Fungal Endophyte Infection Research Articles

Cultivation of Fungal Endophytes with Tissue Culture Grapevine Seedlings Reprograms Metabolism by Triggering Defence Responses.

In this study, the transcriptome profiles of tissue-cultured grapevine (Vitis vinifera L. × Vitis labrusca L.: Rose Honey) seedlings inoculated with fungal endophytes Epicoccum layuense R2-21 (Epi R2-21) and Alternaria alternata XHYN2 (Alt XHYN2), were analyzed at three different time points (6 h, 6 d, and 15 d). A total of 4783 differentially expressed genes (DEGs) was found, of which 1853 (6 h), 3878 (6 d), and 4732 (15 d) were differentially expressed relative to those of the control in endophyte Epi R2-21 treatments, while a total of 5898 DEGs, of which 2726 (6 h), 4610 (6 d), and 3938 (15 d) were differentially expressed in endophyte Alt XHYN2 treatments. DEGs enriched in secondary metabolic pathways, plant-pathogen interaction, and hormone signalling were further analysed. The upregulated DEGs in the Epi R2-21 and Alt XHYN2 treatments, both enriched in the Kyoto Encyclopedia of Genes and Genomes (KEGG), were mainly involved in flavonoid biosynthesis, phenylpropanoid biosynthesis, stilbenoid, diarylheptanoid and gingerol biosynthesis, phenylalanine metabolism, and circadian rhythms-plant and plant-pathogen interactions, similar to the trend observed in our previous study conducted on the cultivar 'Cabernet Sauvignon' (Vitis vinifera L.). Taken together with the results obtained from the cultivar 'Cabernet Sauvignon', it was found that tissue-cultured seedlings of the cultivar 'Rose Honey' induced a stronger defence response to fungal endophyte infection than that of the cultivar 'Cabernet Sauvignon', and inoculation with the endophyte Alt XHYN2 triggered a stronger response than inoculation with the endophyte Epi R2-21. In addition, the protein-protein interaction (PPI) network revealed that the genes VIT_16s0100g00910, encoding CHS, and VIT_11s0065g00350, encoding CYP73A, were involved in secondary metabolism and thus mediated in the resistance mechanism of grapevine on both the cultivars. The results showed that inoculation with the endophytes Epi R2-21 and Alt XHYN2 had a great ability to induce defence responses and reprogram the gene expression profiles in different grapevine cultivars, which deepens our knowledge of the interaction between fungal endophytes and grapevine and gives hints for grape quality management in viticulture using candidate fungal endophytes.

The influence of timing and planting proportion on the intraspecific competitiveness ability of drunken horse grass (Achnatherum inebrians (Hance) Keng) by fungal endophyte infection

The influence of timing and planting proportion on the intraspecific competitiveness ability of drunken horse grass (Achnatherum inebrians (Hance) Keng) by fungal endophyte infection

Olfactory responses of Argentine stem weevil to herbivory and endophyte-colonisation in perennial ryegrass

Argentine stem weevil adults (ASW, Listronotus bonariensis) feed on the leaves of agricultural grasses and their larvae mine the pseudostem, causing extensive damage that can result in plant death. Plants emit volatiles that serve as signals to host-searching insects and these odours can be altered by both herbivory and fungal endophyte-infection. This study investigated whether ASW adults utilise olfaction to identify their host plants, perennial ryegrass (Lolium perenne), and if conspecific herbivory or the presence of Epichloë festucae var. lolii fungal endophytes (strain wild-type or AR1) influenced such responses. Results from olfactometer bioassays established that ASW adults were able to utilise their olfactory response to orient towards volatiles released by perennial ryegrass and further, the weevils displayed a preference for plants previously damaged by conspecific weevils. However, there was no evidence that weevils had the ability to distinguish between endophyte-infected and endophyte-free plants using olfaction alone. Using a push–pull extraction technique, thirteen volatile compounds were identified in the blend released by perennial ryegrass. Endophyte and herbivory were found to alter these volatile compounds and quantities emitted by this forage grass. This study suggests that despite observing differences in the plant volatile blend, ASW do not perceive endophyte (wild-type and AR1) using olfaction alone and must rely on other cues, e.g. contact chemoreception or post-ingestional malaise, to detect the presence of a bioactive endophyte in an otherwise acceptable host plant.

