Showing papers on "Neotyphodium published in 2005"

Herbivores cause a rapid increase in hereditary symbiosis and alter plant community composition

Abstract: Microbial symbioses are ubiquitous in nature. Hereditary symbionts warrant particular attention because of their direct effects on the evolutionary potential of their hosts. In plants, hereditary fungal endophytes can increase the competitive ability, drought tolerance, and herbivore resistance of their host, although it is unclear whether or how these ecological benefits may alter the dynamics of the endophyte symbiosis over time. Here, we demonstrate that herbivores alter the dynamics of a hereditary symbiont under field conditions. Also, we show that changes in symbiont frequency were accompanied by shifts in the overall structure of the plant community. Replicated 25-m2 plots were enriched with seed of the introduced grass, Lolium arundinaceum at an initial frequency of 50% infection by the systemic, seed-transmitted endophyte Neotyphodium coenophialum. Over 54 months, there was a significantly greater increase in endophyte-infection frequency in the presence of herbivores (30% increase) than where mammalian and insect herbivory were experimentally reduced by fencing and insecticide application (12% increase). Under ambient mammalian herbivory, the above-ground biomass of nonhost plant species was reduced compared with the mammal-exclusion treatment, and plant composition shifted toward greater relative biomass of infected, tall fescue grass. These results demonstrate that herbivores can drive plant–microbe dynamics and, in doing so, modify plant community structure directly and indirectly.

Molecular cloning and genetic analysis of a symbiosis-expressed gene cluster for lolitrem biosynthesis from a mutualistic endophyte of perennial ryegrass

Abstract: Lolitrems are potent tremorgenic mycotoxins that are synthesised by clavicipitaceous fungal endophytes of the Epichloe/Neotyphodium group in association with grasses. These indole–diterpenes confer major ecological benefits on the grass–endophyte symbiotum. A molecular signature for diterpene biosynthesis is the presence of two geranylgeranyl diphosphate (GGPP) synthases. Using degenerate primers for conserved domains of fungal GGPP synthases, we cloned two such genes, ltmG and ggsA, from Neotyphodium lolii. Adjacent to ltmG are two genes, ltmM and ltmK, that are predicted to encode an FAD-dependent monooxygenase and a cytochrome P450 monooxygenase, respectively. The cluster of ltm genes is flanked by AT-rich retrotransposon DNA that appears to have undergone extensive repeat induced point (RIP) mutation. Epichloe festucae, the sexual ancestor of N. lolii, contains an identical ltm gene cluster, but lacks the retrotransposon “platform’‘ on the right flank. Associations established between perennial ryegrass and an E. festucae mutant deleted for ltmM lack detectable levels of lolitrems. A wild-type copy of ltmM complemented this phenotype, as did paxM from Penicillium paxilli. Northern hybridization and RT-PCR analysis showed that all three genes are weakly expressed in culture but strongly induced in planta. The relative endophyte biomass in these associations was estimated by real-time PCR to be between 0.3 and 1.9%. Taking this difference into account, the steady-state levels of the ltm transcripts are about 100-fold greater than the levels of the endogenous ryegrass β-tubulin (β -Tub1) and actin (Act1) RNAs. Based on these results we propose that ltmG, ltmM and ltmK are members of a set of genes required for lolitrem biosynthesis in E. festucae and N. lolii.

Connecting plant–microbial interactions above and belowground: a fungal endophyte affects decomposition

