Stephen C. Alderman

Features and phylogenetic status of an enigmatic clavicipitalean fungus Neoclaviceps monostipa gen. et sp. nov.

A new species and genus of the gramini- colous Clavicipitaceae are described. Neoclaviceps monostipa infects individual florets in the same way as species of genus Claviceps but does not produce sclerotia. In culture it shows dimorphism in produc- tion of a yeast-like microcyclic conidiation (ephelidi- al) phase and a mycelial phase. Phylogenetic analysis of the 26S large subunit rDNA suggests that Neoclav- iceps along with genus Myriogenospora are evolution- arily intermediate between Claviceps and Balansia.

Italian ryegrass and nitrogen source fertilization in western Oregon in two contrasting climatic years. I. Growth and seed yield

Abstract Prescription based nitrogen (N) fertilization of crops in a given local environment begins by understanding factors affecting crop N use and relating these factors to a time scale most directly related to crop growth. For these reasons the following objectives were sought for an economically important grass seed crop in western Oregon, Italian ryegrass (Lolium multiflorum Lam.). One, to determine the influence of N source (NH4‐N and NO3‐N) on crop growth and seed yield. Second, to determine the relationship between accumulated growing degree days (GDD) and plant ontogeny and relate these findings to N‐source effects on growth and seed yield parameters. Field plots were established in 1991 and again in 1992. Five N‐source treatments were applied: calcium nitrate (CN), ammonium nitrate (AN), ammonium sulfate (AS), ammonium chloride (AC), and urea‐dicyandiamide (DCD). Nitrogen‐source treatments had no effect on root and shoot dry mass accumulation in either year. Ammonium‐N fertilization increased t...

A Reevaluation of the Host Range and Geographical Distribution of Claviceps Species in the United States

A listing of host and state reports and distribution maps for 11 taxa of Claviceps occurring in the United States, including C. africana, C. cinerea, C. grohii, C. nigricans, C. paspali, C. pusilla, C. purpurea var. purpurea and var. spartinae, C. tripsaci, C. yanagawensis, and C. zizaniae, was prepared based on literature citations and examination of specimens from herbaria. The occurrence of C. ranunculoides is questioned based on examination of conidia and sclerotia from archived specimens. Collections of C. purpurea var. purpurea from grasses in the Pani-coideae were referred to other Claviceps spp. based on occurrence of macroconidia and micro-conidia. C. purpurea var. purpurea was found on 165 grass species within the continental United States and Alaska. The size of conidia of C. purpurea var. purpurea was found to be relatively stable across host and geographical regions. However, conidia of C. purpurea var. purpurea from hosts in the Aveneae and Meliceae (generally associated with wet habitats) were more variable in size and generally larger than those from other tribes in the Pooideae. Claviceps spp. in the continental United States occurred in diverse habitats, including temperate grasslands of the middle to northern latitudes (C. purpurea var. purpurea, C. nigricans) to the middle to southern latitudes (C. pusilla), coastal habitats (C. purpurea var. spartinae, C. ziza-niae), northern wetlands (C. grohii), southern temperate to subtropical grasslands (C. africana, C. paspali, C. tripsaci, C. yanagawensis), and arid southwestern grasslands (C. cinerea).

The Botanophila–Epichloë association in cultivated Festuca in Oregon: evidence of simple fungivory

We investigated the Botanophila (Diptera: Anthomyiidae)–Epichloë (Ascomycetes: Clavicipitaceae) interaction in cultivated Festuca spp. (fine fescue) in Oregon in western USA. Epichloë spp. are endophytic fungi of grasses in the subfamily Pooideae. They develop a felt‐like stroma on the surface of grass culms and a dense mycelium within the culms that typically prevents seed head emergence. As a result, seed yields are suppressed, and hence the disease is known as choke. Studies of Epichloë spp. on wild grasses indicate that the fly–fungus interaction is an obligatory mutualism. During oviposition, Botanophila transfers Epichloë spermatia between stromata of opposite mating types, and the perithecia that develop after fungal fertilization serve as food for Botanophila larvae. In the current study, we surveyed 19 cultivated fields of Festuca spp. in Oregon, and observed choke caused by Epichloë festucae Leuchtmann, Schardl and Siegl in 10 of these. However, perithecia were observed in only four fields, and on only 1.0–2.6% of stromata. Perithecial development was also low, and rarely covered 50% of the stroma surface. Despite the absence or low frequency of fertilized stromata, Botanophila lobata Collin larvae were present in all choke‐infested fields. Infestation levels ranged from 2.5 to 70.7%, based on an examination of 175–200 stromata from each field. Only eight (= 2%) of the 450 stromata with B. lobata had perithecia, and the greater majority of B. lobata larvae completed development and exited from unfertilized stromata. This is the first report of the B. lobata–E. festucae association in the USA, and of B. lobata larvae developing successfully on unfertilized Epichloë stromata. The average pupal weight (0.0032 g) did not differ significantly from pupae (0.0030 g) originating from larvae that had developed on fertilized stromata of E. typhina on Dactylis glomerata in a neighboring field. This result indicates that in cultivated fine fescue fields in Oregon, B. lobata forages on E. festucae, but fly development is not dependent on the fertilized stromata of Epichloë.

Italian ryegrass and nitrogen source fertilization in western Oregon in two contrasting climatic years. II. Plant nitrogen accumulation and soil nitrogen status.

