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Pasture management oriented towards sustainable intensification and stability of yield must consider the ideal balance between the mass of leaves removed by grazing and the mass left as residual. The former supports high animal production and the later supports an optimum soil–plant carbon balance. This study aimed to evaluate the optimal herbage level from both plant and animal perspectives, through the adjustment of instantaneous herbage accumulation rate as estimated by the Gompertz curve model and short‐term intake rate of sheep. Weekly tall fescue (Schedonorus arundinaceus) herbage accumulation was measured during seven growth periods with initiation dates in October, November and December 2015, and March, April, August and September 2016 and with the initiation dates arranged in a randomized complete block design with four replicates. Total herbage mass, leaf lamina mass, pseudo‐stem + sheath mass, senescent mass, and sward surface height were measured each week. The results demonstrated that a pre‐grazing sward surface height of 22.3 cm of tall fescue promoted the maximum short‐term intake rate of sheep and the optimum herbage accumulation rate in the spring and autumn periods. In general, the convergent point occurred after the maximum instantaneous leaf lamina accumulation rate and before the maximum instantaneous accumulation rate of pseudo‐stem + sheath and senescent material. We suggest the existence of a convergent point in which both primary and secondary production of pastoral ecosystems could be fostered. [ABSTRACT FROM AUTHOR]

Tall fescue (Schedonorus arundinaceus) offers an alternative to kentucky bluegrass (Poa pratensis) for use on athletic fields. Tall fescue has the ability to withstand athletic field traffic, but little is known about the best management practices such as optimal height of cut (HOC). A 2-year study was conducted on established ‘Snap Back’ tall fescue grown over a native soil root zone to determine optimal HOC under simulated athletic field traffic. Plots were maintained at various HOC treatments (1.5, 2, or 3 inches) for the duration of the growing season. Twenty-five simulated traffic events were applied each fall with a modified Baldree traffic simulator. The percentage of green cover (GC) loss per traffic event by HOC varied between years. In 2017, the 1.5-inch HOC improved traffic tolerance (–1.7% GC per event) compared with the other HOC treatments (–2.6% GC per event) in terms of percentage of GC. In 2018, the HOC did not have an impact on traffic tolerance. Differences in traffic tolerance between years could be a result of differences in precipitation (78 mm in 2017, 6 mm in 2018) during the period when traffic occurred, which suggest that the lower HOC performs better under wet conditions compared with the greater HOC. There were no differences among treatments for the safety variables measured (surface hardness, rotational resistance, and soil moisture).

Spring establishment of turfgrass that is managed without herbicides is subject to weed competition, resulting in reduced turfgrass cover. The objective of this experiment was to find an acceptable method for spring turfgrass establishment without the use of pesticides. Thirty-six treatments consisting of three soil amendments combined with three turfgrass species or mixes, and four topdressings or fertilizers in a randomized complete block design were tested. Nutrient-deficient fill soil, fill soil blended with topsoil, and fill soil blended with leaf compost were used as growing media. ‘Firenza’ tall fescue (Schedonorus arundinaceus), an 80/20 mix of ‘Nu Destiny’ kentucky bluegrass (Poa pratensis) and ‘Nexus XD’ perennial ryegrass (Lolium perenne), respectively, and ‘Firefly’ hard fescue (Festuca trachyphylla) were grown with topdressings consisting of biosolids, ash-amended biosolids, 16N–12.2P–3.3K starter fertilizer, and an unfertilized control. The treatments were mowed at 3 inches about once per week. Irrigation was supplied by an overhead sprinkler system (1 inch/week). During the 2010 field study, treatments of tall fescue established in a leaf compost–amended root zone were significantly denser and had a greater percentage of cover (P ≤ 0.05) compared with all other treatments. In 2011, treatments of tall fescue established in fill soil– and leaf compost–amended soils were significantly denser and had a greater percentage of cover (P ≤ 0.05) compared with all other treatments. Kentucky bluegrass/perennial ryegrass and hard fescue treatments had significantly lower (P ≤ 0.05) levels of establishment compared with tall fescue. Topdressing treatments resulted in no significant difference (P ≤ 0.05) in turfgrass establishment.