Abstract: Mutualisms can strongly affect the structure of communities, but their influence on ecosystem processes is not well resolved. Here we show that a plant-microbial mutualism affects the rate of leaf litter decomposition using the widespread interaction between tall fescue grass (Lolium arundinaceum) and the fungal endophyte Neotyphodium coenophialum. In grasses, fungal endophytes live symbiotically in the aboveground tissues, where the fungi gain protection and nutrients from their host and often protect host plants from biotic and abiotic stress. In a field experiment, decomposition rate depended on a complex interaction between the litter source (collected from endophyte-infected or endophyte-free plots), the decomposition microenvironment (endophyte-infected or endophyte-free plots), and the presence of mesoinvertebrates (manipulated by the mesh size of litter bags). Over all treatments, decomposition was slower for endophyte-infected fescue litter than for endophyte-free litter. When mesoinvertebrates were excluded using fine mesh and litter was placed in a microenvironment with the endophyte, the difference between endophyte-infected and endophyte-free litter was strongest. In the presence of mesoinvertebrates, endophyte-infected litter decomposed faster in microenvironments with the endophyte than in microenvironments lacking the endophyte, suggesting that plots differ in the detritivore assemblage. Indeed, the presence of the endophyte in plots shifted the composition of Collembola, with more Hypogastruridae in the presence of the endophyte and more Isotomidae in endophyte-free plots. In a separate outdoor pot experiment, we did not find strong effects of the litter source or the soil microbial/microinvertebrate community on decomposition, which may reflect differences between pot and field conditions or other differences in methodology. Our work is among the first to demonstrate an effect of plant-endophyte mutualisms on ecosystem processes under field conditions.

Mutualistic fungus promotes plant invasion into diverse communities

Abstract: Reducing the biological diversity of a community may decrease its resistance to invasion by exotic species. Manipulative experiments typically support this hypothesis but have focused mainly on one trophic level (i.e., primary producers). To date, we know little about how positive interactions among species may influence the relationship between diversity and invasibility, which suggests a need for research that addresses the question: under what conditions does diversity affect resistance to invasion? We used experimental manipulations of both plant diversity and the presence of an endophytic fungus to test whether a fungal mutualist of an invasive grass species (Lolium arundinaceum) switches the relationship between plant community diversity and resistance to invasion. Association with the fungal endophyte (Neotyphodium coenophialum) increased the ability of L. arundinaceum to invade communities with greater species diversity. In the absence of the endophyte, the initial diversity of the community significantly reduced the establishment of L. arundinaceum. However, establishment was independent of initial diversity in the presence of the endophyte. Fungal symbionts, like other key species, are often overlooked in studies of plant diversity, yet their presence may explain variation among studies in the effect of diversity on resistance to invasion.

Are endophyte-mediated effects on herbivores conditional on soil nutrients?

Abstract: Neotyphodium endophytes are assumed to have mutualistic relationship with their grass hosts, mainly resulting from mycotoxin production increasing plant resistance to herbivores by the fungus that subsists on the plant. To study importance of often ignored environmental effects on these associations, we performed a greenhouse experiment to examine the significance of endophyte infection and nutrient availability for bird-cherry aphid ( Rhopalosiphum padi) performance on meadow fescue ( Lolium pratense). Naturally endophyte-infected (E+), uninfected (E-), or manipulatively endophyte-free (ME-) half-sib families of meadow fescue were grown on two soil nutrient levels. Endophyte infection reduced aphid performance in general. However, to our knowledge, this is the first study to demonstrate experimentally that herbivore performance decreases on E+ host plants with increasing availability of nutrients in soils. Potential improvement in herbivore performance in high nutrient soils and decreased plant performance in low nutrient soils in ME- plants, compared to E- and E+ plants, suggests that loss of endophyte infection after long coevolutionary relationship may be critical to plant fitness.

How does the fungal endophyte Neotyphodium coenophialum affect tall fescue {Festuca arundinacea) rhizodeposition and soil microorganisms?

