Initial symptoms were small, yellow-to-brown spots on leaves. Later, the irregularly shaped spots, ranging from a few millimeters to a few centimeters in diameter, turned white to gray and coalesced to form larger gray patches. Lesions had slightly raised dark margins. On mature lesions, numerous black acervuli, measuring 290 to 328 μm in diameter, developed on the gray necrotic areas. Single conidial isolates of the fungus were identified morphologically as Pestalotiopsis mangiferae (Henn.) Steyaert (2,3) and were consistently isolated from the diseased mango leaves on acidified (0.06% lactic acid) potato dextrose agar (PDA) medium incubated at 25 ± 1°C. Initially, the fungus grew (3 mm per day) on PDA as a white, chalky colony that subsequently turned gray after 2 weeks. Acervuli developed in culture after continuous exposure to light for 9 to 12 days at 20 to 30°C. Abundant conidia oozed from the acervulus as a creamy mass. The conidia (17.6 to 25.4 μm long and 4.8 to 7.1 μm wide) were fusiform and usually straight to slightly curved with four septa. Three median cells were olivaceous and larger than the hyaline apical and basal cells. The apical cells bore three (rarely four) cylindrical appendages. Pathogenicity tests were conducted with either 3-day-old mycelial discs or conidial suspension (105 conidia per ml) obtained from 8- to 10-day-old cultures. Four leaves on each of 10 trees were inoculated. Before inoculation, the leaves were washed with a mild detergent, rinsed with tap water, and then surface sterilized with 70% ethanol. Leaves were wounded with a needle and exposed to either a 5-mm mycelial disc or 0.2 ml of the spore suspension. The inoculated areas were wrapped with cotton pads saturated with sterile water and the leaves were covered with polyethylene bags for 3 days to maintain high relative humidity. Wounded leaves inoculated with PDA discs alone served as controls. The symptoms described above were observed on all inoculated leaves, whereas uninoculated leaves remained completely free from symptoms. Reisolation from the inoculated leaves consistently yielded P. mangiferae, thus fulfilling Koch's postulates. Gray leaf spot is a common disease of mangos in the tropics and is widely distributed in Africa and Asia (1–3); however, to our knowledge, this is the first report of gray leaf spot disease affecting mango in Taiwan. References: (1) T. K. Lim and K. C. Khoo. Diseases and Disorders of Mango in Malaysia. Tropical Press. Malaysia, 1985. (2) J. E. M. Mordue. No. 676 in: CMI Descriptions of Pathogenic Fungi and Bacteria. Surrey, England, 1980. (3) R. C. Ploetz et al. Compendium of Tropical Fruit Diseases. The American Phytopathological Society. St. Paul, MN, 1994.

scholarly journals First Report of Leaf Spot Caused by Cladosporium tenuissimum on Panicle Hydrangea (Hydrangea paniculate) in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Chenxu Li ◽  
Peng Cao ◽  
Chuanjiao Du ◽  
Xi Xu ◽  
Wensheng Xiang ◽  
...  
Keyword(s):  
Dna Sequences ◽  
Leaf Spot ◽  
Disease Incidence ◽  
Elongation Factor ◽  
Flowering Plant ◽  
Leaf Spot Disease ◽  
Infected Leaf ◽  
Conidial Suspension ◽  
First Report ◽  
Dark Green

Panicle Hydrangea (Hydrangea paniculate) is an ornamental flowering plant native to China and Japan. In August 2019, leaf spot symptoms with about 30% disease incidence were observed on panicle hydrangea in two grower fields (about 0.1 ha in total) of Northeast Agriculture University, China (126.72°E, 45.74°N). Symptoms initially appeared on the lower and older leaves and showed small subcircular brown spots with dark-brown edges on both sides. As the disease progressed, the necrotic spots enlarged, became irregular, coalesced, and the infected leaf blighted in approximately 2 weeks. Panicle hydrangea leaf samples (n=15) from different plants that showed spot symptoms were collected and surface sterilized with 70% ethanol for 10 s, followed by 0.5% NaClO treatment for 4 min, and rinsed in sterile water 3 times. Thereafter, leaf samples were placed on potato dextrose agar (PDA) and incubated at 25°C for 7 days. Fifteen hyphal-tipped pure cultures were obtained. Colonies growing on PDA for 7 days were olive green to dark green, exhibited a velvet-like texture and sometimes were radially furrowed and wrinkled. Margins varied from white gray to dark green without prominent exudates. The back of the plate showed dark green to black. Conidiophores were up to 180 to 600 µm long, 2.8 to 4.5 µm wide (n=50), subcylindrical-filiform, straight, septate, and unbranched or rarely branched. Ramoconidia were 0 to 1 septate, cylindrical to clavate, smooth-walled, 8 to 22 μm long (n=50). Conidia were single-celled, lemon-shaped, smooth-walled and 2.0 to 5.0 µm (diameter) (n=50). To confirm the identity, three genomic DNA regions, internal transcribed spacer (ITS), partial translation elongation factor-1 alpha (EF), and actin (ACT) of the representative isolate BAI-1 were amplified with primer pairs ITS1/4, EF1-728F/986R, and ACT-512F/783R, respectively (Bensch et al. 2012; Jo et al. 2018). DNA sequences of the isolate from ITS, EF, and ACT showed 99.81% (514/515 bp), 99.10% (219/221 bp), and 99.54% (216/217 bp) nucleotide identity with those of C. tenuissimum CBS 125995, respectively (GenBank accession nos. HM148197, HM148442, and HM148687). The sequences of isolate BAI-1 were deposited in GenBank (accession nos. MW045455, MW052465, and MW052466). To fulfill Koch’s postulates, five healthy 2-year-old panicle hydrangea plants grown in pots were surface sterilized with 70% ethanol, washed twice with sterile distilled water, and sprayed with a conidial suspension of strain BAI-1 (adjusted to 1×106 conidia/ml using a hemocytometer), maintained in a greenhouse at 25°C and 85% relative humidity. Five plants sprayed with sterilized water served as controls. The inoculated plants showed leaf spot symptoms that were similar to those previously observed in the fields after 7 days, whereas control leaves remained healthy. The fungus was reisolated from symptomatic leaves and its identity was confirmed by morphological and molecular method. These experiments were repeated twice. So far, C. tenuissimum was reported to cause leaf spot of alfalfa (Han et al. 2019) and castor (Liu et al. 2019). To our knowledge, this is the first report of leaf spot disease in panicle hydrangea caused by C. tenuissimum in China. Leaf spot has a negative effect on the aesthetic value of panicle hydrangea, and this report will assist with monitoring distribution of the disease as well as developing management recommendations.

