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

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.

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

Plant Disease ◽

10.1094/pd-89-0433c ◽

2005 ◽

Vol 89 (4) ◽

pp. 433-433 ◽

Cited By ~ 5

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.

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First Report of Pyricularia grisea Causing Gray Leaf Spot on Lily in Korea

Plant Disease ◽

10.1094/pdis-94-2-0280a ◽

2010 ◽

Vol 94 (2) ◽

pp. 280-280

Author(s):

Y. P. Zhang ◽

J. H. Wang ◽

L. F. Wu ◽

X. W. Wu ◽

G. F. Cui ◽

...

Keyword(s):

Leaf Spot ◽

Disease Incidence ◽

Morphological Characteristics ◽

Gray Leaf Spot ◽

Tween 20 ◽

Pyricularia Grisea ◽

First Report ◽

Plastic Bags ◽

Initial Symptoms ◽

Plant Nursery

Lily is an economically important ornamental crop in Korea. In August 2008, severe leaf spot symptoms were observed on an oriental Lily ‘Action’ in a plant nursery in Daegu, Korea. Disease incidence was 20 to 30%. Initial symptoms were olive green-to-brown lesions on the leaf that developed into tan, elliptical, necrotic lesions. On severely infected leaves, lesions coalesced and killed the entire leaf blade. Infected leaves were surface disinfested with 70% ethanol for 30 s and 2% chlorox for 15 min before plating 1 cm2 sections onto potato dextrose agar. Hyphae appeared 5 days after inoculation and pure culture. Conidia were hyaline, transversely septate with one to three septa; most had two. Conidia were obpyriform and measured 29 to 46 μm long and 7 to 17 μm wide. Mycelia morphology and conidia production were consistent with that described previously for Pyricularia grisea (1). Koch's postulates were fulfilled by spraying five, healthy, vegetative-stage plants with 2 × 105 conidia per ml of sterile distilled water plus 0.05% Tween 20. As a control, five similar plants were sprayed with sterile water plus 0.05% Tween 20 only. Plants were placed inside plastic bags to maintain high relative humidity and incubated in a growth chamber at 25°C under fluorescent light for 14 h and at 20°C in darkness for 10 h. After 3 days, the plastic bags were removed and plants were maintained under the same conditions. Initial symptoms were observed 7 days after inoculation. Ten days after inoculation, disease symptoms on inoculated plants were similar to those previously described in the nursery. Control plants did not show any symptoms. Fungi isolated from these lesions had the same morphological characteristics as the ones isolated previously from plants in the nursery. To our knowledge, this is the first report of gray leaf spot on lily caused by P. grisea in Korea. References: (1) M. B. Ellis. Dematiaceous Hyphomycetes. CMI, Kew, Surrey, UK, 1971.

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

Plant Disease ◽

10.1094/pdis.2000.84.10.1151b ◽

2000 ◽

Vol 84 (10) ◽

pp. 1151-1151 ◽

Cited By ~ 12

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.

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First Report of Gray Leaf Spot on Perennial Ryegrass in Indiana

Plant Health Progress ◽

10.1094/php-2000-0607-01-hn ◽

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

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Pyricularia grisea Causing Gray Leaf Spot of Perennial Ryegrass Turf: Population Structure and Host Specificity

Plant Disease ◽

10.1094/pdis.2001.85.8.817 ◽

2001 ◽

Vol 85 (8) ◽

pp. 817-826 ◽

Cited By ~ 38

Author(s):

G. Viji ◽

B. Wu ◽

S. Kang ◽

W. Uddin ◽

D. R. Huff

Keyword(s):

