Tall fescue and endophyte genetics influence vertical transmission and seed characteristics under climate change scenarios

Authors: MCGRAIL, REBECCA - University Of Kentucky; CARLISLE, ELIZABETH - University Of Kentucky; NELSON, JIM - University Of Kentucky; Dinkins, Randy; MCCULLEY, REBECCA - University Of Kentucky

Submitted to: Phytobiomes Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/2024
Publication Date: 6/19/2024
Citation: McGrail, R.K., Carlisle, E.A., Nelson, J.A., Dinkins, R.D., McCulley, R.L. 2024. Tall fescue and endophyte genetics influence vertical transmission and seed characteristics under climate change scenarios. Phytobiomes Journal. https://doi.org/10.1094/PBIOMES-09-23-0102-R.
DOI: https://doi.org/10.1094/PBIOMES-09-23-0102-R

Interpretive Summary: Tall fescue is a highly adaptable forage, pasture and turf grass that is a dominant species in managed grassland systems in the eastern half of the United States and in other temperate regions of the world. A significant factor in adaptability, productivity and stand persistence under stress conditions is in part due to the presence of an intercellular maternally-transmitted endophytic fungus, Epichloë coenophiala. Epichloë endophytes have been shown to produce a number of alkaloid compounds in planta, some which are beneficial in repelling insects, while others are toxic to animals resulting in production losses for animal producers. Because E. coenophiala reproduces asexually, there is concern that climate change may negatively impact maternal transmission, resulting in subsequent fescue stands with lower infection frequencies and reduced grassland resiliency. The goal of this work was to evaluate the impact of increased temperature, altered precipitation, and their combination on vertical transmission, seed number, and seed weight in tall fescue clones containing the common toxic (CTE) or a novel non-mammalian toxic (NTE) E. coenophiala strain. Our results demonstrated that temperature did not affect transmission, but altered precipitation reduced transmission in CTE clones. NTE clones responded to increased temperatures by reducing seed number, while CTE clones responded oppositely. NTE clones produced seeds of similar mass across all growing years suggesting greater stability under varying environmental conditions. This work illustrates that both plant and endophyte genetics influence fungal transmission, and that climate change is unlikely to significantly impact endophyte transmission in the southeastern transition zone of the United States.

Technical Abstract: Cool season grasses, including tall fescue, are dominant plants within managed grassland systems. A symbiotic relationship between tall fescue (Lolium arundinaceum (Schreb.) Darbysh) and fungal endophyte (Epichloë coenophiala) can affect grassland response to perturbations, including changing rainfall patterns and increasing temperatures associated with climate change. Because E. coenophiala reproduces asexually, there is concern that climate change may negatively impact vertical transmission, resulting in subsequent fescue stands with lower infection frequencies and reduced grassland resiliency. This three-year study evaluated the impact of increased temperature, altered precipitation, and their combination on vertical transmission, seed number, and seed weight in tall fescue clones containing common toxic (CTE) or novel non-mammalian toxic (NTE) E. coenophiala. NTE clones exhibited greater transmission than CTE clones. Temperature did not affect transmission, but altered precipitation reduced transmission in CTE clones. NTE clones responded to increased temperatures by reducing seed number, while CTE clones responded op-positely. NTE clones produced seeds of similar mass across all growing years suggesting greater stability under varying environmental conditions. Our work illustrates both plant and endophyte genetics influence vertical transmission and that climate change is unlikely to significantly impact endophyte transmission in the southeastern transition zone of the United States.