The objective of this greenhouse study was to evaluate tall fescue (Festuca arundinacea) seedling growth when seeded after herbicide application. Herbicide treatments included a nontreated control; 1.19 lb/acre 2,4-dichlorophenoxyacetic acid (2,4-D) + 0.32 lb/acre methylchlorophenoxypropionic acid (MCPP) + 0.32 lb/acre dicamba; 0.75 lb/acre quinclorac; and 0.06 lb/acre halosulfuron-methyl. Seeding was done at 0, 3, 7, or 14 days after herbicide application to soil media. Two identical experiments were conducted in the greenhouse: Expt. 1 seedling growth from January to March and Expt. 2 from May to July (temperatures higher). Seeding dates after herbicide application did not influence growth. Average dry shoot weight reductions and dry root weight reductions caused by postemergence herbicides were 2,4-D + MCPP + dicamba (33% shoot and 27% root in Expt. 2), quinclorac (30% shoot and 37% root in Expt. 2), and halosulfuron-methyl (51% shoot in Expt. 2; 81% root in Expts. 1 and 2). Although application of these herbicides before seeding in the field may result in no visual impact, they can impact seedling shoot and root growth, particularly under higher growth temperatures.

Tall fescue (Schedonorus arundinaceus) is a cool-season grass which is commonly infected with the fungal endophyte Epichloë coenophiala. Although the relationship between tall fescue and E. coenophiala is well-studied, less is known about its broader fungal communities. We used next-generation sequencing of the ITS2 region to describe the complete foliar fungal microbiomes in a set of field-grown tall fescue plants over two years, and whether these fungal communities were affected by the presence of Epichloë. We used the Georgia 5 cultivar of tall fescue, grown in the field for six years prior to sampling. Plants were either uninfected with E. coenophiala, or they were infected with one of two E. coenophiala strains: The common toxic strain or the AR542 strain (sold commerically as MaxQ). We observed 3487 amplicon sequence variants (ASVs) across all plants and identified 43 ASVs which may make up a potential core microbiome. Fungal communities did not differ strongly between Epichloë treatments, but did show a great deal of variation between the two years. Plant fitness also changed over time but was not influenced by E. coenophiala infection. [ABSTRACT FROM AUTHOR]

Soil pollution is a pressing problem requiring solutions that can be applied without large-scale side effects directly in the field. Phytoremediation is an effective strategy combining plant and root-associated microbiome to immobilize, degrade, and adsorb pollutants from the soil. To improve phytoremediation, it is necessary to think of plants, fungi, and bacteria not as individual entities, but as a meta-organism that reacts organically, synergistically, and cooperatively to environmental stimuli. Analyzing the tripartite enzymatic activity in the rhizosphere is necessary to understand the mechanisms underlying plant–microorganism communication under abiotic stress (such as soil pollution). In this work, the potential of a microbial consortium along with a plant already known for its phytoremediation capabilities, Schedonorus arundinaceus (Scheb.) Dumort., was validated in a mesocosm experiment with pluricontaminated soil (heavy metals, PAHs, and PCBs). Chemical analyses of the soil at the beginning and end of the experiment confirmed the reduction of the main pollutants. The microscopic observation and chemical analyses confirmed the greater root colonization and pollutant removal following the microbial treatment. To obtain a taxonomic and functional picture, tripartite (plant, fungi, and bacteria) enzyme activity was assessed using a metatranscriptomic approach. Total RNA was extracted from a sample of rhizosphere sampled considering 2 centimeters of root and soil attached. From the total reads obtained, mRNAs were filtered, and analysis focused on reads identified as proteins with enzymatic activity. The differential analysis of transcripts identified as enzymes showed that a general increase in potential enzyme activity was observed in the rhizosphere after our biotechnological treatment. Also from a taxonomic perspective, an increase in the activity of some Phyla, such as Actinobacteria and Basidiomycota, was found in the treated sample compared to the control. An increased abundance of enzymes involved in rhizospheric activities and pollutant removal (such as dehydrogenase, urease, and laccase) was found in the treated sample compared to the control at the end of the experiment. Several enzymes expressed by the plant confirmed the increase in metabolic activity and architectural rearrangement of the root following the enhancement of the rhizospheric biome. The study provides new outcomes useful in rhizosphere engineering advancement. [ABSTRACT FROM AUTHOR]

