Neotyphodium-Grass Interactions and Their Economic Importance

Abstract

Neotyphodium endophytes occur as intercellular mycelium within their grass hosts and are transmitted as mycelium in seed. They have a mutualistic relationship with the grass and assist in the survival of their host plants. Plant growth and competitive ability can be enhanced through better utilization of nutrients and through production of phytohormones by the endophyte. Endophytes produce compounds which deter predation from some insects and nematodes and make the plant resistant to some diseases. A major benefit of endophyte-infection is the protection they give their hosts from drought stress. Although endophytes are beneficial to the persistence of grasses some of the alkaloids they produce affect the health of animals which feed on the grass. Lolitrem B is the cause of Ryegrass Staggers and ergovaline is believed to be responsible for Fescue Toxicosis in animals which eat endophyte-infected perennial ryegrass and tall fescue. Thus endophytes are beneficial to plant persistence but not to livestock production. Strains of the two Neotyphodium endophytes that infect these grasses have been found which do not produce these toxins and they have been infected into seedlings of ryegrass and tall fescue. Agronomic and animal grazing trials with cultivars infected with these strains have shown the endophytes still protect the plants from environmental stresses but they do not appear to affect the health of animals. Cultivars infected with these novel strains will be available to farmers in the next 1-2 years.