Fungal endophyte infection increases tall fescue's survival, growth, and flowering in a reconstructed prairie

Grasslands in North America are increasingly threatened by land conversion and ecological degradation, prompting restoration efforts to increase native plant species diversity and improve wildlife habitat. A major challenge is the removal and management of nonnative invasive species such as tall fescue (Schedonorus arundinaceus), which has a symbiotic association with a fungal endophyte (Epichloë coenophiala) that modifies its ecological interactions. Using transplanted clumps of the cultivar Kentucky‐31, we tested the effects of endophyte infection on tall fescue's survival and performance (tiller production, flowering, and basal area) for 5 years in a central Kentucky reconstructed prairie. We predicted that endophyte infected (E+) clumps would have increased performance compared to endophyte‐free (E−) clumps. Overall, E+ clumps had greater survival, tiller production, flowering tiller production, and basal area, but not reproductive effort (proportion of tillers flowering) as compared to E− clumps. However, survival and trends in tiller number and basal area over the 5‐year period suggested experimental tall fescue populations were in decline in the reconstructed prairie, although the E− population declined more rapidly. Our study provides evidence that endophyte infection improved tall fescue's growth and survival in a postreconstruction plant community, at least in the early years following reconstruction, and may increase the invasive potential of this nonnative species in prairie restorations.

Infection by the fungal endophyte Epichloë bromicola enhances the tolerance of wild barley (Hordeum brevisubulatum) to salt and alkali stresses

Salinization is considered as a major environmental threat to agricultural systems. Infection with Epichloe fungal endophytes has been shown to increase tolerance to NaCl stress for several host grass species, but limited information is available regarding the effects of these endophytes under mixed salt (NaCl and Na2SO4) and mixed alkali (NaHCO3 and Na2CO3) stresses. Since these four compounds are considered very harmful to many inland areas in China, we conducted a study to determine the impact of Epichloe fungal endophyte infection on wild barley (Hordeum brevisubulatum) under both salt stress (SS) and alkali stress (AS). Wild barley with (E+) and without (E-) Epichloe endophyte was subjected to mixed salt (molar ratio of NaCl:Na2SO4 = 1:1) and mixed alkali (molar ratio of NaHCO3:Na2CO3 = 1:1) treatments (0, 100, 200, 300 and 400 mM). Photosynthetic parameters and chlorophyll content were measured after 21 days exposure to stress, and growth parameters, physiological indexes, sodium (Na+), potassium (K+), calcium (Ca2+), nitrogen (N), phosphorus (P) and carbon (C) contents were determined after 22 days exposure to stress. The harmful effect of alkali stress on the growth of wild barley was stronger than those of salt stress, irrespective of endophyte infection. Alkali stress had a greater impact on photosynthesis and chlorophyll content compared to salt stress and also accumulated more of the osmoprotectant glycine betaine. However, salt stress appeared to increase total antioxidant capacity as well as increasing K+ content (resulting in a relative low Na+/K+ ratio). Under alkali stress, Ca2+ content sharply increased in roots as opposed to a decrease under salt stress. In roots, the C, N, P contents and the C:N ratio was higher under salt stress compared to alkali stress whereas the C:P and N:P ratios were lower. In shoots, the N and P contents were higher under salt stress compared to alkali stress whereas the C content and the C:P and C:N ratios were lower. Interestingly, the presence of Epichloe endophyte infection on wild barley under both salt stress and alkali stress led to significant amelioration of both stresses. Epichloe infection significantly increased photosynthesis, chlorophyll content, total antioxidant capacity and glycine betaine content, whilst lowering leaf malondialdehyde content. Furthermore, Epichloe infection reduced Na+ content, the Na+/K+ ratio and shoot Ca2+ content but increased K+ content and the root Ca2+ content. Epichloe infected plants also had higher C, N and P contents but lower ratios of C:N, C:P and N:P than uninfected plants. The presence of the Epichloe endophyte suppresses the negative effect of salt stress and alkali stress on wild barley seedling growth. The possible mechanisms by which the presence of Epichloe endophyte enhances growth of plants exposed to those two stresses include improved photosynthetic ability, increased antioxidant potential, increased nutrient absorption, and osmotic and ionic adjustment. The study also found that alkali stress is more harmful to wild barley than salt stress.

