|Phillips, Tim -|
Submitted to: Forage and Grazinglands
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 5, 2009
Publication Date: November 2, 2009
Citation: Phillips, T., Aiken, G.E. 2009. Novel endophyte-infected tall fescues. Forage and Grazinglands. doi:10.1094/FG-2009-1102-01-RV. Interpretive Summary: Tall fescue is the most widely grown forage grass in the southeastern USA. It owes its wide adaptation, persistence, and productivity in large part to its symbiosis with the Neotyphodium endophyte. Tall fescue infected with the common toxic strain of this endophyte contains an array of alkaloids produced by this fungus. Ergot alkaloids are implicated as a primary cause of symptoms in grazing mammals (i.e., elevated body temperature, reduced prolactin concentrations, retention of rough hair coats into the summer, etc.) collectively termed fescue toxicosis. Early disappointing performance of endophyte-free varieties, especially seen in more stress-prone locations created an opening for the concept of deploying nontoxic strains of Neotyphodium endophytes as suggested by Bacon and Siegel. Ideally, novel endophyte-containing tall fescue should have the stress tolerance and persistence of tall fescue infected with the common toxic endophyte, but provides animal performance that is comparable to endophyte-free tall fescue (or other cool season forage grasses with no harmful endophytes or alkaloid content). With the development and commercial release of the first novel endophyte tall fescue, ‘Jesup’ MaxQ®, forage producers were given an option in alleviating fescue toxicosis. Other companies and universities are developing new novel endophyte tall fescues to provide alternatives to Jesup MaxQ®. This review presents an update on novel endophyte tall fescue cultivars in the USA for forage-based livestock production.
Technical Abstract: Tall fescue (Schedonorus arundinaceus (Schreb.) Dumort. = Lolium arundinaceum (Schreb.) Darbysh., formerly Festuca arundinacea Schreb. and before that, Festuca elatior L.) is a cool-season perennial grass that is well adapted in the upper transition zone between the temperate northeast and subtropical southeast. This hardiness in the “fescue belt” is primarily due to a fungal endophyte, Neotyphodium coenophialum Morgan-Jones & Gams.) Glen Bacon & Hanlin, that imparts tolerances to moisture, heat, and grazing stresses. Unfortunately, ergot alkaloids produced by the endophyte are toxic to grazing livestock and cause a toxicosis. Cattle exhibiting fescue toxicosis are vasoconstrictive (regardless of prevailing ambient temperature), retain rough hair coats into the summer, and reduced dry matter (DM) intake. Novel endophytes that do not produce ergot alkaloids have been developed to alleviate symptoms of toxicosis. Grazing experiments have shown similar animal performance and well being between novel endophyte and endophyte-free tall fescues. These experiments further indicate that novel endophyte tall fescue can persist under grazing. Results of these experiments will be presented and discussed.