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

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.     

Contribution of ergot alkaloids to suppression of a grass-feeding caterpillar assessed with gene knockout endophytes in perennial ryegrass

Neotyphodium and Epichloë species (Ascomycota: Clavicipitaceae) are fungal symbionts (endophytes) of grasses. Many of these endophytes produce alkaloids that enhance their hosts’ resistance to insects or are toxic to grazing mammals. The goals of eliminating from forage grasses factors such as ergot alkaloids that are responsible for livestock disorders, while retaining pasture sustainability, and of developing resistant turf grasses, require better understanding of how particular alkaloids affect insect herbivores. We used perennial ryegrass Lolium perenne L. (Poaceae) symbiotic with Neotyphodium lolii × Epichloë typhina isolate Lp1 (a natural interspecific hybrid), as well as with genetically modified strains of Lp1 with altered ergot alkaloid profiles, to test effects of ergot alkaloids on feeding, growth, and survival of the black cutworm, Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae), a generalist grass‐feeding caterpillar. Neonates or late instars were provided clippings from glasshouse‐grown plants in choice and rearing trials. Wild‐type endophytic grass showed strong antixenosis and antibiosis, especially to neonates. Plant‐endophyte symbiota from which complex ergot alkaloids (ergovaline and lysergic acid amides such as ergine) or all ergot alkaloids were eliminated by endophyte gene knockout retained significant resistance against neonates. However, this activity was reduced compared to that of wild‐type Lp1, providing the first direct genetic evidence that ergot alkaloids contribute to insect resistance of endophytic grasses. Similarity of larval response to the two mutants suggested that ergovaline and/or ergine account for the somewhat greater potency of wild‐type Lp1 compared to the knockouts, whereas simpler ergot alkaloids contribute little to that added resistance. All of the endophyte strains also produced peramine, which was probably their primary resistance component. This study suggests that ergot alkaloids can be eliminated from an endophyte of perennial ryegrass while retaining significant insect resistance.     

Family issues: fungal endophyte protects host grass from the closely related pathogen Claviceps purpurea

Certain cool season grasses establish systemic and asymptomatic symbioses with clavicipitaceous fungi of the genus Neotyphodium, which affect multiple biotic interactions within host neighborhood. The presumed symbiont-mediated plant resistance to pathogens is mostly based on studies performed under laboratory and greenhouse conditions. Here we investigated, in two outdoor experiments, the relation between two fungi of the same family with opposite effects on Lolium multiflorum plants: the mutualist endophyte Neotyphodium occultans, and the pathogen Claviceps purpurea. Natural infection and its consequences on symbiotic and non-symbiotic plants were studied under varying conditions of stress by herbicide. In both experiments, N. occultans reduced significantly the infection by C. purpurea at population levels (70 % less). The percentage of spikes infected by C. purpurea was almost three times lower in endophyte-symbiotic plants than in non-symbiotic ones. However, the protective effect was not maintained under stress condition. Our results show that constitutive symbionts such as the systemic fungal endophytes mediate the interaction between host grasses and pathogens, although the effect may depend on the level of stress in the environment.     

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

The symbiotic relationships between Neotyphodium endophytes (Clavicipitacea) and certain cool‐season (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.     

Stroma-forming endophyte Epichloë glyceriae provides wound-inducible herbivore resistance to its grass host

Fungal endophyte-grass associations are diverse and complex. Some endophytes (e.g. Neotyphodium spp.) reproduce asexually by growing vegetatively into host seeds and many of these vertically-transmitted endophytes form mutualisms with their hosts by providing high levels of alkaloids, such as lolines, that reduce herbivore performance. Additionally, Neotyphodium coenophialum provides wound-inducible herbivore resistance through increased production of lolines. Neotyphodium likely evolved from Epichloë spp. which are sexually reproducing endophytes that are transmitted horizontally to the next host generation through production of stromata (fruiting bodies), which sterilize host grasses. We asked if wound-inducible resistance like that in N . coenophialum also occurs in the ancestral, sexually reproducing Epichloë glyceriae , which infects Glyceria striata . Host grasses were damaged by fall armyworm caterpillars, artificially cut, or left undamaged. An aphid bioassay tested the plant's toxicity to herbivores, expression of lolc (a gene in the loline biosynthesis pathway) was quantified using real-time RT-PCR, and loline concentration was quantified using gas chromatography and mass spectrometry. Artificially-damaged plants supported fewer live aphids, had greater lolc mRNA expression, and greater loline concentration than undamaged plants. Herbivore-damaged plants supported intermediate performance by aphids, low lolc mRNA expression, and minimal loline concentration. Our study is the first to demonstrate sexual endophytes can produce lolines following wounding. This suggests wound-induced responses are ancestral within the Epichloë / Neotyphodium clade and reveals a trait of grass endophytes that may have predisposed them for the evolution of defensive mutualisms with their hosts.     

