Effects Of Endophytes Research Articles

Fungal symbionts maintain a rare plant population but demographic advantage drives the dominance of a common host

SummaryA potential driver of species abundance that remains understudied is the interaction between host species and their microbial symbionts. Beneficial symbionts could promote the dominance of common host species by increasing their population growth rates more than they do for rare species, and symbiont benefits could be important for maintaining rare species in communities. Alternatively, intrinsic differences in demography, independent of interactions with symbionts, could be the main driver of species’ relative abundances.Here, we used demographic modelling with 5 years of data from experimental host populations to compare how symbiotic fungal endophytes, which are vertically transmitted from parent plant to offspring, influenced the population dynamics of one pair of co‐occurring, congeneric rare versus common host grasses (genusPoa).The common plant species achieved higher population growth than the rare species. Endophyte symbiosis increased the geometric population growth rate (λ) of rare and common species by 18% and 32%, respectively, but only the rare species was predicted to decline (λ < 1) in the absence of the endophyte, demonstrating that symbiosis was essential to maintain this species in the community.Endophyte symbiosis differentially affected the demographic transitions of the two hosts, increasing survival and growth for the common host,Poa sylvestris, and increasing survival but decreasing the probability of flowering for the rare host,Poa alsodes. The total contribution of the endophyte effects on host demographic rates to the overall difference in population growth between host species was small compared to the plants’ intrinsic differences in demography. However, low rates of vertical transmission inP. sylvestrislessened its advantage in intrinsic demography overP. alsodesand thus decreased the projected difference in population growth between host plants.Synthesis. Our results highlight the importance of plant–symbiont interactions in the persistence of a rare plant population, as well as the utility of demographic models in teasing apart the relative importance of plant demographic rates versus host–symbiont interactions on the regional abundance of rare and common host plant species.

Fungal endophytes associated with roots of nurse cushion species have positive effects on native and invasive beneficiary plants in an alpine ecosystem

Abstract Facilitation has been proposed to be a fundamental mechanism for plant coexistence, being particularly important in highly stressful environments such as alpine environments. In this type of environment, species called “cushion plants” can ameliorate the stressful conditions, acting as nurses for other plants. Of the several mechanisms proposed in the positive-interactions framework, plant–microorganism interaction may be one of the most common, but least documented. Here we show that the presence of endophytes isolated from the roots of cushion plants Laretia acaulis can play a fundamental role in the establishment, performance and survival of both native and exotic plant seedlings that are known to be facilitated by the cushion species. To test this, we measured survival and growth of two native and one invasive species at 3200 m in the Andes of Central Chile. Plants were grown inside artificial cushions filled with native soil, with or without sterilization, and with or without fungal endophytic inoculation to evaluate the role of fungal endophytes on survival and growth. In addition, we conducted a second experiment in a greenhouse with the invasive species to evaluate the effect of fungal endophytic infection/association on plant ecophysiological performance, dry biomass and seed output. Overall, our results showed a strong positive effect of fungal endophytes on the survival and growth of both native and invasive species. Moreover, maximum quantum efficiency (Fv/Fm), biomass accumulation and seed production were enhanced in the invasive species when soils were inoculated with endophytes. Thus, facilitation by root endophytic fungi on native and invasive alpine plants could determine survival and establishment in this harsh environment. Several studies have shown that direct facilitation by cushion plants in alpine environments improves the performance and fitness of both native and exotic plants. Our results suggest that there are indirect effects, mediated by microorganism associations that may also help to explain the successful establishment of native and invasive species in these environments. If indirect plant–plant facilitation through root fungal endophytes proves to be a widespread phenomenon in alpine ecosystems, it could be a key component in the structuring of plant communities in those stressful environments.

