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Context: Data are lacking on the effects of selected endophytes of perennial ryegrass (Lolium perenne L.) on ryegrass persistence. Aim: We aimed to determine the impact of Epichloë endophyte on the persistence of mid- and late-heading perennial ryegrass cultivars. Method: Two mid-heading (Samson, Bronsyn) and two late-heading (One50, Rohan) cultivars, infected with selected endophytes (AR37, nea2/6) or with standard toxic endophyte, were established in a replicated plot study grazed by cattle in a subtropical environment of the upper North Island of New Zealand. Persistence characteristics were quantified at least five times per annum, over 4 years. Key results: Endophyte strain had an effect on persistence; infection with standard endophyte resulted in higher ryegrass ground cover percentage, ryegrass content in pasture dry matter and autumn yield than infection with nea2/6 on many occasions, and with AR37 on some occasions. There were negligible impacts on ryegrass tiller density or nutritive value. Trends were dominated by the main effect of endophyte; interactions with heading date were inconsistent. Conclusions: Cultivars were more persistent when infected with standard endophyte than with selected endophytes, although persistence declined over 4 years for all cultivars and irrespective of heading date. Implications: Reliance on selected endophyte is unlikely to prevent persistence decline of perennial ryegrass in a subtropical environment. Other strategies will be required to maintain the persistence of high-quality pastures based on perennial ryegrass. We determined the impact of endophyte strain (standard toxic endophyte, selected strains nea2/6 and AR37), on the persistence of four perennial ryegrass cultivars. Standard endophyte resulted in greater persistence than the selected endophytes, with higher ryegrass ground cover percentage and content in pasture dry matter by the end of the study, and higher herbage yields in autumn. Persistence declined over 4 years for all cultivars, regardless of endophyte. [ABSTRACT FROM AUTHOR]

Many temperate grasses are both hyper‐accumulators of silicon (Si) and hosts of Epichloë fungal endophytes, functional traits which may alleviate environmental stresses such as herbivore attack. Si accumulation and endophyte infection may operate synergistically, but this has not been tested in a field setting, nor in the context of changing environmental conditions. Predicted increases in atmospheric CO2 concentrations can affect both Si accumulation and endophyte function, but these have not been studied in combination.We investigated how elevated atmospheric CO2 (eCO2), Si supplementation, endophyte‐presence and insect herbivory impacted plant growth, stoichiometry (C, N, P and Si), leaf gas exchange (rates of photosynthesis, stomatal conductance, transpiration rates) and endophyte production of anti‐herbivore defences (alkaloids) of an important pasture grass (tall fescue; Lolium arundinaceum) in the field.eCO2 and Si supplementation increased shoot biomass (+52% and +31%, respectively), whereas herbivory reduced shoot biomass by at least 35% and induced Si accumulation by 24%. Shoot Si concentrations, in contrast, decreased by 17%–21% under eCO2. Si supplementation and herbivory reduced shoot C concentrations. eCO2 reduced shoot N concentrations which led to increased shoot C:N ratios. Overall, shoot P concentrations were 26% lower in endophytic plants compared to non‐endophytic plants, potentially due to decreased mass flow (i.e. observed reductions in stomatal conductance and transpiration). Alkaloid production was not discernibly affected by any experimental treatment. The negative impacts of endophytes on P uptake were particularly strong under eCO2.We show that eCO2 and insect herbivory reduce and promote Si accumulation, respectively, incorporating some field conditions for the first time. This indicates that these drivers operate in a more realistic ecological context than previously demonstrated. Reduced uptake of P in endophytic plants may adversely affect plant productivity in the future, particularly if increased demand for P due to improved plant growth under eCO2 cannot be met. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Aphids are major pests of cereal and pasture grasses throughout the world, vectoring disease and reducing plant production. There are few control options other than insecticides. Epichloë endophytes that produce loline alkaloids in their hosts provide a possible mechanism of control, with both meadow fescue and tall fescue naturally infected with loline-producing endophytes showing a resistance to Rhopalosiphum padi. We screened Elymus spp. naturally infected with endophytes that produced loline alkaloids at concentrations known to affect aphids on fescue but found no effect on these insects infesting Elymus. A synthetic loline-producing endophyte association with rye also had no effect on the aphids. After hypothesizing that the lolines were being translocated in the xylem in Elymus and rye rather than the phloem, we tested the rye and meadow fescue infected with loline-producing endophytes against a xylem feeding spittlebug. The endophyte in rye inhibited the feeding of the insect and reduced its survival, whereas the endophyte-infected meadow fescue had no effect on the spittlebug but reduced the number of aphids. Lolines applied to the potting medium of endophyte-free and endophyte-infected rye, ryegrass, and tall fescue resulted in a decrease in the aphid populations on the endophyte-free pasture grasses relative to the untreated controls but had no effect on aphid numbers on the rye. We tentatively conclude that lolines, produced in both natural and synthetic association with Elymus and rye, are partitioned in the xylem rather than the phloem, where they are inaccessible to aphids. [ABSTRACT FROM AUTHOR]