Contribution of fungal loline alkaloids to protection from aphids in a grass-endophyte mutualism

Fungal endophytes provide grasses with enhanced protection from herbivory, drought, and pathogens. The loline alkaloids (saturated 1-aminopyrrolizidines with an oxygen bridge) are fungal metabolites often present in grasses with fungal endophytes of the genera Epichlo? or Neotyphodium. We conducted a Mendelian genetic analysis to test for activity of lolines produced in plants against aphids feeding on those plants. Though most loline-producing endophytes are asexual, we found that a recently described sexual endophyte, Epichlo? festucae, had heritable variation for loline alkaloid expression (Lol+) or nonexpression (Lol-). By analyzing segregation of these phenotypes and of linked DNA polymorphisms in crosses, we identified a single genetic locus controlling loline alkaloid expression in those E. festucae parents. We then tested segregating Lol+ and Lol- full-sibling fungal progeny for their ability to protect host plants from two aphid species, and observed that alkaloid expression cosegregated with activity against these insects. The in planta loline alkaloid levels correlated with levels of anti-aphid activity. These results suggested a key role of the loline alkaloids in protection of host plants from certain aphids, and represent, to our knowledge, the first Mendelian analysis demonstrating how a fungal factor contributes protection to plant-fungus mutualism.     

Mollusc herbivory influenced by endophytic clavicipitaceous fungal infections in grasses

Clavicipitaceous fungi of the genus Neotyphodium occur widely as mutualistic, systemic, seed‐borne infections in festucoid grasses. Grass infection by these fungi is associated with the presence of a range of secondary metabolites (SM), several of which have been demonstrated to confer to the plant resistance against herbivorous vertebrates and insects. An initial experiment demonstrated that endophytic infection by Neotyphodium can influence the utilisation of grasses by Deroceras, with feeding preferences and impact on plant yields affected differentially by endophytes with different SM profiles. The role of Neotyphodium SM in feeding preferences of Deroceras slugs were then evaluated in artificial diets. Among the indole diterpenoids tested, lolitrem B was demonstrated to reduce feeding, while diets containing paxilline, lolitriol, α‐paxitriol and β‐paxitriol tended to be preferred over that of untreated diet. The pyrrolopyrazine alkaloid peramine had no effect. Among the ergopeptine alkaloids tested in the diets, ergotamine and ergovaline were demonstrated to be phagostimulatory. These results with artificial diets were generally consistent with Deroceras reticulatum preferences among plants of known Neotyphodium endophyte strain and SM profile. Deroceras slugs obtained from sites containing contrasting frequencies of Neotyphodium‐infected grasses, exhibited differential responses to Neotyphodium SM incorporated into artificial diet. This study demonstrates that infection of grasses by different isolates of Neotyphodium endophytes differentially influence herbivory by molluscs, reflecting their SM profile. These results offer an explanation for variable acceptability of grasses to molluscs and their importance in the diet of molluscs in the field reported in previous studies in both natural and agricultural systems. Neotyphodium endophytes potentially offer novel approaches to management of mollusc pests in agricultural gramineous crops.     

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

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.     