An endophyte-rich diet increases ant predation on a specialist herbivorous insect

1. All plants form symbioses with microfungi, known as endophytes, which live within plant tissues. Numerous studies have documented endophyte–herbivore antagonism in grass systems, but plant–endophyte–insect interactions are highly variable for forbs and woody plants. 2. The net effect of endophytes on insect herbivory may be modified by their interactions with higher trophic levels, such as predators. Including these multitrophic dynamics may explain some of the variability among endophyte studies of non-grass plants, which are currently based exclusively on bitrophic studies. 3. The abundance of natural foliar endophytes in a Neotropical vine was manipulated and beetles were fed high or low endophyte diets. Experimental assays assessed whether dietary endophyte load affected beetle growth, leaf consumption, and susceptibility to ant predation. 4. Beetles feeding on high- versus low-endophyte plants had almost identical growth and leaf consumption rates. 5. In a field bioassay, however, it was discovered that feeding on an endophyte-rich diet increased a beetle's odds of capture by predatory ants nine-fold. 6. Endophytes could thus provide an indirect, enemy-mediated form of plant defence that operates even against specialist herbivores. We argue that a multitrophic approach is necessary to untangle the potentially diverse types of endophyte defence among plants.

Plant population and genotype effects override the effects ofEpichloëendophyte species on growth and drought stress response ofAchnatherum robustumplants in two natural grass populations

Aims: In cool-season grasses, systemic and vertically transmitted Epichloe infections often provide a suite of benefits including increased growth, reproduction and competitive abilities. However, these effects of Epichloe endophytes on their hosts often depend upon host and endophyte genotype and environmental factors. Methods: Achnatherum robustum (sleepygrass) harbors at least two Epichloe species within natural populations in the Southwest USA. We tested the effects of endophyte infection and species, host population and plant genotype (by experimentally removing the endophyte), and soil moisture (a key limiting factor) on growth and drought stress response of infected A. robustum plants from two populations (Weed and Cloudcroft) in the Sacremento Mountains of New Mexico, USA). Important Findings: Although the two populations harbor distinct Epichloe species each with very different chemoprofiles, neither endophyte status (infected vs. uninfected) nor endophyte species affected most growth parameters at 8 or 25 weeks of the experiment, except for leaf length. In high water treatment, infected plants from the Weed population had longer leaf length compared with uninfected plants. In contrast, the population of origin affected all growth parameters, including plant height, leaf number, length and width, tiller number and shoot and root biomass, as well as wilting time. Grasses from the Cloudcroft population generally showed greater growth than grasses from the Weed population. Endophyte infection did affect wilting time, with infection in the Weed population generally reducing time to wilting under low and high water, whereas infection in the Cloudcroft population reduced time to wilting only under high water conditions. Our results suggest that plant population and their associated plant genotypes may play a much larger role in endophyte–host grass interactions in varying environments than previously thought. Asexual Epichloe species may be compatible with only specific host genotypes within populations such that the phenotypic effects due to population may be greater than phenotypic changes influenced by variation in the endophyte.

Effects of symbiotic Epichloë gansuensis endophyte on drunken horse grass (Achnatherum inebrians) growth and seed production

The effects of the fungal endophyte Epichloë gansuensis on drunken horse grass (Achnatherum inebrians) were determined over a 4-year period in a field growth experiment near Lanzhou, Gansu, China. Endophyte-infected (E+) A. inebrians vs non-infected (E−) control plants were compared for height, tiller number, weight of above-ground biomass, seed production and plant survival. Plant parameters were observed to be significantly higher (P < 0.05) for E+ specimens (vs E− plants) on most occasions. Growth parameters, seed yield and plant survival decreased significantly (P < 0.05) over time, while the differences between E+ and E− plants increased over the duration of the investigation. Endophyte infection was concluded to be of benefit to the growth, seed yield and plant survival of A. inebrians under conditions in the field.

Interactive effect of biochar and plant growth-promoting bacterial endophytes on ameliorating salinity stress in maize.

