First Report of Barley virus G in Switchgrass (Panicum virgatum)

L. M. Kumar; J. A. Foster; C. McFarland; M. Malapi-Wight

doi:10.1094/pdis-09-17-1390-pdn

First report of Rhizoctonia cerealis causing sharp eyespot in Panicum virgatum in the UK

Plant Pathology ◽

10.1046/j.1365-3059.2001.00630.x ◽

2001 ◽

Vol 50 (6) ◽

pp. 807-807 ◽

Cited By ~ 6

Author(s):

J. V. Etheridge ◽

L. Davey ◽

D. G. Christian

Keyword(s):

Panicum Virgatum ◽

First Report ◽

Sharp Eyespot ◽

The Uk ◽

Rhizoctonia Cerealis

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

Plant Disease ◽

10.1094/pdis-01-13-0070-pdn ◽

2013 ◽

Vol 97 (12) ◽

pp. 1654-1654 ◽

Cited By ~ 3

Author(s):

A. L. Vu ◽

M. M. Dee ◽

J. Zale ◽

K. D. Gwinn ◽

B. H. Ownley

Keyword(s):

Leaf Spot ◽

Panicum Virgatum ◽

Morphological Characteristics ◽

Its Region ◽

Spore Production ◽

Post Inoculation ◽

Sterile Water ◽

Bipolaris Oryzae ◽

First Report ◽

Symptomatic Leaf

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

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First Report of a Leaf Spot Caused by Bipolaris oryzae on Switchgrass in New York

Plant Disease ◽

10.1094/pdis-03-11-0231 ◽

2011 ◽

Vol 95 (9) ◽

pp. 1192-1192 ◽

Cited By ~ 8

Author(s):

K. D. Waxman ◽

G. C. Bergstrom

Keyword(s):

New York ◽

North Dakota ◽

Leaf Spot ◽

Panicum Virgatum ◽

Perennial Grass ◽

Leaf Tissue ◽

Nucleotide Identity ◽

Bipolaris Oryzae ◽

First Report ◽

Mist Chamber

Switchgrass (Panicum virgatum L.) is a perennial grass with biofuel potential. From 2007 to 2010, foliar lesions were observed on first year and mature stands of switchgrass in various locations in New York. Foliar lesions were purple, elliptical (up to 1 cm) with either distinct or diffuse margins, and occasionally with yellow halos and/or white necrotic centers. After 2 to 5 days of moist chamber incubation, surface-sterilized, symptomatic leaf tissue produced conidia that when streaked onto potato dextrose agar containing 0.3 g of streptomycin per liter gave rise to cultures with gray-to-black mycelium that developed brown conidia. The fungus was identified as Bipolaris oryzae (Breda de Haan) Shoemaker on the basis of conidial morphology (1,2). Conidiophores were brown, straight, cylindrical, and multiseptate. Conidia were brown, curved, ellipsoidal tapering to rounded ends, with 3 to 14 septa. Conidia averaged 105 μm (54 to 160 μm) long and 16 μm (12 to 20 μm) wide. Sequences of the glyceraldehyde-3-phosphate dehydrogenase (GDP) gene of three isolates from Tompkins County (Cornell Accession and corresponding GenBank Nos.: Bo005NY07 [cv. Cave-in-Rock], JF521648; Bo006NY07 [cv. Kanlow], JF521649; and Bo038NY07 [cv. Shawnee], JF521650) exhibited 100% nucleotide identity to B. oryzae isolates (GenBank Nos. AY277282–AY277285) collected from switchgrass in North Dakota (1). Sequences of the rDNA internal transcribed spacer (ITS) regions of the isolates (Cornell Accession and corresponding GenBank Nos.: Bo005NY07, JF693908; Bo006NY07, JF693909; and Bo038NY07, JF693910) exhibited 100% nucleotide identity to B. oryzae isolates (GenBank Nos. GU222690–GU222693) collected from switchgrass in Mississippi (3). Pathogenicity of two of the sequenced isolates (Bo006NY07 and Bo038NY07) along with one other isolate (Bo116NY09 from ‘Cave-in-Rock’ in Cayuga County) was evaluated in the greenhouse. Six- to eight-week-old switchgrass plants were inoculated with conidial suspensions (40,000 conidia/ml) of B. oryzae. Inoculum or sterilized water was applied until runoff. There were three plants per treatment of each of ‘Blackwell’, ‘Carthage’, ‘Cave-in-Rock’, ‘Kanlow’, ‘Shawnee’, ‘Shelter’, and ‘Sunburst’. After inoculum had dried, plants were placed in a mist chamber for 24 h and then returned to the greenhouse. Symptoms developed 2 to 4 days after inoculation for all cultivars. No symptoms developed on the control plants. Foliar lesions closely resembled those observed in the field. B. oryzae was consistently reisolated from symptomatic tissue collected from greenhouse experiments. B. oryzae was first reported as a pathogen of switchgrass in North Dakota (1) and more recently in Mississippi (3). To our knowledge, this is the first report of B. oryzae causing a leaf spot on switchgrass in New York. Observation of severe leaf spot in several field plots suggests that switchgrass populations should be screened for their reaction to regional isolates of B. oryzae prior to expanded production of switchgrass as a biofuel crop. References: (1) J. M. Krupinsky et al. Can. J. Plant Pathol. 26:371 2004. (2) R. A. Shoemaker. Can. J. Bot. 37:883, 1959. (3) M. Tomaso-Peterson and C. J. Balbalian. Plant Dis. 94:643 2010.

