Competition between foliar Neotyphodium lolii endophytes and mycorrhizal Glomus spp. fungi in Lolium perenne depends on resource supply and host carbohydrate content

Abstract

Summary1. Cool-season grasses can be simultaneously infected by foliar fungal endophytes and colonised by mycorrhizal fungi, the integrated functions of which are strong predictors of plant fitness within grassland ecosystems. Evidence has been presented previously that infection of grass species with foliar endophytes can negatively affect mycorrhizal colonisation. Here, we tested the hypothesis that mycorrhizal colonisation in turn adversely affects Neotyphodium endophyte concentrations and that the competitive interaction between the two endosymbionts is affected by resource supply. 2. Specifically, we report how competition between Glomus (G. mosseae -GM, G. intraradices -GI) mycorrhizal fungi and N. lolii (common strain (CS) and AR1) foliar endophytic strains is affected by P supply and water-soluble carbohydrate (WSC) content in two Lolium perenne (perennial ryegrass) cultivars: a high sugar grass, AberDart, and a conventional (control) grass, Fennema. 3. The presence of Glomus mycorrhizae reduced the concentrations of endophytes and alkaloids in leaf blades and pseudostems. The reduction depended on P supply, ryegrass cultivar (notably WSC content) and endophyte strain. Conversely, foliar endophyte infection reduced mycorrhizal colonisation rates and concentrations in the roots of the control cultivar Fennema, although not in the high sugar cultivar, AberDart. 4. Neither GM nor N. lolii infection had an effect per se on the yield of root or blade compared with mycorrhiza-free (M-) and endophyte-free (E-) plants, respectively; though, yield of roots and blades was reduced by GI infection and at low P. 5. Competitive interactions between ecologically widespread foliar endophytes (valuable for plant protection) and mycorrhizal endosymbionts (valuable for P acquisition) as seen in this study are of critical importance especially in areas of high pest prevalence and low P availability. Our work stresses the need for elucidating the physiological ⁄ metabolic basis for such interactions between endosymbionts to understand how these processes contribute to plant performance and fitness in grassland ecosystems.

Evidence for leaf endophyte regulation of root symbionts: effect of Neotyphodium endophytes on the pre-infective state of mycorrhizal fungi

“…Although Neotyphodium endophytes occur exclusively in aerial plant tissues, their effects on below-ground processes have been documented (White and Cole 1985;Omacini et al 2004;Jenkins et al 2006). Previous studies, performed on selected agronomic grasses (Schedonorus arundinaceum, L. multiflorum and L. perenne) showed that endophyteinfected plants had lower levels of mycorrhizal colonization (Chu-chou et al 1992;Guo et al 1992;Müller 2003;Omacini et al 2006;Mack and Rudgers 2008;Liu et al 2011) and this was mainly attributed to alkaloid production by endophytes. In contrast, the studies we have conducted in native grasses from Argentina (Novas et al 2005(Novas et al , 2009 showed that roots from endophyte-infected populations displayed a significantly higher frequency of colonisation by mycorrhizal fungi than those free of endophytes.…”

An Extracellular Siderophore Is Required to Maintain the Mutualistic Interaction of Epichloë festucae with Lolium perenne

“…Production of all three is minimal or undetectable in axenic cultures, but all are produced in significant amounts (of the order of µg/g) in planta [62]–[64]. Many biotic and abiotic factors influence the production of fungal alkaloids in planta , including mineral stress, for example nitrogen and phosphorous availability [60], [65], [66]. To test if the altered phenotype of ΔsidN 85 infected plants may have an effect on alkaloid production, we determined alkaloid concentrations in infected plants on at least 3 occasions.…”

cAMP Signaling Regulates Synchronised Growth of Symbiotic Epichloë Fungi with the Host Grass Lolium perenne

“…There were three replicate plants per strain. Hyphal biomass (expressed as endophyte concentration) was determined by quantitative PCR of the single copy E. festucae NRPS-1 gene (EFM3.005350, http://www.endophyte.uky.edu/) from 1 ng of genomic DNA using a MyiQ™ cycler (Bio-Rad Laboratories, Hercules, California, USA), with primers 1-1F, and 1-1R (Supplementary Table 1) as described (Rasmussen et al, 2007; Liu et al, 2011). Hyphal biomass between strains was compared using one way ANOVA.…”