Understanding Tall Fescue Endophytes through Genotypic and Chemotypic Diversity

Tall fescue (Lolium arundinaceum) is a valuable and broadly adapted forage grass occupying approximately 14 million hectares across the United States. Much of the success of tall fescue can be attributed to a fungal seed borne symbiont that aids host persistence. Using molecular analyses, four independent tall fescue-Epichloë associations have been identified, representing tall fescue infected with E. coenophiala, Epichloë sp. FaTG-2, Epichloë sp. FaTG-3, or Epichloë sp. FaTG-4. Each of these species is considered an interspecific hybrid with two or three contributing ancestral genomes. These Epichloë species can be further distinguished based on genetic variation that equates to differences found at the alkaloid gene loci for production of ergot alkaloids, indole-diterpenes, lolines, and peramine, which provide protection to the plant host from herbivory. Genome sequences of isolates representing each tall fescue endophyte species have provided insight in to the genetic makeup and contributing ancestral progenitors. Unfortunately, most tall fescue within the United States, commonly referred to as “Kentucky-31” (KY31), harbors strains of E. coenophiala that cause toxicity to grazing livestock due to the production of ergot alkaloids. However, elite tall fescue endopyte-infected cultivars have been released that are unable to produce the detrimental ergot alkaloids and thus provide better quality forage for livestock. Variations across isolates allow us to track the success of different endophyte-infected associations under various environmental conditions to develop the best endophyte-infected cultivar for each environment.