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First Report of the Head Smut Fungus Tilletia maclaganii Infecting Switchgrass (Panicum virgatum) in Indiana

Plant Disease ◽

10.1094/pdis-03-19-0478-pdn ◽

2019 ◽

Vol 103 (8) ◽

pp. 2135

Author(s):

G. E. Ruhl ◽

T. Creswell ◽

E. M. Karlsen-Ayala ◽

B. Stefancik ◽

K. Johnson ◽

...

Keyword(s):

Panicum Virgatum ◽

Smut Fungus ◽

Head Smut ◽

First Report

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First Report of Bipolaris oryzae Causing Leaf Spot of Switchgrass in Mississippi

Plant Disease ◽

10.1094/pdis-94-5-0643a ◽

2010 ◽

Vol 94 (5) ◽

pp. 643-643 ◽

Cited By ~ 5

Author(s):

M. Tomaso-Peterson ◽

C. J. Balbalian

Keyword(s):

Leaf Spot ◽

Panicum Virgatum ◽

Morphological Characteristics ◽

Seed Transmission ◽

Forest Products ◽

Its Region ◽

Infested Soil ◽

Bipolaris Oryzae ◽

Diagnostic Laboratory ◽

First Report

‘Alamo’ switchgrass (Panicum virgatum L.) seedlings growing in a soilless mix exhibiting dark brown, irregular-shaped foliar lesions with black borders were submitted to the Mississippi State University Plant Disease Diagnostic Laboratory in the summer of 2009 from a local forest products company. Symptomatic tissues were plated onto water agar (WA) and incubated for 21 days on a laboratory bench top with a 12-h photoperiod at 22°C. An asexual, sporulating, dematiaceous hyphomycete identified as Bipolaris oryzae (Breda de Haan) Shoemaker was observed. Conidiophores were single, mostly straight, multiseptate, brown, and ranging from 138 to 306 × 7.7 to 15.3 μm and averaged 221.6 × 10.7 μm. Conidia were golden brown, multiseptate, ranging from 3 to 10 septa, straight to slightly curved to fusoid, wider midway, and tapering toward the terminal cells. Conidia measured 40.8 to 109.7 × 10.2 to 20.4 μm and averaged 75.8 × 13.8 μm. Morphological characteristics of B. oryzae were similar to those described by Drechsler (1) and Sivanesan (3). The internal transcribed spacer (ITS) region of ribosomal DNA from four pure culture colonies derived from single conidia was amplified by PCR using ITS1 and ITS4 primers. The resultant 572 bp was sequenced for isolates 86 through 89 (GenBank Accession Nos. GU222690–93). The sequences were 99% similar to the sequence of B. oryzae strain ATCC-MYA 3330 (GenBank No. FJ746665) isolated from P. virgatum. Pathogenicity of isolates 86 and 88 was confirmed by inoculating sterile potting mix with a fungal slurry. Sterile Alamo switchgrass seeds were sown into the infested soil in Magenta boxes and incubated for 6 weeks in a growth chamber with a 14-h photoperiod at 30°C. Leaf lesions and leaf blight were observed in seedling stands growing in B. oryzae-infested soil. Lesions were excised and plated onto WA. Sporulation of B. oryzae was observed on symptomatic tissue. In the interim, 300 nonsterilized Alamo switchgrass seeds of the same seed lot as the original symptomatic seedlings and originating from Oklahoma were plated onto WA (10 seed per plate). The seeds were incubated on the bench top as previously described. The experiment was repeated and B. oryzae colonized 1.4% of the total switchgrass seeds evaluated, indicating seed transmission and subsequent seedling infection as previously observed in the original seedlings. Leaf spot, caused by B. oryzae, was first reported as a new disease of switchgrass in North Dakota (2). In the summer of 2009, the authors observed leaf spot in four cultivars of switchgrass, including Alamo, growing in research plots in Webster County, MS. Twenty-two isolates of B. oryzae were recovered from diseased leaves of these switchgrass cultivars. To our knowledge, this is the first report of B. oryzae causing leaf spot of switchgrass in Mississippi, which broadens the natural distribution of this disease. References: (1) C. Drechlser. J. Agric. Res. 24:641, 1923. (2) J. M. Krupinsky et al. Can. J. Plant Pathol. 26:371, 2004. (3) A. Sivanesan. Mycol. Pap. 158:201, 1987.

