Fungal Endophytes of Grasses

The tenn endophyte (Greek: endo == within + phyte = plant) has been defined as an organism contained or growing (entirely) within the substrate plant, whether parasitically or not ( 100, 106). Using this tenn in its broadest sense, the subject of this chapter could include all fungi that spend all or nearly all of their life cycles in the host grasses. We do not discuss such endophytic fungi as the smuts and vesicular-arbuscular mycorrhizas that infect grass. Instead, our interests lie primarily with a specific group of c1avicipitaceous fungi that belong or are related to fungi in the tribe Balansiae (5, 24). These fungi either are true endophytes that never produce external fructifications on the plant or else may produce external mycelium andlor spores that affect flower and seed production. We focus specifically on those grass-endophyte complexes that may also cause maladies of grazing animals. Using the above criteria, two recent events involving grass-endophyte associations have important implications for the livestock industry. In 1977 Bacon et al (9) reported the close association of an endophyte (Sphacelia typhina) in infected tall fescue (Festuca arundinacea) and the incidence of