Levels Of Endophyte Infection Research Articles

Endophytic Fungal Infection of Meadow Fescue in the Driftless Area of the Upper Mississippi River Valley: Impacts on Agronomic Fitness

Meadow fescue, Schedonorus pratensis (Huds.) P. Beauv., has recently been discovered as a common but previously unknown pasture grass in the Driftless Area of the upper Mississippi River Valley, USA. Preliminary data also indicated that many meadow fescue pastures were infected with an endophytic fungus, Epichloë uncinata (W. Gams, Petrini & D. Schmidt) Leuchtm. & Schardl. Therefore, the objective of this study was to determine if the endophyte impacts agronomic fitness of the host meadow fescue. Meadow fescue plants from eight farm sites were intensively sampled, and endophyte infection levels were determined to range from 82 to 95%. Paired endophyte-infected (E+) and endophyte-free (E−) meadow fescue subpopulations from each collection site were then created, and were subsequently compared for greenhouse and field drought tolerance, forage mass, and persistence under frequent defoliation. There was no impact of the endophyte under a wide range of drought conditions for either greenhouse or field studies. Furthermore, there was a small forage-mass-enhancement effect in the E+ subpopulation for only one of the eight collection sites. The only consistent effect was an average of 9% increased ground cover (persistence) in endophyte-infected meadow fescue under frequent defoliation. As per other studies, enhanced root growth, fungal-disease resistance, and/or reduced insect feeding could be mechanisms for this increased survivorship. We conclude that the meadow fescue endophytes present in the Driftless Area do not help protect their host from drought or provide any consistent forage-growth enhancement; however, we found evidence that the endophyte provides some protection against frequent defoliation at low residual sward heights.

Use of endophytic fungi in turfgrasses: Difficulties in delivery to the market

AbstractThe agronomic benefits of endophytic Epichloë fungi for the performance of ryegrass (Lolium spp.) and fescue (Festuca spp.) species were first reported in the 1980s. Various Epichloë endophyte species and strains have been shown to produce a series of different alkaloids with considerable impact on insect pests and grazing animals, some effects on nematodes and diseases, and improvements in plant stress tolerance. However, the impact of these alkaloids on plant performance and turf resilience varies across environments, and often relates to specific insect pressures and stressful summer conditions. Over 40 insect pests and diseases have been documented as responding to endophyte infection.As many Epichloë fungi are seed transmitted, endophyte transmission to the seed is controlled by the levels found in the parent plants and how well the endophyte is maintained during seed production. Endophyte viability in seed lots can drop during storage and transport, especially when stored under high temperatures and humidity. Endophyte growth into seed during seed production can be influenced by the weather, use of fungicides and growth regulators, and the timing of combining after swathing. In the United States, the endophyte infection levels in breeders’ seed of the cultivars used in the National Turfgrass Evaluation Program trials have been reported but currently, no standards exist for labeling cultivars delivered with high endophyte levels. Without suitable protocols and standards, challenges exist in delivering high endophyte infection levels to tall fescue (Festuca arundinacea Schreb.), ryegrass, and fine fescues.

Endophytes shape the legacy left by the above‐ and below‐ground litter of the host affecting the establishment of a legume

Abstract Plant litter is a key component of plant–soil feedback (PSF), given its strong potential impacts on plant establishment and growth, through chemical and physical pathways. Although PSF of the layer of dead plant material on the soil surface (above‐ground litter) has been widely studied, little is known about the role of dead roots (below‐ground litter) and the impact of plant symbionts on host litter legacy. Here, we examined whether the fungal endophyte Epichloë occultans changed the effects of above‐ and below‐ground litter of Lolium multiflorum plants on the establishment of Trifolium repens. We hypothesized that both types of litter deposited by the grass‐endophyte symbiosis reduce the establishment of the legume due to the release of allelopathic compounds during the decomposition and leaching processes. To test this, we performed two experiments with different quantities of litter produced by plants of the same grass population, with high and low levels of endophyte infection (E+ and E−). Seeds of T. repens were exposed to the above‐ground litter with or without the addition of below‐ground litter, or to their leachates, to separate the physical and chemical pathways. We found that the treatments with the combination of the above‐ and below‐ground litter produced by E+ plants increased the germination speed and seedling emergence of T. repens by 56% compared with both types of litter produced by E− plants. A similar effect was also observed with only the above‐ground litter. However, the below‐ground litter of E+ plants reduced the germination speed, seedling emergence by 76% and establishment of T. repens by 73% compared with the below‐ground litter of E− plants. Besides, the below‐ground litter had positive effects on the root colonization by arbuscular mycorrhizal fungi and reduced the root nodulation of T. repens. The quantity of litter did not affect any of these responses. Our results suggest that these litter legacy effects could be due to the release of endophyte‐induced secondary metabolites, such as phenolic and flavonoid compounds. Changes in host plant litter inputs may have consequences for the prevalence of legume plants in grasslands and pastures, affecting their quality and dynamics. A free Plain Language Summary can be found within the Supporting Information of this article.

