Showing papers on "Neotyphodium published in 1998"

Influence of phosphorus on the growth and ergot alkaloid content of Neotyphodium coenophialum-infected tall fescue (Festuca arundinacea Schreb.)

Abstract: Tall fescue (Festuca arundinacea Schreb.) plants infected by the fungal endophyte Neotyphodium coenophialum (Morgan-Jones & Gams) (Glenn et al., 1996) often perform better than noninfected plants, especially in marginal resource environments. There is a lack of information about endophyte related effects on the rhizosphere of grasses. In a greenhouse experiment, four endophyte-infected (E+) tall fescue clones (DN2, DN4, DN7, DN11) and their endophyte-free (E−) forms were grown in limed (pH 6.3) Porter soil (low fertility, acidic, high aluminum and low phosphorus content, coarse-loamy mixed mesic Umbric Dystrochrept) at three soil P levels (17, 50, and 96 mg P kg-1 soil) for five months. Excluding the genotype effect, endophyte infection significantly increased cumulative herbage DM yield by 8% at 17 mg P kg-1 soil but reduced cumulative herbage DM yield by 12% at 96 mg P kg-1 soil. With increased P availability in the soil, shoot and root DM, and root/shoot ratio in E+ plants were significantly less when compared to E− plants. Endophyte infection increased specific root length at 17 and 50 mg P kg-1soil. At soil P level of 17 mg P kg-1soil, E+ plants had significantly higher P concentrations both in roots and shoots. Similar relationships were found for Mg and Ca. E+ plants had significantly higher Zn, Fe, and Al concentration in roots, and lower Mn and Al concentration in shoots when compared to E− plants. Ergot alkaloid concentration and content in shoot of E+ plants increased with increasing P availability in the soil from 17 to 50 mg P kg-1 but declined again at 96 mg P kg-1 soil. Ergot alkaloid accumulation in roots increased linearly with P availability in the soil. Results suggest that endophyte infection affects uptake of phosphorus and other mineral nutrients and may benefit tall fescue grown on P-deficient soils. Phosphorus seems also to be involved in ergot alkaloid accumulation in endophyte-infected tall fescue.

Endophytic fungi in indigenous Australasian grasses associated with toxicity to livestock.

Abstract: Grazing of Echinopogon spp. by livestock in Australia has caused symptoms similar to those of perennial ryegrass staggers. We observed an endophytic fungus in the intercellular spaces of the leaves and seeds of New Zealand and Australian specimens of Echinopogon ovatus. Culture of surface-sterilized seeds from New Zealand specimens yielded a slow-growing fungus. An examination in which immunoblotting and an enzyme-linked immunosorbent assay (ELISA) were used indicated that E. ovatus plants from Australia and New Zealand were infected with fungi serologically related to Neotyphodium lolii (the endophyte of perennial ryegrass) and other Epichloe and Neotyphodium spp. endophytic in pooid grasses. No lolitrems (the indole-diterpenoids implicated as the causative agents of perennial ryegrass staggers), peramine analogs, or ergot alkaloids were detected in the infected specimens by high-performance liquid chromatography or ELISA. However, in endophyte-infected E. ovatus plants from New Zealand, analogs of the indole-diterpenoid paxilline (thought to be a biosynthetic precursor of the lolitrems and related tremorgens) were detected by ELISA, and N-formylloline was detected by gas chromatography. Endophyte-free specimens of New Zealand E. ovatus did not contain detectable paxilline analogs or lolines and were more palatable than infected specimens to adults of the pasture pest Listronotus bonariensis (Argentine stem weevil). Hyphae similar to those of the E. ovatus endophyte were also found in herbarium specimens of Echinopogon nutans var. major, Echinopogon intermedius, Echinopogon caespitosus, and Echinopogon cheeli. This appears to be the first time that an endophytic Neotyphodium species has been identified in grasses endemic to New Zealand or Australia.

Extraordinary Ribosomal Spacer Length Heterogeneity in a Neotyphodium Endophyte Hybrid: Implications for Concerted Evolution

Abstract: An extraordinary level of length heterogeneity was found in the ribosomal DNA (rDNA) of an asexual hybrid Neotyphodium grass endophyte, isolate Lp1. This hybrid Neotyphodium endophyte is an interspecific hybrid between two grass endophytes, Neotyphodium lolii, and a sexual form, Epichloe typhina, and the length heterogeneity was not found in either of these progenitor species. The length heterogeneity in the hybrid is localized to the intergenic spacer (IGS) and is the result of copy-number variation of a tandemly repeated subrepeat class within the IGS, the 111-/119-bp subrepeats. Copy number variation of this subrepeat class appears to be a consequence of mitotic unequal crossing over that occurs between these subrepeats. This implies that unequal crossing over plays a role in the concerted evolution of the whole rDNA. Changes in the pattern of IGS length variants occurred in just two rounds of single-spore purification. Analysis of the IGS length heterogeneity revealed features that are unexpected in a simple model of unequal crossing over. Potential refinements of the molecular details of unequal crossing over are presented, and we also discuss evidence for a combination of homogenization mechanisms that drive the concerted evolution of the Lp1 rDNA.