庞泉沟自然保护区常见禾本科植物内生真菌分布及其影响因素

PDF HTML阅读 XML下载 导出引用 引用提醒 庞泉沟自然保护区常见禾本科植物内生真菌分布及其影响因素 DOI: 10.5846/stxb201605311040 作者: 作者单位: 山西大学黄土高原研究所,山西大学黄土高原研究所,山西大学黄土高原研究所,山西大学黄土高原研究所,山西大学黄土高原研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 山西省应用基础研究面上青年基金项目（201601D021101）；山西省回国留学人员科研资助项目（2016-006）；山西省科技攻关项目（20150313001-3）；国家自然科学基金资助项目（31600308） Distribution of endophyte fungi associated with common plants and preliminary assessment of impact factors in Pangquangou Nature Reserve Author: Affiliation: Institute of Loess Plateau,Shanxi University,Institute of Loess Plateau,Shanxi University,Institute of Loess Plateau,Shanxi University,Institute of Loess Plateau,Shanxi University,Institute of Loess Plateau,Shanxi University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以庞泉沟自然保护区4种不同群落类型林地和灌丛下的优势禾草为研究对象，调查不同禾草内生真菌感染率，研究内生真菌感染的禾草种群与原生生境的土壤理化性质、土壤酶活性及土壤微生物群落结构的相互关系。结果发现，影响紫羊茅、中亚薹草和野燕麦染菌率的主要因子是土壤水分含量和碳氮比，且土壤C、N、S以及土壤水分含量与紫羊茅的内生真菌染菌率成正相关，土壤蔗糖酶、脲酶和酸性磷酸酶与紫羊茅的感染率显著正相关，但中亚薹草与紫羊茅的结果相反。丝盖伞科是华北落叶松林和油松林土壤微生物群落的优势真菌，但不同染菌植被群落类型下的优势细菌微生物群落组成不同。总体看来，4种森林群落类型下禾草内生真菌染菌率与土壤理化性质相关性不同，且受到的生态因子影响大小也有差异，内生真菌感染导致各植被群落类型的土壤微生物群落结构具有差异，其优势土壤真菌和土壤细菌组成不同，这有助于进一步认识原生生境下不同感染率的禾草种群对土壤微生物群落结构的影响及其在生态系统中的各异生态学功能。 Abstract:Fungal endophytes are fungi that live for a significant part of their life cycle internally and asymptomatically (without causing any apparent tissue damage) in plants. For grasses, these endophytes are often specialized, systemic, and vertically transmitted. Pangquangou Nature Reserve is located in the middle of the of Luliang Mountain range. It was established for the conservation of the first-grade State protection animal, Crossoptilon mantchuricum, and the cold-temperate coniferous forest. It plays a significant role in water conservation, eco-tourism, biodiversity maintenance, and other functions in Pangquangou Nature Reserve. Many studies have been conducted; however few of them have examined the distribution and mechanism of fungal endophytes associated with common plants in Pangquangou Nature Reserve. In the present study, we assessed the endophyte infection rate of dominant plants in four different forest communities. Our objective was to investigate the effects of endophyte fungi association on soil properties, soil enzyme activity, and soil microbial communities in native habitats. We surveyed endophyte infection rates of four common plants (Festuca rubra, Avena fatua, Carex alexeenkoana, and Poa annua). We also analyzed the soil total carbon (C), total nitrogen (N), and total sulfur (S) with an Elemental Analyzer, and soil microbial community composition were assayed by using the high-throughput sequencing technique. Our results showed that soil water content and ratio of carbon and nitrogen were the main factors affecting the endophyte infection rates of Festuca rubra and Carex alexeenkoana, and the soil C, N, S and soil water content were positively correlated with the endophyte infection rate of Festuca rubra. There were strong positive correlations between soil invertase and endophyte infection rates of Festuca rubra, as well as urease and acid phosphatase. However, Carex alexeenkoana exhibited opposite results to those of Festuca rubra. Inocybaceae is the dominant fungi of soil microbial community in Larix principis-rupprechtii community, but had different bacterial compositions in soil microbial community under four forest communities. Overall, there were different correlations between fungal endophyte infection rate and soil properties under different communities, and the effects of ecological factors were also different. Endophyte fungal contributed to change soil microbial community structure, and led to varying soil fungi and bacteria compositions in different forest communities. Our findings can help with further understanding the distribution of fungal endophytes associated with common plants in native habitats and the influence of endophyte infected plants on soil microbial community structure and ecological functions in ecosystems. 参考文献 相似文献 引证文献

Transcriptomic analyses giving insights into molecular regulation mechanisms involved in cold tolerance by Epichloë endophyte in seed germination of Achnatherum inebrians