Abstract: The goal of our study was to investigate the impact of fungal endophytes in tall fescue (Festuca arundinacea) on rhizodeposition and in turn, the soil microbial community Sand-based, aseptic microlysimeter units were constructed for the collection of rhizodeposit solutions for chemical analyses from the roots of endophyte-free (E−) and endophyte-infected (E+) tall fescue plants E+ plants were infected with Neotyphodium coenophialum, the most common endophyte found in tall fescue Rhizodeposit solutions collected over nine weeks from E+ grass contained more organic carbon and carbohydrates than E− These solutions were allowed to percolate through columns of plant-free soils to assess the response of the soil microbial communities Soils to which solutions from E+ grass were applied had significantly higher respiration rates than those receiving solutions from E− grass, suggesting that microbial activity was stimulated by changes in the rhizodeposits Culture-based assays of the soil microbial community (plate counts and community-level physiological profiling) suggest that the basic structure of the microbial community was not affected by application of rhizodeposit solutions from E+ plants as compared to E− Our results indicate that the presence of a fungal endophyte may enhance rhizodeposition by tall fescue and could consequently influence microbial mineralization processes in the soil In grasslands where nutrients may be limiting, hosting a fungal endophyte has the potential to enhance plant nutrient supply indirectly via a stimulatory effect on the soil microbial biomass

Occurrence and impact of pasture mealybug (Balanococcus poae) and root aphid (Aploneura lentisci) on ryegrass (Lolium spp.) with and without infection by Neotyphodium fungal endophytes

Abstract: Pasture mealybug (Balanococcuspoae) was found infesting two field trials evaluating the performance of selected strains of the endophyte Neotyphodium lolii in ryegrass (Lolium spp.) in Canterbury, New Zealand. Deterioration of endo‐phyte‐free plots relative to endophyte‐infected plots had been observed. In Trial A, pasture mealybug were sampled in plots of the perennial ryegrass cultivar ‘Grasslands Nui’, without endophyte (nil), or infected with the wild‐type endophyte, or the selected strains, AR1 and AR37. In Trial B, mealybug numbers on six ryegrass cultivars infected with AR1 or wild‐type were compared with those on the same cultivars without endophyte. In sampling these trials, the presence of a root aphid, Aploneura lentisci, was also noted. Populations of mealybug in both trials were similar on all endophyte‐infected treatments and significantly lower than populations on nil treatments. Neither AR1 nor wild‐type appeared to reduce root aphid numbers, while AR37 may have had some effect. T...

Endophytic fungi (Neotyphodium coenophialum) affect the growth and mineral uptake, transport and efficiency ratios in tall fescue (Festuca arundinacea)

Abstract: Neotyphodium coenophialuminteracts mutualistically with its host grasses. Tall fescue (Festuca arundinacea Schreb.) plants infected by the fungal endophyte,Neotyphodium coenophialum(Morgan-Jones and Gams) Glenn, Bacon and Hanlin, often perform better than non-infected plants, especially in limited resource environments. However, there is a scarcity of information about endophyte-grass ecotypes interaction in Andisols of temperate regions. Clones of three tall fescue ecotypes (Fukaura, Koiwai and Showa) either infected with N. coenophialum (E+) or noninfected (E−) were grown in Andisols (Black Andisol: naturally low content of phosphorus, high in other nutrients; Red Andisol: naturally high content of phosphorus, low in other nutrients) for 133 days in a controlled environment. Cumulative shoot dry weight, daily regrowth rates (tiller number, plant height and shoot dry matter) after clippings and nutrient uptake, transport and efficiency ratios were measured. In Black Andisol, E+ plants had significantly higher cumulative shoot dry weight as well as daily regrowth rates than E− plants, while in Red Andisol the reverse was true. Among the ecotypes studied, Showa had the highest shoot growth. Significantly higher phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) uptake as well as transport were identified in E+ vs. E− plants grown in Black Andisol. With few exceptions, values for nutrient efficiency ratios were not significantly different between E+ and E− plants grown in both soils. Significant three-way interaction (endophyte × ecotype × soil) for cumulative shoot dry weight and regrowth rate revealed that the ecotype specific regrowth responses to endophyte infection were depended on soil nutrient conditions. Vegetative growth and nutrient acquisition in tall fescue varied with ecotype and were modified by abiotic (soil fertility status) as well as biotic (endophyte infection) factors.

