Showing papers on "Neotyphodium published in 2013"

Tall fescue endophyte effects on tolerance to water-deficit stress.

Abstract: Background: The endophytic fungus, Neotyphodium coenophialum, can enhance drought tolerance of its host grass, tall fescue. To investigate endophyte effects on plant responses to acute water deficit stress, we did comprehensive profiling of plant metabolite levels in both shoot and root tissues of genetically identical clone pairs of tall fescue with endophyte (E+) and without endophyte (E-) in response to direct water deficit stress. The E- clones were generated by treating E+ plants with fungicide and selectively propagating single tillers. In time course studies on the E+ and E- clones, water was withheld from 0 to 5 days, during which levels of free sugars, sugar alcohols, and amino acids were determined, as were levels of some major fungal metabolites. Results: After 2–3 days of withholding water, survival and tillering of re-watered plants was significantly greater for E+ than E- clones. Within two to three days of withholding water, significant endophyte effects on metabolites manifested as higher levels of free glucose, fructose, trehalose, sugar alcohols, proline and glutamic acid in shoots and roots. The fungal metabolites, mannitol and loline alkaloids, also significantly increased with water deficit. Conclusions: Our results suggest that symbiotic N. coenophialum aids in survival and recovery of tall fescue plants from water deficit, and acts in part by inducing rapid accumulation of these compatible solutes soon after imposition of stress.

Forages and pastures symposium: fungal endophytes of tall fescue and perennial ryegrass: pasture friend or foe?

Abstract: Tall fescue (Lolium arundinaceum (Schreb.) Darbysh. syn. Festuca arundinacea Schreb.) and perennial ryegrass (Lolium perenne L.) are impor- tant perennial forage grasses utilized throughout the moderate- to high-rainfall temperate zones of the world. These grasses have coevolved with symbiotic fungal endophytes (Epichloe/Neotyphodium spp.) that can impart bioactive properties and environmental stress tolerance to the grass compared with endophyte-free individuals. These endophytes have proven to be very important in pastoral agriculture in the United States, New Zealand, and Australia, where forage grasses are the principal feed for grazing ruminants. In this review, we describe the biology of these grass-endophyte associations and implications for the livestock indus- tries that are dependent on these forages. Endophyte alkaloid production is put in context with endophyte diversity, and we illustrate how this has facilitated uti- lization of grasses infected with different endophyte strains that reduce livestock toxicity issues. Utilization of tall fescue and use of perennial ryegrass in the United States, New Zealand, and Australia are compared, and management strategies focused predominantly on the success of endophyte-infected perennial ryegrass in New Zealand and Australia are discussed. In addition, we consider the impact of grass-endophyte associations on the sustainability of pasture ecosystems and their likely response to future changes in climate.

Fungal endophyte presence and genotype affect plant diversity and soil-to-atmosphere trace gas fluxes

Abstract: Aims Novel fungal endophyte (Neotyphodium coenophialum; Latch, Christensen and Samuels; Glenn, Bacon, and Hanlin) genotypes in symbiosis with tall fescue (Lolium arundinaceum; Schreb. Darbysh.) have been recently introduced to agricultural seed markets. These novel endophytes do not produce the full suite of toxins that the ‘common toxic’ form does, and therefore, may not have the same consequences on plant and soil processes. Here, we evaluated the effects of endophyte presence and genotype on ecosystem processes of tall fescue stands.

Susceptibility of tall fescue to Rhizoctonia zeae infection as affected by endophyte symbiosis