Patch burning tall fescue invaded grasslands alters alkaloids and tiller defoliation with implications for cattle toxicosis

Tall fescue (Schedonurus arundinaceus), an exotic invasive grass in North America, can associate with a fungal endophyte that causes livestock toxicity. Native prairies are frequently managed with interactive fire and grazing, yet little is known regarding tall fescue's endophytic and toxicological responses. From 2012 to 2014, we applied patch-burn grazing (PBG—burning a different third annually) or graze and burn (GAB—burning completely in 2012 but no fire in 2013 or 2014) treatments to tall fescue−invaded grasslands. Burning happened in March/April, and cattle grazing occurred during the growing season. Tall fescue tillers were analyzed for Epichloë endophyte presence and alkaloid concentrations (ergovaline, ergovalinine, N-acetylnorloline, N-formylloline, N-acetylloline). Cattle toxicosis was assessed via fecal ergovaline levels. With PBG, tiller defoliation was greater in burned patches versus unburned and was greater than any years in GAB. In GAB, tiller defoliation was no different the year of the burn than the years without fire. Cattle did not discriminate between endophyte-infected or endophyte-free tillers in either treatment. Endophyte infection levels were inversely related to years since fire (YSF), and various alkaloids displayed asynchronous responses to YSF. Cattle had no detectable fecal ergovaline when managed with patchy or complete pasture fires. Only two herds had detectable fecal ergovaline (> 100 ppb), which were in pastures managed without fire and only in 2013. Thus, patch burning tall fescue−invaded grasslands alters alkaloids and tiller defoliation with implications for cattle toxicosis. Future research should incorporate greater intra-annual resolution of plant phenology relative to focal grazing and alkaloid expression.

Endophyte-Infected Tall Fescue Affects Rumen Microbiota in Grazing Ewes at Gestation and Lactation.

Tall fescue (Schedonorus arundinaceus) is a cool-season perennial grass that is widely used as a forage for many livestock species including sheep. An endophyte (Neotyphodium coenophialum) in tall fescue produces ergot alkaloids that enhance plant survival but produce toxicosis in animals. The objective of this study was to investigate the rumen microbiota from gestation and lactation in ewes grazing tall fescue pastures with high (HA) or moderate (MA) levels of endophyte infection, and their relationship with serum parameters. Data were collected at the beginning of the study (d1), the week before initiation of lambing (d51), and at the end of the trial (d115). The rumen microbiota was evaluated using 16S rRNA gene sequencing. Ewes grazing HA had greater serum non-esterified fatty acid (NEFA) (P = 0.024) levels compared with ewes in MA pasture at d115. Both the number of observed OTUs and Shannon diversity index tended (P = 0.08, P = 0.06) to be greater for HA than for MA on d115. At the genus level, Prevotella relative abundance increased with time in both MA and HA (on d1, d51, and d115: 15.17, 25.59, and 24.78% in MA; 14.17, 18.10, and 19.41% in HA). Taxa unclassified at the genus level including (unclassified) Lachnospiraceae, Coriobacteriaceae, and Veillonellaceae exhibited higher abundances in HA at d51 (3.72, 2.07, and 11.22%) compared with MA (2.06, 1.28, and 7.42%). The predictor microbiota for HA and MA were identified by a random forest classification model. The HA predictors included bacteria associated with unclassified Coriobacteriaceae and Ruminococcaceae. Other OTUs classified as Prevotella and Clostridiales could be microbial predictors for MA. The OTUs classified as Prevotella and Lachnospiraceae were negatively correlated with serum concentration of prolactin. Negative correlations with NEFA were observed in the microbiota such as species affiliated to unclassified Clostridiales and Prevotella. OTUs classified as Bacteroidetes and Coriobacteriaceae exhibited a positive correlation with NEFA. Our study confirmed that the rumen microbiota populations were affected by high levels of toxins in endophyte-infected tall fescue and were associated with host hormone and energy metabolism.