Influence of the endophyte (Neotyphodium lolii) on morphology, physiology, and alkaloid synthesis of perennial ryegrass during high temperature and water stress

Abstract: The influence of the endophyte (Neotyphodium lolii) on morphology and physiology of perennial ryegrass (Lolium perenne) ’Grasslands Nui’ was examined in a replicated glasshouse experiment. Ryegrass plants either free of endophyte or infected with its endemic endophyte (wildtype) or AR6 (low lolitrem B‐producing endophyte strain) were grown under combinations of water (well watered versus water stressed) and temperature (25°C (hot) average versus 20°C (low) average) treatments. Endophyte‐free plants had significantly higher shoot and total weight, higher water use and water use efficiency, and were more wilted than endophyte‐infected plants. There was a significant (P < 0.05) endophyte × temperature interaction and endophyte × temperature × water interaction for lolitrem B concentration and wilt score, and the endophyte × water interaction was significant (P < 0.05) for ergovaline concentration and wilt score.

Isolation of Lolicine A, Lolicine B, Lolitriol, and Lolitrem N from Lolium perenne Infected with Neotyphodium lolii and Evidence for the Natural Occurrence of 31-Epilolitrem N and 31-Epilolitrem F.

Abstract: Lolicines A (1a) and B (2a), late-eluting lolitrem-like compounds, were identified in extracts of perennial ryegrass (Lolium perenne) seed that was infected with the endophytic fungus Neotyphodium lolii. The lolicines were isolated as their 11-O-propionates (1b and 2b) and their structures determined by mass spectrometry and one- and two-dimensional NMR spectroscopy. The structures of lolicines A and B were similar to those of paspaline (5a) and paspaline B (5b), compounds known to be biosynthetic precursors of several groups of more complex indole−diterpenoids, suggesting that the lolicines might be biosynthetic precursors of the lolitrem group of indole−diterpenoid neurotoxins. During purification of 1b and 2b, a third compound, lolitrem N (4c), was isolated as its propionate (4d) and identified as 35-epilolitriol. A further late-eluting compound was isolated as its acetate from the same fraction as the lolicines. This compound was found to be identical with lolitriol 10-O-acetate (4b) prepared from lol...

Influence of Neotyphodium coenophialum on copper concentration in tall fescue.

Abstract: Poor performance of livestock that graze tall fescue (Festuca arundinacea Schreb.) has been associated with the endophyte fungus Neotyphodium coenophialum [Morgan-Jones and Gams] Glenn, Bacon, and Hanlin). Recent evidence suggests lowered Cu status and a depression of Cu-related immune function in steers that graze endophyte-infected (E+) tall fescue. Greenhouse and field studies investigated relationships between the endophyte and Cu concentrations in tall fescue. Seventeen infected 'Kenhy' clones were divided, and one plant of each pair was treated three times with Benomyl to remove the endophyte (E-). Plants were watered with nutrient solution in a greenhouse for 6 mo before sampling. Copper concentrations were greater (P 70% infection level) and E- (< 5% infection level) tall fescue were grown in Virginia at two locations with three rates of N fertilizer. Copper concentrations were higher (P < .05) in E- than in E+ tall fescue (4.8 vs 4.5 microg/g; SE, .1) and increased (P < .01) linearly in response to N. Our data demonstrate that the presence of the endophyte is associated with lower Cu concentrations in tall fescue, which may contribute to lowered Cu status in animals and thus contribute to the etiology of fescue toxicity.

A PCR-Based Technique for Detection of Neotyphodium Endophytes in Diverse Accessions of Tall Fescue

Abstract: A previously described polymerase chain reaction (PCR)-based method used for detection of Neotyphodium coenophialum in tall fescue detected Neotyphodium endophytes in some, but not all, infected plants from a geographically diverse sample. In the study reported here, a different set of primers, based on intervening sequences of the tubulin 2 gene, were prepared and used for PCR. PCR with these primers yielded the expected 444 base pair amplification product with DNA from 104 of the 106 infected accessions tested. In addition, one accession originally scored as endophyte-free on the basis of a tissue culture test was correctly rated as endophyte-infected using the PCR procedure. Results suggest that primers based on intervening sequences of the tubulin 2 gene can be used for PCR-based detection of Neotyphodium endophytes in tall fescue accessions of diverse origin.

Changes in Neotyphodium coenophialum infestation levels in tall fescue pastures due to different grazing pressures

Abstract: Infection of tall fescue (Festuca arundinacea Schreb.) with the mutualistic fungal endophyte Neotyphodium coenophialum (Morgan-Jones & Gams) Glenn, Bacon & Hanlin results in numerous biochemical and physiological changes that increase host persistence. This study was conducted to determine effects of steer (Bos taurus L.) grazing on changes in endophyte infestation levels of tall fescue pastures. Eighteen 1.2-ha pastures were seeded in 1992 in 20-cm drill rows involving combinations of high, medium, or low grazing pressure and 'Ky 31' tall fescue infested with N. coenophialum at four levels ranging from endophyte-free (E - ) to 80% infestation (E + ). Pastures were grazed for about 10 mo. each year from fall 1993 until summer 1996, although animals on some of the high grazing pressure pastures occasionally had to be removed because of insufficient forage. Endophyte levels were monitored yearly with protein-A sandwich enzyme-linked immunosorbent assay (PAS-ELISA). Stand density of tall fescue remained satisfactory throughout the study. After 2 yr, endophyte infestation levels in low grazing pressure pastures were at the same level as at the beginning of the study, and E + levels remained constant in all pastures that started at high E + , regardless of grazing pressure. However, in high and medium grazing pressure pastures, E + levels increased by 20 to 30%. Based on these data, we conclude that moderate and high grazing pressures influence endophyte infestation level of pastures and must be taken into account when designing pasture management systems.

