Stephen C. Alderman

National Forage Seed Production Research Center

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Philip B. Hamm

Oregon State University

Darrin L. Walenta

Oregon State University

Jeremiah K. S. Dung

Oregon State University

Ruth C. Martin

Oregon State University

Navneet Kaur

Oregon State University

Kenneth E. Frost

Oregon State University

James F. White

Rutgers, The State University of New Jersey

James E. Dombrowski

National Forage Seed Production Research Center

Joseph W. Spatafora

Oregon State University

Sujaya Rao

University of Minnesota

Cooperative Institutions

Oregon State University

United States Department of Agriculture

Agricultural Research Service

Horticultural Crops Research Laboratory

Washington State University

National Forage Seed Production Research Center

Rutgers, The State University of New Jersey

National Clonal Germplasm Repository

University of Minnesota

University of Idaho

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Distribution and ethological role of strands of Phymatotrichum omnivorm (Shear) dug.

Stephen C. Alderman

Viable strand lengths (VSL) of Phymatdtrichum dmriivdrum (per 50 g soil) of 0,1 and 0*2 cm were recovered at 15-30 and 30-60 cm depths 9 respectively9 in cotton fields near Marana? Arizona in June, 1979; none were recovered at depths of 0-15 and 60-90 cm. Maximum VSL occurred from August into November„ These were 0.5, '0.4, 1.0, and 0.6 cm at depths of 0-15, 15-30, 30-60, and 60-90 cm, respective ly. By April, 1980, VSL at the same depths were 0,05 9 0.2, 0.3, and 0.05 cm, respectively. All infected cotton roots from depths of 1545 cm in August contained viable strands, generally fewer roots con tained viable strands in other months and at 0-15 cm depths. Phymatotrichum omnivorum was isolated from tissues of infected cotton roots in August but not from rotted roots after October. Inoculations of cotton plants with strands were unsuccessful. However, 46% of the plants became diseased when naturally infected roots were used as inoculum in the field and 50%-100% were infected : : ' • • when sclerotia or infected sorghum seeds were used as inoculum in the . i greenhouse. Sclerotia from field or laboratory cultures germinated M only from attached broken strands. / ?

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Diseases in Seed Production

Agronomy monograph/Agronomy (2013)

Stephen C. Alderman W. F. Pfender Cynthia M. Ocamb

In the U.S. Pacific Northwest, the most significant diseases affecting seed production of tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] are fungal diseases, including stem rust, caused by Puccinia graminis (Pers.) subsp. graminicola (Urban), and blind seed, caused by Gloeotinia temulenta (Prill & Delacr.) Wilson, Noble & Gray. Stem rust is an especially destructive foliar disease with potential for significant yield reductions. Blind seed is a disease of the developing seed, characterized by low seed germination. Other important fungal diseases but generally less destructive than rust or blind seed include Fusarium head blight, caused by Fusarium species; ergot, caused by Claviceps purpurea (Fr.:Fr.) Tul.; and leaf spotting diseases, caused by species of Cercosporidium, Dreschlera, Rhynchosporium, and Septoria. In addition, damage to seed stalks from insects or fungi can result in death and subsequent bleached or silvery-white appearance of the seed heads, a condition commonly referred to as silver top. Disease control recommendations, including registered fungicides and application rates, for specific diseases in the Pacific Northwest are available at (verified 11 May 2009). Although many other pathogens can infect tall fescue, they have not been found to be troublesome in tall fescue seed production in the Pacific Northwest.

Rust (programming language)

Puccinia

Stem rust

10.2134/agronmonogr53.c24

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Timing of Occurrence of Claviceps purpurea Ascospores in Northeast Oregon

Plant Health Progress (2010)

Stephen C. Alderman Darrin L. Walenta Philip B. Hamm

Ergot, caused by Claviceps purpurea, is an important floral disease of grasses, characterized by sclerotium formation within the host flowers. To determine whether annual variation in ergot severity in Kentucky bluegrass is a result of ascospore density and/or timing of ascospore occurrence, Burkard 7-day volumetric spores traps were used to monitor ascospores of C. purpurea in each of two Kentucky bluegrass fields in the Grand Ronde Valley in northeastern Oregon between mid-May and late June, 2008-2010. Ascospores were typically trapped between midnight and 6:00 a.m. In 2008 and 2010, most ascospores were released prior to flowering in Kentucky bluegrass, corresponding to no observed ergot in 2008 and a low level of ergot in 2010. In 2009, ascospore release and pollination coincided, but few airborne ascospores were present, resulting in a low level of ergot. Similar ergot levels were observed in fungicide trials, suggesting that fungicides for ergot control were unnecessary. In years when there are few ascospores during flowering in Kentucky bluegrass, a reduction of up to two fungicide applications may be possible. Accepted for publication 2 November 2010. Published 23 November 2010.

