Rapid detection of fungal endophytes in grasses for large‐scale studies

Koh, Saewan; Vicari, Mark; Ball, John P.; Rakocevic, Tomo; Zaheer, Shahram; Hik, David S.; Bazely, Dawn R.

doi:10.1111/j.1365-2435.2006.01150.x

Cited by 24 publications

(41 citation statements)

References 25 publications

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“…We evaluated endophyte infection status of individual F. rubra plants by preserving samples in acidified alcohol (1:2 glacial acetic acid : 95% ethanol) and screening the pseudostem of each tiller for endophyte infection using a Phytoscreen Immunoblot Assay (Agrinostics Inc., Watkinsville, GA, USA) (Koh et al. 2006).…”

Section: Methodsmentioning

confidence: 99%

Environmental stresses mediate endophyte–grass interactions in a boreal archipelago

et al. 2010

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Summary1. Both evolutionary theory and empirical evidence from agricultural research support the view that asexual, vertically transmitted fungal endophytes are typically plant mutualists that develop high infection frequencies within host grass populations. In contrast, endophyte-grass interactions in natural ecosystems are more variable, spanning the range from mutualism to antagonism and comparatively little is known about their range of response to environmental stress. 2. We examined patterns in endophyte prevalence and endophyte-grass interactions across nutrient and grazing (from Greylag and Canada geese) gradients in 15 sites with different soil moisture levels in 13 island populations of the widespread grass Festuca rubra in a boreal archipelago in Sweden. 3. In the field, endophyte prevalence levels were generally low (range = 10-53%) compared with those reported from agricultural systems. Under mesic-moist conditions endophyte prevalence was constantly low (mean prevalence = 15%) and was not affected by grazing pressure or nutrient availability. In contrast, under conditions of drought, endophyte prevalence increased from 10% to 53% with increasing nutrient availability and increasing grazing pressure. 4. In the field, we measured the production of flowering culms, as a proxy for host fitness, to determine how endophyte-infected plants differed from uninfected plants. At dry sites, endophyte infection did not affect flowering culm production. In contrast, at mesic-moist sites production of flowering culms in endophyte-infected plants increased with the covarying effects of increasing nutrient availability and grazing pressure, indicating that the interaction switched from antagonistic to mutualistic. 5. A concurrent glasshouse experiment showed that in most situations, the host appears to incur some costs for harbouring endophytes. Uninfected grasses generally outperformed infected grasses (antagonistic interaction), while infected grasses outperformed uninfected grasses (mutualistic interaction) only in dry, nutrient-rich conditions. Nutrient and water addition affected tiller production, leaf number and leaf length differently, suggesting that tillers responded with different strategies. This emphasizes that several response variables are needed to evaluate the interaction. 6. Synthesis. This study found complex patterns in endophyte prevalence that were not always correlated with culm production. These contrasting patterns suggest that the direction and strength of selection on infected plants is highly variable and depends upon a suite of interacting environmental variables that may fluctuate in the intensity of their impact, during the course of the host life cycle.

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Section: Methodsmentioning

confidence: 99%

Environmental stresses mediate endophyte–grass interactions in a boreal archipelago

et al. 2010

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“…One set of subsamples was tested for endophytic infection using a field immunoblot assay to detect monoclonal antibodies specific to Neotyphodium (Phytoscreen Immunoblot Kit #ENDO7973, Agrinostics, Watkinsville, Georgia, USA; see also Koh et al 2006). At each of the distances, we flagged individual F. altaica tussocks and selected one tiller from the edge of a tussock.…”

