Artificial Inoculation of Epichloë festucae into Lolium perenne, and Visualisation of Endophytic and Epiphyllous Fungal Growth

Abstract

Natural hosts for the fungal endophyte Epichloë festucae include Festuca rubra (fine fescue) and Festuca trachyphylla (hard fescue). Some strains also form stable associations with Lolium perenne (perennial ryegrass). L. perenne is a suitable host to study fungal endophyte–grass interactions, such as endophytic fungal growth within the plant and epiphyllous growth on the plant surface. Here we provide a detailed protocol based on work by, for artificial inoculation of E. festucae into L. perenne, and newly developed staining and visualization techniques for observing endophytic and epiphyllous hyphae and the expressorium, an appressorium-like structure used by the fungus to exit the plant. The staining method uses a combination of glucan binding aniline blue diammonium salt (AB) and chitin binding wheat germ agglutinin-conjugated Alexa Fluor®488 -(WGA-AF488). This protocol will be a useful tool to study Epichloë-grass interactions, particularly the comparison of different Epichloë-grass associations, various endophyte-host developmental stages, as well as the analysis of mutant Epichloë strains.