Seed Transmission of Epichloë Endophytes in Lolium perenne Is Heavily Influenced by Host Genetics.

Vertical transmission of symbiotic Epichloë endophytes from host grasses into progeny seed is the primary mechanism by which the next generation of plants is colonized. This process is often imperfect, resulting in endophyte-free seedlings which may have poor ecological fitness if the endophyte confers protective benefits to its host. In this study, we investigated the influence of host genetics and environment on the vertical transmission of Epichloë festucae var. lolii strain AR37 in the temperate forage grass Lolium perenne. The efficiency of AR37 transmission into the seed of over 500 plant genotypes from five genetically diverse breeding populations was determined. In Populations I–III, which had undergone previous selection for high seed infection by AR37, mean transmission was 88, 93, and 92%, respectively. However, in Populations IV and V, which had not undergone previous selection, mean transmission was 69 and 70%, respectively. The transmission values, together with single-nucleotide polymorphism data obtained using genotyping-by-sequencing for each host, was used to develop a genomic prediction model for AR37 seed transmission. The predictive ability of the model was estimated at r = 0.54. While host genotype contributed greatly to differences in AR37 seed transmission, undefined environmental variables also contributed significantly to seed transmission across different years and geographic locations. There was evidence for a small host genotype-by-environment effect; however this was less pronounced than genotype or environment alone. Analysis of endophyte infection levels in parent plants within Populations I and IV revealed a loss of endophyte infection over time in Population IV only. This population also had lower average tiller infection frequencies than Population I, suggesting that AR37 failed to colonize all the daughter tillers and therefore seeds. However, we also observed that infection of seed by AR37 may fail during or after initiation of floral development from plants where all tillers remained endophyte-infected over time. While the effects of environment and host genotype on fungal endophyte transmission have been evaluated previously, this is the first study that quantifies the relative impacts of host genetics and environment on endophyte vertical transmission.

Meta-analysis of endophyte-infected tall fescue effects on cattle growth rates.

The objective of this study was to quantitatively summarize literature reporting endophyte-infected (Neotyphodium coenophialum) tall fescue (Festuca arundinacea) effects on cattle ADG. This meta-analysis evaluated endophyte infection level, climate, and forage yield using a literature dataset of 138 treatments from 20 articles. Three infection level measurements were tested: endophyte infection as a percentage of infected tillers (E%); ergovaline concentration in ppb ([E]); and total ergot alkaloid concentration ([TEA]). Three types of climate variables were used: base values (temperature, humidity, and relative humidity), climate indices (heat index and temperature-heat index [THI]), and novel climate variables accounting for duration of climate effects. Mixed effect models, weighted by 1/SEM, including a random effect of study were built for each factorial combination of measurement method and climate variable group. Because many studies were missing SEM, two datasets were used: one containing only data with SEM reported and one that also included missing-SEM data. For the complete-SEM dataset (CSD), models were weighted by 1/SEM. In the missing-SEM dataset (MSD) the mean reported 1/SEM was assigned as the weight for all missing SEM treatments. Although 18 initial models were created (2 × 3 × 3 factorial approach), the backward stepwise derivation resulted in models that included only endophyte infection level, suggesting a negative relationship between infection level and ADG. The CSD models predicted ADG to decrease 39 and 33 g/d with each increase of 100 ppb of [TEA] and [E], and by 39 g/d for each increase of 10% E%. In the MSD dataset, predicted ADG decreased by 39 and 33 g/d with each increase of 100 ppb of [TEA] and [E], and by 47 g/d for each increase of 10% E%. All relationships reported had P < 0.05. After visual inspection of the data, piecewise regression was used to identify an infection threshold (IT) of 60 ppb [E] and 11 E%, where the effect of infection level was constant on either side of the IT. The ADG was 40% and 49% greater for infection levels below the IT for [E] and E%, respectively. Across THI values in the analysis, ADG decreases ranged from 11.2% to 45.0% for cattle grazing endophyte-infected tall fescue compared to non-ergot alkaloid endophyte infected tall fescue. Pasture E%, [E], and [TEA] have a negative relationship with ADG in growing cattle, and increasing temperature decreases ADG when infection level is greater than the IT.