The objective of this work was to study the interactive effect of biochar and plant growth-promoting endophytic bacteria containing 1-aminocyclopropane-1-carboxylate deaminase and exopolysaccharide activity on mitigating salinity stress in maize (Zea mays L.). The plants were grown in a greenhouse under controlled conditions, and were subjected to separate or combined treatments of biochar (0% and 5%, w/w) and two endophytic bacterial strains (Burkholderia phytofirmans (PsJN) and Enterobacter sp. (FD17)) and salinity stress. The results indicated that salinity significantly decreased the growth of maize, whereas both biochar and inoculation mitigated the negative effects of salinity on maize performance either by decreasing the xylem Na+ concentration ([Na+]xylem) uptake or by maintaining nutrient balance within the plant, especially when the two treatments were applied in combination. Moreover, in biochar-amended saline soil, strain FD17 performed significantly better than did PsJN in reducing [Na+]xylem. Our results suggested that inoculation of plants with endophytic baterial strains along with biochar amendment could be an effective approach for sustaining crop production in salt-affected soils.

Neotyphodium Endophyte Changes Phytoextraction of Zinc in Festuca arundinacea and Lolium perenne

The effect of Neotyphodium endophytes on growth parameters and zinc (Zn) tolerance and uptake was studied in two grass species of Festuca arundinacea and Lolium perenne. Plants were grown under different Zn concentrations (control, 200, 400, 800, and 1800 mg kg−1) in potted soil for 5 months. The results showed that the number of plant tillers was 85 and 51% greater in endophyte infected Festuca (FaEI) and Lolium (LpEI), respectively, compared to their endophyte free (EF) plants. Roots and shoots dry weights in infected Festuca were 87 and 9% greater than non-infected counterparts but in opposite, EF Lolium had 47 and 8% greater root and shoot dry weights than LpEI. Endophyte infected Festuca and Lolium improved chlorophyll fluorescence as Fv/Fm at high concentrations of Zn, showing their better chlorophyll functions and significant reduction of Zn stress in endophyte infected plants. Shoots of endophyte infectedFestuca had 82% greater concentration of Zn than EF Festuca when grown in soil containing 1800 mg kg−1 Zn. Festuca and Lolium may tolerate high Zn concentration in soil without reduction in shoot and root growth. Endophyte infection in Festuca may help the grass accumulate and transport more Zn in aboveground parts under Zn-stress, thereby aiding phytoremediation of contaminated soils.

Competitive outcomes depend on host genotype, but not clavicipitaceous fungal endophytes, in Lolium perenne (Poaceae).

• Cool-season grasses infected by endophytic fungal symbionts sometimes show improved tolerance of herbivory and abiotic stresses, but the potential effects of endophytes on host competitive ability are unclear. This study examined intraspecific competition among variable genotypes of Lolium perenne with and without the endophyte Epichloë festucae var. lolii (Clavicipitaceae, Ascomycota) to assess the effect of infection on competitive outcomes.• Eleven host genotypes distributed among infected plants of four cultivars of L. perenne were used for two pairwise competition experiments. In the greenhouse, an infected or uninfected ramet of each genotype was grown alone and paired in competition with a ramet of an uninfected genotype of a native accession of L. perenne. Tiller numbers and root and shoot dry mass were determined for targets and competitor plants after 15 wk.• Competition and host genotype had highly significant effects on all measured variables. However, endophyte-mediated effects on hosts were minor, and those that occurred depended on genotype. In addition, endophytic status of target plants did not influence tiller number or dry mass in 10 of 11 competitor genotypes, although these native genotypes did significantly vary in their competitive performance.• Genotypic variation among cultivars and accessions from native populations of L. perenne determines the effect of both intraspecific competition and infection by a fungal endophyte. However, in the absence of herbivory, asexual clavicipitaceous endophytes may not be as important to host success in competitive environments as previously thought in this globally important grass species.

Effects of endophyte colonization of Vicia faba (Fabaceae) plants on the life-history of leafminer parasitoids Phaedrotoma scabriventris (hymenoptera: braconidae) and Diglyphus isaea (hymenoptera: eulophidae).