Soil pollution is a pressing problem requiring solutions that can be applied without large-scale side effects directly in the field. Phytoremediation is an effective strategy combining plant and root-associated microbiome to immobilize, degrade, and adsorb pollutants from the soil. To improve phytoremediation, it is necessary to think of plants, fungi, and bacteria not as individual entities, but as a meta-organism that reacts organically, synergistically, and cooperatively to environmental stimuli. Analyzing the tripartite enzymatic activity in the rhizosphere is necessary to understand the mechanisms underlying plant–microorganism communication under abiotic stress (such as soil pollution). In this work, the potential of a microbial consortium along with a plant already known for its phytoremediation capabilities, Schedonorus arundinaceus (Scheb.) Dumort., was validated in a mesocosm experiment with pluricontaminated soil (heavy metals, PAHs, and PCBs). Chemical analyses of the soil at the beginning and end of the experiment confirmed the reduction of the main pollutants. The microscopic observation and chemical analyses confirmed the greater root colonization and pollutant removal following the microbial treatment. To obtain a taxonomic and functional picture, tripartite (plant, fungi, and bacteria) enzyme activity was assessed using a metatranscriptomic approach. Total RNA was extracted from a sample of rhizosphere sampled considering 2 centimeters of root and soil attached. From the total reads obtained, mRNAs were filtered, and analysis focused on reads identified as proteins with enzymatic activity. The differential analysis of transcripts identified as enzymes showed that a general increase in potential enzyme activity was observed in the rhizosphere after our biotechnological treatment. Also from a taxonomic perspective, an increase in the activity of some Phyla, such as Actinobacteria and Basidiomycota, was found in the treated sample compared to the control. An increased abundance of enzymes involved in rhizospheric activities and pollutant removal (such as dehydrogenase, urease, and laccase) was found in the treated sample compared to the control at the end of the experiment. Several enzymes expressed by the plant confirmed the increase in metabolic activity and architectural rearrangement of the root following the enhancement of the rhizospheric biome. The study provides new outcomes useful in rhizosphere engineering advancement.

The grass Festuca arundinacea is often planted for slope stabilisation in South Korea, and is spreading widely beyond the introduction sites. This study used a functional group approach to examine the resistance of plant combinations to invasion by F. arundinacea based on the limiting similarity and diversity-resistance hypotheses, and to elucidate the process of colonisation. The study simulated the environment of construction sites and surrounding areas that might be encountered by expanding populations of F. arundinacea. The role of nutrient condition in the ranking of functional group competitive ability was also examined. Twelve native plant species were categorised into three functional groups using combinations of functional traits. Pairwise (one-to-one competition), multiple (four different neighbouring species) and monoculture experimental settings were designed using two nutrient levels. The Relative Competition Index was used to interpret the competitive effect of neighbouring species on F. arundinacea. Species of the same functional group as F. arundinacea were unable to resist invasion, but annual plants with niche preemption ability could outcompete it. Competitive relationships between native plants and F. arundinacea were explained partially by functional group identity but were inconsistent with the limiting similarity hypothesis and the diversity-interaction. Unforeseen interactions within the artificial communities also produced unexpected effects. In designing artificial plant communities, it is necessary to consider functional traits that reflect the species characteristic of particular periods and indirect effects that modify the interaction between other species. [ABSTRACT FROM AUTHOR]

Context: Vegetation quantity and quality influence the degree to which large grazers shape grassland structural heterogeneity. Invasive plants threaten the function of cross-scale interactions that exist when multi-scale effects such as fire and grazing interplay to form patterns of grassland structural heterogeneity. Objectives: We investigated how grazing pressure and time since fire at the patch scale influenced patch utilization and production as well as forage quality in experimental grassland pastures dominated by an invasive grass, tall fescue (Schedonorus arundinaceous). We also assessed the response of tall fescue utilization and production to interactive fire-and-grazing under moderate and heavy grazing pressure. Methods: We collected data on vegetation quantity and quality over two grazing seasons to evaluate the role of fire and grazing across time in shaping structural heterogeneity among patches in invaded tallgrass prairie in Iowa, USA. We anticipated greater initial patch-scale utilization in patches burned for the first time in two years than patches not burned in two years in our experimental pastures. We expected that greater utilization in recently-burned patches would reduce tall fescue production, mostly where grazing pressure was highest. Results: The contrast in the availability of live herbage between patches was half the level typical for native-dominated tallgrass prairie. Under increased grazing pressure, the interplay between fire and grazing did not result in greater broad-scale heterogeneity (among-patch heterogeneity) or an invasive grass reduction in experimental pastures. Yet, increased grazing early in the season did promote native-grass production in this invaded grassland landscape. Conclusion: Our results suggest that the dominance of tall fescue mediates the lack of structural heterogeneity induced by patch-level prescribed fire and grazing. Unlike native perennial grasses, tall fescue provides access to forage in unburned patches through its low-stature growth form. Diminished cross-scale interactions through a weak coupling of fire and focal grazing in invaded tallgrass prairie may facilitate structural homogenization of fire-dependent grassland. [ABSTRACT FROM AUTHOR]

Tall fescue (Schedonorus arundinaceus) is a cool-season grass which is commonly infected with the fungal endophyte Epichloë coenophiala. Although the relationship between tall fescue and E. coenophiala is well-studied, less is known about its broader fungal communities. We used next-generation sequencing of the ITS2 region to describe the complete foliar fungal microbiomes in a set of field-grown tall fescue plants over two years, and whether these fungal communities were affected by the presence of Epichloë. We used the Georgia 5 cultivar of tall fescue, grown in the field for six years prior to sampling. Plants were either uninfected with E. coenophiala, or they were infected with one of two E. coenophiala strains: The common toxic strain or the AR542 strain (sold commerically as MaxQ). We observed 3487 amplicon sequence variants (ASVs) across all plants and identified 43 ASVs which may make up a potential core microbiome. Fungal communities did not differ strongly between Epichloë treatments, but did show a great deal of variation between the two years. Plant fitness also changed over time but was not influenced by E. coenophiala infection.