Interaction between a tannin-containing legume and endophyte-infected tall fescue seed on lambs' feeding behavior and physiology.

It was hypothesized that a tannin-rich legume such as sainfoin attenuates the negative postingestive effects of ergot alkaloids in tall fescue. Thirty-two 4-mo-old lambs were individually penned and randomly assigned to a 2 × 2 factorial arrangement with 2 legume species, sainfoin (SAN; 2.9% condensed tannins) or cicer milkvetch (CIC; without tannins) and a mixed ration containing tall fescue seed (50:30:20 seed:beet pulp:alfalfa) with 2 levels of endophyte infection (endophyte-infected tall fescue seed [E+; 3,150 ug/L ergovaline] or endophyte-free tall fescue seed [E-]). For a 10-d baseline period, half of the lambs were fed SAN and half were fed CIC and all lambs had ad libitum amounts of E-. In an ensuing 10-d experimental period, the protocol was the same except half of the lambs fed SAN or CIC received E+ instead of E-. Subsequently, all lambs could choose between their respective legume and seed-containing ration and between E+ and E-. Finally, an in vitro radial diffusion assay was conducted to determine whether tannins isolated from SAN would bind to alkaloids isolated from E+. All groups consumed similar amounts of E- during baseline period ( > 0.10), but lambs ate more E- than E+ during the experimental period ( < 0.05) and lambs offered SAN ate more E+ than lambs offered CIC ( < 0.05). Groups fed E- during the baseline and experimental periods had similar rectal temperatures ( > 0.10), but lambs fed E+ had lower rectal temperatures per gram of feed ingested when supplemented with SAN than with CIC ( < 0.05). Lambs fed E+ had greater concentrations of hemoglobin and more red blood cells than lambs fed E- ( < 0.05), but plasmatic concentrations of cortisol and prolactin did not differ among treatments ( > 0.10). All lambs preferred their treatment ration over their treatment legume, but lambs in the SAN and E+ treatment ate more legume + ration than lambs in the CIC and E+ (CIC-E+; < 0.05) treatment. All lambs preferred E- over E+, but lambs in the CIC-E+ treatment ate the least amount of E+ ( < 0.05). Binding of isolated SAN tannins to protein was reduced by the E+ isolate ( < 0.05), suggesting a tannin-alkaloid complexation but only from tannins extracted from SAN fed early in the experimental period. In summary, SAN supplementation increased intake of and preference for E+ and reduced rectal temperatures relative to CIC supplementation. Our results suggest that these effects were mediated by the condensed tannins in SAN through alkaloid inactivation, an interaction that declined with plant maturity.

Runoff under natural rainfall from small tall fescue catchments in the Georgia Piedmont, United States