Section: Methodsmentioning

confidence: 99%

Herbivory Mediates Grass–endophyte Relationships

Koh¹,

Hik

2007

Ecology

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Endophytic fungi are plant symbionts living asymptomatically within plant tissues. Neotyphodium spp., which are asexual vertically transmitted systemic fungal endophytes of cool-season grasses, are predicted to be plant mutualists. These endophytes increase host plant resistance to environmental stresses and/or increase the production of alkaloid-based herbivore deterrents. The ubiquity of this defense mutualism is unclear, and a variety of alternative mechanisms may explain the observed variation in infection rates, levels of deterrence, and the maintenance of asexual endophytes in grass populations. We found that grass-endophyte interactions are variable and ordered along an herbivory gradient in an undisturbed subarctic alpine ecosystem. Native grass populations in grazed sites had significantly greater frequency of Neotyphodium infection compared to ungrazed sites. Tillers from grazed sites had significantly higher hyphal densities compared to ungrazed sites. The ability of grass-Neotyphodium constituents to deter vertebrate herbivory in natural systems is thought to be rare. In grazed meadows, we showed that endophyte infection resulted in the deterrence of grazing by native vertebrate herbivores. However, the same herbivores did not distinguish between infected and uninfected grass harvested from ungrazed areas. These results demonstrate that the relationship between vertically transmitted endophytes and grasses in the alpine tundra vary greatly within populations. This may be based in part on defense mutualism and is consistent, under varying levels of herbivory, with the predictions of optimal defense theory.

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“…From the parts that had been left when the grasses were cut to remove the aphids, a cross section of the base tiller was extracted with a razor blade. After carrying out the assay, the immunoblot card was photographed with a Canon EOS 350D digital camera and the tiller tissue imprints were analysed for colour intensity as described by Koh et al (2006). The measured intensity was compared with the reference sample of Neotyphodium provided on the immunoblot card.…”

Section: (B) Experimentsmentioning

confidence: 99%

Endophytic fungi decrease available resources for the aphid Rhopalosiphum padi and impair their ability to induce defences against predators

Züst

Härri

Müller

2007

Ecological Entomology

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Abstract1. The production of winged morphs is a well known mechanism of induced defence in aphids to escape from natural enemies, and is also a reaction to poor resource quality. 2. Host plants of aphids often associate with endophytic fungi that have been shown to reduce the fitness of some species of aphids. 3. It was hypothesised that endophyte infection of host plants that represent a low quality plant resource should increase the aphid's induced response to a predator because both low plant quality and predator presence represent a stronger cue for wing production than predator presence alone. 4. In a laboratory experiment, bird cherry-oat aphids Rhopalosiphum padi L. were exposed to the factors predator threat and endophyte infection and the effects of these factors on the proportion of winged morphs produced by the aphid colonies was analysed. 5. The presence of endophytic fungi strongly decreased aphid colony sizes. When a predator threat was present, all colonies on endophyte-free grasses produced winged morphs whereas only a few colonies were able to produce winged morphs on endophyteinfected grasses. However, these few colonies produced larger proportions of winged morphs than colonies on endophyte-free grasses. Without a predator threat, no colonies on endophyte-infected grasses produced any winged morphs. 6. These results show that aphids in stressed conditions and with reduced fitness will only invest in inducible defences when predators are present but are unable to produce winged morphs in response to endophyte presence. Abstract1. The production of winged morphs is a well known mechanism of induced defence in aphids to escape from natural enemies, and is also a reaction to poor resource quality.2. Host plants of aphids often associate with endophytic fungi that have been shown to reduce the fitness of some species of aphids.3. We hypothesised that endophyte infection of host plants that represents a low quality plant resource should increase the aphid's induced response to a predator because both, low plant quality and predator presence represent a stronger cue for wing production than predator presence alone.4. In a laboratory experiment bird cherry-oat aphids Rhopalosiphum padi L. were exposed to the factors 'predator threat' and 'endophyte infection' and the effects of these factors on the proportion of winged morphs produced by the aphid colonies was analysed.5. The presence of endophytic fungi strongly decreased aphid colony sizes. When a predator threat was present all colonies on endophyte-free grasses produced winged morphs whereas only a few colonies were able to produce winged morphs on endophyte-infected grasses.However, these few colonies produced larger proportions of winged morphs than colonies on endophyte-free grasses. Without a predator threat, no colonies on endophyte-infected grasses produced any winged morphs.6. These results show that aphids in stressed conditions and with reduced fitness will only invest in inducible defences when predators are present but are unable to pr...

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Rapid detection of fungal endophytes in grasses for large‐scale studies

Cited by 24 publications

References 25 publications

Environmental stresses mediate endophyte–grass interactions in a boreal archipelago

Environmental stresses mediate endophyte–grass interactions in a boreal archipelago

Herbivory Mediates Grass–endophyte Relationships

Endophytic fungi decrease available resources for the aphid Rhopalosiphum padi and impair their ability to induce defences against predators

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