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First Report of Leaf Spot Caused by Alternaria alternata on Switchgrass in Tennessee

Plant Disease ◽

10.1094/pdis-09-11-0785 ◽

2012 ◽

Vol 96 (5) ◽

pp. 763-763 ◽

Cited By ~ 2

Author(s):

A. L. Vu ◽

M. M. Dee ◽

T. Russell ◽

J. Zale ◽

K. D. Gwinn ◽

...

Keyword(s):

Alternaria Alternata ◽

Leaf Spot ◽

Panicum Virgatum ◽

Leaf Tissue ◽

Its Region ◽

Sporulation Medium ◽

Sterile Water ◽

One Pot ◽

First Report ◽

Leaf Spots

Field-grown seedlings of ‘Alamo’ switchgrass (Panicum virgatum L.) from Vonore, TN exhibited light brown-to-dark brown leaf spots and general chlorosis in June 2009. Symptomatic leaf tissue was surface sterilized (95% ethanol for 1 min, 20% commercial bleach for 3 min, and 95% ethanol for 1 min), air dried on sterile filter paper, and plated on 2% water agar amended with 10 mg/liter rifampicin (Sigma-Aldrich, St. Louis, MO) and 5 μl/liter miticide (2.4 EC Danitol, Valent Chemical, Walnut Creek, CA). Plates were incubated at 26°C for 4 days in darkness. An asexual, dematiaceous mitosporic fungus was isolated and transferred to potato dextrose agar. Cultures were transferred to Alternaria sporulation medium (3) to induce conidial production. Club-shaped conidia were produced in chains with branching of chains present. Conidia were 27 to 50 × 10 to 15 μm, with an average of 42.5 × 12.5 μm. Morphological features and growth on dichloran rose bengal yeast extract sucrose agar were consistent with characteristics described previously for Alternaria alternata (1). Pathogenicity studies were conducted with 5-week-old ‘Alamo’ switchgrass plants grown from surface-sterilized seed. Nine pots with approximately 20 plants each were prepared. Plants were wounded by trimming the tops. Eight replicate pots were sprayed with a conidial spore suspension of 5.0 × 106 spores/ml sterile water and subjected to high humidity by enclosure in a plastic bag for 7 days. One pot was sprayed with sterile water and subjected to the same conditions to serve as a control. Plants were maintained in a growth chamber at 25/20°C with a 12-h photoperiod. Foliar leaf spot symptoms appeared 5 to 10 days postinoculation for all replicate pots inoculated with A. alternata. Symptoms of A. alternata infection were not observed on the control. Lesions were excised, surface sterilized, plated on water agar, and identified in the same manner as previously described. The internal transcribed spacer (ITS) region of ribosomal DNA and the mitochondrial small sub-unit region (SSU) from the original isolate and the reisolate recovered from the pathogenicity assay were amplified with PCR, with primer pairs ITS4 and ITS5 and NMS1 and NMS2, respectively. Resultant DNA fragments were sequenced and submitted to GenBank (Accession Nos. HQ130485.1 and HQ130486.1). A BLAST search (BLASTn, NCBI) was run against GenBank isolates. The ITS region sequences were 537 bp and matched 100% max identity with eight A. alternata isolates, including GenBank Accession No. AB470838. The SSU sequences were 551 bp and matched 100% max identity with seven A. alternata isolates, including GenBank Accession No. AF229648. A. alternata has been reported from switchgrass in Iowa and Oklahoma (2); however, this is the first report of A. alternata causing leaf spot on switchgrass in Tennessee. Switchgrass is being studied in several countries as a potentially important biofuel source, but understanding of the scope of its key diseases is limited. References: (1) B. Andersen et al. Mycol. Res. 105:291, 2001. (2) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , September 22, 2011. (3) E. A. Shahin and J. F. Shepard. Phytopathology 69:618, 1979.

