Evaluation of Diverse Endophyte Strains for Effects On Tall Fescue Drought Tolerance.

Tall fescue [Lolium aroundinaceum (Schreb.) Darbysh.] is the best adapted cool-season perennial grass in east central U.S. for forage yet is susceptible to summer drought stress, which can reduce persistence. The plant naturally possesses a fungal endophyte (Neotyphodium coenophialum), which produces ergot alkaloids, leading to fescue toxicosis in animals. Endophyte-infected (E+) plants generally maintain higher viable tiller density under drought than endophyte-free (E-) plants. We investigated a collection of endophyte strains, which lack ergot alkaloid production, for their ability to enhance drought survival of tall fescue in relation to the wild­-type, toxic strain that commonly resides in cv. Kentucky-31. Specific objectives were to screen nontoxic endophyte strains for host-survival enhancement in greenhouse and field trials. All strains were inoculated into a common host of Kentucky-31 tall fescue. The seeds were produced with those endophytes in separate populations, including two controls consisting of E- and E+ (with wild-type toxic endophyte), and used to establish the trials. Drought stress was imposed by termination of watering in the greenhouse and by the ambient summer conditions in the field. Results will be reported on tiller-base water content, tiller survival rate, and leaf regrowth length. Data from two trials will be compared to determine the predictability of the greenhouse screening procedure for the field performance. Nonstructural carbohydrate concentrations in tiller bases will be analyzed to investigate their association with plant persistence.