Tall Fescue Online Monograph

Abstract

Abiotic stresses consist of nonorganismal, nonpathogenic factors that inhibit plant function. Tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] is widely symbiotic with a naturally occurring endophytic fungus [Neotyphodium coenophialum (Morgan-Jones and Gams) Glenn, Bacon, and Hanlin], which confers many benefits to its host that favor its ecological fitness for growth, persistence, and reproduction. Tolerance or resistance to water deficit (drought) and soil chemical stresses, such as low pH and low mineral availabilities, comprise the two principal categories of abiotic stresses. However, endophyte infection does not always result in superior performance of the host in stress conditions, and the mechanisms by which the symbiosis imparts such benefits are not well understood. Plant responses to endophytes involve a complex of physiological, biochemical, and morphologic adjustments that are conditioned by host genotype, endophyte genotype, environment, and their interactions. Endophyte strains that lack ergot-alkaloid production capability have been discovered recently, culminating the 30-yr search for ways to combat the deleterious effects of wild endophytes in Lolium species. When some of these novel endophytes are transferred into elite tall fescue germplasm, host plant persistence and vigor are enhanced. These innovations will allow grassland managers to exploit the agronomic benefits, while avoiding the detrimental aspects of the tall fescue-endophyte symbiosis, for profitable livestock production.

Keywords: antiherbivory, antioxidants, drought stress, mineral nutrients, persistence, phenolic root exudates, soil acidity.

Abbreviations: E-, endophyte free, free of Neotyphodium; E+, infected by wild Neotyphodium endophyte.