Prairies in the Pacific Northwest are dominated by perennial bunchgrasses. A Mycena in the citrinomarginata complex was observed to tightly co-occur with bunchgrasses at several prairie study sites. Mapping and spatial statistics showed that it was strongly and significantly associated with Festuca roemeri tussocks. We further found that this fungus is attached to F. roemeri roots (17/17 examined) and both specific primers and next-generation DNA sequencing established that the fungus is in the roots, suggesting that M. citrinomarginata may be endophytic or biotrophic in some contexts, and not simply saprotrophic. These results combined with a literature review indicate that Mycena species are often found as endophytes in grass roots. Given the importance of grasses and grasslands for humans, this ecological association deserves further study. [ABSTRACT FROM AUTHOR]

Festuca alta, Schedonorus arundinaceus (Schreb.) Dumort, es una de las gramíneas perennes templadas más sembradas en Argentina, tanto en pasturas puras como en mezclas. Entre las principales cualidades agronómicas de esta especie se destacan su alta productividad, rusticidad, plasticidad y perennidad. Las plantas de festuca alta suelen estar infectadas por un hongo endófito asexual, Epichloë coenophiala, que es asintomático y solo se propaga vía semillas infectadas (transmisión vertical). Si bien el hongo les confiere ventajas adaptativas a las plantas hospedantes, también puede sintetizar metabolitos tóxicos para el ganado en pastoreo. Estos metabolitos provocan diferentes síndromes denominados, en general, festucosis, que ocasionan importantes pérdidas en la producción ganadera. En esta revisión se describen, en primer lugar, la gramínea festuca alta, el hongo endófito, su interacción y los efectos perjudiciales que originan el consumo de festuca alta infectada en los herbívoros domésticos. Posteriormente, se analizan los mecanismos que explican el avance de la incidencia de festuca alta infectada en pasturas libres de endófito y se indican algunas estrategias de manejo más comunes empleadas en los sistemas de producción ganadera para mitigar los efectos negativos del endófito sobre los animales. Se presenta información obtenida tanto a nivel local, como internacional, y se señalan áreas que presentan vacíos de información, cuyo conocimiento es necesario para mejorar el manejo productivo de esta asociación.

ABSTRACT Little is known about the impacts and effects of exotic, invasive grasses on wildlife in the Southeast United States. We selected 3 species of exotic grasses common to the Southeast and review the literature on their regional distribution, ecosystem impacts, wildlife impacts, and management. These grasses have the potential to harm indigenous wildlife species, such as northern bobwhite (Colinus virginianus), that need grasslands with a shrub component for nesting, brood‐rearing, and loafing. These exotic, invasive grasses are sod‐forming in nature, typically forming dense monotypic stands that provide little bare ground and have low plant species and insect diversity. Furthermore, it appears that wildlife do not prefer to consume these plant species. Control is often difficult and usually requires the use of herbicides in combination with mechanical treatment, such as disking, to provide adequate habitat. Attempts should be encouraged to convert these idle grasslands to a mixture of native grasses and forbs to make stands more suitable for wildlife species. We provide suggestions for future research and management needs regarding exotic, invasive grasses and wildlife in the Southeast United States. © 2013 The Wildlife Society.

Birds are a major issue for airport authorities worldwide creating hazards to operating aircraft. The effect of a species of grass, Schedonorus arundinaceus, colonised by a unique strain of the mutualistic fungal endophyte Epichloé coenophiala on bird abundance was examined during a series of trials at two New Zealand airports between 2007 and 2012. Fewer birds were observed on S. arundinaceus cv. Jackal AR601 plots compared with the original uncultivated ground cover for many months of the year across many years of trials. This corresponds with data collected by airport authorities on the number of bird strikes experienced by these airports before and after the introduction and establishment of S. arundinaceus cv. Jackal AR601. This plant-fungal association was later developed into the product known as Avanex. [ABSTRACT FROM AUTHOR]

