Endophytic fungal infection of meadow fescue in the driftless area of the upper Mississippi River Valley: Impacts on agronomic fitness

Authors: CASLER, MICHAEL - Retired ARS Employee; Waldron, Blair

Submitted to: Grassland Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2023
Publication Date: 11/16/2023
Citation: Casler, M.D., Waldron, B.L. 2023. Endophytic fungal infection of meadow fescue in the driftless area of the upper Mississippi River Valley: Impacts on agronomic fitness. Grassland Research. https://doi.org/10.3390/grasses2040019.
DOI: https://doi.org/10.3390/grasses2040019

Interpretive Summary: During the past 25 years, meadow fescue has become an important perennial grass for use in management-intensive grazing systems (MIGS). The Driftless Area, part of the Upper Mississippi River watershed, contains hundreds of livestock farms that are principally based on use of MIGS, many of which contain healthy populations of meadow fescue. A survey of numerous farms in the region demonstrated that all of these meadow populations are infected with an endophytic fungus that lives inside the plant, most with high levels of infection, greater than 80%. Similar fungi have been shown to confer drought tolerance, fungal disease resistance, and reduced insect feeding to other grasses that are closely related to meadow fescue. This research demonstrated, through both field and greenhouse studies, that the fungus does not confer any advantage to meadow fescue under drought conditions. However, all eight meadow fescue populations tested under frequent and low mowing showed a significant response, with fungus-infected populations averaging about 10% greater survival compared to fungus-free populations. These results are of great significance to agronomists and to the grass seed industry, indicating that the meadow fescue fungus is highly beneficial for survival under frequent and intensive defoliation, as is practiced in many grazing operations.

Technical Abstract: Meadow fescue, Schedonorus pratensis (Huds.) P. Beauv., has recently been discovered as a common but previously unknown pasture grass in the Driftless Area of the upper Mississippi River Valley. Surveys have demonstrated that numerous meadow fescue pastures are infected with an endophytic fungus, Epichloë uncinata (W. Gams, Petrini & D. Schmidt) Leuchtm. & Schardl, often at a very high infection frequency. The objectives of this study were to document infection frequencies and to determine if the endophyte impacts agronomic fitness of the host. Eight farm sites were intensively sampled, with endophyte infection levels ranging from 82 to 95%. Paired endophyte-infected (E+) and endophyte-free (E-) subpopulations from each farm site were created for subsequent testing. There was no impact of endophyte under a wide range of drought conditions for either greenhouse or field studies. There was a small and consistent forage yield enhancement for one of the eight farm sites. The only strongly consistent effect of the endophyte was for ground cover (persistence) under frequent defoliation. Approximately 12 to 15 mow events per year at a residual sward height of 5 cm resulted in an average increase in ground cover of 9% associated with the endophyte. We hypothesize that enhanced root growth, fungal disease resistance, and/or reduced insect feeding could be mechanisms for this enhanced survivorship.