The environmental outcomes from tall fescue (<i>Lolium arundinaceum</i> [Schreb.] Darbysh.) pastures managed with different levels of endophyte (<i>Neotyphodium coenophialum</i>) infection and choices of harvest and fertilization methods are not well known. We monitored runoff from 14 tall fescue paddocks, 0.9 to 1.1 ha (2.2 to 2.7 ac) each, from April of 2002 to April of 2010 near Watkinsville in the Georgia Piedmont. Three grazed Jesup tall fescue-endpohyte associations (endophyte infected high alkaloid—Wild, endophyte infected low alkaloid—MaxQ, and endophyte free—Free), and two sources of fertilization (inorganic and broiler litter), were replicated twice in a randomized block design. A replicated hayed treatment was planted to Jesup MaxQ with inorganic fertilization as a grazing control. Drought reduced the maximum number of runoff events to 77. A Standardized Precipitation Index analysis showed that the degree of drought was dependent on the time scale considered. The near normal period peaked at a 1-month (74%) scale and was least at a 9-month time scale (32%). Considering a 1-month time scale, there were on average 4 times as many runoff events per month during the near normal, and 16 times as many during the wet and wetter period, as those in the dry and drier period. Fertilizer and fertilizer by fescue interactions in grazed paddocks had significant effect on runoff, whereas main effects of fescue type and harvest methods (graze versus hay) did not. Inorganically fertilized paddocks had 30% greater runoff than those with broiler litter fertilization. The largest runoff amount occurred with inorganic fertilizer and endophyte-free fescue, suggesting a combined impact of reduced persistence of the endophyte-free fescue, with low organic matter input from the inorganic fertilizer. Grazing of Piedmont pastures with MaxQ-endophyte association of tall fescue, and fertilized with broiler litter, does not appear to pose additional risk for runoff, compared to tall fescue pastures under the common wild-type-endophyte association that are hayed or grazed, and fertilized inorganically or with broiler litter. These results further support a previous recommendation for increased adoption of MaxQ with broiler litter fertilization in the southeastern United States, because of excellent average daily gain by cattle and stand persistence of MaxQ.

A Neotyphodium endophyte from Festuca myuros L. in Nanjing, China

Some Festuca species are infected by seed-transmitted Neotyphodium fungi without significant pathogenic symptoms. Fungal isolates were obtained from Festuca myuros L. growing in Nanjing. The endophyte infection level was estimated as high as 91.4% in 148 plant samples from different sites, indicating that endophyte infection is common in F. myuros in Nanjing. Morphological characteristics of all 11 isolates were identical with each other. Phylogenetic analysis based on tefA and tubB loci indicated that these fungal isolates clustered with Neotyphodium sinofestucae, a previously reported species harbored in Festuca parvigluma. These fungal endophytes from F. myuros in China were then identified as N. sinofestucae. Small differences in morphological features and close evolutionary relationship in tefA and tubB genes were demonstrated among isolates from these two different host species. This exhibit species diversity of grass endophytes in Festuca spp.

Endophyte-Mediated Resistance to Black Cutworm as a Function of Plant Cultivar and Endophyte Strain in Tall Fescue

To improve Neotyphodium endophyte-mediated resistance to black cutworm Agrotis ipsilon (Hufnagel) (BCW), a series of experiments was conducted by using several different cultivars of tall fescue, Schedonorus arundinaceus (Schreb.) Dumort. in combination with several different haplotypes of the endophyte Neotyphodium coenophialum (Morgan-Jones & Gams) (plant cultivar × endophyte haplotype = plant line), each producing unique alkaloid profiles. BCW settling response, survival at 5 and 10 d, and larval biomass varied significantly among plant lines. In general, greater variation BCW performance was observed within a single plant cultivar infected with different endophyte haplotypes than among different plant cultivars infected with the same endophyte haplotype, but comparisons among the former were far more numerous. Although five endophyte-mediated alkaloids representing three alkaloid classes were quantified in the plants, the pyrrolizidine alkaloid N-acetyl norloline was consistently the single best predictor of BCW performance. BCW settling response, 5-d survival, and 10-d survival decreased as levels of the alkaloid N-acetyl norloline increased. The same three response variables also decreased with increasing levels of peramine, but increased with increasing levels of ergovaline. Minor variation in endophyte infection levels occurring among infected plant lines had no significant influence on BCW performance. Results indicate a potentially important role for N-acetyl norloline and peramine in providing resistance to black cutworm whereas ergovaline appears to be much less important. Therefore, endophyte haplotypes expressing high levels of N-acetyl norloline and peramine may be of particular importance for developing 'friendly' endophyte-enhanced turf and pasture grasses that resist challenging lepidopteran pests, although remaining safe for wildlife and grazing mammals.