Reduced herbivore resistance from a novel grass–endophyte association

Abstract: Summary 1 Endophytic fungi in agricultural grasses confer agronomic advantages but can be detrimental to the health and production of grazing mammals. Attempts have been made to resolve this dilemma by creating novel associations of high-yielding grass cultivars and ‘safe endophytes’ that do not naturally co-occur. Recently, researchers created a novel association by combining a Moroccan strain of Neotyphodium coenophialum, called AR542, with the tall fescue Festuca arundinacea cultivar Georgia 5. This novel association is marketed commercially and has no doubt become naturalized; it is therefore important to assess its impact on other organisms. 2 The bird-cherry-oat aphid Rhopalosiphum padi uses tall fescue as an alternative host. We assessed the performance of R. padi feeding on Georgia 5 that had been artificially infected with AR542, naturally infected by the common strain (CS) of N. coenophialum or was endophyte-free (EF). We cross-factored these three levels of endophyte infection with four levels of nitrogen fertilizer, and used two different methods of assessing aphid performance, clip-cages and enclosed populations. 3 Endophyte-infected plants produced approximately 20% more dry mass than EF plants. In both the clip-cage and enclosed-population experiments, aphid populations grew fastest on the EF plants, slower on AR542-infected plants and slowest (or not at all) on the CS-infected plants. 4 Synthesis and applications. Our results suggest that AR542 infection does not provide the same degree of protection from aphids as the commonly occurring CS infection. If similar results are found for other invertebrate herbivores, then the use of this novel endophyte association may be less useful than previously thought. The widespread conversion of tall fescue pastures, currently infected with the CS endophyte, to pastures infected with AR542 could result in a general increase in the prevalence of cereal aphids and, potentially, the diseases that they spread. However, such conversion might be beneficial to native invertebrate herbivores.

Interaction between grass endophytes and mycorrhizas in Bromus setifolius from Patagonia, Argentina

Abstract: The interaction between grass endophytes and mycorrhizas of Bromus setifolius from Patagonia, Argentina was examined. To determine effects of the endophyte (Neotyphodium sp.) on the colonisation of B. setifolius by arbuscular mycorrhizal fungi (AM), we analysed roots collected from the field and we also experimentally evaluated the association. Two populations of B. setifolius differing in endophyte colonisation were grown in either presence or absence of AM fungi using two different sources of soil. We also analysed the combined influence of these fungi on host growth. Roots of endophyte-colonised populations (E+) obtained from the field showed a higher frequency of colonisation by AM fungi than noncolonised populations (E-). The assay showed that there was a significant difference in the extent of colonisation of roots between the two populations used. E+ population roots were colonised more extensively than those of E- populations. The E+ population also showed increased growth characteristics in comparison to the E- population. The source of soil did not affect any of the host parameters analysed. For the first time, a positive interaction between Neotyphodium endophytes and arbuscular mycorrhiza is reported.

Transfer of endophyte‐origin defensive alkaloids from a grass to a hemiparasitic plant

Abstract: Plants growing in natural environments experience myriad interactions with a diverse assemblage of pathogens, parasites and mutualists. Many of these interactions involve symbiotic bacteria and fungi, but they also include macroparasitic plants. In this study, we investigated the interactions among a host grass (Lolium pratense, ex., Festuca pratensis), its symbiotic endophytic fungus (Neotyphodium uncinatum), a root hemiparasitic plant (Rhinanthus serotinus) of the host grass and a generalist herbivore (aphid Aulacorthum solani) of the hemiparasite. We demonstrate that the hemiparasitic plant acquires defending mycotoxins produced by the endophytic fungus living within their shared host grass. The uptake of defensive mycotoxins from the endophyte-infected host grass enhances the resistance of the hemiparasitic plant to the generalist aphid herbivore. Endophyte infection increases the performance of the hemiparasitic plant, but reduces the growth of the host grass. In other words, the mutualistic endophytic fungus becomes parasitic in the presence of the hemiparasitic plant. Our results suggest that the outcomes of grass–endophyte interactions are conditional on the complexity of community-level interactions; thus, the outcome of multispecies interactions may not be predictable from pair-wise combinations of species.