In identifying endophytes for use in pastures in New Zealand there have been two strategies used, either exclusion of ergopeptine and lolitrem alkaloids or, retaining some ergopeptine expression to enhance the stability of natural defences against invertebrate pests. Both have their strengths and weaknesses. It is a matter of balancing these to ensure the end-user has access to a product that satisfies their needs – a persistent pasture with low to nil animal toxicity in terms of animal production and welfare. The range and intensity of ergot alkaloids in grazed pasture on both pasture and ruminants is reviewed, with emphasis on New Zealand. Ergot alkaloids associated with pasture are produced by associations between certain Epichloë endophyte strains and temperate grasses. Ergot alkaloids have been shown to improve persistence of pasture through providing resistance/deterrence to insect pests as well as deterring grazing animals. However, ergovaline is toxic to grazing animals. Some commercially available ryegrass-endophyte associations can produce ergovaline concentrations close to those found in associations between ryegrass and the standard endophyte. It is feasible to eliminate ergot alkaloids from pasture grasses in New Zealand as endophyte strains are commercially available that do not express ergovaline and yet still provide excellent pest resistance. [ABSTRACT FROM AUTHOR]

Grasses have developed a wide range of morphological and physiological mechanisms to resist herbivory. For instance, they accumulate silicon (Si) in tissue, as physical defence, and associate symbiotically with foliar Epichloë‐endophytes that provide chemical defence via antiherbivore alkaloids. Recent evidence showed that some Epichloë‐endophytes increase foliar Si in forage grasses; however, whether this impacts insect herbivores is unknown. Furthermore, while Si is primarily a physical defence, it also affects production of plant defensive secondary metabolites; Si supply might therefore affect Epichloë‐alkaloids, although this remains untested.We grew endophyte‐free (Nil) and Epichloë‐infected tall fescue and perennial ryegrass in a factorial combination with or without Si supplementation, in the absence or presence of Helicoverpa armigera. Epichloë‐endophyte strains were AR584 for tall fescue, and AR37, AR1 or Wild‐type (WT) for perennial ryegrass. We assessed how Si supply and Epichloë‐endophytes in interaction with herbivory affected foliar Si and mutualist‐derived alkaloid concentrations. Subsequently, their effects on H. armigera relative growth rates (RGRs) were evaluated.Endophytes generally increased Si concentrations in Si‐supplied plants. In tall fescue AR584 and perennial ryegrass AR37, endophytes increased constitutive (herbivore‐free) and induced (herbivore‐inoculated) Si concentrations by at least 25%; in contrast, in perennial ryegrass, the AR1 endophyte only increased constitutive levels. Si supply did not affect alkaloids produced by AR584 or AR1/WT endophytes; however, in the presence of herbivory, Si supply decreased the induction of alkaloids produced by AR37 endophytes by 33%. For tall fescue, Si supply reduced H. armigera RGR by at least 76%, regardless of endophytic status, whereas, endophyte‐alkaloids played a secondary role only reducing herbivore growth in the absence of Si supply. Conversely, in perennial ryegrass, both Si and endophyte‐alkaloids (regardless of Si supply) reduced herbivore RGR although not synergised.Novel interactions between constitutive and induced Si‐ and alkaloid‐based antiherbivore defences in grasses were observed. Overall, Si had a greater effect on the folivore than endophytes in both grasses. Endophyte defences contributed more to herbivore resistance in perennial ryegrass than tall fescue. We demonstrate that Si and endophytes were not antagonistic and highlight that the protective nature of their interaction varies with the grass‐endophyte species tested. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