Plants have developed mutualistic symbiosis with diverse fungal endophytes that increase their fitness by conferring abiotic and biotic stress tolerance. However, the molecular regulation mechanisms involved in stress tolerance remain largely unknown. Drunken horsegrass (Achnatherum inebrians), an important perennial bunchgrass in China, forms a naturally occurring symbiosis with an asexual symbiotic fungus Epichloe gansuensis. The effect of temperature on germination was determined for E. gansuensis-infected (E+) versus non-infected (E−) A. inebrians. Our results indicate that E+ seed have a higher germination rate under low temperature (10 °C) conditions compared with E− seed. To gain insight into the molecular mechanisms involved in the low temperature resistance of E+ drunken horsegrass, Solexa deep-sequencing was used to identify candidate genes showing differential expression. In total, 152 differentially expressed tags were identified, representing 112 up-regulated and 40 down-regulated genes, which were classified into eight functional categories. Many genes were found to be associated with low temperature response, such as genes participating in biosynthesis of alkaloids and unsaturated fatty acids. This study provides the first comprehensive examination of gene expression changes induced by fungal endophyte infection response to low temperature which is essential for understanding the molecular basis of this aspect of endophyte-enhanced plant improvement.

Infection with a Shoot-Specific Fungal Endophyte (Epichloë) Alters Tall Fescue Soil Microbial Communities.

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.

Ecophysiological Responses of Tall Fescue Genotypes to Fungal Endophyte Infection and Elevated Temperature and Precipitation

Ecophysiological Responses of Tall Fescue Genotypes to Fungal Endophyte Infection and Elevated Temperature and Precipitation

Ecophysiological Responses of Tall Fescue Genotypes to Fungal Endophyte Infection, Elevated Temperature, and Precipitation

ABSTRACTTall fescue (Schedonorus arundinaceus (Schreb.) Dumort., nom. cons.) can form a symbiosis with the fungal endophyte Epichloë coenophiala, whose presence often benefits the plant, depending on plant and fungal genetics and the prevailing environmental conditions. Despite this symbiosis having agricultural, economic, and ecological importance, relatively little is known regarding its response to predicted global climate change. We quantified the ecophysiological responses of four tall fescue genetic clone pairs, where each pair consisted of one endophyte‐infected (E+) and one endophyte‐free clone, to climate change factors of annually elevated temperature and seasonally increased precipitation. Endophyte presence increased fescue tillering and biomass production in the elevated temperature treatment and greatly enhanced the ability of two of the fescue clones to recover from the hot and unusually dry summer. Surprisingly, endophyte infection also stimulated biomass production and photosynthesis rates (for one clone) in the most mesic treatment (additional precipitation). Toxic ergot alkaloid concentrations increased in E+ individuals exposed to elevated temperatures, particularly in the fall, but the strength of the response varied across E+ genotypes. Overall, this study suggests that choice of plant and endophyte genetic material will be important in determining the productivity, toxicity, and resilience of tall fescue pastures under future climate conditions.

Role of fungal endophyte of tall fescue (Epichloë coenophiala) on water availability, wilting point and integral energy in texturally-different soils

Managing soil water and water uptake by plant roots is more crucial in the arid and semi-arid regions comparing to the other places. Beside the well-known plant available water (PAW) concept, integral energy (EI) is recently suggested to quantify the energy required by plants for water uptake. A greenhouse study was conducted to examine the effect of aboveground fungal endophyte infection (Epichloë coenophiala) in tall fescue (Festuca arundinacea Schreb.=Schedonorus arundinaceus and Lolium arundinaceum) on soil water availability indices such as PAW and EI in six texturally-different soils. The PAW was calculated as the difference between field capacity, θFC [at matric suction, h, of 100 or 330hPa (1hPa=0.1kPa)] and permanent wilting point, θPWP (nominal value at h of 15000hPa or actual h value determined in the greenhouse experiment). The EI was computed by integration of soil water retention curve (determined using undisturbed soil samples) over the nominal and actual PAW ranges. The results indicated that hPWP, the matric suction at actual permanent wilting point, of tall fescue is considerably greater than the conventional value (i.e., 15000hPa) and its value was greater in endophyte-infected (E+) plant associated soils compared to endophyte-free (E−) ones (27572hPa/2757kPa for E+ vs. 21780hPa/2178kPa for E−) and the difference was greater in the coarse- to medium-textured soils. Moreover, E+ treatments, especially in the coarse- and medium-textured soils, had greater values of actual PAW and EI. This shows that E+ plants were able to tolerate higher h values at similar conditions presumably due to induced drought-tolerance mechanisms. The effect of endophyte presence on increment of PAWactual and EI(actual) in comparison with nominal values was much more evident in the coarse- and medium textured soils. This indicates that the error in calculations of the PAW and EI values by considering θPWP at h=15000hPa is relatively smaller in fine-textured soils. Nevertheless, nominal EI values were lower for E+ treatments indicating that in similar PAW, the plant needed lower energy to take up water from the PAW range because endophyte presence can affect soil water release path in the PAW range. Greater contribution of structural pores to water retention in E+ plant associated soils compared to E− ones was related to greater sub-critical water repellency and aggregate stability and better physical quality in E+ plant associated soils. It is concluded that the presence of endophyte in tall fescue, especially in coarse- and medium-textured soils, affects soil water release path, increases PAW and thereby might raise water productivity in drought periods.