Extirpation of the ecosystem engineer (bison) and its interaction with fire, coupled with the utilitarian concept of moderate grazing, have contributed to homogenization of grassland habitat in North America. Although cattle may serve as a proxy for bison, combining fire with cattle grazing has been uncommon and to date managers have not always successfully applied cattle and controlled burns as tools to manipulate grassland vegetation heterogeneity and increase habitat diversity. Using an information-theoretic approach, we assessed factors constraining the fire-grazing interaction ecological process to engineer habitat structure of grasslands via patch-burn grazing. We assessed how grazing, fire, and biotic and abiotic features in tallgrass prairie influenced establishment and maintenance of low vegetative structure in burned patches, the positive feedback driving the fire-grazing interaction, and subsequent structural heterogeneity across a pasture. Four pastures were divided into three patches with a different patch burned annually in March/April from 2007 to 2013. Cattle were stocked from light to heavy (1.1–4.4 AUM/ha) from May to October (∼150 days) with access to the entire pasture. We hypothesized that the exotic C3 grass tall fescue ( Schedonorus arundinaceus ), lag-time between burning date and the date cattle were put into experimental pastures, and burn date would be the constraining factors. However, the most informative model included stocking rate, date of burn completion, and precipitation. The lightest cattle stocking rate did not establish low vegetative structure in the burn patch, which resulted in the lowest heterogeneity among patches. The heaviest cattle stocking rate established but did not maintain low vegetative structure in the burn patch. The intermediate cattle stocking rate maintained the lowest vegetative structure in the burn patch and the greatest heterogeneity among patches, i.e., the best efficacy of patch-burn grazing to engineer habitat structural heterogeneity. The relationships of stocking rate to burn patch vegetative structure and to landscape heterogeneity were both quadratic and were both optimized at intermediate stocking rate. [ABSTRACT FROM AUTHOR]

Tall fescue ( Schedonorus arundinaceus) is a widespread grass that can form a symbiotic relationship with a shoot-specific fungal endophyte ( Epichloë coenophiala). While the effects of fungal endophyte infection on fescue physiology and ecology have been relatively well studied, less attention has been given to how this relationship may impact the soil microbial community. We used high-throughput DNA sequencing and phospholipid fatty acid analysis to determine the structure and biomass of microbial communities in both bulk and rhizosphere soils from tall fescue stands that were either uninfected with E. coenophiala or were infected with the common toxic strain or one of several novel strains of the endophyte. We found that rhizosphere and bulk soils harbored distinct microbial communities. Endophyte presence, regardless of strain, significantly influenced soil fungal communities, but endophyte effects were less pronounced in prokaryotic communities. E. coenophiala presence did not change total fungal biomass but caused a shift in soil and rhizosphere fungal community composition, increasing the relative abundance of taxa within the Glomeromycota phylum and decreasing the relative abundance of genera in the Ascomycota phylum, including Lecanicillium, Volutella, Lipomyces, Pochonia, and Rhizoctonia. Our data suggests that tripartite interactions exist between the shoot endophyte E. coenophiala, tall fescue, and soil fungi that may have important implications for the functioning of soils, such as carbon storage, in fescue-dominated grasslands. [ABSTRACT FROM AUTHOR]

Mycorrhizal fungi are key microorganisms for enhancing phytoremediation of soils contaminated with heavy metals. In this study, the effects of the arbuscular mycorrhizal fungus (AMF) Funneliformis mosseae (= Glomus mosseae) on physiological and molecular mechanisms involved in the nickel (Ni) tolerance of tall fescue ( Festuca arundinacea = Schedonorus arundinaceus) were investigated. Nickel addition had a pronounced negative effect on tall fescue growth and photosynthetic pigment contents, as well as on AMF colonization. Phosphorus content increased markedly in mycorrhizal plants (M) compared to non-inoculated (NM) ones. However, no significant difference was observed in root carbohydrate content between AMF-inoculated and non-inoculated plants. For both M and NM plants, Ni concentrations in shoots and roots increased according to the addition of the metal into soil, but inoculation with F. mosseae led to significantly lower Ni translocation from roots to the aboveground parts compared to non-inoculated plants. ABC transporter and metallothionein transcripts accumulated to considerably higher levels in tall fescue plants colonized by F. mosseae than in the corresponding non-mycorrhizal plants. These results highlight the importance of mycorrhizal colonization in alleviating Ni-induced stress by reducing Ni transport from roots to shoots of tall fescue plants. [ABSTRACT FROM AUTHOR]

Rising atmospheric CO2 has been shown to alter plant nitrogen metabolism, growth and secondary chemistry. We hypothesized that altered aphid performance under elevated CO2 is linked to phloem nitrogen chemistry., Rhopalosiphum padi performance on endophyte-infected or uninfected tall fescue was examined under three levels of CO2 (ambient, 800 and 1000 p.p.m.) and high and low nitrogen fertilization. Ethylenediaminetetracetic acid-facilitated exudation was used to sample phloem sap, followed by quantification of relative amino acid concentrations using reverse-phase high-performance liquid chromatography., Aphid abundance was reduced at 800 p.p.m. relative to ambient CO2 but returned to baseline at 1000 p.p.m. The density of aphids was reduced in both the elevated CO2 treatments. Aphids were unsuccessful at colonizing endophyte-infected plants, possibly as a result of the presence of loline alkaloids., Multivariate analysis showed that certain groups of phloem amino acids were altered by nitrogen fertilization and CO2. We found that four amino acids (valine, arginine, glutamine and aspartate) were correlated with aphid performance. These findings partially explained the effect of plant nitrogen fertilization and elevated CO2 on aphids., The present study represents a first step toward providing a mechanistic explanation of the aphid performance changes that may result from rising atmospheric CO2. [ABSTRACT FROM AUTHOR]