The root-feeding scarab insect Costelytra giveni causes severe damage to pasture ecosystems in New Zealand. Loline alkaloids produced by some Epichloë endophytes deter this insect. In two experiments, tall fescue infected with E. coenophiala, strain AR584, and endophyte-free (Nil) controls were subjected to pulse drought stress (DS) or well-watered conditions (WW). The second experiment also included meadow fescue infected with E. uncinata. After 4–6 weeks exposure to the different conditions, roots were excised and fed to C. giveni larvae for 7 days. Relative root consumption (RC), frass production, and relative weight change (RWC) of larvae were measured and the loline content of roots determined. RC and frass output were higher for larvae feeding on Nil DS tall fescue than WW and reduced by AR584. RWC was also greater on DS than on WW Nil plants but reduced by endophyte only in DS plants. RC, frass output, and RWC of larvae were reduced by endophyte in DS and WW meadow fescue, but the effect was greater for WW plants. Loline alkaloid concentration in roots was significantly higher in DS than WW tall fescue in Experiment I but higher in WW than DS meadow fescue in Experiment II. These experiments have demonstrated that moisture status interacts with endophyte to differentially affect root herbivory in tall fescue and meadow fescue. [ABSTRACT FROM AUTHOR]

Water deficit stress largely limits plant growth and survival in natural and managed ecosystems. We studied the morpho-physiological responses of plants associated with distinct strains of Epichloë fungal endophytes to water deficit. We hypothesised that Epichloë symbionts would alleviate the negative effects of water deficit on plants and that both magnitude and mechanisms of endophyte-based alleviation would vary depending on the Epichloë strain. Perennial ryegrass (Lolium perenne) plants from the experimental cultivar GA66 associated with the Epichloë strains AR1, AR5, AR6, and AR37 were subjected to a treatment of sustained water deficit in a pot experiment under controlled growth conditions. We measured plant biomass (shoot and root), water retention, stress-related phytohormones (abscisic acid, jasmonic acid), proline and other water-soluble amino acids, and Epichloë -derived antiherbivore alkaloids. Alleviation of the negative effects of water deficit on plants depended on the Epichloë strain, with AR37 and AR5 providing the greatest protection followed by AR1, while AR6 did not alleviate stress. The AR37-derived water deficit alleviation was associated with enhanced root biomass and plant water retention, and increased concentrations of abscisic acid, proline, and fungal alkaloids. The AR5-derived stress alleviation was associated with enhanced plant water retention and increased proline concentrations, and the AR1-derived alleviation with increased fungal alkaloid concentrations and mycelial biomass. Although AR6 did not alleviate the water deficit, the stress increased Epichloë -derived alkaloid concentrations (and enhanced root biomass) which could provide an advantage for resisting herbivory. Our study highlighted that while Epichloë generally alleviated the effects of water deficit on plants, the mechanisms of stress alleviation varied among associations, and that the host fitness could be increased even in those associations where endophytes did not alleviate direct water deficit stress if herbivores would be present. • Epichloë fungal strains alleviated plant water deficit stress via varied mechanisms. • AR37 increased root biomass, water retention, ABA, proline, and fungal alkaloids. • AR5 increased plant water retention and proline. • AR1 increased fungal alkaloids and mycelial biomass. • AR6 increased root biomass and fungal alkaloids. [ABSTRACT FROM AUTHOR]