Epichloë coenophiala, the fungal endophyte found in tall fescue, can cause toxicosis by producing ergot alkaloids, but not all isolates are identical. For example, dogs are the same species, Canis familiaris, but different breeds represent genetic diversity of the species. Most Epichloë coenophiala in the fescue belt of the United States produce ergot alkaloids and cause fescue toxicosis, but other isolates have now been identified that are either unable to produce ergot alkaloids or produce very low levels of these compounds. These novel endophytes are safe for grazing because they do not cause symptoms of fescue toxicosis.
Evaluation of the genomes of different Epichloë coenophiala isolates shows variation within the genes required for production of ergot alkaloids. Some isolates with fully functional genes produce ergot alkaloids whereas other isolates lack essential genes or have nonfunctional sequences, so they are unable to make these toxins. Using this type of natural genetic variation, breeders have developed tall fescue cultivars with livestock-friendly strains (sometimes referred to as “novel endophytes”) that provide fescue with persistence but do not cause animal toxicity.
Creating a novel endophyte-infected tall fescue cultivar. The endophyte (C) is introduced into a young seedling (A) at a wound near the crown meristem (B and D). Once the seedling has recovered, endophyte-infected plants (E) are selected for further evaluation in the field and in animal safety trials before being released as a new cultivar.
Symptoms of fescue toxicosis can be partially mitigated with various management practices, including alternate feed or forage supplementation. However, the toxic effects do not disappear completely and can still impact producer profitability. The best option is to renovate toxic pastures with safe tall fescue cultivars to keep livestock from ingesting toxic ergot alkaloids. Although pasture replacement comes at a cost, the availability of a persistent nontoxic pasture improves livestock health and productivity with initial costs recouped over time as a direct result of the improvements.
A similar pasture replacement strategy targeting a toxic endophyte-infected perennial ryegrass that causes ryegrass staggers was used successfully in New Zealand. Although the endophyte was a different species in that case, the approach was the same. By renovating toxic pastures with novel endophyte-infected cultivars, livestock producers chose to make the investment to keep their livestock safe. Novel endophyte-infected tall fescue cultivars are available through Pennington Seed (Jesup MaxQ II, Texoma MaxQ II, Lacefield MaxQ II), Barenbrug (BarOptima Plus E34), Mountain View Seed (Estancia with ArkPlus) and DLF Trifolium (Martin 2 with Protek, and Tower with Protek).
Fun fact: Tall fescue is not the only grass to host Epichloë endophytes. Many cool-season grasses, including a lot of grasses native to the United Sates, are endophyte infected, but they harbor different Epichloë species. The endophyte Epichloë canadensis was discovered by Young and her colleagues in the native grass Elymus canadensis.
About the Authors: Dr Carolyn Young runs the Mycology lab at the Noble Research Institute. She has a passion for working with endophyte infected-grasses and understanding the important role they have in forage-based systems. She works closely with the Noble Research Institute grass breeder, Mike Trammell, on the development of new tall fescue cultivars that are safe for grazing livestock. The Noble Research Institute developed and released Texoma MaxQ II. Amy Flanagan is a research associate in the Mycology lab at the Noble Research Institute.
The Alliance for Grassland Renewal is a national organization focused on enhancing the appropriate adoption of novel endophyte tall fescue technology through education, incentives, self-regulation and promotion. For more resources or to learn more about the Alliance for Grassland Renewal, go to www.grasslandrenewal.org
The Alliance for Grassland Renewal 