Claviceps purpurea

Smut

10.1094/php-2010-1123-01-rs

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Citations (5)

Epidemiology of Anguina agrostis on Highland Colonial Bentgrass.

PubMed (1994)

John N. Pinkerton Stephen C. Alderman

The epidemiology of Anguina agrostis was investigated in field plots of Colonial bentgrass (cv. Highland), Agrostis tenuis, near Corvallis, Oregon. Each October from 1990-92, nylon mesh pouches, each containing 10 galls, were buried in the field or placed on the soil surface in microplots. Pouches were collected monthly or bimonthly between December and June and nematodes per gall counted. Nematode egression from galls began in late March and was completed by mid-May, corresponding to the period of floral initiation in bentgrass. In 1991 and 1992, 0.09-m(2) plots were inoculated with 0, 1, 5, 15, 50, 120, or 200 galls/plot. The disease severity (number of galls) and disease incidence (% seed heads with galls) increased linearly at inoculum densities below 50 galls/ plot. At higher inoculum densities, disease increase approached an asymptote. In 1991, plots were established to determine the characteristics of disease spread. Disease foci were established by placing 0, 5, 50, or 500 galls along 30-cm sections of row in the fall. In July 1992, seed heads were harvested at 30 and 60 cm from each focus within and across plant rows. Most infestations were found within 30 cm of foci at all inoculum levels. At high inoculum densities, the distribution of galls was aggregated with the majority of galls located on less than 10% of the seed heads. These disease spread and incidence data suggest populations of A. agrostis increase slowly in bentgrass in Oregon.

Agrostis

Agrostis stolonifera

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Fusarium Species Associated with Tall Fescue Seed Production in Oregon

Plant Health Progress (2004)

Cynthia M. Ocamb Stephen C. Alderman

Seed samples were collected from 15 commercial tall fescue seed production fields and examined for Fusarium spp. The percentage of seeds from which Fusarium spp. were recovered ranged from 0 to 32%, while disinfesting seeds with 3% hydrogen peroxide reduced the recovery of Fusarium to 7% or less. The predominant Fusarium spp. isolated from the tall fescue seeds included F. avenaceum, F. culmorum, F. pseudograminearum, and F. sambucinum. Greenhouse inoculations of tall fescue panicles with F. avenaceum, F. culmorum, and F. pseudograminearum resulted in higher seedborne rates of each respective Fusarium sp. than that recovered from noninoculated plants. Seeds recovered from panicles treated with F. avenaceum or F. pseudograminearum had significantly lower germination rates relative to panicles sprayed with water or a suspension of F. culmorum. Our work confirms that Fusarium spp. decrease seed germination and expands the pathogen list to include F. avenaceum and F. pseudograminearum. Accepted for publication 17 February 2004. Published 19 March 2004.

Fusarium culmorum

Panicle

10.1094/php-2004-0319-01-rs

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Simple sequence repeat markers that identify Claviceps species and strains

Fungal Biology and Biotechnology (2016)

Barbara Gilmore Stephen C. Alderman Brian J. Knaus Nahla Bassil Ruth C. Martin

is a pathogen that infects most members of Pooideae, a subfamily of Poaceae, and causes ergot, a floral disease in which the ovary is replaced with a sclerotium. When the ergot body is accidently consumed by either man or animal in high enough quantities, there is extreme pain, limb loss and sometimes death.

Sequence (biology)

10.1186/s40694-016-0019-5

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Citations (27)

Spatial Patterns of Ergot and Quantification of Sclerotia in Perennial Ryegrass Seed Fields in Eastern Oregon

Plant Disease (2015)

Jeremiah K. S. Dung Stephen C. Alderman Darrin L. Walenta Philip B. Hamm

Ergot, caused by Claviceps purpurea, is a major disease of perennial ryegrass grown for seed in eastern Oregon. The objective of this research was to quantify and describe the spatial patterns of ergot severity in each of three 50-ha commercial fields of perennial ryegrass grown for seed in 2012 and 2013. In total, 1,433 and 1,405 quadrats were sampled among the three fields in 2012 and 2013, respectively, and the percentage of quadrats with ergot ranged from 59 to 90%. The mean incidence of infected seed heads in each quadrat ranged between 13 and 29%, while mean severity in each quadrat ranged from 0.2 to 0.5 sclerotia per seed head. Significant autocorrelation and clustering were observed in all three fields in both years, as indicated by Moran’s I and spatial analysis by distance indices of aggregation. The mean number of ergot sclerotia collected from each field after harvest ranged between 4 and 15 sclerotia m −2 in 2012 and 18 and 119 sclerotia m −2 in 2013. Sclerotia left in perennial fields after harvest are a significant source of inoculum that should be targeted for control. This is the first study to quantify spatial patterns of ergot in perennial ryegrass and provides insights into possible mechanisms that contribute to ergot etiology and epidemiology.