Presence of Neotyphodium-like endophytes in European grasses

In order to improve knowledge of Neotyphodium‐likc fungi in European grasses, microscopic detection of endophytic mycelium was achieved in living grasses and in seeds. Samples of grasses were gathered near permanent pastures or along paths in France (93 samples, 13 genera, 22 species). Typical convoluted mycelium was found inside leaf sheaths of four genera, especially in Festuca and Lolium spp. The results suggest that endophytes were present most often in the southern regions where plants may suffer from summer drought. Endophytes were looked for in 489 seed samples (63 genera, 237 species) received from 24 European botanical gardens. Neotyphodium was found in seeds of only six genera (22 species), especially in Festuca (15 species) and Lolium (three species). No endophytic mycelium was found in the other 215 species, although other work had demonstrated the presence of the fungus in 39 of the species analysed. Neotyphodium‐likc mycelium was detected for the first time in Festuca juncifolia, F. trachyphylla, F. vaginata, F. pseudodalmatica, F. rupicaprina, F. arenaria, Vulpia ciliata and Micropyrum tenellum. Further studies are needed for the correct identification of the Neotyphodium species observed.     

The plant hormone salicylic acid interacts with the mechanism of anti‐herbivory conferred by fungal endophytes in grasses

The plant hormone salicylic acid (SA) is recognized as an effective defence against biotrophic pathogens, but its role as regulator of beneficial plant symbionts has received little attention. We studied the relationship between the SA hormone and leaf fungal endophytes on herbivore defences in symbiotic grasses. We hypothesize that the SA exposure suppresses the endophyte reducing the fungal‐produced alkaloids. Because of the role that alkaloids play in anti‐herbivore defences, any reduction in their production should make host plants more susceptible to herbivores. Lolium multiflorum plants symbiotic and nonsymbiotic with the endophyte Epichloë occultans were exposed to SA followed by a challenge with the aphid Rhopalosiphum padi. We measured the level of plant resistance to aphids, and the defences conferred by endophytes and host plants. Symbiotic plants had lower concentrations of SA than did the nonsymbiotic counterparts. Consistent with our prediction, the hormonal treatment reduced the concentration of loline alkaloids (i.e., N‐formyllolines and N‐acetylnorlolines) and consequently decreased the endophyte‐conferred resistance against aphids. Our study highlights the importance of the interaction between the plant immune system and endophytes for the stability of the defensive mutualism. Our results indicate that the SA plays a critical role in regulating the endophyte‐conferred resistance against herbivores.     

Peramine and other fungal alkaloids are exuded in the guttation fluid of endophyte-infected grasses

Many grasses live in association with asymptomatic fungi (Neotyphodium spp. endophytes), which grow in the intercellular spaces of the grass. These endophytes produce a range of alkaloids that protect the grass against grazing by mammals and insects. One of these alkaloids is an unusual pyrrolopyrazine, peramine. Peramine appears to be continuously produced by the endophyte, but does not progressively accumulate. No mechanism for the removal of peramine by its further metabolism or any other process has been reported. Our aim was to detect peramine or peramine metabolites in plant fluids to determine if peramine is mobilized, metabolized or excreted by the plant. We also wanted to determine if other fungal metabolites are mobilized by the plant, as has been proposed for the loline alkaloids.We developed a highly sensitive method for the analysis of peramine, using a linear ion trap mass spectrometer. We studied the fragmentation pathway of peramine using ESI MSⁿ and ESI FTICRMS. Based on these results we developed a single reaction monitoring method using the fragmentation of the guanidinium moiety. Cut leaf fluid and guttation fluid of different grass endophyte associations (Lolium perenne with Neotyphodium lolii, Festuca arundinacea with Neotyphodium coenophialum, and Elymus sp. with Epichloë sp.) were analysed. Peramine was detected in the cut leaf fluid of all grass-endophyte associations, but not in the guttation fluid of all associations. In some associations we also detected lolines and ergot peptide alkaloids. This is the first report showing the mobilization of fungal alkaloids into plant fluids by the host plant in grass-endophyte associations.     

Population studies of native grass-endophyte symbioses provide clues for the roles of host jumps and hybridization in driving their evolution