United States ◽

Population Structure ◽

Winter Wheat ◽

Perennial Ryegrass ◽

Leaf Spot ◽

Genetic Relationships ◽

The United States ◽

Gray Leaf Spot ◽

Pyricularia Grisea ◽

Highly Virulent

Gray leaf spot is a serious disease of perennial ryegrass (Lolium perenne) turf in the United States. Isolates of Pyricularia grisea causing the disease in perennial ryegrass were characterized using molecular markers and pathogenicity assays on various gramineous hosts. Genetic relationships among perennial ryegrass isolates were determined using different types of trans-posons as probes. Phylogenetic analysis using Pot2 and MGR586 probes, analyzed with AMOVA (analysis of molecular variance), showed that these isolates from perennial ryegrass consist of three closely related lineages. All the isolates belonged to a single mating type, MAT1-2. Among 20 isolates from 16 host species other than perennial ryegrass, only the isolates from wheat (Triticum aestivum) and triticale (× Triticosecale), showed notable similarity to the perennial ryegrass isolates based on their Pot2 fingerprints. The copy number and fingerprints of Pot2 and MGR586 in isolates of P. grisea from perennial ryegrass indicate that they are genetically distinct from the isolates derived from rice (Oryza sativa) in the United States. The perennial ryegrass isolates also had the same sequence in the internal transcribed spacer (ITS) region of the genes encoding ribosomal RNA as that of the wheat and triticale isolates, and exhibited rice isolate sequence polymorphisms. In pathogenicity assays, all the isolates of P. grisea from Legacy II perennial ryegrass caused characteristic blast symptoms on Marilee soft white winter wheat, Bennett hard red winter wheat, Era soft white spring wheat, and Presto triticale, and they were highly virulent on these hosts. An isolate from wheat and one from triticale (from Brazil) were also highly virulent on perennial ryegrass and Rebel III tall fescue (Festuca arundinacea). None of the isolates from perennial ryegrass caused the disease on Lagrue rice, and vice versa. Understanding the population structure of P. grisea isolates infecting perennial ryegrass and their relatedness to isolates from other gramineous hosts may aid in identifying alternate hosts for this pathogen.

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Detection of Pyricularia grisea Causing Gray Leaf Spot of Perennial Ryegrass Turf by a Rapid Immuno-Recognition Assay

Plant Disease ◽

10.1094/pdis.2003.87.7.772 ◽

2003 ◽

Vol 87 (7) ◽

pp. 772-778 ◽

Cited By ~ 11

Author(s):

W. Uddin ◽

G. Viji ◽

G. L. Schumann ◽

S. H. Boyd

Keyword(s):

Monoclonal Antibody ◽

Rhode Island ◽

Perennial Ryegrass ◽

Leaf Spot ◽

The United States ◽

Gray Leaf Spot ◽

In Vitro Assays ◽

Pyricularia Grisea ◽

Curvularia Lunata ◽

Colletotrichum Graminicola

An immuno-recognition assay using a monoclonal antibody was developed to detect Pyricularia grisea, the causal agent of gray leaf spot of perennial ryegrass (Lolium perenne). In vitro assays with isolates of P. grisea from perennial ryegrass, tall fescue (Festuca arundinacea), St. Augustinegrass (Stenotaphrum secundatum), crabgrass (Digitaria sanguinalis), finger millet (Eleusine coracana), wheat (Triticum aestivum), triticale (× Triticosecale rimpaui), and rice (Oryza sativa) showed positive reactions; however, the strength of the reactions differed among isolates. Reactions were more intense with isolates from perennial ryegrass, wheat, and triticale. All P. grisea isolates from perennial ryegrass collected from various regions of the United States showed positive reactions. P. grisea was detected at antigen dilution rates of 0.5×, 0.25×, 0.13×, 0.06×, and 0.03×. Dot-blot assays with Bipolaris sorokiniana, Colletotrichum graminicola, Curvularia lunata, Microdochium nivale, Pythium aphanidermatum, Rhizoctonia solani, or Sclerotinia homoeocarpa isolated from turfgrasses were negative. In vivo assays of symptomatic leaves of perennial ryegrass plants inoculated with P. grisea also showed positive reactions, and those inoculated with B. sorokiniana, P. aphanidermatum, R. solani, or S. homoeocarpa were negative. Intensity of reaction between the monoclonal antibody and P. grisea was proportional to disease severity in perennial ryegrass inoculated with P. grisea; however, there was no reaction in dot blots of leaf tissue collected during the latent period. P. grisea was detected in perennial ryegrass samples from golf course fairways affected by gray leaf spot in Connecticut, Massachusetts, Maine, New Jersey, Pennsylvania, and Rhode Island using this procedure. The monoclonal antibody recognition system is highly sensitive to P. grisea and can be used effectively for the rapid diagnosis of gray leaf spot of perennial ryegrass turf.

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Field Resistance to Strobilurin (QoI) Fungicides in Pyricularia grisea Caused by Mutations in the Mitochondrial Cytochrome b Gene

Phytopathology ◽

10.1094/phyto.2003.93.7.891 ◽

2003 ◽

Vol 93 (7) ◽

pp. 891-900 ◽

Cited By ~ 144

Author(s):

Yun-Sik Kim ◽

Edward W. Dixon ◽

Paul Vincelli ◽

Mark L. Farman

Keyword(s):