Abstract: Endophytic fungi belonging to the genus Neotyphodium often form symbiotic associations with grasses. The host plants usually benefit from the association with an endophyte. Presence of the symbiont may increase host resistance to infection by some pathogens. However, the exact mechanism of the lower susceptibility of endophyte-infected plants to diseases is still unclear. Growth chamber trials were conducted to determine whether (a) tall fescue plants infected with the endophyte Neotyphodium coenophialum (E+) are more resistant to sheath and leaf spot disease caused by Rhizoctonia zeae than endophyte-free (E−) plants, and (b) R. zeae growth inhibition is associated with endophyte presence. Tall fescue genotypes, each symbiotic with a genetically different native endophyte strain, were inoculated with isolates of R. zeae. The tillers infection by R. zeae, density of endophyte hyphae and content of total phenolic compounds in tillers were studied. Antifungal activity of the N. coenophialum towards R. zeae, Rhizoctonia solani, Bipolaris sorokiniana and Curvularia lunata was also investigated in dual-culture assays. For Tf3, Tf4, TfA2 and TfA9 tall fescue genotypes, the E+ plants had reduced R. zeae infection. In the Tf9 and Tf8085 genotypes, R. zeae infection was similar for both E+ and E− plants. The strongest effect was observed for the Tf4 endophyte. A strongly positive correlation (r = 0.94) occurred between endophyte hyphal density and disease index across all tall fescue genotypes. Dual-culture assays showed no inhibitory interaction between the seven endophyte strains and the R. zeae isolates; however, some endophytes inhibited R. solani, B. sorokiniana and C. lunata. Endophyte presence increased the production of phenolic compounds by the host grasses. The level of phenolics also differed significantly depending on the time of analysis after inoculation of plants by R. zeae. The results indicate that N. coenophialum can suppress disease severity caused by R. zeae infection. The mechanism of higher resistance of E+ plants is likely not based on direct inhibition such as antibiosis or competition. Thus, the induction of specific mechanisms in the host plant, for example, production of phenolic compounds, seems to be the main way of providing resistance to the grass by the endophyte.

Peramine and lolitrem B from endophyte-grass associations cascade up the food chain.

Abstract: Endophytic fungi in cool-season grass species produce herbivore-toxic alkaloids, which are assumed to harm higher trophic levels along food chains. Previous studies have shown fitness disadvantages for higher trophic levels that feed on aphids that were exclusively reared on perennial ryegrass (Lolium perenne) infected with the endophytic fungus Neotyphodium lolii. However, it is unknown whether the alkaloids produced by the fungus-grass association can be assimilated by plant sap-sucking insects like aphids. Using an ultra high performance liquid chromatography method combined with mass spectrometry, we provide the first evidence that the alkaloids peramine and lolitrem B are present in aphids (Rhopalosiphum padi) and in aphid predators when the aphids are reared on endophyte-infected grass. We conclude that alkaloids can enter the plant sap of the grass and are responsible for longer pupal stages of the ladybird Harmonia axyridis and for fitness disadvantages of aphids and their predators as shown in previous studies.

Diversity and taxonomy of endophytes from Leymus chinensis in the Inner Mongolia steppe of China

Abstract: Epichloe species and their anamorphic relatives in genus Neotyphodium are fungal symbionts of grasses ubiquitously existing in temperate regions all over the world To date, 13 Epichloe species and 22 Neotyphodium species have been formally described, based on morphological characters and phylogenetic analyses Leymus chinensis (Poaceae) is a dominant grass native to the Inner Mongolia steppe of China Previously, it was reported to harbor endophytes, but little was known about these endophytes To investigate their diversity and taxonomy, 96 fungal isolates were obtained from three field populations of L chinensis The isolates were classified into three morphotypes based on morphological characters and phylogenetic analyses of sequences of genes for β-tubulin (tubB), translation elongation factor 1-α (tefA), and actin (actG) The dominant morphotype, morphotype I, was identified as a choke disease endophyte, Epichloe bromicola This broadened the host range and phylogenetic definition of E bromicola

Neotyphodium fungal endophyte in tall fescue (Schedonorus phoenix): a comparison of three Northern European wild populations and the cultivar Kentucky-31

Abstract: Pooideae grasses may be colonized by systemic fungal endophytes. The fitness of endophyte depends entirely on resources and seed transmission from the host plant, while colonized plants may gain increased survival, growth, and reproduction relative to their uncolonized conspecifics. Most research of endophyte-grass interactions have been carried out on few cultivars of tall fescue (Schedonorus phoenix) and their symbiont Neotyphodium coenophialum. Lack of studies using wild populations of tall fescue across the species natural distribution range, however, limits the understanding of the ecological and evolutionary role of the symbiosis in nature. We performed a common garden experiment in Southern Finland with three wild, tall fescue populations from northern Europe and the forage cultivar Kentucky-31 (KY-31). For each population, we used naturally endophyte-colonized, naturally endophyte-colonized but endophyte removed (decolonized), and naturally uncolonized plants to separate effects due to the host genotype from the endophyte. We evaluated growth variables and survival in four environmental treatments of varying water and nutrients. Supply of water and nutrients increased plant biomass and reproductive effort in all populations. This effect was higher for KY-31 plants which produced on average 55 % more seeds than wild plants, indicating better adaptation to high resource environments. However, the higher incidence of Claviceps sp. and the low winter survival indicated KY-31 tall fescue is mal-adapted to Northern European conditions. Naturally colonized plants had greater plant biomass (≈12 %), reproductive effort (≈22 %) and seed mass (≈29 %) than naturally uncolonized and decolonized plants. Nonetheless, endophyte colonization did not affect plant survival, and the effects of endophyte colonization on tiller number, panicle/tiller ratio and Claviceps sp. incidence depended on the population origin. In the wild populations, endophyte removal only reduced the number of tillers (≈29 % lower), while the difference between naturally colonized and naturally uncolonized plants was not significant. Our results show that endophyte symbiont increases tall fescue performance in general, but the differences between wild populations and cultivars indicate adaptation to local habitats and agronomic management, respectively. The comparison of naturally endophyte-colonized and decolonized plants suggests certain plant genotype-endophyte combinations found within populations result from local selection pressures.