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First Report of Spot Blotch and Common Root Rot Caused by Bipolaris sorokiniana on Switchgrass in Tennessee

Plant Disease ◽

10.1094/pdis-12-10-0880 ◽

2011 ◽

Vol 95 (9) ◽

pp. 1195-1195 ◽

Cited By ~ 7

Author(s):

A. L. Vu ◽

M. M. Dee ◽

K. D. Gwinn ◽

B. H. Ownley

Keyword(s):

Root Rot ◽

Panicum Virgatum ◽

Bipolaris Sorokiniana ◽

The United States ◽

Small Subunit ◽

Spot Blotch ◽

Cochliobolus Sativus ◽

Common Root ◽

First Report ◽

Common Root Rot

Light-to-dark brown, irregular-shaped leaf spots, chlorosis, necrotic roots, and severe stunting were observed on ‘Alamo’ switchgrass (Panicum virgatum L.) grown on the campus of the University of Tennessee in December 2007. Symptomatic leaf and root samples were surface sterilized, air dried on sterile filter paper, and plated on 2% water agar amended with 10 mg/liter of rifampicin (Sigma-Aldrich, St. Louis, MO) and 10 μl/liter of 2,4 EC Danitol miticide (Valent Chemical, Walnut Creek, CA). Plates were incubated at 25°C in darkness for 4 days. A sporulating, dematiaceous mitosporic fungus was noted and transferred to potato dextrose agar (PDA). Conidia were ovate, oblong, mostly straight, and olive to brown with three to nine septa. Conidial dimensions were 12.5 × 27.5 (17.5) to 20 × 77.5 (57) μm. Conidia were produced on single, light brown, multiseptate conidiophores that were polytretic, geniculate, and sympodial. Morphological features were as described for Bipolaris sorokiniana (Sacc.) Shoemaker (teleomorph = Cochliobolus sativus) (2,3). Disease assays were conducted with 5-week-old ‘Alamo’ switchgrass grown from surface-sterilized seed. Ten 9 × 9-cm2 with ~20 switchgrass seedlings were sprayed with 2.4 × 105 spores/ml of sterile water. Plants were subjected to high humidity created by enclosure in a plastic bag for 45 h. The bag was removed and plants were incubated at 25/20°C with 50 to 60% relative humidity. During the incubation, plants were maintained in growth chamber with a 12-h photoperiod of fluorescent and incandescent lighting. Foliar leaf spot symptoms appeared 6 to 10 days postinoculation for plants in all 10 replicates and necrotic lesions were observed on roots. Foliar lesions and diseased roots were surface sterilized, plated on water agar, and resultant fungal colonies were identified as B. sorokiniana. The internal transcribed spacer (ITS) and mitochondrial small subunit (SSU) regions of ribosomal DNA from the original isolate, and the isolate recovered from plants in the pathogenicity assay, were amplified with PCR, with primer pairs ITS4 and ITS5 and NMS1 and NMS2. PCR amplicons of ~551 and 571 bp were obtained with the two primer pairs, respectively. Both amplicons were obtained from both isolates and sequenced. Amplicon sequences from the original isolate and re-isolate were identical and the sequences were submitted to GenBank (Accession Nos. HQ611957 and HQ611958). The ITS sequences had 98% homology to 23 B. sorokiniana isolates, including B. sorokiniana strain DSM 62608 (GenBank Accession No. EF187908); SSU sequences had 99% homology to Cochliobolus sativus isolate AFTOL-ID 271 (GenBank Accession No. FJ190589). Spot blotch caused by B. sorokiniana has been reported on switchgrass in Iowa, Nebraska, Pennsylvania, and Virginia (1). To our knowledge, this is the first report of B. sorokiniana causing spot blotch or common root rot of switchgrass in Tennessee, which extends the current known distribution of these diseases. More recently, we isolated B. sorokiniana from switchgrass seed received from commercial sources in the United States, indicating a seedborne transmission. References: (1) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , 15 November 2010. (2) R. F. Nyvall and J. A. Percich. Plant Dis. 83:936, 1999. (3) A. Sivanesan and P. Holliday. CMI Descr. Pathog. Fungi bact. 71:701, 1981.