Response of Pratylenchus spp. in tall fescue infected with different strains of the fungal endophyte Neotyphodium coenophialum

Abstract: Summary – The presence of the fungal endophyte Neotyphodium coenophialum in tall fescue (Festuca arundinacea) confers resistance to some plant-parasitic nematodes but also results in the production of ergot alkaloids. Recently, new strains of N. coenophialum have been isolated from wild tall fescue and artificially inoculated into elite tall fescue cultivars. These strains produce low to nil levels of ergot alkaloids and are referred to as non-ergot strains. Our objective was to determine whether non-ergot strains of the endophyte confer the same level of resistance to Pratylenchus spp. as the endemic strain in tall fescue. In a glasshouse experiment, nematode resistance was compared in two fescue cultivars (Jesup and Georgia 5) infected with either the endemic strain (E + ), or two non-ergot strains, AR542 and AR584. An additional non-ergot strain, AR514, was tested only in cv. Jesup. Cultivars Georgia 5 and Jesup without endophytes (E − ) were used as controls. The endophtye status of the plants was confirmed and then three plants per cultivar/endophyte combination were transplanted into 10 cm square pots. The pots were inoculated with a mixed culture of Pratylenchus zeae and P. scribneri in the first trial and a pure culture of P. scribneri in the second trial of the experiment. After 8 weeks, the number of nematodes within the roots from each pot was determined. Numbers of Pratylenchus spp. in either cv. Georgia 5 or cv. Jesup containing the nonergot strain AR542 were not different from numbers in E − plants. AR514 also did not confer resistance to the nematodes in cv. Jesup. By contrast, the non-ergot strain AR584 appears to confer resistance to Pratylenchus spp. in cv. Georgia 5, but not in cv. Jesup; however, the level of resistance in cv. Georgia 5 was less than the resistance conferred by the endemic endophyte. Genetic differences between the two tall fescue cultivars may affect growth of the endophyte or production of a nematode toxin or deterrent by the endophyte. As only a small subset of endophyte strains has been tested, we are screening additional non-ergot strains for resistance to P. scribneri.

Specificity of host-endophyte association in tall fescue populations from Sardinia, Italy.

Abstract: Tall fescue [Festuca arundinacea Schreb. var. arundinacea Schreb. (2n = 6x = 42)] breeding objectives are to exploit the natural variation of the associated endophytic fungi and to select specific plant-fungus combinations that optimize the host fitness but do not cause detrimental effects on grazing animals. This study investigated the presence of endophytes in 60 tall fescue natural populations from Sardinia, Italy; identified the endophytes and assessed some important metabolites produced by their interaction with the host plant; and characterized the tall fescue populations for morphological traits, relating the variation among populations to possible differences in the associated endophytes. The high frequency of infected populations (58 out of 60), and high levels of infection (on average, 80% infected seed), suggested an adaptive advantage of E + plants under harsh Mediterranean conditions. Morphological identification of fungal isolates, in comparison with Neotyphodium coenophialum (Morgan-Jones et Gams) Glenn, Bacon et Hanlin check isolates, made it possible to separate two groups of populations. One, infrequent, associated with a long-conidia endophyte (attributable to N. coenophialum), and another associated with a short-conidia form, likely belonging to the Festuca arundinacea Taxonomic Grouping-2 (FaTG-2), which was previously isolated in a few Mediterranean accessions. Chemical analysis revealed the presence of loline alkaloids only in populations associated to the long-conidia endophyte, thus corroborating that form's attribution to the loline-inducing N. coenophialum. A difference was also observed in ergovaline concentration between long-conidia (= N. coenophialum) and short-conidia endophyte variants, the latter producing only about 25% of the ergovaline produced by the former. A coevolutionary specificity between the native Sardinian fescue germplasm and its associated endophyte was suggested by the agreement between morphology of the host plant (distinct from germplasm originating in temperate environments) and morphological and biochemical characteristics of the harbored fungus.

