Endophyte Status in Summer Dormant Tall Fescue Under Grazing.

It is commonly accepted that non-toxic fungal endophytes provide persistence-related benefits to summer-active, Continental-type tall fescue (Festuca arundinacea Schreb.), however the relationship between endophytes and summer-dormant, Mediterranean-type tall fescue is unclear. The status of the endophyte AR542 [Neotyphodium coenophialum (Morgan-Jones and Gams) Glenn, Bacon, and Hanlin] in summer-dormant ‘Flecha’ tall fescue was documented in two experiments. In experiment I, commercially-available Flecha AR542 was planted during the autumn each year from 2004 to 2010 on two sites (upland and lowland) at Vashti, TX. Tillers were randomly collected from each paddock during spring 2007, 2010, 2011, and 2012 for each existing stand, and analyzed using PCR using primers specific to the endophyte to estimate the percent infection. In experiment II, Flecha AR542 and Flecha Nil (endophyte-free) lines were planted at Burneyville, OK in 2005 and at Vernon, TX and Burneyville, OK in 2008. Plant persistence was visually estimated at each location. Endophyte infection was approximately 59% initially and generally increased with increasing stand life, ranging from 67-92%, until the severe heat and drought of 2011 (100 d greater than 38°C and 65% below-normal rainfall). After severe drought, older Flecha stands tended to maintain endophyte infection levels, while endophyte levels were reduced in younger Flecha stands. Endophyte infection (14-17%) varied by establishment year, while tall fescue stand persistence was greatly reduced from 95% to 1-30% (upland site) and 70% (lowland site). In experiment II, tall fescue stand persistence was excellent (100%) initially and decreased after the 2011 season, however persistence did not differ between Flecha AR542 and Flecha Nil. The beneficial effect of AR542-infected summer-dormant tall fescue is considerably less than that observed with AR542-infected summer-active tall fescue, indicating that AR542 may not improve the persistence of summer-dormant tall fescue under grazing in the Southern Great Plains.