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First Report of Anthracnose Caused by Colletotrichum navitas on Switchgrass in New York

Plant Disease ◽

10.1094/pdis-03-11-0164 ◽

2011 ◽

Vol 95 (8) ◽

pp. 1032-1032 ◽

Cited By ~ 2

Author(s):

K. D. Waxman ◽

G. C. Bergstrom

Keyword(s):

New York ◽

New Jersey ◽

Panicum Virgatum ◽

Molecular Phylogenetics ◽

Perennial Grass ◽

Leaf Tissue ◽

Morphological Characters ◽

Sensu Stricto ◽

First Report ◽

Greenhouse Experiments

Switchgrass (Panicum virgatum L.) is a perennial grass with significant potential as a biofuel crop. From 2007 to 2010, foliar lesions were observed in new and mature stands of switchgrass in various locations in New York. Lesions were elliptical with purple margins and white necrotic centers, generally <3 cm long, ~1 mm wide, often coalesced, and containing black setae. Upon incubation, symptomatic leaf tissue developed acervuli with masses of salmon-colored spores. The fungus was identified as Colletotrichum nativas Crouch on the basis of typical cultural characteristics and conidial morphology (1). Conidia were one-celled, hyaline, fusiform, and generally falcate. Conidial length averaged 40 μm (22 to 47 μm) and width averaged 5 μm (4 to 7 μm). Compared with other graminicolous species of Colletotrichum, the conidia were larger and varied from straight to irregularly bent. Sequences of the rDNA internal transcribed spacer (ITS) regions of three isolates (Cornell accession and corresponding GenBank Nos.: Cn071NY08 (from a >20-year-old naturalized stand of switchgrass in Steuben County), JF437053; Cn080NY08 (from ‘Pathfinder’ in Chemung County), JF437054; and Cn101NY09 (from ‘Blackwell’ in Chemung County), JF437055) exhibited 100% nucleotide identity to the type isolate of C. nativas (GenBank No. GQ919068) collected from switchgrass selection ‘Brooklyn’ in New Jersey (1). Pathogenicity of the sequenced isolates along with seven other isolates (Cn105NY09 from ‘Sunburst’ in Tompkins County; Cn107NY09 from ‘Trailblazer’ in Tompkins County; Cn109NY09 from ‘Forestburg’ in Tompkins County; Cn111NY09 and Cn112NY09 from ‘Shelter’ in Tompkins County; and Cn122NY09 and Cn123NY09 from ‘Cave-in-Rock’ in Genesee County) was evaluated in greenhouse experiments. Seven- to eight-week-old switchgrass plants were inoculated with conidial suspensions (1 × 106 conidia/ml) of C. nativas. Inoculum or sterilized water was sprayed until runoff. Three plants of each of ‘Cave-in-Rock’ and ‘Kanlow’ were sprayed per treatment and the experiment was repeated for 3 of the 10 isolates. Inoculated plants were placed in a mist chamber for 48 h before they were returned to the greenhouse and observed for disease development, which occurred within 1 week of inoculation for both cultivars. No symptoms developed on the control plants. Foliar lesions closely resembled those observed in the field. C. nativas was consistently reisolated from symptomatic tissue collected from greenhouse experiments. Switchgrass anthracnose associated with C. graminicola sensu lata has been reported in many U.S. states (2). On the basis of molecular phylogenetics and distinguishing morphological characters, Crouch et al. erected C. navitas as a novel species distinct from C. graminicola sensu stricto, a taxon restricted to the corn anthracnose pathogen (1). C. nativas was first documented on switchgrass in New Jersey (1) and appears to be the same pathogen causing anthracnose of switchgrass in the adjoining state of Pennsylvania (1,3). To our knowledge, this is the first report of C. nativas causing anthracnose of switchgrass in New York. References: (1) J. A. Crouch et al. Mycol. Res. 113:1411, 2009. (2) D. F. Farr and A. Y. Rossman. Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , May 5, 2011. (3) M. A. Sanderson et al. Agron. J. 100:510, 2008.