Detrimental and neutral effects of wild barley–Neotyphodium fungal endophyte associations on insect survival

Abstract: Neotyphodium (Clavicipitaceae: Balansieae) fungal endophyte infection does not always confer temperate grass resistance to insect herbivores, although reports indicate that over 40 species are adversely affected by its infection. Laboratory and glasshouse experiments were conducted to improve our knowledge of the anti-insect properties of Neotyphodium-infected (E+) non-commercial grasses, and E+ wild barley (Hordeum) specifically. Neotyphodium infection of four plant inventory (PI) lines of wild barley conferred resistance to Mayetiola destructor (Say) (Diptera: Cecidomyiidae), whereas none of the E+ wild barley accessions reduced the survival of Rhopalosiphum padi (L.) (Homoptera: Aphididae). Metopolophium dirhodum (Walker) (Homoptera: Aphididae) densities were significantly lower on the E+ clones of Hordeum brevisubulatum ssp. violaceum (Boissier and Hohenacker) (PI 440420), compared with densities on endophyte-free (E-) plants of this species in population growth experiments. Neotyphodium infection of three Hordeum bogdanii (Wilensky) PI lines did not confer resistance to M. dirhodum; however, one of these E+ lines (PI 314696) was resistant to this aphid in a second population growth experiment. Our results provide additional evidence that the outcome of a grass-endophyte-insect interaction is influenced by the host grass species or genotype, Neotyphodium species or genotype, and the insect species involved. They also reinforce this phenomenon for non-commercial grass-endophyte-insect interactions and underscore the potential role of endophytes in mediating wild barley-insect interactions and their potential to act as defensive mutualists.

Influence of temperature on alkaloid levels and fall armyworm performance in endophytic tall fescue and perennial ryegrass

Abstract: The symbiotic relationships between Neotyphodium endophytes (Clavicipitacea) and certain coolseason (C3) grasses result in the synthesis of several alkaloids that defend the plant against herbivory. Over a 3 month period we evaluated the effects of temperature on the expression of these alkaloids in tall fescue, Festuca arundinacea Schreb, and perennial ryegrass, Lolium perenne L. (Poaceae). Response surface regression analysis indicated that month, temperature, and their interaction had an impact on the alkaloid levels in both grasses. We aimed to identify the alkaloids most closely associated with enhanced resistance to the fall armyworm, Spodoptera frugiperda JE Smith (Lepidoptera: Noctuidae), and clarify the role of temperature in governing the expression of these alkaloids. The dry weights and survival of fall armyworms feeding on endophyte-infected tall fescue or perennial ryegrass were significantly lower than for those feeding on uninfected grass, whereas endophyte infection had no significant influence on survival. For tall fescue, a four-alkaloid model consisting of a plant alkaloid, perloline, and the fungal alkaloids ergonovine chanoclavine, and ergocryptine, explained 47% of the variation in fall armyworm dry weight, whereas a three-alkaloid model consisting of the plant alkaloid perloline methyl ether and the fungal alkaloids ergonovine and ergocryptine explained 70% of the variation in fall armyworm dry weight on perennial ryegrass. Although temperature had a significant influence on overall alkaloid expression in both grasses, the influence of temperature on individual alkaloids varied over time. The levels of those alkaloids most closely linked to armyworm performance increased linearly or curvilinearly with increasing temperature during the last 2 months of the study. We conclude that the growth temperature of grasses can influence the performance of fall armyworm, and that this effect may be mediated through a set of plant- and endophyte-related alkaloids.

Fungal endophyte infection changes growth attributes in Lolium multiflorum Lam

Abstract: Lolium multiflorum is a successful invader of postagricultural succession in the Inland Pampa grasslands in Argentina, becoming a dominant species in the plant community. Individual plants of this annual species are naturally highly infected with fungal endophytes (Neotyphodium sp.) from early successional stages. We assessed the effect of Neotyphodium infection on the biology of L. multiflorum. We evaluated growth attributes between endophyte infected (E+) and uninfected (E-) plants under non-competitive conditions during the normal growing season. E+ plants produced significantly more vegetative tillers and allocated more biomass to roots and seeds. Although seed germination rates were greater in endophyte free plants, the rate of emergence and the final proportion of emerged seedlings were similar between the biotypes. The greater production of vegetative tillers, and the greater resource allocation to roots and seeds are likely to confer an ecological advantage to E+ plants, thus enabling their dominance over the E- individuals in natural grasslands.