Variation in Endophyte–Plant Associations Influence Black Cutworm (Lepidoptera: Noctuidae) Performance and Susceptibility to the Parasitic NematodeSteinernema carpocapsae

This study examined how variability in Neotyphodium endophyte-grass associations influences black cutworm Agrotis ipsilon Hufnagel performance and susceptibility to the entomopathogenic nematode Steinernema carpocapsae (Weiser). Second-instar cutworm larvae were confined to greenhouse pots containing four different tall fescue Schedonorus phoenix (Scop.) Holub cultivars. After 1 wk, larvae were recovered from the pots, weighed, and individually exposed to 20 infective juvenile nematodes. Nematode-induced mortality was monitored for 72 h after exposure. Endophyte infection levels and ergot alkaloid concentrations varied between tall fescue cultivars, but endophyte infection level was not a significant predictor of ergot alkaloid concentrations in above-ground plant tissue. Larval survival also varied between cultivars, but neither endophyte infection level nor ergot alkaloid concentration was a significant covariate. Larval susceptibility to the entomopathogenic nematode varied between cultivars at 48 and 72 h after exposure. In all but one cultivar (Plantation), cumulative mortality at 72 h decreased significantly as ergot alkaloid concentrations increased. Neither larval biomass nor endophyte infection levels in tall fescue were significant predictors of larval susceptibility to the nematode. Results show that variation in endophyte-plant associations can influence black cutworm performance and susceptibility to entomopathogenic nematodes and that susceptibility to the nematode H. bacteriophora may be partially tied to ergot alkaloid levels in the insects' food. Findings further support the assertion that black cutworm may use certain endophyte-mediated toxins, particularly ergot alkaloids, as a form of acquired chemical defense against nematode-induced septicaemia.

Endophyte infection level of tall fescue stockpiled for winter grazing does not alter the gain of calves nursing lactating beef cows1

We examined the effect of endophyte infection level of tall fescue (Festuca arundinacea Schreb.) used for stockpiled forage on the performance of lactating, fallscalving beef cows and their calves. Treatments were endophyte infection levels of 20% (low; SEM = 3.5), 51%, (medium; SEM = 1.25), and 89% (high; SEM = 2.4; 4 replications/treatment). Five cow-calf pairs grazed in each replicate (n = 60 cow-calf pairs/yr) for 84 d (phase 1) starting on December 2, 2004 (yr 1), and December 1, 2005 (yr 2). After 84 d of grazing each treatment, the cattle were commingled and fed as a single group (phase 2) until weaning in April of each year. Phase 2 allowed measurement of residual effects from grazing stockpiled tall fescue with varying levels of endophyte infection. Pregrazing and postgrazing forage DM yield, forage nutritive value, and total ergot alkaloid concentrations of forage were collected every 21 d during phase 1. Animal performance data included cow BW, ADG, and BCS, as well as calf BW and ADG. Animal performance was monitored during both phases. Endophyte infection did not affect (P = 0.52) apparent intake (pregrazing minus postgrazing forage DM yield) of stockpiled tall fescue, because each cow-calf pair consumed 16 +/- 1.7 kg/d regardless of treatment. Cow ADG during phase 1 was -0.47 +/-0.43 kg for the low treatment, which was greater (P < 0.01) than either the medium (-0.64 +/-0.43 kg) or high (-0.74 +/- 0.43 kg) treatments. However, cows that had grazed the high or medium treatments in phase 1 lost -0.43 and -0.57 (+/-0.24) kg/d, respectively, which was less (P < 0.01) BW loss than the cows in the low (-0.78 +/- 0.24 kg/d) treatment during phase 2. By the end of phase 2, cow BW did not differ (528 +/-27 kg; P = 0.15). Body condition score for cows in the low treatment was greater (P = 0.02) than that of the medium and high treatments at the end of phase 1. Body condition scores did not change appreciably by the end of phase 2, and differences among treatments remained the same as at the end of phase 1 (P = 0.02). In contrast to cow performance, calf ADG was unaffected (P = 0.10) by endophyte level and averaged 0.73 +/- 0.07 kg during phase 1 and 0.44 +/- 0.04 kg during phase 2. Our data suggest that fall-calving herds can utilize highly-infected tall fescue when stockpiled for winter grazing, with little impact on cow performance and no impact on calf gain.

Metabolic profiling of endophyte-infected and endophyte-free ryegrass grown under sufficient water supply and drought

Metabolic profiling using gas-chromatography mass spectrometry was performed for endophyte-infected (E+) and corresponding endophyte-free (E-) clones of two ryegrass genotypes cultivated under sufficient water supply and drought stress. In total, 243 metabolites representing both known and unknown compounds were analysed for samples taken at the end of the drought stress period and after rewatering (n=10 replications per level of genotype, endophyte infection, and water supply).