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First Report of Tilletia pulcherrima Bunt on Switchgrass (Panicum virgatum) in Texas

Plant Disease ◽

10.1094/pdis-92-12-1707c ◽

2008 ◽

Vol 92 (12) ◽

pp. 1707-1707 ◽

Cited By ~ 5

Author(s):

L. M. Carris ◽

L. A. Castlebury ◽

J. Zale

Keyword(s):

Internal Transcribed Spacer ◽

Panicum Virgatum ◽

Washington State ◽

Karnal Bunt ◽

Spore Morphology ◽

State University ◽

First Report ◽

5.8S Rdna ◽

Washington State University ◽

Internal Transcribed Spacer Regions

Switchgrass seed samples of ‘Blackwell’ and ‘Alamo’ from Bailey County, TX were examined for bunt fungi. Fourteen completely bunted seeds of ‘Blackwell’ and four of ‘Alamo’ were found. No partially bunted seeds were found. Bunted seeds were darker and occasionally slightly swollen relative to noninfected seeds. Teliospores were globose to subglobose, 21 to 28 × 20 to 27 μm in diameter, dark reddish brown to nearly black, with blunt warts 1 to 1.8 μm long, enveloped in a hyaline sheath, and often with a short apiculus. Sterile cells were globose to subglobose, 17.5 to 22 μm, with smooth, laminated walls as much as 2.6 μm thick, and often with a short apiculus. This bunt was identified as Tilletia pulcherrima Ellis & Galloway on the basis of host and spore morphology (2). The internal transcribed spacer regions 1 and 2, including the 5.8S rDNA, were sequenced from bunted ‘Blackwell’ seeds (GenBank Accession No. EU915293, WSP 71501). The sequence was distinct from all Tilletia sequences in GenBank, including Tilletia barclayana (Bref.) Sacc. & Syd. on Panicum obtusum Kunth (GenBank Accession No. AF 310169) (1). To our knowledge, this is the first report of T. pulcherrima from switchgrass in Texas. Plant pathologists and regulatory officials should be aware of the potential for misidentification of T. pulcherrima as T. indica Mitra, the Karnal bunt pathogen of wheat that has similar spores, occurs in Texas, and has quarantine status. References: (1) R. Durán and G. W. Fischer. The Genus Tilletia, Washington State University, Pullman, WA, 1961. (2) K. Vánky, Mycotaxon 91:217, 2005.