scholarly journals First Report of Gray Leaf Spot on Perennial Ryegrass Turf in California

Plant Disease ◽  
2002 ◽  
Vol 86 (1) ◽  
pp. 75-75 ◽  
Author(s):  
W. Uddin ◽  
G. Viji ◽  
L. Stowell
Keyword(s):  
United States ◽  
Perennial Ryegrass ◽  
Leaf Spot ◽  
Disease Incidence ◽  
The United States ◽  
Gray Leaf Spot ◽  
Water Soluble ◽  
Distilled Water ◽  
First Report ◽  
Polyethylene Bags

Gray leaf spot of perennial ryegrass (Lolium perenne L.) turf was first reported in the United States in 1991. The disease epidemic was primarily confined to golf course fairways in southeastern Pennsylvania (1). Subsequently, moderate to severe outbreaks of gray leaf spot occurred in perennial ryegrass fairways and roughs in numerous locations throughout the eastern and midwestern United States. In August 2001, a serious decline of perennial ryegrass turf was observed in a bermudagrass (Cynodon dactylon (L.) Pers) baseball field in Dodger Stadium in Los Angeles, CA, that had been overseeded with perennial ryegrass. The bermudagrass turf was not affected. The perennial ryegrass turf developed necrotic lesions that resulted in blighting of leaf blades. In laboratory assays, Pyricularia grisea (Cooke) Sacc., was consistently isolated from symptomatic ryegrass blades from turf samples collected from the site. Of the 12 P. grisea isolates collected from the assayed leaf blades, five isolates were selected for a pathogenicity assay. Twenty-five ‘Legacy II’ perennial ryegrass plants were grown from seeds in 4 × 4 in.-plastic pots, (10 × 10 cm) which were filled to 1 cm below the rim with granular calcine clay medium (Turface MVP, Allied Industrial Material Corp., Buffalo Grove, IL). Three weeks after seeding, plants were fertilized with a water-soluble 20-20-20 N-P-K fertilizer (1.3 g/liter of water) once per week. Treatments (isolates of P. grisea and a control) were arranged as a randomized complete block design with five replications. Five-week-old plants were sprayed with an aqueous suspension of P. grisea conidia (≈5 × 104 conidia per ml of sterilized distilled water with 0.1% Tween 20) using an atomizer until the leaves were completely wet. Plants sprayed with sterilized distilled water served as the control. After inoculation, individual pots were covered with clear polyethylene bags and placed in a controlled environment chamber maintained at 28°C and continuous fluorescent light (88 μE m-2 s-1). Four days after inoculation, necrotic lesions (<2 mm diameter) developed on ryegrass blades inoculated with each isolate of P. grisea. Lesions did not develop on leaves of control plants. Seven days after inoculation, the polyethylene bags were removed, and 50 symptomatic blades from each pot were collected, and disease incidence (percent infected leaves) and severity (index 0 to 10; 0 = none, 10 = >90% of the leaf blade necrotic ) were assessed. P. grisea was isolated from symptomatic leaves of plants inoculated with the fungus. Disease incidence and severity on inoculated plants were 92 to 96% and 8.8 to 10, respectively. There were no significant differences in disease incidence and severity (P = 0.05) among the isolates of P. grisea included in the test. To our knowledge, this is the first report of gray leaf spot of perennial ryegrass turf in California. Reference: (1) P. J. Landschoot and B. F. Hoyland. Plant Dis. 76:1280, 1992.

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