Fungal Endophyte Removal Does Not Reduce Cold Tolerance of Tall Fescue

Tall fescue [ Schenodorus phoenix (Scop.) Holub.] has historically been of minor importance to livestock agriculture in cooler regions of the temperate zone. As its use in these regions expands, it becomes increasingly important to understand the effect of infection by its fungal endophyte ( Neotyphodium coenophialum Morgan‐Jones and Gams) on agronomic fitness of tall fescue. Our objective was to determine the effect of endophyte infection status on forage yield and survival of tall fescue under field conditions in which freezing temperatures, combined with lack of persistent snow cover, constitute the most significant stress factor. In Experiment 1, we evaluated 427 half‐sib families of four tall fescue cultivars, half endophyte‐infected (E+) and half endophyte‐free (E−), for forage yield and survival. There was no effect of endophyte removal on either forage yield or survival, despite complete stand loss of one cultivar during two winters. In Experiment 2, we evaluated 640 clones of confirmed endophyte status, half E+ and half E−, for survival under two management regimes at four Wisconsin locations. Results were nearly identical to those for Experiment 1, with complete mortality in the unadapted cultivar and high survival rates in the three adapted cultivars, regardless of endophyte status, management, or location. In conclusion, we found no evidence that endophyte removal resulted in any disadvantage to tall fescue host‐plant survival under harsh winter conditions. In regions where freezing temperatures and desiccating winds provide the only or most important abiotic stress factor, removal of endophytic fungi do not appear to reduce fitness of their tall fescue host.