Effects of the fungal endophytes Beauveria bassiana (isolates ICIPE 279, G1LU3, S4SU1) and Hypocrea lixii (isolate F3ST1) on the life-history of Phaedrotoma scabriventris and Diglyphus isaea, parasitoids of the pea leafminer Liriomyza huidobrensis, were studied in the laboratory. Parasitoids were allowed to parasitize 2nd and 3rd instar L. huidobrensis larvae reared on endophytically-inoculated faba bean, Vicia faba. In the control, parasitoids were reared on non-inoculated host plants. Parasitism, pupation, adult emergence and survival were recorded. No significant difference was observed between the control and the endophyte-inoculated plants in terms of parasitism rates of P. scabriventris (p = 0.68) and D. isaea (p = 0.45) and adult' survival times (p = 0.06). The survival period of the F1 progeny of P. scabriventris was reduced (p<0.0001) in B. bassiana S4SU1 to 28 days as compared to more than 40 days for B. bassiana G1LU3, ICIPE 279 and H. lixii F3ST1. However, no significant difference (p = 0.54) was observed in the survival times of the F1 progeny of D. isaea. This study has demonstrated that together, endophytes and parasitoids have beneficial effects in L. huidobrensis population suppression.

Foliar endophytic fungi as potential protectors from pathogens in myrmecophytic Acacia plants

In defensive ant-plant interactions myrmecophytic plants express reduced chemical defense in their leaves to protect themselves from pathogens, and it seems that mutualistic partners are required to make up for this lack of defensive function. Previously, we reported that mutualistic ants confer plants of Acacia hindsii protection from pathogens, and that the protection is given by the ant-associated bacteria. Here, we examined whether foliar endophytic fungi may potentially act as a new partner, in addition to mutualistic ants and their bacteria inhabitants, involved in the protection from pathogens in myrmecophytic Acacia plants. Fungal endophytes were isolated from the asymptomatic leaves of A. hindsii plants for further molecular identification of 18S rRNA gene. Inhibitory effects of fungal endophytes were tested against Pseudomonas plant pathogens. Our findings support a potential role of fungal endophytes in pathogen the protection mechanisms against pathogens in myrmecophytic plants and provide the evidence of novel fungal endophytes capable of biosynthesizing bioactive metabolites.

Mixed fitness effects of grass endophytes modulate impact of enemy release and rapid evolution in an invasive grass

Endophytic fungi in grasses are often considered to be mutualistic because they can increase host resistance to herbivory and drought. However, not all endophytes are beneficial to their hosts, but may instead be specialist enemies. Brachypodium sylvaticum is an invasive grass in the USA. In its European native range, it is nearly always infected by the host-specific endophyte Epichloe sylvatica. While this fungus decreases herbivory, it also decreases the growth rate and size of infected plants, making them less competitive. After showing that B. sylvaticum has lost its endophyte in the invaded range, we use greenhouse assays to deconfound the effects of endophyte infection and range origin to test assumption of the evolution of increased competitive abilities (EICA) hypothesis. Brachypodium in its invaded range appears to have lost tolerance mechanisms present in the native range, allowing Epichloe to greatly increase seedling mortality and reduce growth rates. Additionally, there is some evidence for increased competitive abilities in the form of increased seedling growth rates in the invasive range. Together, these results provide strong support of the EICA hypothesis.