Fungal endophytes in the genera Epichloë and Neotyphodium, collectively termed the epichloae, have fascinated biologists for decades. These intriguing fungi, also referred to as ‘class 1 or clavicipitaceous endophytes’, spend the large majority, or even their entire life cycle, within the tissues of their cool‐season grass hosts without eliciting any symptoms of infection. While all epichloae reside within the intercellular spaces of aboveground vegetative grass tissues, the species at the symbiotic extreme are known as Neotyphodium, and the intimacy of their interaction extends to the reproductive (flowering) stage. At this point, fungal filaments (hyphae) nondestructively invade the developing ovaries of their host and are incorporated into perfectly viable, healthy seeds. Thus, these endophytes live solely within the tissues of their host plants and are transmitted maternally from generation to generation. A second life history characteristic of interest is that while all Epichloë and some Neotyphodium species are haploid, a great many of the strictly seed‐transmitted Neotyphodium spp. are interspecific hybrids. This phenomenon may be critical for the success of these symbioses over longer spans of evolutionary time and will be discussed in greater detail below. A third characteristic, and one of the primary reasons these grass endophytes have received so much attention over the last three decades, is the strong mutualistic nature these relationships often exhibit. In exchange for photosynthetically derived carbon, the endophytes protect their cool‐season grass hosts from grazing herbivores and a variety of abiotic stresses. It has been hypothesized that these three biological phenomena are related ( Schardl & Craven 2003 ), perhaps with the former two driving the third, and it is here that the recent article in Molecular Ecology entitled ‘Genetic diversity in epichloid endophytes of Hordelymus europaeus suggests repeated host jumps and interspecific hybridizations’, by Oberhofer & Leuchtmann (2012) , provides critical clues to linking these traits together. While the large majority of studies have focused on documenting the ever‐increasing list of mutualistic qualities attributed to these fungi, very few have taken an exhaustive population‐level approach to document plant and endophyte genotypes within a naturally occurring system ( Faeth et al. 2010 ; Jani et al. 2010 ; Tintjer & Rudgers 2006 ). Such information is crucial to more fully elucidate the factors shaping grass‐endophyte symbioses and those often driving these relationships to mutualistic extremes.     

Flowers for <Emphasis Type="Italic">Neotyphodium</Emphasis> endophytes detection: a new observation method using flowers of host grasses

Neotyphodium endophytes are vertically transmitted fungal symbionts of grasses. Being pest-repelling and growth-promoting agents for their hosts, and also potential mycotoxin producers, their detection in plants is important. Observation of chemically cleared flowers of infected grasses (Festuca arundinacea, F. pratensis, Lolium perenne, and L. multiflorum) using differential interference contrast microscopy revealed the existence of endophytes within immature ovaries of host plants. This observation method provides an accurate and easy way to detect and distinguish Neotyphodium endophytes in flowering host grasses and to investigate the seed transmission process, which is critical to their life cycle, and the practical use of infected plants.     

Conspicuous epiphytic growth of an interspecific hybrid Neotyphodium sp. endophyte on distorted host inflorescences

Selected Neotyphodium sp. endophytes are now commonly used to enhance pasture persistence and livestock productivity, with seed of perennial ryegrass and tall fescue cultivars with these selected endophytes being commercially available. In a large population of perennial ryegrass plants infected with a Neotyphodium sp. endophyte that was being grown for seed production a small percentage of inflorescences were distorted and covered with a conspicuous white mycelial growth. Within individual plants only a small number of inflorescences were affected and the amount of distortion differed between affected inflorescences. This Neotyphodium sp. is an interspecific hybrid of Epichloë typhina and Neotyphodium. lolii and like nearly all other Neotyphodium spp is symptomless in host grasses. The fungus isolated from distorted inflorescences had colonies that were identical to those isolated from symptomless inflorescences and these were characteristic of this Neotyphodium sp. This is the first report of distorted inflorescences covered with epiphytic hyphal growth on host grasses infected with an interspecific hybrid Neotyphodium sp.     

Evaluation of the potential role of water in spread of conidia of the Neotyphodium endophyte of Poa ampla

Neotyphodium endophytes are asexual, filamentous fungi, mutualistically associated with diverse cool season grasses. Infected seeds and vegetative organs of infected host plants are the only known modes of propagation of the asexual endophytes. In the last decade certain Epichloë and Neotyphodium-infected grass species have been shown to have epiphyllous structures of the endophytes, hyphae, conidiophores, and conidia, growing on leaf blades. The production of epiphyllous conidia suggests the possibility that some of these endophytes may have the ability for plant-to-plant spread. The objective of this study was to determine the possible mechanisms involved in liberation and dispersal of asexual spores of Neotyphodium growing in vitro and epiphyllously on leaves of Poa ampla. Our results indicate that water dispersal is the most likely means of dissemination of conidia of the Neotyphodium sp. Wind generated by dry compressed air does not dislodge the conidia from slide cultures or from P. ampla leaves.     