Fungal endophyte infection of ryegrass reprograms host metabolism and alters development.

Summary Beneficial associations between plants and microbes play an important role in both natural and agricultural ecosystems. For example, associations between fungi of the genus Epichloë, and cool‐season grasses are known for their ability to increase resistance to insect pests, fungal pathogens and drought. However, little is known about the molecular changes induced by endophyte infection.To study the impact of endophyte infection, we compared the expression profiles, based on RNA sequencing, of perennial ryegrass infected with Epichloë festucae with noninfected plants.We show that infection causes dramatic changes in the expression of over one third of host genes. This is in stark contrast to mycorrhizal associations, where substantially fewer changes in host gene expression are observed, and is more similar to pathogenic interactions. We reveal that endophyte infection triggers reprogramming of host metabolism, favouring secondary metabolism at a cost to primary metabolism. Infection also induces changes in host development, particularly trichome formation and cell wall biogenesis.Importantly, this work sheds light on the mechanisms underlying enhanced resistance to drought and super‐infection by fungal pathogens provided by fungal endophyte infection. Finally, our study reveals that not all beneficial plant–microbe associations behave the same in terms of their effects on the host.

Effects of Epichloë festucae Fungal Endophyte Infection on Drought and Heat Stress Responses of Strong Creeping Red Fescue

Strong creeping red fescue (Festuca rubra ssp. rubra) is an important cool season turfgrass species. Cultivars are often infected with the fungal endophyte Epichloë festucae. Endophyte infection is known to confer insect and disease resistance to the plants. The effect of endophyte infection on drought or heat stress tolerance of strong creeping red fescue is not yet established. The objectives of this controlled-environment study were to determine if endophyte infection had any effect on physiological parameters associated with plant tolerance to drought or heat stress or the combination of the two stresses. In this study, endophyte status had no effect on turf quality (TQ), relative water content (RWC), photochemical efficiency, chlorophyll content, electrolyte leakage (EL), or malondialdehyde (MDA) content of the plants under any of the stress treatments. Our results suggested that E. festucae infection had no physiological effects on improving drought, heat or the combined stress tolerance in strong creeping red fescue.

Aboveground fungal endophyte infection in tall fescue alters rhizosphere chemical, biological, and hydraulic properties in texture-dependent ways

Background and aims Information regarding the influence of endophyte-tall fescue symbiosis on soil hydraulic properties is rare. The hypothesis in this study was that the presence of Epichloe coenophialum in the tall fescue shoot may alter chemical and biological properties of rhizospheric soil and, as a consequence, the soil hydraulic properties and aggregate stability in texture-dependent ways.

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.

Climate drivers, host identity and fungal endophyte infection determine virus prevalence in a grassland ecosystem

Summary 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.

Does Fungal Endophyte Infection Improve Tall Fescue’s Growth Response to Fire and Water Limitation?

