Endophytes in Summer Dormant Tall Fescue: Are There Benefits?.

Continental (summer active, SA) tall fescue is a successful forage grass, widely utilized in the eastern USA where its success is attributed to a beneficial endophytic fungus. However, much of this region is planted with endophyte-infected tall fescue that is toxic to grazing livestock, known as common toxic endophyte (CTE). Naturally occurring endophyte strains (selected endophytes) have been identified that retains the host benefits while eliminating livestock toxicity. These new endophyte strains are now commercially available within SA tall fescue cultivars (e.g. Texoma MaxQ II) as a value-added trait that aids host persistence. Mediterranean (summer dormant, SD) tall fescue has a survival strategy by going dormant during summer, thus offering multi-year persistence in the hot, water limited environments of the southern Great Plains. SD tall fescue can potentially complement or replace traditional, annual small grains graze-out systems in the southern Great Plains, providing high quality forage from fall through spring, thereby reducing livestock production costs for producers by eliminating the feeding of hay. Research is currently under way to evaluate SD tall fescue in the hot, low rainfall regions of western Oklahoma, Texas and Argentina, but the impact of the associated endophyte as a value-added trait is unclear. We propose to evaluate the role endophyte (CTE and selected) plays in improving persistence of SD tall fescue using clonal pairs (endophyte-infected and endophyte-free) that have been generated from ten host lines, two SA and eight SD, representing 15 unique genotypes /population. Seed from these populations have been established in sward plots across multiple environments for evaluation under intensive grazing and mechanical harvesting. This study should provide insight into the impact of endophyte infection under abiotic and biotic stresses in the field.