Influence of the ryegrass endophyte (Neotyphodium lolii) in a cool moist environment IV. Plant parasitic nematodes

Abstract: The influence of the ryegrass endophyte on plant‐parasitic nematodes in a cool moist environment in New Zealand was evaluated in a pot and a grazing experiment. Nematodes of the genus Paratylenchus made up 99% of the fraction of plant‐parasitic nematodes and their numbers were higher (P > 0.05) on endophyte‐free plants in the pot experiment and in fields containing mono‐cultures of endophyte‐free ryegrass. Nui endophyte‐free plants and pastures had higher dry matter yields than endophyte‐infected plants and pastures. The effect of endophyte strains on nematodes was inconclusive.

Occurrence of the fungal endophyte Neotyphodium coenophialum in leaf blades of tall fescue and implications for stock health

Abstract: Leaf blades of tall fescue (Festuca arundinaced) plants infected with the endophytic fungus Neotyphodium coenophialum (= Acre‐monium coenophialum) have often been assumed to be endophyte‐free. However, fungal colonies identified as N. coenophialum developed following incubation of surface‐sterilised leaf blades from endophyte‐infected tall fescues on antibiotic potato dextrose agar. A standardised fungal isolation technique was developed to assess the distribution of hyphae within tall fescue leaf blades in three USA‐bred cultivars ('Georgia 5’, ‘Kentucky 31’, ‘Jesup') and a roadside population (MRSP) from the Manawatu region, New Zealand. Leaf blades of the three USA‐bred cultivars were typically sparsely colonised. In contrast, extensively colonised leaf blades were present in many MRSP plants, particularly in autumn. Ergovaline concentrations of up to 3.9 ppm (mean 2.5) were present in leaf blades of the MRSP grown in a glasshouse. Ergovaline at lower concentrations (mean 0.4 ppm) was also det...

Influence of the ryegrass endophyte (Neotyphodium lolii) in a cool‐moist environment III. Interaction with white clover

Abstract: White clover was grown together with either endophyte‐free or endophyte‐infected (strain either AR6 or wildtype) Nui ryegrass under four environmental conditions (covering low or moderate temperatures, moist or draughted soil, clippings removed or returned) in a glasshouse experiment. The presence of wildtype endophyte in ryegrass plants had in general, but especially under optimal growing conditions, a significant positive effect (P < 0.05) on white clover stolon length, number of growing points, and the number of nodules. No endophyte effect was observed on the distribution of nodules over root depth, size, and colour classes under any environment. It is postulated that endophyte‐associated compounds in root leachates may have an effect on mycorrhiza, the size of the effect increasing with the level of abiotic stress to which ryegrass plants are subjected.

A new group of endophytes in European grasses

Abstract: Summary Poaceae of subfamily Festucoideae frequently harbour endophytic, symbiotic fungi in their aerial parts. Isolations were made from 21 different species of Poaceae, belonging mainly to the genera Lolium and Festuca. Pure cultures of 45 fungal isolates were obtained. Morphology, isozyme and molecular analysis showed the presence of three groups of endophytes. Most of the isolates could be accommodated with the previously described species of Neotyphodium and Epichloe (the e endophytes). Two new endophytes isolated from Koeleria cristata and Melica ciliata were shown to belong to this group. Gliocladium like and Phialophora like isolates were obtained from Lolium perenne and Festuca gigantea respectively (the p endophytes). Nine isolates especially those from annual Lolium produced rod like conidia. These isolates belong to Acremonium sensu stricto and are morphologically similar to Acremonium chilense.

Nutritional requirements for growth of fungal endophytes of grasses

Abstract: Fifteen isolates of fungal endophytes of grasses were studied for their ability to metabolize different sources of carbon and nitrogen. These endophytes had been isolated from 12 different species of Poaceae and included Clavicipitaceae with or without a teleomorph (genera Epichloe and Neotyphodium, respectively) and species belonging to the genus Acremonium sensu stricto (Acremonium chilense-like). Pectin and cellulose as carbon sources and tryptophan and methionine as nitrogen sources appeared to support poorly the growth of most isolates. Hexoses, disaccharides, complex nitrogen sources, asparagine, and glutamine supported growth of all isolates. The isolates of genus Neotyphodium were characterized by limited growth whatever the substrate, the inhibition of their growth by high concentrations of glucose and fructose, and their inability to assimilate pentoses (xylose, arabinose) and nitrates. The isolates of genus Epichloe showed better growth than those of the previous group and their growth was not ...