1. Elevated CO2 can alter plant physiology and morphology, and these changes are expected to impact diet quality for insect herbivores. While the plastic responses of insect herbivores have been well studied, less is known about the propensity of insects to adapt to such changes. Genetic variation in insect responses to elevated CO2 and genetic interactions between insects and their host plants may exist and provide the necessary raw material for adaptation. 2. We used clonal lines of Rhopalosiphum padi (L.) aphids to examine genotype-specific responses to elevated CO2. We used the host plant Schedonorus arundinaceus (tall fescue; Schreb), which is capable of asexual reproduction, to investigate host plant genotype-specific effects and possible host plant-by-insect genotype interactions. The abundance and density of three R. padi genotypes on three tall fescue genotypes under three concentrations of CO2 (ambient, 700, and 1000 ppm) in a controlled greenhouse environment were examined. 3. Aphid abundance decreased in the 700 ppm CO2 concentration, but increased in the 1000 ppm concentration relative to ambient. The effect of CO2 on aphid density was dependent on host plant genotype; the density of aphids in high CO2 decreased for two plant genotypes but was unchanged in one. No interaction between aphid genotype and elevated CO2 was found, nor did we find significant genotype-by-genotype interactions. 4. This study suggests that the density of R. padi aphids feeding on tall fescue may decrease under elevated CO2 for some plant genotypes. The likely impact of genotype-specific responses on future changes in the genetic structure of plant and insect populations is discussed. [ABSTRACT FROM AUTHOR]

1. Elevated CO2 can alter plant physiology and morphology, and these changes are expected to impact diet quality for insect herbivores. While the plastic responses of insect herbivores have been well studied, less is known about the propensity of insects to adapt to such changes. Genetic variation in insect responses to elevated CO2 and genetic interactions between insects and their host plants may exist and provide the necessary raw material for adaptation. 2. We used clonal lines of Rhopalosiphum padi (L.) aphids to examine genotype-specific responses to elevated CO2. We used the host plant Schedonorus arundinaceus (tall fescue; Schreb), which is capable of asexual reproduction, to investigate host plant genotype-specific effects and possible host plant-by-insect genotype interactions. The abundance and density of three R. padi genotypes on three tall fescue genotypes under three concentrations of CO2 (ambient, 700, and 1000 ppm) in a controlled greenhouse environment were examined. 3. Aphid abundance decreased in the 700 ppm CO2 concentration, but increased in the 1000 ppm concentration relative to ambient. The effect of CO2 on aphid density was dependent on host plant genotype; the density of aphids in high CO2 decreased for two plant genotypes but was unchanged in one. No interaction between aphid genotype and elevated CO2 was found, nor did we find significant genotype-by-genotype interactions. 4. This study suggests that the density of R. padi aphids feeding on tall fescue may decrease under elevated CO2 for some plant genotypes. The likely impact of genotype-specific responses on future changes in the genetic structure of plant and insect populations is discussed. [ABSTRACT FROM AUTHOR]

Under climate change, alterations to precipitation and temperature regimes are expected to impact ecosystem structure and function. These impacts may in part be determined by feedbacks between plants and associated microbes, including both endophytic fungal symbionts and viral pathogens., To test potential key components of these feedbacks in a grassland system, we conducted a field experiment that factorially manipulated temperature regime, precipitation regime and endophyte infection of a dominant species, Schedonorus arundinaceus. After one growing season, we evaluated the four most frequently occurring grass species for infection by three species of barley and cereal yellow dwarf viruses (B/ CYDVs). For S. arundinaceus, we also tracked changes in viral prevalence over an additional two growing seasons, for a total of three growing seasons., Plant species identity played a strong role in determining virus prevalence; Poa pratensis and Paspalum dilatatum were more frequently infected than either S. arundinaceus (endophyte infected or endophyte free) or Eleusine indica. Both elevated temperature and elevated precipitation impacted virus prevalence, but effects varied among years and interacted with fungal endophyte symbiosis for S. arundinaceus., In the final year of data collection, elevated precipitation increased virus prevalence in endophyte-infected, but not endophyte-free, S. arundinaceus. In the same year, but regardless of endophyte infection, elevated temperature by itself increased virus prevalence for S. arundinaceus. This effect of temperature on virus prevalence may have been driven by vector abundance because the viruses are obligately aphid-transmitted, and aphids were found more frequently in heated plots., Synthesis. Overall, our investigation experimentally demonstrates strong combined impacts of biotic and abiotic factors on disease dynamics in a grassland system. Impacts of climate change on virus prevalence in grasslands may depend on the responses of aphid vectors and the presence of endophytic fungal symbionts. [ABSTRACT FROM AUTHOR]