Fungos endofíticos isolados de ápices caulinares de pupunheira cultivada in vivo e in vitro

Abstract: Losses of micropropagated plants occur in its majority due to presence of microorganisms responsible for plant death both in culture beginning and plant establishment in field. Two years in vitro cultivated pejibaye shoot tips, showed the presence of fungi colonies after transference for new culture medium. This paper aimed at identifying fungi, by classical taxonomy and by molecular methods, present in shoot tip of healthy pejibaye plants, cultivated in the field, and to compare them with isolated ones of in vitro plants. The isolates of endophytic fungi community of the in vitro plants were Fusarium oxysporum, Neotyphodium sp. and Epicoccum nigrum; from the in vivo plants were Fusarium sp., F. proliferatum, F. oxysporum, Colletotrichum sp., Alternaria gaisen, Neotyphodium sp. and E. nigrum. The seven species of fungi were reinoculated in host plant, revealing different behaviour. Neotyphodium sp. and E. nigrum established an endophytic interaction with the host; the other fungi acted as pathogens causing decrease in seedlings development when compared to the non-inoculated plants. Species acting as endophytes present a potential use in biocontrol of pejibaye pathogens.

Photosynthetic activity of Lolium perenne as a function of endophyte status and zinc nutrition

Abstract: Grass infection by endophyte fungi can confer host resistance to different types of stress, but limited evidence is available on the related effects on the photosynthetic mechanism of the grasses. Zinc has direct and indirect effects on this mechanism and is one of the more important environmental pollutants. To measure whether photosynthesis of the host plant is affected by fungal infection when endophyte-free and endophyte-infected grasses contain similar excess zinc concentrations in their leaves, two batches of Lolium perenne L. cv. Apollo plants were established, one batch was infected with Neotyphodium lolii, the other was not. Both batches were then treated for 8 d with a nutrient solution containing 0, 1, 5, 10 or 20 mm ZnSO4. The increase in zinc concentration induced some reduction in photosystem II (PSII) activity but not enough to account for the total drop in the net photosynthetic rate. Endophyte fungus favoured maintenance of the PSII activity, but did not significantly modify the net photosynthesis and similar zinc concentration levels were observed in leaves of both types of plant. Interactive effects of zinc and light induced less photodamage to the PSII of the host, which is able to react to an increase in photon flux density (PFD). In endophyte-free plants, the reaction centre contributed more than antenna complexes to energy dissipation. In endophyte-infected plants, the quenching of the reaction centre and antenna complexes rose simultaneously and at a constant rate, as zinc concentrations increased.

Resistance to the rice leaf bug, Trigonotylus caelestialium, is conferred by Neotyphodium endophyte infection of perennial ryegrass, Lolium perenne

Abstract: Neotyphodium fungal endophytes form mutualistic symbiotic associations with many grasses of the subfamily Pooideae, including important forage and turfgrass species. This relationship provides a competitive advantage to the host plant by increasing abiotic/biotic stress tolerance, such as its resistance to drought, diseases, and insect pests. The insect deterrent effects of endophytes are now receiving attention in Japan, as insect pests growing in meadows are causing problems in adjacent rice paddies. One of the most serious problems is the kernel spotting of rice grains caused by the rice leaf bug, Trigonotylus caelestialium Kirkaldy (Heteroptera: Miridae), which reproduces on Lolium species grown as forage. To determine the potential of Neotyphodium endophytes to reduce the invasion of rice crops by T. caelestialium from adjacent Lolium crops, we carried out choice and no-choice feeding tests using endophyte-infected and endophyte-free clonal perennial ryegrass (Lolium perenne L.) (Poaceae). Our experiments revealed that the presence of the Neotyphodium endophyte strongly deterred the feeding of both first-instar larvae and adults of T. caelestialium. These results show the potential of Neotyphodium endophytes to reduce the number of T. caelestialium in forage fields and grasslands, and thus to reduce the damage to rice grains caused by this insect pest.