Effects of systemic fungal endophytes on the performance of meadow fescue and tall fescue in mixtures with red clover

AbstractA symbiosis between grasses and systemic fungal endophytes exists in both natural and agricultural grassland communities. Our objective was to examine the effects of systemic endophytes on the competitive ability of two agronomically important grass species: meadow fescue [Festuca pratensis (Huds.) syn. Schedonorus pratensis (Huds.) P. Beauv] and tall fescue [Festuca arundinacea (Schreb.) syn. Schedonorus phoenix (Scop.)]. Plants of meadow and tall fescue were grown for 48 days in replacement series of interspecific mixture with a legume (red clover, Trifolium pratense L.) in different nutrient environments in a greenhouse. Neither of the grass species gained endophyte‐promoted competitive advantage over red clover in grass–clover mixtures. Endophyte infection increased the growth of meadow fescue monocultures by 89% compared to endophyte‐free monocultures in high‐nutrient soils, but plant competition or the cost of endophyte infection to the meadow fescue decreased the yield in resource‐limited conditions. On average, endophyte‐infected and endophyte‐free meadow fescues produced 0·15 and 0·17 g, and 0·14 and 0·14 g dry biomass per plant in mixtures with red clover in high‐ and low‐nutrient soils respectively. In contrast to meadow fescue, endophyte‐promoted growth of tall fescue monocultures was not detected. Endophyte‐infected and endophyte‐free tall fescue monocultures produced 0·76 and 0·95 g biomass per pot, respectively, in the high‐nutrient environment. Endophyte infection can increase the performance of the host grass, but the positive effects depend on the host species, the species composition and soil nutrient availability.

An asexual Epichloë endophyte modifies the nutrient stoichiometry of wild barley (Hordeum brevisubulatum) under salt stress

Background and aims Salinization of soils causes severe problems to plant growth. With the important role of stoichiometry in many ecological processes, this study investigated the effect of an asexual Epichloe endophyte on the nutrient stoichiometry of wild barley (Hordeum brevisubulatum) under salt stress.

Isolation, characterization and plant growth promotion effects of putative bacterial endophytes associated with sweet sorghum (Sorghum bicolor (L) Moench)

Sweet sorghum (Sorghum bicolor) is cultivated in Uruguay in complementation with sugarcane (Saccharum officinarum) as a feedstock for bioethanol production. It requires the application of high levels of chemical fertilizer for optimal growth, which causes environmental degradation. Plant growth-promoting (PGP) bacteria are of biotechnological interest since they can improve the growth of several important agronomical crops. Of particular interest are endophytes, which are those bacteria that can be detected at a particular moment within the internal tissues of healthy plants from where they can promote their growth. The aims of this work were to isolate and characterize, as well as identify putatively endophytic bacteria associated with sweet sorghum (cv-M81E), and also to study the inoculation effects of selected isolates on sorghum growth. A collection of 188 putative endophytes from surface-sterilized stems and roots was constructed and characterized. Bacterial isolates were shown to belong to different genera including Pantoea, Enterobacter, Pseudomonas, Acinetobacter, Stenotrophomonas, Ralstonia, Herbaspirillum, Achromobacter, Rhizobium, Chryseobacterium, Kocuria, Brevibacillus, Paenibacillus, Bacillus and Staphylococcus. PGP and infection features were investigated in vitro, and revealed some promising biotechnological candidates. In addition, isolates UYSB13 and UYSB45 showed PGP effects in greenhouse assays. This work provides the basis for further studies under field conditions, with the final aim of developing an effective inoculant for sorghum.

Host genotype overrides endophyte infection effects on growth, physiology, and nutrient content of a native grass, Achnatherum sibiricum