Characterisation of novel perennial ryegrass host–Neotyphodium endophyte associations

Abstract: The temperate pasture grass Lolium perenne L. is commonly found in symbiotic association with the asexual fungal endophyte Neotyphodium lolii. Levels of endophyte colonisation and alkaloid content were evaluated in associations formed by plant genotypes from cv. Bronsyn with the standard endophyte (SE) and five distinct commercial endophyte strains. Bronsyn–SE produced all of the measured alkaloids (lolitrem B, peramine, and ergovaline). Bronsyn–AR1 produced only peramine, while Bronsyn–AR37 produced none of the tested alkaloids. Bronsyn–NEA2, Bronsyn–NEA3, and Bronsyn–NEA6 produced both ergovaline and peramine. Both endophyte strain and host genotype exerted significant effects on alkaloid production. Analysis of endophyte colonisation using qPCR revealed differences between each association. With the exception of Bronsyn–AR1 and Bronsyn–NEA3, host genotype also significantly affected colonisation levels. Phenotypic performance of each association was also assessed, based on measurement of morphological traits under glasshouse conditions in hydroponic culture. Significant variation due to different endophyte and host genotypes was observed. Collectively, these studies confirm that differences in both endophyte and host genotypes contribute to host–endophyte performance in a complex interactive manner.

The Epichloe endophytes associated with the woodland grass Hordelymus europaeus including four new taxa.

Abstract: Epichloe endophytes (Clavicipitaceae, Ascomycota), including asexual forms placed in Neotyphodium, are common in cool-season grasses. Here we characterize the endophytes of the European woodland grass Hordelymus europaeus based on growth characteristics, morphology of conidiophores and conidia and phylogenetic relationships. Of the six different taxa found on H. europaeus, four are new, for which we propose the species names E. hordelymi, E. disjuncta, E. danica and subspecies E. sylvatica subsp. pollinensis. The other two are assigned to previously described E. bromicola and E. sylvatica. E. hordelymi, E. disjuncta and E. danica are asexual interspecific hybrids, while the other taxa are haploid. Only E. sylvatica subsp. pollinensis was found to reproduce sexually on H. europaeus. The high diversity of endophytes may be explained by repeated host jumps to H. europaeus with and without subsequent interspecific hybridizations.

Phylogenomics of fescue grass-derived fungal endophytes based on selected nuclear genes and the mitochondrial gene complement

Abstract: Tall fescue and meadow fescue are important as temperate pasture grasses, forming mutualistic associations with asexual Neotyphodium endophytes. The most frequently identified endophyte of Continental allohexaploid tall fescue is Neotyphodium coenophialum, while representatives of two other taxa (FaTG-2 and FaTG-3) have been described as colonising decaploid and Mediterranean hexaploid tall fescue, respectively. In addition, a recent study identified two other putatively novel endophyte taxa from Mediterranean hexaploid and decaploid tall fescue accessions, which were designated as uncharacterised Neotyphodium species (UNS) and FaTG-3-like respectively. In contrast, diploid meadow fescue mainly forms associations with the endophyte taxon Neotyphodium uncinatum, although a second endophyte taxon, termed N. siegelii, has also been described. Multiple copies of the translation elongation factor 1-a (tefA) and β-tubulin (tub2) ‘house-keeping’ genes, as well as the endophyte-specific perA gene, were identified for each fescue-derived endophyte taxon from whole genome sequence data. The assembled gene sequences were used to reconstruct evolutionary relationships between the heteroploid fescue-derived endophytes and putative ancestral sub-genomes derived from known sexual Epichloe species. In addition to the nuclear genome-derived genes, the complete mitochondrial genome (mt genome) sequence was obtained for each of the sequenced endophyte, and phylogenetic relationships between the mt genome protein coding gene complements were also reconstructed. Complex and highly reticulated evolutionary relationships between Epichloe-Neotyphodium endophytes have been predicted on the basis of multiple nuclear genes and entire mitochondrial protein-coding gene complements, derived from independent assembly of whole genome sequence reads. The results are consistent with previous studies while also providing novel phylogenetic insights, particularly through inclusion of data from the endophyte lineage-specific gene, as well as affording evidence for the origin of cytoplasmic genomes. In particular, the results obtained from the present study imply the possible occurrence of at least two distinct E. typhina progenitors for heteropoid taxa, as well the ancestral contribution of an endophyte species distinct from (although related to) contemporary E. baconii to the extant hybrid species. Furthermore, the present study confirmed the distinct taxonomic status of the newly identified fescue endophyte taxa, FaTG-3-like and UNS, which are consequently proposed to be renamed FaTG4 and FaTG5, respectively.

