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Asexual Epichloë are endophytic fungi that form mutualistic symbioses with cool-season grasses, conferring to their hosts protection against biotic and abiotic stresses. Symbioses are maintained between grass generations as hyphae are vertically transmitted from parent to progeny plants through seed. However, endophyte transmission to the seed is an imperfect process where not all seeds become infected. The mechanisms underpinning the varying efficiencies of seed transmission are poorly understood. Host gene expression in response to Epichloë sp. LpTG-3 strain AR37 was examined within inflorescence primordia and ovaries of high and low endophyte transmission genotypes within a single population of perennial ryegrass. A genome-wide association study was conducted to identify population-level single nucleotide polymorphisms (SNPs) and associated genes correlated with vertical transmission efficiency. For low transmitters of AR37, upregulation of perennial ryegrass receptor-like kinases and resistance genes, typically associated with phytopathogen detection, comprised the largest group of differentially expressed genes (DEGs) in both inflorescence primordia and ovaries. DEGs involved in signaling and plant defense responses, such as cell wall modification, secondary metabolism, and reactive oxygen activities were also abundant. Transmission-associated SNPs were associated with genes for which gene ontology analysis identified "response to fungus" as the most significantly enriched term. Moreover, endophyte biomass as measured by quantitative PCR of Epichloë non-ribosomal peptide synthetase genes, was significantly lower in reproductive tissues of low-transmission hosts compared to high-transmission hosts. Endophyte seed-transmission efficiency appears to be influenced primarily by plant defense responses which reduce endophyte colonization of host reproductive tissues. [ABSTRACT FROM AUTHOR]

Background. Plants possess a sophisticated immune system to defend from herbivores. These defence responses are regulated by plant hormones including salicylic acid (SA) and jasmonic acid (JA). Sometimes, plant defences can be complemented by the presence of symbiotic microorganisms. A remarkable example of this are grasses establishing symbiotic associations with Epichloë fungal endophytes. We studied the level of resistance provided by the grass' defence hormones, and that provided by Epichloë fungal endophytes, against an introduced herbivore aphid. These fungi protect their hosts against herbivores by producing bioactive alkaloids. We hypothesized that either the presence of fungal endophytes or the induction of the plant salicylic acid (SA) defence pathway would enhance the level of resistance of the grass to the aphid. Methods. Lolium multiflorum plants, with and without the fungal endophyte Epichloë occultans, were subjected to an exogenous application of SA followed by a challenge with the aphid, Sipha maydis. Results. Our results indicate that neither the presence of E. occultans nor the induction of the plant's SA pathway regulate S. maydis populations. However, endophytesymbiotic plants may have been more tolerant to the aphid feeding because these plants produced more aboveground biomass. We suggest that this insect insensitivity could be explained by a combination between the ineffectiveness of the specific alkaloids produced by E. occultans in controlling S. maydis aphids and the capacity of this herbivore to deal with hormone-dependent defences of L. multiflorum. [ABSTRACT FROM AUTHOR]

Perennial ryegrass is an important pasture, forage and turf plant, and in New Zealand, it is commonly and intentionally inoculated with selected beneficial endophyte strains. These endophytes provide enhanced traits to their host grasses with AR37, a market leading strain, conferring a broad spectrum of insect deterrence coupled with excellent animal performance. The effect of different nitrogen forms, with and without potassium, on a range of seed quality parameters, and presence of AR37, was determined. TSW and seed germination did not respond to nitrogen application. However, a combination of nitrogen and potassium reduced TSW and seed germination and increased empty seed percentage. There was no influence of spikelet position on any of the seed quality parameters measured. However, within a spikelet, there was an effect of floret position on TSW, empty seed and endophyte presence. The effect varied depending on whether nitrogen was applied as nitrate or ammonium. [ABSTRACT FROM AUTHOR]

Earthworms are not a direct pest of turf grass but they are considered a problem on many sports fields, disrupting playability and aesthetics due to the castings they deposit on the playing surface. Also, a number of slug species are well-known foliage destroying pests of a number of agriculturally important crop species. Perennial ryegrass and tall fescue cultivars associated with selected Epichloë endophytes, originally developed for bird management at airports, were assessed to determine their deterrent properties towards worms and slugs. Plots sown with endophyte-free ryegrass had significantly higher numbers of worms and slugs than plots containing the same grass cultivar infected with the endophyte strain AR95. Also, plots sown with endophyte-free tall fescue had significantly higher numbers of slugs (but not worms) than plots containing the same grass cultivar infected with the endophyte strain AR601. Although more research is required on the exact mechanism of action, these results suggest selected novel endophyte-infected grass associations, such as those including the endophyte AR95, may substantially reduce populations of worms and slugs in areas where these grasses are sown. [ABSTRACT FROM AUTHOR]

Atmospheric CO 2 concentrations are predicted to double within the next century. Despite this trend, the extent and mechanisms through which elevated CO 2 affects grass-endophyte symbionts remain uncertain. In the present study, the growth, chemical composition and pathogen resistance of endophyte-infected (E+) and uninfected (E-) tall fescue were compared under elevated CO 2 conditions. The results showed that the effect of endophyte infection on the growth of tall fescue was significantly affected by elevated CO 2 . Significant advantage of E+ over E- tall fescue in tiller number, maximum net photosynthetic rate and shoot biomass occurred only under ambient CO 2 . With CO 2 concentration elevated, the beneficial effect of endophyte infection on the growth disappeared. Similarly, endophyte infection reduced lesion number and spore concentration of Curvularia lunata only under ambient CO 2 . These results suggest that the beneficial effect of endophyte infection on the growth and pathogen resistance of tall fescue could be counteracted by elevated CO 2. An explanation for the counteraction may be found in a change in photosynthesis and nutritive quality of leaf tissue.