10.1094/pdis-08-14-0787-re

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Molecular and Alkaloid Characterization of Claviceps purpurea Sensu Lato From Grass Seed Production Areas of the U.S. Pacific Northwest

Phytopathology (2020)

Jeremiah K. S. Dung Jennifer M. Duringer Navneet Kaur Jeness C. Scott Kenneth E. Frost

Ergot, caused by Claviceps purpurea sensu lato, is an economically important seed replacement disease of Kentucky bluegrass (Poa pratensis) and perennial ryegrass (Lolium perenne) seed crops. C. purpurea sensu stricto is considered the primary Claviceps species responsible, but genetic diversity and cryptic species within C. purpurea sensu lato have previously been reported. Fifty-six C. purpurea sensu lato isolates collected from P. pratensis (n = 21) and L. perenne (n = 35) in Oregon and Washington between 2010 and 2014 were characterized via random amplified polymorphic DNA (RAPD), partial internal transcribed spacer (ITS), β-tubulin and elongation factor-1α (EF-1α) sequences, conidial size, and ergot alkaloid chemotype. Based on RAPD analysis, seven isolates from P. pratensis and 33 isolates from L. perenne collected in Oregon corresponded to C. purpurea sensu stricto, and 13 isolates collected from P. pratensis in Washington and Oregon were identified as C. humidiphila. Partial ITS, β-tubulin, and EF-1α sequences identified 10 isolates from P. pratensis as C. humidiphila, and seven isolates from P. pratensis and 33 isolates from L. perenne were identified as C. purpurea sensu stricto. Several isolates generated ambiguous RAPD bands or sequences that prevented identification. Ergot alkaloid chemotype profiling found that ergocornine and its epimer were predominant in sclerotia from P. pratensis, whereas ergotamine and its epimer were most abundant in sclerotia from L. perenne. This study confirms the presence of the C. purpurea sensu lato species complex in the U.S. Pacific Northwest and suggests that more research is needed to characterize and mitigate Claviceps spp. infection of grass seed crops in North America.

Poa pratensis

Sensu

Chemotype

Claviceps purpurea

10.1094/phyto-07-20-0289-r

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Infestation of Bent Grass by a New Seed Pest, Chirothrips manicatus (Thysanoptera: Thripidae), in Oregon

Journal of the Entomological Society of British Columbia (2005)

Sujaya Rao Stephen C. Alderman

the Willamette Valley in western Oregon. In each field, 17 to 50 panicles were col-lected at random along each of four tran-sects in a diamond pattern. Panicles were examined under a stereo microscope and the number of thrips recorded (Table 1). Seeds from each panicle were threshed by hand to avoid seed loss. Caryopses were separated from the lemma and palea using a scarifier (Model PSS1000, Mater Interna-tional, Inc., Corvallis, OR) and debris was removed with an air column (Alderman

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Detection and Quantification of Airborne Claviceps purpurea sensu lato Ascospores from Hirst-Type Spore Traps using Real-Time Quantitative PCR

Plant Disease (2018)

Jeremiah K. S. Dung Jeness C. Scott Qunkang Cheng Stephen C. Alderman Navneet Kaur

The U.S. Pacific Northwest states of Oregon and Washington are major producers of cool-season grass seed. Ergot, caused by fungi in the Claviceps purpurea sensu lato group, is an important seed replacement disease of grass worldwide. Microscopic methods that are currently used to quantify airborne Claviceps ascospores captured by spore traps are not currently rapid enough to allow for detecting and reporting of spore numbers in a timely manner, hindering growers from using this information to help manage ergot. We developed a SYBR Green real-time quantitative polymerase chain reaction (qPCR)-based assay for fast and efficient detection and quantification of C. purpurea sensu lato ascospores from Hirst-type spore traps. Species-specificity of the qPCR assay was confirmed against 41 C. purpurea sensu lato isolates collected from six hosts and six other Claviceps spp. Significant relationships were observed between cycle threshold (Ct) values and standard curves of serial dilutions of DNA ranging from 1 pg to 10 ng (R 2 = –0.99; P = 0.0002) and DNA extracted from a conidial suspension representing 8 to 80,000 conidia (R 2 = –0.99; P = 0.0004). Ct values from qPCR were significantly correlated with results from microscopic examination of spore trap samples from the field (r = –0.68; P < 0.0001) and the procedure was able to detect a single ascospore from spore trap tape samples. The qPCR procedure developed in this study provided a means for quantifying airborne Claviceps ascospores that was highly specific and useful over a wide range of spore densities, and could be performed in a matter of hours instead of days. The qPCR assay developed in this study could be part of an integrated pest management approach to help grass seed growers make risk-based fungicide application decisions for ergot management in grass grown for seed.

Sensu

Claviceps purpurea

10.1094/pdis-02-18-0310-re

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Citations (10)