The effect of infection by the fungal endophyte Neotyphodium, host genotype, and their interaction on growth and physiology, as well as photosynthesis, was investigated in the native grass Achnatherum sibiricum. We artificially inoculated the endophyte into mature tillers of endophyte-free A. sibiricum. Plants were clipped to 5 cm height after recording growth traits, and analyzed for total nonstructural carbohydrates (TNC %), the percentage of nitrogen (N %), and carbon (C %) in leaves before and after clipping. In our study, the prominent host genotype–endophyte infection interactions detected in A. sibiricum indicates that, for many growth and storage traits, endophyte infection can impact a little change. However, there is no overriding consistently positive effect of the endophyte on growth or storage in A. sibiricum before or after clipping. Our study showed that the interaction between endophyte and host grasses was highly contingent on plant genotypes. We found host genotype overrode fungal endophyte infection in influencing tiller number and photosynthetic properties of A. sibiricum before clipping. After clipping, host genotype accounted for more of the variation in regrowth and above-ground biomass of A. sibiricum than endophyte infection. Our study showed that host genotype affected the total nonstructural carbohydrates of A. sibiricum before and after clipping, whereas endophyte infection increased the carbon content after clipping. Genotype by infection interactions for plant height, leaf mass, total nonstructural carbohydrates, and photosynthetic characteristics indicated genotype-specific effects of endophytes on A. sibiricum physiology and photosynthetic capacity. The host genotype–endophyte infection interactions detected in A. sibiricum suggest that host genotype overrides fungal endophyte infection on growth, physiology, and nutrient content of this native grass. In contrast, endophyte effects did not appear to positively affect growth, physiology, or photosynthetic capacity before or after clipping.

Fungal endophyte mediated occurrence of seminiferous and pseudoviviparous panicles in Festuca rubra

Fungal endophytes are suggested to manipulate host grass reproduction. Using different grass-endophyte combinations in a four year common garden experiment, we show that endophyte can retain control over the reproductive functions of the host. Plants were collected as seeds from two different environments, meadows and riverbanks. Natural endophyte infection (E+) increased reproductive effort of plants; 13 and 15 % higher proportion of E+ plants produced panicles compared to naturally uninfected (E-) and manipulatively endophyte-infected (ME+) plants, respectively. Meadow-origin E+ plants produced also higher number of panicles compared to E- in the last two years, and both meadow- and riverbank-origin ME+ plants produced higher number of panicles compared to ME- plants in most of the years. Pseudovivipary was recorded in 5 % of the plants each year. Pollen limitation appears not to induce pseudovivipary. Both E+ and ME+ plants produced higher number of seminiferous panicles compared to E- and ME- plants. The higher proportion of pseudoviviparism in ME+ plants compared to E+, E- and ME- plants from meadows suggests specific genotype-genotype cross-talk between endophyte and grass. Pseudovivipary was affected by year and primarily explained by plant reproductive effort since most vigorous plants produced more pseudoviviparous panicles. We propose that endophytes can promote host grass reproduction in a habitat-specific manner and depending on genetic compatibility between partners. However, reproductive behavior depended on maternal habitat and the annual environmental conditions highlighting the importance of long-term experiments to estimate the effects of endophytes on host plant ecology.

Hybridization inPopulusalters the species composition and interactions of root-colonizing fungi: consequences for host plant performance

Interactions among plants and soil microbes can significantly influence plant communities, yet we understand little about how hybridization of plant species might alter these interactions. In addition, few studies have explored the effects of different components of soil microbial communities on plant performance. We tested for feedbacks between soil microbes within a Populus hybridizing system using approaches that allowed us to isolate the effects of arbuscular mycorrhizal fungi (AMF) and root endophytes. We found significant differences among the arbuscular mycorrhizal (AM) fungal spore communities cultured from Populus angustifolia James, Populus fremontii S. Watson, and their F1hybrids. Populus angustifolia cuttings grew 40% larger when inoculated with AM fungal spores from F1hybrids than with spores from P. fremontii, while growth with spores from P. angustifolia was intermediate. However, parental and hybrid inocula promoted growth equally when soil inoculum was used. Roots inoculated with AM fungal spores alone were colonized principally by AMF, while those inoculated with soil were colonized mostly by dark septate endophytes. These results indicate that genetic variation among hybridizing plant species can influence both microbial communities and their interactions with host plants, but these effects depend upon the type of microbe. Furthermore, our results suggest that interactions among fungi during root colonization may alter the composition and function of the plant microbiome.