Abstract To develop optimum nitrogen (N) fertilization practices with the least impact on environmental quality and with the greatest economic return, it is imperative that a greater understanding of crop and soil N dynamics be sought. This paper reports on research conducted with these objectives: (i) to determine the relationship between plant N and dry matter accumulation and soil N status as affected by N‐source fertilization as a function of accumulated growing degree days (GDD), and (ii) to determine if western Oregon soil conditions favor ammonium (NH4) over nitrate (NO3) nutrition during the period of grass seed crop growth. In a companion paper, plant growth and seed yield component data were discussed in relation to N‐source treatments and climatic year effects. Western Oregon field plots of Italian ryegrass (Lolium multiflorum Lam.) were fertilized with calcium nitrate, ammonium nitrate, ammonium sulfate, ammonium chloride, and urea‐dicyandiamide (DCD) to manipulate soil NH4 and NO3 ratios. Ita...

Survival, Germination, and Growth of Epichloë typhina and Significance of Leaf Wounds and Insects in Infection of Orchardgrass

Epichloë typhina is an important stroma-producing endophytic ascomycete that is responsible for significant yield loss in orchardgrass (Dactylis glomerata) seed production fields. Infection is presumed to occur through leaves or stems, although details of the infection process and conditions that favor leaf infection are not well understood. The primary objectives of this study were to investigate the early stages of infection, including the effect of temperature or water potential on ascospore germination and subsequent growth of E. typhina, the tolerance of ascospores to desiccation, the requirement of leaf wounds for infection of orchardgrass by E. typhina, and the potential for insects to facilitate infection. Ascospores tolerated dry conditions, with at least 40% surviving 12 days under desiccation. Germination and growth of E. typhina was greatest at 25°C, with little to no growth at 5 and 35°C. Mycelial growth decreased with decreasing water potential from -0.3 to -10 MPa. Ascospore germination on leaves was predominantly hyphal at wound sites and iterative (conidiogenous) at sites without wounds. E. typhina typically entered leaves through wounds. Direct penetration was rarely observed and appeared to be associated with ascospore clusters. Germ tubes were significantly longer at sites with honeydew deposits from the bird cherry-oat aphid than at sites without honeydew. Growth of E. typhina was also observed at feeding sites of eriophyid mites, suggesting that leaf-wounding or sap-excreting insects support epiphyllous growth of E. typhina on leaves.

Gloeotinia temulenta and G. granigena, two distinct species

Specimens of Gloeotinia temulenta from Germany, Netherlands, Norway, Scotland, and the United States were examined and microanatomical features compared with the type specimen of G. granigena from ...

First report of Cocksfoot mottle virus infecting Dactylis glomerata in Oregon and the United States.

Cocksfoot mottle virus (CfMV) is a mechanically and beetle-transmitted, non-seedtransmitted sobemovirus associated with orchardgrass (Dactylis glomerata L.) stand decline in Europe, Japan, New Zealand (Mahy and Van Regenmortel 2010), and Canada (Bittman et al. 2006). Additional hosts, reported from New Zealand (Delmiglio et al. 2010), include Festuca novae-zelandiae, Lolium spp., Poa anceps, Poa cita, Chionochloa rubra, and Dichelachne crinita. To determine if the virus is present in the United States, surveys for CfMV were conducted in 2014 and 2015 in orchardgrass seed production fields in the Willamette Valley in Oregon, where most of the orchardgrass seed produced in the United States is grown. During June, in each of 2014 and 2015, 18 orchardgrass fields were selected arbitrarily. Stand age of the seed production fields ranged from 2 to 24 years. Two of the fields were sampled in both years. Four samples (each containing 4 leaves, one from each of four plants) were collected along each of four transects in an M-shape pattern from each field. All plants sampled appeared healthy. In 2014, samples were placed in separate plastic bags and in 2015 samples were placed in deep well plates (VWR, International LLC, Radnor, PA). In each year, samples were transported over ice and stored at 5°C until processed. Samples were homogenized and tested for CfMV using DAS-ELISA, with antibodies derived from an isolate of CfMV from British Columbia, Canada. In 2014 and 2015, CfMV was detected in 61% and 72% of the fields, respectively. Symptoms were not present at the time of sampling. In 2015, eight ELISA positive samples were further examined with RT-PCR. RNA was extracted with the Direct-zol RNA MiniPrep kit (Zymo Quick Links Add to favorites

Afternoon Ascospore Release in Claviceps purpurea Optimizes Perennial Ryegrass Infection

In Kentucky bluegrass (Poa pratensis), Claviceps purpurea, the causal agent of ergot, typically releases ascospores during the early-morning hours, between about midnight and 10:00 a.m., corresponding to time of flowering, when the unfertilized ovaries are most susceptible to infection. During aeromycology studies of C. purpurea in perennial ryegrass (Lolium perenne) in northeastern Oregon during 2008 to 2010 and 2013, a strain of C. purpurea was found that released ascospores in the afternoon, coinciding with flowering in perennial ryegrass. Under controlled environmental conditions, sclerotia from perennial ryegrass and Kentucky bluegrass released spores in the afternoon and morning, respectively, consistent with timing of spore release under field conditions. Internal transcribed spacer (ITS) sequences of single sclerotial isolates from Kentucky bluegrass and perennial ryegrass were consistent with C. purpurea, although minor variations in ITS sequences among isolates were noted. Differences between Kentucky bluegrass and perennial ryegrass isolates were observed in random amplified polymorphic DNA. Evidence is provided for adaptation of C. purpurea to perennial ryegrass by means of delayed spore release that coincides with afternoon flowering in perennial ryegrass.

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

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 Morans 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.