Endophyte fungus levels in perennial ryegrass and tall fescuse varieties grown for seed in Oregon, USA - implications for responsible grass straw use as livestock feed

Baling of perennial ryegrass (Lolium perenne) and tall fescue (Festuca arundinacea) straw residue following seed harvest has become a common practice in Oregon's grass seed industry. In 2005, almost 670 000 tons [607 000 Mg (tonne)] of grass straw was exported to Japan and Korea for use as livestock feed. Most of the grass seed varieties grown today are turf-type, which in recent years have been developed with high levels of fungal endophyte infection. Currently, over 73% and 43% of perennial ryegrass and tall fescue varieties, respectively, are ranked as having a "High" (&gt;61% infected) infection level. Concern for the safe use of these grass straw residues had led to their routine analysis for toxin content before shipment to consuming markets. These chemical analyses provide assurances against deleterious effects to livestock fed Oregon grass straw. Keywords: straw, endophyte-infected, perennial ryegrass, tall fescue

Short-term Responses of Soil C and N Fractions to Tall Fescue Endophyte Infection

Tall fescue (Festuca arundinacea Schreb.) is naturally infected with a fungal endophyte, Neotyphodium coenophialum, which produces toxic ergot alkaloids that negatively affect herbivores and that may alter soil organic matter dynamics. A 60-week mesocosm study with a factorial arrangement of soil type (clay loam and loamy sand) and endophyte infection (with and without) was conducted to determine potential changes in soil C and N fractions. Forage and root dry-matter production were greater with than without endophyte infection, while forage C and N concentrations were unaffected. Total, particulate, mineralizable, and aggregate-associated C and N fractions increased several fold during the course of the experiment due to large rhizosphere inputs in all treatments. The fraction of total C and N in water-stable macroaggregates (>0.25 mm) was initially 0.43±0.10 and 0.46±0.16, respectively, and increased during the course of the experiment to 0.68±0.06 and 0.56±0.15 when averaged across soil type and endophyte infection level as a result of organic matter cycling and deposition in this active biophysical fraction. Changes in soil C and N fractions due to endophyte infection were minimal. The lack of detectable changes in soil C and N fractions due to endophyte infection may have been a result of the overwhelming input of C from roots and/or the relatively short-term nature (60 weeks). Greater plant productivity of endophyte-infected tall fescue is likely a contributing mechanism for eventual changes in total and active C and N fractions that have been observed in long-term pastures. Abbreviations: E) – endophyte free; E+ – endophyte infected

Widespread occurrence ofNeotyphodium-like endophyte in populations ofBromus tomentellusBoiss. in Iran

Neotyphodium species occur as endophytic fungi in cool-season grasses around the world. The beneficial aspects of grass-Neotyphodium associations have provoked researchers to look for a novel association in plant species where this symbiotum has not been reported. We surveyed Russian bromegrass (Bromus tomentellus Boiss.) accessions from a germplasm collection for the presence of Neotyphodium spp. fungi and determined levels of endophyte infection in B. tomentellus populations in native rangelands of Iran. Among 50 collected accessions, symbiotic fungi were detected in 45 accessions without any symptoms of choke disease on host plants. In culture medium, fast-growing endophytes appeared from seeds after 7-14 days. Plants grown from seed collections were 80-100% infected. Based on morphological characteristics and PCR analysis, we concluded that this fungus is a member of the Neotyphodium group of endophytic fungi. Lack of apparent toxicity to grazing animals suggests a place for endophyte-infected B. tomentellus in rangeland renovation, providing this infected grass exhibits increased tolerance to abiotic stresses.