Asexual Neotyphodium Endophytes in Arizona Fescue: A Test of the Seed Germination and Pathogen Resistance Hypothesis

Abstract: Asexual, systemic, and seed borne endophytes that live symbiotically in pooid grasses are thought to interact mutualistically with their hosts. The mutualism should be most evident in seed and seedling stages, where host fitness is directly affected. We tested the hypothesis that the seed borne endophyte, Neotyphodium, increases seed germination success and seedling survival for a native grass host. We compared germination success and speed and seedling survival, between infected (E+) and uninfected (E-) of seeds from: 1) wild maternal plants and 2) four genotypes of E+ maternal plants from which the endophyte had been experimentally removed. In both experiments, infection did not increase germination success, as predicted. Wild E+ seeds harbored more weedy fungi, which were associated with reduced germination success and seedling survival and slower germination, than E-seeds. Contrary to prevailing notions, seed borne endophytes do not increase, and instead may decrease germination and seedling survival, and delay germination.

Structural analysis of a peptide synthetase gene required for ergopeptine production in the endophytic fungus Neotyphodium lolii.

Abstract: Lysergyl peptide synthetase 1 catalyzes the assembly of toxic ergopeptines from activated D-lysergic acid and three amino acids. The gene encoding this enzyme in the endophytic fungus Neotyphodium lolii was analyzed and compared to a homologous gene from the ergot fungus Claviceps purpurea. Each gene contained two introns, which were found in the same relative position within two modules of the gene. The 5′ ends of the two genes were unusually divergent. Signature sequences determining substrate specificity were similar in adenylation domains that recognized identical amino acids but differed within the adenylation domain for the amino acid that varies between the major ergopeptines of the two fungi. Homologues were detected in several related endophytic fungi; the tall fescue endophyte Neotyphodium coenophialum contained a divergent, second copy of the gene. Our results provide new information on the structure and distribution of this important peptide synthetase involved in ergot alkaloid biosynthesis.

Soil biota associated with endophyte-infected tall fescue in the field.

Abstract: Invertebrates present in soil samples taken from plots of tall fescue (Festuca arundinacea) infected with two non-toxic strains of Neotyphodium endophyte (AR501 and AR542) at Aorangi near Palmerston North and one strain (AR501) at Lincoln in Canterbury, together with endophyte-free controls at both sites, were determined in autumn 2002. Roots taken from these samples were stained and checked for the presence of arbuscular mycorrhiza. At Lincoln, numbers of root aphid (Aploneura lentisci) associated with plants infected with AR501 were signifi cantly less than those on endophyte-free plants, while grass grub numbers (Costelytra zealandica) did not differ between treatments. Benefi cial invertebrates, Collembola, mites and earthworms, were not affected by endophyte at either site and neither was colonisation of roots by mycorrhiza.

The impact of tall fescue (festuca arundinacea) endophyte (neotyphodium spp.) on non-target soil nematodes

Abstract: Non-target effects of Neotyphodium endophyte infection in fi eld-sown tall fescue were studied as a model for investigating non-target effects of genetically-modifi ed plants. Two strains of Neotyphodium endophyte (AR501 and AR542) in tall fescue at a site near Palmerston North (Aorangi) and one strain (AR501) at a site near Lincoln were sampled in March and April 2002 respectively. The only consistent effect of either endophyte strain on nematode abundance was an increase of large omnivorous nematodes beneath AR501 tall fescue at both sites. This was refl ected in omnivorous nematodes constituting a signifi cantly greater proportion of the nematode fauna over the two sites. The nematode results show that relatively minor effects on this component of soil biota were observed as a result of plant changes associated with endophyte-infection, even after long-term growth in fi eld plots.