Invasive species may owe some of their success in competing and co-existing with native species to microbial symbioses they are capable of forming. Tall fescue is a cool-season, non-native, invasive grass capable of co-existing with native warm-season grasses in North American grasslands that frequently experience fire, drought, and cold winters, conditions to which the native species should be better-adapted than tall fescue. We hypothesized that tall fescue’s ability to form a symbiosis with Neotyphodium coenophialum, an aboveground fungal endophyte, may enhance its environmental stress tolerance and persistence in these environments. We used a greenhouse experiment to examine the effects of endophyte infection (E+ vs. E−), prescribed fire (1 burn vs. 2 burn vs. unburned control), and watering regime (dry vs. wet) on tall fescue growth. We assessed treatment effects for growth rates and the following response variables: total tiller length, number of tillers recruited during the experiment, number of reproductive tillers, tiller biomass, root biomass, and total biomass. Water regime significantly affected all response variables, with less growth and lower growth rates observed under the dry water regime compared to the wet. The burn treatments significantly affected total tiller length, number of reproductive tillers, total tiller biomass, and total biomass, but treatment differences were not consistent across parameters. Overall, fire seemed to enhance growth. Endophyte status significantly affected total tiller length and tiller biomass, but the effect was opposite what we predicted (E−>E+). The results from our experiment indicated that tall fescue was relatively tolerant of fire, even when combined with dry conditions, and that the fungal endophyte symbiosis was not important in governing this ecological ability. The persistence of tall fescue in native grassland ecosystems may be linked to other endophyte-conferred abilities not measured here (e.g., herbivory release) or may not be related to this plant-microbial symbiosis.

Effects of fungal endophyte infection on soil properties and microbial communities in the host grass habitat

Effects of fungal endophyte infection on soil properties and microbial communities in the host grass habitat

Fungal endophyte infection and host genetic background jointly modulate host response to an aphid‐transmitted viral pathogen

Summary Despite their ubiquitous nature, interactions between multiple micro‐organisms and their effects on host growth and each other's success have received limited scientific attention. In particular, grasses can be commonly infected by both endophytic fungi and viruses, which are typically transmitted by aphids. In this study, we investigated how an aphid‐transmitted viral pathogen and a symbiotic endophytic fungus altered host growth and allocation. We hypothesized that, by reducing aphid feeding, endophyte infection would lower viral titre and consequently decrease the negative effects of virus infection on host biomass production. In a greenhouse experiment, we manipulated fungal endophyte status and virus infection (Barley Yellow Dwarf Virus – PAV) of two tall fescue cultivars with different genetic backgrounds [KY 31 and pasture demonstration farm (PDF)]. In one cultivar (PDF), we also manipulated endophyte strain, using two strains that had been selected for differences in alkaloid production. We assessed host, virus and vector responses. As hypothesized, endophyte infection decreased reproduction and abundance of aphid vectors; however, in contrast to our hypothesis, this response by aphids did not impact viral titre. For both tall fescue cultivars, endophyte infection alleviated the negative effect of virus infection on the proportion of total plant biomass allocated to roots. On the other hand, for the KY 31 cultivar only, virus infection decreased tillering in endophyte‐infected individuals, but not endophyte‐free individuals. Within the PDF cultivar, both endophyte strains produced similar effects on host, virus and vector responses. Synthesis These results indicate that some of the beneficial effects provided by endophyte infection, particularly alleviating the negative effect of virus infection on the proportion of total plant biomass allocated to roots, do not arise strictly from altering host interactions with herbivores (aphids), but also occur by changing host responses to viral infection. Furthermore, these results emphasize the importance of exploring multispecies microbial interactions and genetic controls on these interactions in order to more fully understand their role in community‐ and ecosystem‐level dynamics.

Consequences of simultaneous interactions of fungal endophytes and arbuscular mycorrhizal fungi with a shared host grass

Plants simultaneously associate with multiple microbial symbionts throughout their lifetimes. To address the question of whether the effects of simultaneous symbionts are contingent on the specific identities, we conducted a greenhouse experiment manipulating the presence and identities of arbuscular mycorrhizal fungi (AMF) and fungal endophytes on the shared host grass Elymus hystrix. Each plant host was inoculated with one of two AMF species having varying effects on host growth, or a sterile soil control. Further, we used naturally occurring endophyte‐infected (E+) and uninfected (E–) individuals from two populations of the endophyte Epichloë elymi that varied in their interaction with E. hystrix. We then measured responses of plants, AMF, and fungal endophytes. Overall, we found that the combined effects of AMF and fungal endophytes on plant growth were additive, reflecting the mutualistic quality of each symbiont independently interacting with host plants. However, fungal endophyte infection differentially altered hyphal colonization of the two AMF species and the identity of the coinfecting AMF species affected fungal endophyte fitness traits. The results of this study demonstrate that the outcome of interspecific symbiotic interactions varies with partner identity such that the effects of simultaneous symbioses can not be generalized.