The popularly cited enemy release hypothesis, which states that non-native species are released from population control by their enemies, has not been adequately tested in plants. Many empirical studies have compared damage to native versus non-native invaders only in the invaded range, which can lead to erroneous conclusions regarding enemy release. Biogeographical studies that have compared natural enemies in native and introduced ranges have typically focused on a small area of the plants' distributions in each range, only one plant species, and/or only one guild of natural enemies. To test enemy release, we first surveyed both pathogens and herbivores in multiple populations in both the native and naturalized ranges of three commonly co-occurring perennial bunchgrasses introduced to the United States from Europe. We then compared our field results to the number of fungal pathogens that have been documented on each species from published host-pathogen data compilations. Consistent with enemy release, our field survey showed less herbivory and denser populations in the naturalized range, but there was no evidence of release from pathogens. In contrast, the published host-pathogen data compilations produced evidence of enemy release from pathogens. The difference in results produced by the two approaches highlights the need for multiple approaches to testing mechanisms of invasions by introduced species, which can enable well supported theory to inform sound management practices. [ABSTRACT FROM AUTHOR]

The spread of invasive species is complicated and multifaceted. Enemy spillover (i.e. the transfer of a natural enemy from a reservoir host to a novel host) is one mechanism that facilitates the spread of non-native species. The reservoir host is a species that harbors high abundance of the enemy with little cost to fitness. We asked whether Schedonorus arundinaceus (tall fescue), a highly invasive grass species in North America, is a potential reservoir host for the ubiquitous genus of fungi, Alternaria. We also asked whether spillover of Alternaria is possible among grasses that commonly occur with S. arundinaceus in grassland ecosystems. We performed a greenhouse cross inoculation of three isolates of Alternaria and six grass species (three native, three invasive, including S. arundinaceus). We determined that spillover is possible because the fungal isolates infected and caused disease symptoms on all six grasses and decreased biomass in two of the grass species. We also determined that the invasive grass species appear to be more competent hosts than the native species and that S. arundinaceus could be a likely reservoir host for Alternaria spp. because it can harbor the pathogen with no apparent fitness cost. [ABSTRACT FROM AUTHOR]

Abstract: Potential antagonism towards plant-parasitic nematode Meloidogyne incognita by grass–endophyte associations and their corresponding endophytes was evaluated. The following grass-endophyte associations were studied: (1) the cultivated grass Schedonorus arundinaceus-Neotyphodium coenophialum, (2) the wild grass Leymus chinensis-Neotyphodium sp. and (3) the wild grass Achnatherum sibiricum-Neotyphodium sibiricum. The cultivated grass Schedonorus arundinaceus was used to evaluate the effect of the endophyte fungus on chemotaxis of M. incognita. The results showed a significant negative effect on chemotaxis of the second-stage juveniles (J2) of M. incognita towards S. arundinaceus-N. coenophialum plants (P <0.05). The associations of the grass S. arundinaceus-N. coenophialum and the wild grass A. sibiricum-N. sibiricum were used for testing their effect on penetration of grasses by J2. The wild grass A. sibiricum-N. sibiricum association appeared to suppress J2 penetration. N. coenophialum, Neotyphodium sp. and N. sibiricum isolated from cultivated and wild grasses respectively were used for measuring their effect on J2 mortality. Undiluted culture filtrates of all endophytic fungi caused significantly high J2 mortality 72.6% for N. coenphialum, 91.7% for Neotyphodium sp. and 66.8% for N. sibiricum. Finally, the penetration of cucumber roots by J2 pretreated by the filtrates of the three endophytic fungi was also tested. N. sibiricum filtrate significantly reduced the number of J2 penetrations by 44.5% and no significant effect in the treatment of the filtrates of Neotyphodium sp. from L. chinensis. Taken together, endophytic fungi of the genus Neotyphodium might be a potential source of biological control agents for plant parasitic nematodes. [Copyright &y& Elsevier]