Stability and viability of novel perennial ryegrass host–Neotyphodium endophyte associations

Abstract: The temperate pasture grass Lolium perenne L. is commonly found in association with the fungal endophyte Neotyphodium lolii. Viability of both seed and endophyte was evaluated by inoculation of individual genotypes from the host cultivar Bronsyn with six distinct endophyte strains. The resulting populations were subjected to either long-term storage under various temperature conditions, or accelerated ageing (AA) treatments. High temperature storage was detrimental to endophyte viability. The AA variables (relative humidity [RH] and time) and subsequent temperature and duration of storage significantly (P < 0.05) affected both seed germination and endophyte viability. Significant interaction effects between the AA treatment and storage conditions were also observed. Endophyte viability following AA treatment was inversely correlated with both increasing RH and duration of treatment. Differential responses between different endophytes within the Bronsyn host were also apparent. The standard endophyte (SE) strain and the novel endophytes AR1 and AR37 exhibited higher viability than NEA2, NEA3, and NEA6 during seed storage, suggesting the importance of identification and selection for compatible symbiotic associations in agronomic varieties. The observed similarity between assessments of endophyte viability after AA treatments and following long-term storage confirmed the capacity of moderate conditions (e.g. 80% RH for 7 days or 100% RH for 4 days) to predict variation in viability between different endophyte strains.

Effects of Storage Conditions on Endophyte and Seed Viability in Pasture Grasses

Abstract: Several important temperate pasture grasses have co-evolved with mutualistic Epichloe fungal endophytes. These endophytes impart beneficial attributes to their host as they enhance the fitness of the grass when under biotic and abiotic stresses. The asexual species of these fungi (formerly classed as Neotyphodium) are obligate symbionts, and efficiently colonise newly formed tillers and infect seed by direct colonisation of the embryo. These endophytes are strictly seed transmitted. Survival of the fungus in this seed is therefore critical for the dissemination of endophyte-infected seed to grassland farmers. Longevity of endophyte in stored seed is primarily determined by the length of storage, temperature, and relative humidity as this is in equilibrium with seed moisture. Elevated temperature and relative humidity both reduce endophyte viability. The relative importance of each of these environmental parameters is unclear. Longevity may be further modified by grass species, cultivar, seed lot, and endophyte strain. Valuable seed requiring long term storage can utilise controlled storage facilities where temperature is preferably o C and relative humidity

Symbiotic interactions as drivers of trade-offs in plants: effects of fungal endophytes on tall fescue

Abstract: Studying the controls on biomass allocation trade-offs in plants are important since they affect harvestable product yields and are critical to understanding symbiotic interactions. Epichloae fungal endophytes associate with cool-season grasses, growing systemically within the plant inter-cellular spaces and are transmitted through seeds. We explore the endophytes influence on the relationship between the plant reproductive and vegetative aboveground biomass (reproductive effort: RE) and on the trade-off between two components of the reproductive biomass, number and weight of panicles (RPN), using tall fescue as a model system. Naturally endophyte-colonized, manipulatively endophyte-free, and naturally endophyte-free plants from Northern European wild-populations together with the cultivar Kentucky-31 were grown under different environmental conditions (nutrients x water). The endophyte had an effect on the RPN (E+: 6.19, ME-: 4.68 and E-: 4.40) which indicates how reproductive biomass is partitioned into number and mass of panicles, but not on RE (≈0.06). As expected, wild plants showed higher reproductive effort (≈0.06) compared to the cultivar KY-31 (0.05), irrespective of endophyte presence. Endophyte-colonized plants had lighter panicles than endophyte-free plants, a pattern that was clear among low-yielding plants. Similarly, the trade-off between RPN and RE was higher for endophyte-colonized plants. This was again evident among plants with low RE indicating that colonized plants split the yield into either greater number of panicles and/or lighter panicles. The effect of vertically transmitted endophytes has earlier been studied as ratios (e.g. RE); however, our study shows that this approach may hide size-dependent endophyte effects on these relationships. Our study reveals that Neotyphodium endophyte affects trade-offs in tall fescue plants in a complex manner, and is influenced by a number of biological and abiotic factors.

