Technical Abstract: Choke, caused by the endophytic fungus Epichloë typhina is an important disease of orchardgrass (Dactylis glomerata L.) grown for seed. Very little is known concerning the conditions necessary for successful infection of orchardgrass by E. typhina. Detection of E. typhina early in the disease cycle can be difficult due to sparse distribution of hyphae in the plant. Therefore a sensitive method to detect fungal infection in plants would provide an invaluable tool in elucidating the conditions and establishment of the infection in orchardgrass. Utilization of a marker gene, such as the green fluorescent protein (GFP), transformed into Epichloë will facilitate the identification of the initial stages of infection and progression of the disease in plants. We have developed an efficient and reproducible transformation method using electroporation of germinating Epichloë conidia isolated from infected plants. The GFP labelled E. typhina provides a valuable molecular tool to researchers studying conditions and mechanisms involved in the establishment of choke in orchardgrass.