Sequence Analysis ◽

Cytochrome B ◽

Perennial Ryegrass ◽

Leaf Spot ◽

Mutant Allele ◽

Field Resistance ◽

Gray Leaf Spot ◽

Cytochrome B Gene ◽

Nucleotide Sequence Analysis ◽

Pyricularia Grisea

Gray leaf spot caused by Pyricularia grisea is a highly destructive disease of perennial ryegrass turf. Control of gray leaf spot is dependent on the use of preventative fungicide treatments. Strobilurin-based (QoI) fungicides, which inhibit the cytochrome bc1 respiratory complex, have proven to be very effective against gray leaf spot. However, in August 2000, disease was diagnosed in QoI-treated perennial ryegrass turf on golf courses in Lexington, KY, Champaign, IL, and Bloomington, IL. To determine if resistance was due to a mutation in the fungicide target, the cytochrome b gene (CYTB) was amplified from baseline and resistant isolates. Nucleotide sequence analysis revealed an intronless coding region of 1,179 bp. Isolates that were resistant to QoI fungicides possessed one of two different mutant alleles, each of which carried a single point mutation. The first mutant allele had a guanine-to-cytosine transition at nucleotide position +428, resulting in a replacement of glycine 143 by alanine (G143A). Mutant allele two exhibited a cytosine-to-adenine transversion at position +387, causing a phenylalanine-to-leucine change (F129L). Cleavable amplified polymorphic sequence analysis revealed that neither mutation was present in a collection of baseline isolates collected before QoI fungicide use and indicated that suspected QoI- resistant isolates found in 2001 in Indiana and Maryland possessed the F129L mutation. The Pyricularia grisea isolates possessing the G143A substitution were significantly more resistant to azoxystrobin and trifloxystrobin, in vitro, than those having F129L. DNA fingerprinting of resistant isolates revealed that the mutations occurred in just five genetic backgrounds, suggesting that field resistance to the QoI fungicides in Pyricularia grisea is due to a small number of ancestral mutations.

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

Plant Disease ◽

10.1094/pdis.2002.86.1.75c ◽

2002 ◽

Vol 86 (1) ◽

pp. 75-75 ◽

Cited By ~ 19

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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Pyricularia grisea Isolates Causing Gray Leaf Spot on Perennial Ryegrass (Lolium perenne) in the United States: Relationship to P. grisea Isolates from Other Host Plants

Phytopathology ◽

10.1094/phyto.2002.92.3.245 ◽

2002 ◽

Vol 92 (3) ◽

pp. 245-254 ◽

Cited By ~ 49

Author(s):

Mark L. Farman

Keyword(s):

United States ◽

Molecular Markers ◽

Lolium Perenne ◽

Perennial Ryegrass ◽

Tall Fescue ◽

Leaf Spot ◽

The United States ◽

Gray Leaf Spot ◽

Group Method ◽

Pyricularia Grisea

Gray leaf spot of perennial ryegrass (prg) (Lolium perenne), caused by the fungus Pyricularia grisea (teleomorph = Magnaporthe grisea), has rapidly become the most destructive of all turf grass diseases in the United States. Fungal isolates from infected prg were analyzed with several molecular markers to investigate their relationship to P. grisea strains found on other hosts. All of the molecular markers used in this study revealed that isolates from prg are very distantly related to those found on crabgrass. Fingerprinting with MGR586 (Pot3) revealed zero to three copies of this transposon in the prg pathogens, distinguishing them from isolates pathogenic to rice, which typically have more than 50 copies of this element. RETRO5, a newly identified retroelement in P. grisea, was present at a copy number of >50 in isolates from rice and Setaria spp. but only six to eight copies were found in the isolates from prg. The MAGGY retrotransposon was unevenly distributed in the prg pathogens, with some isolates lacking this element, some possessing six to eight copies, and others having 10 to 30 copies. These results indicated that the P. grisea isolates causing gray leaf spot are distinct from those found on crabgrass, rice, or Setaria spp. This conclusion was supported by an unweighted pair-group method with arithmetic average cluster analysis of single-copy restriction fragment length polymorphism haplo-types. Fingerprints obtained with probes from the Pot2 and MGR583 transposons revealed that the prg pathogens are very closely related to isolates from tall fescue, and that they share similarity with isolates from wheat. However, the wheat pathogens had fewer copies of these elements than those found on prg. Therefore, I conclude that P. grisea isolates commonly found on other host plant species did not cause gray leaf spot epidemics on prg. Instead, the disease appears to be caused by a P. grisea population that is specific to prg and tall fescue.

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First Report of Gray Leaf Spot on Perennial Ryegrass in Indiana

Plant Disease ◽

10.1094/pdis.2000.84.4.492b ◽

2000 ◽

Vol 84 (4) ◽

pp. 492-492 ◽

Cited By ~ 22

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.

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