Root endophytes enhance stress‐tolerance of Cicuta virosa L. growing in a mining pond of eastern Japan

AbstractCicuta virosa L. plants can grow in a pond subjected to heavy‐metal inputs at the Hitachi mine, eastern Japan. They accumulate heavy‐metal elements, especially high concentrations of zinc (Zn), in their roots. We focused on the role that root bacterial endophytes play in the heavy‐metal uptake of plants and the provision of heavy‐metal tolerance within plants. Our purpose was to clarify the effects of endophytes on: (i) Zn accumulation in C. virosa roots; (ii) growth of C. virosa seedlings; and (iii) heavy‐metal tolerance of C. virosa plants. Root endophytic Pseudomonas putida and Rhodopseudomonas sp., which induced the high production of Zn‐chelating compounds, were selected for the seedling inoculation test. The results of the inoculation test demonstrated that both strains of endophytes increased Zn accumulation in C. virosa roots by solubilizing Zn in the sediment. Both strains also increased the growth of seedlings by possible production of indole‐3‐acetic acid in the plant. The heavy‐metal tolerance of C. virosa seedlings was likely promoted by producing metal‐chelating compounds that detoxify the metals in the plant tissues, and by decreasing the heavy‐metal contents in the tissues via rapid seedling growth. Thus, such mutualistic interactions between plants and bacteria contribute to the persistence of C. virosa in this severe environment.

Endophytes inconsistently affect plant communities across Schedonorus arundinaceus hosts

Fungal endophytes in cool-season grasses may affect communities at multiple trophic levels. However, it is unclear whether community-scale endophyte effects arise due to the endophyte itself or as a result of unique, endophyte–host interactions. We used a long-term field experiment to test whether common-toxic (CT) and non-ergot alkaloid-producing (novel) endophytes in Schedonorus arundinaceus (tall fescue) forage cultivars consistently affect communities across tall fescue hosts. Tilled plots (2 × 2 m; Guelph, ON) were seeded with Georgia 5 and Jesup cultivars containing either the CT or AR542 (novel) endophyte and allowed to be re-colonized by plant species from the local propagule pool. Non-seeded control plots were included to assess effects of seeding the non-native grass. We assessed plant, invertebrate, soil moisture, and soil nutrient responses to the endophyte–cultivar treatments after four growing seasons. Seeding tall fescue affected plant species abundances, but not richness, and did not consistently alter soil moisture and nutrient pools. Endophyte identity in the tall fescue cultivars affected the communities, but effects were not consistent between cultivars. Within Georgia 5, the AR542 endophyte reduced tall fescue abundance and altered the invertebrate community relative to CT plots. Within Jesup, the AR542 endophyte reduced species evenness and decreased soil moisture during dry periods relative to CT plots. Endophyte effects were not consistent between cultivars, and it is probable that the community-scale effects of endophyte infection in tall fescue cultivars arise due to unique interactions between cultivar and endophyte.

Fungal endophyte effects on leaf chemistry alter the in vitro growth rates of leaf-cutting ants' fungal mutualist, Leucocoprinus gongylophorus

Fungal symbionts that colonize leaf tissue asymptomatically (endophytes) can alter the foraging behaviour of leaf-cutting ants, and decrease the productivity of this herbivore's mutualistic fungal cultivar, Leucocoprinus gongylophorus. This negative effect of endophytes on the ant's cultivar could be the result of direct fungal–fungal interaction or indirect reductions in the quality of leaves, the cultivar's growth substratum. To test for the indirect effects, we measured in vitro growth rates of cultivars in media that contained sterilized leaf extracts from plants with high (Ehigh) and low (Elow) endophyte colonization. We found that, opposite to our expectations, cultivars grew significantly faster in Ehigh leaf extracts compared to Elow extracts. Our results suggest that endophyte-driven changes in leaf chemistry are a less likely explanation for the observed in vivo reduction in the ant's symbiotic fungal growth and imply that the effect of direct endophyte–cultivar interactions inside nests are potentially more important.