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First Report of Rust on Switchgrass (Panicum virgatum) Caused by Puccinia emaculata in Tennessee

Plant Disease ◽

10.1094/pdis-92-12-1710b ◽

2008 ◽

Vol 92 (12) ◽

pp. 1710-1710 ◽

Cited By ~ 19

Author(s):

J. Zale ◽

L. Freshour ◽

S. Agarwal ◽

J. Sorochan ◽

B. H. Ownley ◽

...

Keyword(s):

Panicum Virgatum ◽

Large Subunit ◽

Perennial Grass ◽

Apical Cell ◽

Total Biomass ◽

Cell Width ◽

Ploidy Levels ◽

First Report ◽

Leaf Surfaces ◽

Extension Center

In the spring of 2007, switchgrass accessions and cultivars Alamo, Kanlow, SL-93-2001, and NSL 2001-1 (lowland), Blackwell (upland), and Grenville, Falcon, and Miami (unknown ploidy levels) were sown at the East Tennessee Research and Extension Center in Knoxville for evaluation and controlled hybridizations. In July and August of 2007, uredinia were observed primarily on the upper leaf surfaces, and to a lesser extent on the undersides of leaves, of switchgrass cvs. Alamo, Blackwell, Grenville, Falcon, Kanlow, and Miami. Uredinia were observed on all cultivars and accessions in 2008. Dimensions of spores are reported as mean ± standard deviation. Uredinia were epiphyllous, adaxial, caulicolous, oblong, and the color of cinnamon brown. Urediniospores were globose to broadly ellipsoid, 26.0 ± 3.0 × 23.2 ± 2.4 μm, with a wall that was cinnamon brown, 1.5 to 2.0 μm thick, finely echinulate with three to four equatorial pores, corresponding to Puccinia emaculata Schw. (3). Abundant teliospores were isolated from Grenville, Falcon, and Blackwell, with fewer teliospores isolated from Alamo. Telia were epiphyllous, adaxial, and caulicolous, densely crowded to scattered, oblong, and dark brown to black. Teliospores were dark brown, two-celled, ellipsoid to oblong, 33.6 ± 4.8 μm long with an apical cell width of 17.5 ± 1.2 μm and basal cell width of 15.9 ± 2.5 μm. Teliospore walls were 1.5 to 2.0 μm wide at the sides and 4 to 6 μm apically. Pedicels were brown or colorless and up to approximately one length of the teliospore, 28.5 ± 7.4 μm. Teliospore morphology confirmed the identification of this rust as P. emaculata (3), which has been reported to infect upland and lowland populations of switchgrass (2). A 2,109-bp fragment containing the internal transcribed spacer (ITS) 1, 5.8S, ITS 2, and D1/D2 region of the large subunit ribosomal DNA was sequenced for a specimen on ‘Falcon’ (GenBank Accession No. EU915294 and BPI No. 878722) from two overlapping PCR fragments amplified with primers PRITS1F (L. A. Castlebury, unpublished data) and ITS4B (1) for one fragment and Rust5.8SF (L. A. Castlebury, unpublished data) and LR7 (4) for the second fragment. No sequences of P. emaculata were available for comparison; however, BLAST searches of the ITS resulted in hits to P. asparagi DC (527 of 576, 91%) and P. andropogonis Schw. (523 of 568, 92%) placing this fungus in the genus Puccinia Pers. The alternate hosts of this rust are species of the Euphorbiaceae (2,3), which are ubiquitous in this area although the aecial stage has not been observed. To our knowledge, this is the first report of P. emaculata on switchgrass in Tennessee. Given the highly susceptible response of certain varieties of switchgrass to this rust in field plots, reduction in total biomass in large acreages is likely and long-standing fields of this perennial grass will compound the problem. References: (1) M. Gardes and T. D. Bruns. Mol. Ecol. 2:113, 1993. (2) D. M. Gustafson et al. Crop Sci. 43:755, 2003. (3) P. Ramachar and G. Cummins. Mycopathol. Mycol. Appl. 25:7, 1965. (4) R. Vilgalys and M. Hester. J. Bacteriol. 172:4238, 1990.

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