Color Doppler ultrasonography was used to compare blood flow characteristics in the caudal artery of heifers fed diets with endophyte (Neotyphodium coenophialum) infected (E+) or noninfected (E-) tall fescue seed. Eighteen crossbred (Angus × Brangus) heifers were assigned to 6 pens and were fed chopped alfalfa hay for 5 d and chopped alfalfa hay plus a concentrate that contained E- tall fescue seed for 9 d during an adjustment period. An 11-d experimental period followed, with animals in 3 pens fed chopped alfalfa hay plus a concentrate with E+ seed and those in the other 3 pens fed chopped hay plus concentrate with E- seed. Color Doppler ultrasound measurements (caudal artery area, peak systolic velocity, end diastolic velocity, mean velocity, heart rate, stroke volume, and flow rate) and serum prolactin were monitored during the adjustment (baseline measures) and during the experimental period. Three baseline measures were collected on d 3, 5, and 6 during the adjustment period for comparison to post E+ seed exposure. Statistical analyses compared the proportionate differences between baseline and response at 4, 28, 52, 76, 100, 172, and 268 h from initial feeding of E+ seed. Serum prolactin concentrations on both diets were lower (P < 0.001) than baseline beginning at 4 h from the start of the experimental period. However, trends in serum prolactin concentrations for heifers on the E- diet suggested ambient temperature was affecting these concentrations. Caudal artery area in E+ heifers had declined (P < 0.10) from baseline by 4 h and was consistently lower (P < 0.05) for the remainder of the period. Heart rates for E+ heifers were lower than the baseline rate from 4 (P < 0.10) to 100 (P < 0.00 1) h, but were similar (P> 0.10) to the baseline for 172 and 268 h measures. Blood flow in E+ heifers was consistently lower than the baseline from 4 (P < 0.05) to 172 (P <0.001) h, but was similar to the baseline at 268 h when heart rate was similar to the baseline rate. Caudal artery areas for the E- diet were similar to baseline areas except at 100 h when it was greater than baseline. Heart rates and flow rates for E- heifers did not differ (P> 0.10) from baseline measures during the experimental period. Results indicated that onset of toxicosis was within 4 h of cattle exposure to E+ tall fescue and is related to vasoconstriction and reduction in heart rate. [ABSTRACT FROM AUTHOR]

The runoff or leaching of nitrogen fertilizers from monoculture turfgrass lawns contri-butes to water pollution, and such lawns are susceptible to insect pests and provide few resources for pollinators. One approach to creating more sustainable lawns is to incorporate white clover (Trifolium repens L.), a nitrogen-fixing legume, into grass seed mixtures or existing turfgrass swards. "Dutch" white clover (DWC), a ubiquitous landrace, forms non-uniform clumps when intermixed with turfgrasses, thus it is often considered to be a lawn weed. Recently, several dwarf varieties of white clover have been selected for their small leaf size and low growth habit, allowing them to tolerate low mowing heights and blend better with grasses. To date, there have been no studies published on the entomological aspects of dwarf clover in pure stands or intermixed with turfgrass. We established field plots with combinations of DWC, two cultivars of dwarf clover, and tall fescue (Schedonorus arundinaceus (Schreb.) Dumort.) in monoculture or mixed swards, and compared the invertebrate communities therein. Predatory arthropods and earthworm numbers were similar in all plot types. The clover monocultures were resistant to white grubs, but the grub densities in the clover–tall fescue dicultures were similar to those found in the pure tall fescue swards. Dwarf clovers and DWC were similarly attractive to bees and supported similar bee assemblages. The tall fescue foliar N content was elevated 17–27% in the dicultures with clovers. [ABSTRACT FROM AUTHOR]

A field experiment was performed to study the effect of Epichloë endophytes of the wild forage grass Bromus auleticus on mycorrhizal colonization, seedling emergence and growth parameters in three heterospecific grasses of agronomic interest. Plots with B. auleticus associated with Epichloë (E+) and non-associated (E-) plants were established and 3 y later, seeds of Lolium multiflorum (E+ or E-), Schedonorus arundinaceus (E+ or E-) and Bromus catharticus (which does not establish associations with Epichloë) were sown as B. auleticus neighbors. While B. auleticus E+ plants induced a significant increase in mycorrhizal colonization of the neighbor grasses, even higher in the E- neighbor plants (L. multiflorum and S. arundinaceus), in comparison to B. auleticus E- neighbors, seedling emergence, root length, leaf number or shoot dry weight were not affected. This is the first approach to studying these triple interactions (endophyte-grass-mycorrhiza) involving wild and forage grasses in the field. Our results show that the effect of Epichloë extends further than its own host and suggest an interaction among endophytes of heterospecific neighbors at the rhizosphere level. • Epichloë -native grass symbiota promote mycorrhizal colonization in neighbor grasses. • The influence of Epichloë on mycorrhizal colonization is greater in E- neighbors. • Growth parameters do not correlate with mycorrhizal colonization. [ABSTRACT FROM AUTHOR]