Neotyphodium endophyte strain and superoxide dismutase activity in perennial ryegrass plants under water deficit

Abstract: The presence of Neotyphodium endophyte in forage grass tillers has been associated with increased tolerance of abiotic stresses. The effect of four endophyte treatments (plants with three different strains of Neotyphodium lolii compared with plants without endophyte) on superoxide dismutase (SOD) (EC1.15.1.1) activity in Lolium perenne cv ‘Grasslands Samson’ was measured under high and low dehydration regimes in a glasshouse experiment. SOD activity was assayed by a microplate method utilising the inhibition of reduction of a tetrazolium dye by superoxide radicals. A progressive increase in dehydration over 2 weeks reduced shoot fresh weight, dry weight and shoot water content for high, compared with low, moisture-stressed plants. Mean shoot fresh weight was significantly lower for plants with strain AR37 endophyte than for plants with strain AR1 endophyte, wild-type or endophyte-free plants, but there was no interaction between endophyte treatment and dehydration treatment. There were no differences in mean SOD activity between the dehydration treatments, and the four endophyte treatments at any of the harvests. All harvest mean SOD levels for plants in both stress groups, however, were significantly different from the preceding harvest value. Between the first and second week of moisture stress there was a significant endophyte by harvest interaction for mean percentage change in SOD activity when activity in plants with wild-type strain endophyte increased more rapidly than in AR1, AR37 or endophyte-free plants. The results are in agreement with earlier reports suggesting that Neotyphodium endophytes do not have major effects on the water stress physiology of perennial ryegrass, although water deficits applied were not extreme.

Assessment of fluorescein-based fluorescent dyes for tracing Neotyphodium endophytes in planta.

Abstract: Fluorescent dyes were assessed for their ability to stain viable hyphae of the fungi Neotyphodium lolii and N. coenophialum, symbiotic endophytes of the Pooideae grasses Lolium perenne and Festuca arundinacea, respectively. The fluorescein-based fluorophores; fluorescein diacetate (FDA), 5(6)-carboxy-fluorescein diacetate (CFDA), 5-chloromethylfluorescein diacetate (CMFDA) and the chitin-binding stain, Calcofluor while M2R, were assessed for staining of endophyte hyphae in vitro from axenic fungal cultures and in planta, including epidermal leaf sheath peels, nodes, ovaries, embryos and meristems. CMFDA produced the greatest intensity of staining of fungal hyphae and gave excellent contrast in planta compared to the plant cells. Compared to the other dyes, CMFDA was also the least affected by photo bleaching and continued to fluoresce up to 2 h after initial excitation. None of the fluorescent dyes stained fungal hyphae in seed.

Geographic distribution patterns of vertically transmitted endophytes in two native grasses in Argentina

Abstract: The incidence of epichloid endophytes in populations of wild grasses is usually variable, and the knowledge about distribution patterns and how environmental factors affect such an incidence is limited. Here we performed a broad scale survey data to study whether the distribution patterns and the incidence of vertically-transmitted endophytes in populations of two native grasses from South-America, Poa lanuginosa Poir. and Poa bonariensis (Lam.) Kunth., are associated with environmental characteristics. We also characterized the endophytes from different populations to establish if the genotype of the endophytes is also correlated with environmental variables. The incidence of endophytes ranged from 0 to 100 % in both host species. In P. lanuginosa, endophytes were only found in populations on sandy coastal dunes and their incidence was positively associated with winter regime rainfall and soil water availability in the growing season. In P. bonariensis, endophytes were only found in populations in xerophytic forests and their incidence was highly associated with plant community. The distributions of infested populations suggested that the endophytes are not found in those areas with the most favorable or most stressing growth conditions accordingly to climatic or edaphical characteristics. Only the vertically transmitted hybrid endophyte species Neotyphodium tembladerae was detected in both host species. Under the hypothesis of vertical transmission, these results suggested that the endophyte should have been lost in endophyte free populations but is maintained in populations established in environments presenting moderate stress as salinity or short drought periods.