Reduced herbivore resistance from a novel grass–endophyte association

Summary Endophytic fungi in agricultural grasses confer agronomic advantages but can be detrimental to the health and production of grazing mammals. Attempts have been made to resolve this dilemma by creating novel associations of high‐yielding grass cultivars and ‘safe endophytes’ that do not naturally co‐occur. Recently, researchers created a novel association by combining a Moroccan strain of Neotyphodium coenophialum, called AR542, with the tall fescue Festuca arundinacea cultivar Georgia 5. This novel association is marketed commercially and has no doubt become naturalized; it is therefore important to assess its impact on other organisms. The bird‐cherry‐oat aphid Rhopalosiphum padi uses tall fescue as an alternative host. We assessed the performance of R. padi feeding on Georgia 5 that had been artificially infected with AR542, naturally infected by the common strain (CS) of N. coenophialum or was endophyte‐free (EF). We cross‐factored these three levels of endophyte infection with four levels of nitrogen fertilizer, and used two different methods of assessing aphid performance, clip‐cages and enclosed populations. Endophyte‐infected plants produced approximately 20% more dry mass than EF plants. In both the clip‐cage and enclosed‐population experiments, aphid populations grew fastest on the EF plants, slower on AR542‐infected plants and slowest (or not at all) on the CS‐infected plants. Synthesis and applications. Our results suggest that AR542 infection does not provide the same degree of protection from aphids as the commonly occurring CS infection. If similar results are found for other invertebrate herbivores, then the use of this novel endophyte association may be less useful than previously thought. The widespread conversion of tall fescue pastures, currently infected with the CS endophyte, to pastures infected with AR542 could result in a general increase in the prevalence of cereal aphids and, potentially, the diseases that they spread. However, such conversion might be beneficial to native invertebrate herbivores.

Interactions between endophyte (Neotyphodium spp.) and ploidy in hybrid and perennial ryegrass cultivars and their effects on Argentine stem weevil (Listronotus bonariensis)

Argentine stem weevil damage was assessed in 1998 and 1999 on two diploid perennial ryegrasses (cvs. ‘Yatsyn’ and ‘Samson'), a diploid long‐rotation hybrid ryegrass (cv. ‘Marsden'), a tetraploid perennial ryegrass selection ('4N') and in a tetraploid hybrid (cv. ‘Greenstone') in a field trial in Taranaki. ‘Greenstone’ was infected with a selected Neotyphodium endophyte that produces peramine and ergovaline but not lolitrem B. All other cultivars were naturally infected with endophytes that produce all three alkaloids. In the first year, percent endophyte infection levels were low in ‘Greenstone’ (61%), ‘Marsden’ (70%) and ‘4N’ (71%) relative to ‘Yatsyn’ (85%) and ‘Samson’ (86%), but increased in the second year to greater than 88% in all cultivars. Argentine stem weevil adult feeding and larval damage were greatest on ‘Greenstone’ and least on ‘Yatsyn’ and ‘Samson’ in both years. ‘Greenstone’ tillers damaged by larvae were more severely affected than tillers of other cultivars. Individually and in combination, percent endophyte and peramine and lolitrem B levels in the leaf lamina were correlated with adult activity which in turn was the main factor affecting larval damage. Overall, the tetraploid and hybrid species sustained more damage than the diploids and perennials. This was attributed mainly to lower leaf lamina peramine concentrations in the hybrid and tetraploid combinations which affected adult feeding, but additional attractiveness factors in these cultivars may also play a role in their susceptibility to Argentine stem weevil. The absence of lolitrem B was not a major factor in the number of tillers damaged by larvae in ‘Greenstone’, but may have resulted in more severe damage to those tillers.

Endophytic foliar fungi in Betula spp. and their F1 hybrids

SummaryWe examined foliar endophyte frequencies in two native (Betula pendula and Betula pubescens) and three exotic (Betula ermanii, Betula platyphylla and Betula resinifera) birch species and their hybrids in Punkaharju, Finland. The most frequently isolated endophytic fungi in the experimental trees were Fusicladium betulae and Gnomonia setacea making up 80–90% of all endophyte infections. Total endophyte infection levels varied from 0.5 colony forming units (CFU)/cm2 in B. platyphylla to 8.6 CFU/cm2 in B. pubescens that had highest total infection levels of both examined endophyte species. The resistance of hybrids was generally very close to the more resistant parent (the only exception being Fusicladium in B. platyphylla × B. pendula hybrid) supporting the hypothesis that the resistance of birch hybrids to these fungi is genetically based and caused by dominant inheritance of resistance traits.