Metabolism or behavior: explaining the performance of aphids on alkaloid-producing fungal endophytes in annual ryegrass (<Emphasis Type="Italic">Lolium multiflorum</Emphasis>)

Plant–herbivore interactions are often mediated by plant microorganisms, and the “defensive mutualism” of epichloid fungal endophytes of grasses is an example. These endophytes synthesize bioactive alkaloids that generally have detrimental effects on the performance of insect herbivores, but the underlying mechanisms are not well understood. Our objective was to determine whether changes in the physiology and/or behavior of aphids explain the changes in performance of insects feeding on endophytic plants. We studied the interaction between the aphid Rhopalosiphum padi and the annual ryegrass Lolium multiflorum symbiotic (E+) or not symbiotic (E?) with the fungus Epichloë occultans that can synthesize loline alkaloids. We hypothesized that aphids feeding on E+ plants have higher energetic demands for detoxification of fungal alkaloids, thereby negatively impacting the individual performance, population growth, and structure. Aphids growing on E+ plants had lower values in morphometric and functional variables of individual performance, displayed lower birth rate, smaller population size, and dramatic structural changes. However, aphids exhibited lower values of standard metabolic rate (SMR) on E+ plants, which suggests no high costs of detoxification. Behavioral variables during the first 8 h of feeding showed that aphids did not change the phloem sap ingestion with the presence of fungal endophytes. We hypothesize that aphids may maintain phloem sap ingestion according to their fungal alkaloid tolerance capacity. In other words, when alkaloid concentrations overcome tolerance threshold, ingestion of phloem should decrease, which may explain the observed lower values of SMR in E+ feeding aphids.     

Gene flow in the endophyte Neotyphodium and implications for coevolution with Festuca arizonica

Arizona fescue (Festuca arizonica) often harbours asymptomatic, asexual endophytic fungi from the genus Neotyphodium. In agronomic grasses, Neotyphodium endophytes are often credited with a wide range of mutualistic benefits to its host many of which are related to fungal production of alkaloids for herbivore deterrence. Neotyphodium in the native grass Arizona fescue, however, usually produces alkaloids at levels too low to deter herbivores, and in general, does not behave mutualistically. This study uses microsatellite markers to examine rates of gene flow among four Arizona populations of Neotyphodium. Haplotypic diversity was generally low; only one population contained more than two haplotypes. Haplotypes carrying multiple loci for some or all of the microsatellite loci were also found, indicating a vegetative hybridization event between Neotyphodium and the grass choke pathogen from the genus Epichloë. Gene flow between Neotyphodium populations is very low, and likely much lower than the pollen mediated gene flow of its host. These differing rates of gene flow are predicted to create trait mismatching between endophyte and host and may explain the low, or lack of, alkaloid production by Neotyphodium in Arizona fescue and other native grass species.     

Loline alkaloid production by fungal endophytes of Fescue species select for particular epiphytic bacterial microflora

The leaves of fescue grasses are protected from herbivores by the production of loline alkaloids by the mutualist fungal endophytes Neotyphodium sp. or Epichloë sp. Most bacteria that reside on the leaf surface of such grasses can consume these defensive chemicals. Loline-consuming bacteria are rare on the leaves of other plant species. Several bacterial species including Burkholderia ambifaria recovered from tall fescue could use N-formyl loline as a sole carbon and nitrogen source in culture and achieved population sizes that were about eightfold higher when inoculated onto plants harboring loline-producing fungal endophytes than on plants lacking such endophytes or which were colonized by fungal variants incapable of loline production. In contrast, mutants of B. ambifaria and other bacterial species incapable of loline catabolism achieved similarly low population sizes on tall fescue colonized by loline-producing Neotyphodium sp. and on plants lacking this endophytic fungus. Lolines that are released onto the surface of plants benefiting from a fungal mutualism thus appear to be a major resource that can be exploited by epiphytic bacteria, thereby driving the establishment of a characteristic bacterial community on such plants.     

Potential antagnosim of cultivated and wild grass–endophyte associations towards Meloidogyne incognita

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