Avanex TM Unique Endophyte Technology--Bird Deterrent Endophytic Grass for Amenity Turf and Airports

Abstract: Bird strike is recognised throughout the civil and military aviation industries as a significant cost with more than $US 2 billion/year attributed to this problem globally. To manage this risk the aviation industries have in the past adopted many practices to frighten wildlife from airports rather than reducing the attractiveness of the area by grass habitat management. There has been little proven research on ground cover species evaluation using fungal endophyte to reduce wildlife. Our research has shown that the adoption of a specialist Neotyphodium fungal endophyte (strain AR601) placed in a turf type tall fescue cv. Jackal (Festuca arundinacea Schreb.), is reducing bird numbers and strike rates on the test airfields under study. In the recreational industry, large birds such as Canada geese (Branta canadensis), which forage on tender new shoots and stems, can cause severe damage to turf with the added issue of faecal contamination and associated heath issues. The inoculation of another specialist endophyte (strain AR95) into a turf type ryegrass (Lolium perenne L.) cv. Colosseum offers another tool to reduce this problem. This paper reviews the results from trials of these selected turf type grasses containing the unique fungal endophytes and shows effects on herbivorous, insectivorous and omnivorous birds that visit airfields and surrounding parklands for foraging. Specialty endophyte grasses may also have a place in the viticulture and horticulture industries to reduce the use of insecticides. Extracts and mulches offer a new opportunity to use grass endophyte associations.

OCCURRENCE OF Neotyphodium AND Epichloë FUNGI IN MEADOW FESCUE AND RED FESCUE IN POLAND AND SCREENING OF ENDOPHYTE ISOLATES AS POTENTIAL BIOLOGICAL CONTROL AGENTS

Abstract: Neotyphodium and Epichloe endophytes often influence beneficially on the host plant. Thus, could be used as a biological factor enhancing grass growth and resis- tance to stress factors. A detailed study was made to: (i) determine the infestation of geno- types of meadow fescue and red fescue, which occur in natural grass communities, in Po- land by the Neotyphodium/Epichloe endophytes, (ii) define the level of ergovaline, a toxic alkaloid produced by active associations, (iii) determine the activity of antagonistic dis- tinguishing isolates of endophytic fungi against selected microorganisms. There were ana- lysed 204 genotypes of meadow fescue and 171 genotypes of red fescue. Mean frequency of the infection with endophytes was 74.5% and 64.3% respectively. Ergovaline was pro- duced by 77% of E+ meadow fescue genotypes and 80.9% of red fescue genotypes. Mean content of the alkaloid was 0.202 and 0.151 μg�‹ g DM -1 respectively. FpII30, FpII67, FpII77, FpII168 and FrII82 demonstrated a high ability for protection of the host grasses from all the tested pathogens. These isolates due to high antimicrobial activity and a lack of ergovaline production have a great potential for biological control of grasses.

Incidence of the endophyte fungus Neotyphodium coenophialum in pastures of tall fescue differing in age and soil characteristics

Abstract: Neotyphodium coenophialum is an endophyte fungus living in a mutualistic symbiosis with tall fescue [Schedonorus arundinaceus (Schreb.) Dumont]. The endophyte infection affects both health and animal production given the toxicity of the infected plants (fescue toxicosis). Our objective was to determine the incidence of N. coenophialum in some fescue populations placed in both high and low relief, of sites with different aged pastures as well as to evaluate its relationship with soil and vegetation characteristics. Study sites were three and four fields having old and young pastures, respectively, located southeast of Buenos Aires Province, Argentina. In each field, two populations of tall fescue, one from a low relief and the other from a high one, were sampled. Low relief sites were characterized by poor saline-alkaline soil conditions with halophytic vegetation and relatively low ground cover, and high relief ones had better soil conditions dominated by mesophytic grasses and full ground cover. The endophyte incidence across all the evaluated environmental conditions was higher than 95%. No differences were found attributable to soil characteristics and age of pastures, as predicted from the hypothesis of differential abiotic stress tolerance between infected (E+) and non infected (E-) plants. Therefore, it must be provisionally rejected. Alternative hypothesis must consider either effects of preferential herbivory on E- plants, high propagule pressure of infected fescue dispersing from the field margins, and/or higher recruitment rate for E+ than E- seeds from the soil seed bank. Key words: Endophyte-grass symbiosis, infection, fescue toxicosis, plant invasion, natural reseeding.