Molecular Biology and Genetics of Protective Fungal Endophytes of Grasses

Abstract

Clavicipitaceous endophytes, a group of seedborne fungal symbionts of C3 grasses, may be the most widespread agents of biological plant protection in agriculture, and the unwitting use of them in pasture grasses has continued for many centuries. Endophytes have been recognized in species of the Pooideae (the cool-season grasses) for nearly a century (1), but the agricultural and ecological importance of these associations has been appreciated only in recent decades. Those with evolutionary affinities to the teleomorph (sexual form) Epichloë typhina (Pers: Fr.) Tulasne (family Clavicipitaceae) are referred to as “clavicipitaceous endophytes” (here abbreviated c-endophytes) and can be particularly important for the fitness, competitiveness and persistence of their grass hosts under conditions of biotic or abiotic stress (2–4). The most intensely studied of these interactions have been the tall fescue (Festuca arundinacea Schreb.) and perennial ryegrass (Lolium perenne L.) symbiota. The multitude of fitness enhancements conferred by the c-endophytes (Table 1) are, in no small measure, contributory to the excellent persistence of these grasses in temperature pastures. However, since it was determined that they were associated with livestock toxicosis (5,6), the endophytes have not been considered desirable by pastoralists. The most immediate goal of much of the present endophyte research is to identify or generate strains that cause minimal toxicosis to livestock, but still confer most of their protective benefits upon the host grasses.