Masters Theses

Date of Award

8-1992

Degree Type

Thesis

Degree Name

Master of Science

Major

Entomology and Plant Pathology

Major Professor

Kimberly D. Gwinn

Committee Members

James Hilty, Alan Windham, Mark Windham

Abstract

Tall fescue, Festuca arundinacea, a predominant forage and turfgrass in the United States, is commonly infected with the fungal endophyte, Acremonium coenophialum. The presence of the endophyte in forage is correlated with the occurrence of fescue toxicosis in livestock. However, endophyte-free (E-) tall fescue is difficult to establish and is more susceptible to biotic and abiotic stresses than endophyte-infected (E+) tall fescue. Endophyte-infested Kentucky 31 seed lots are more resistant to seedling disease caused by Rhizoctonia zeae. Greenhouse studies were conducted to determine if E+ tall fescue seed lots are more resistant to three additional soilborne pathogens than Etall fescue seed lots. Endophyte-infected seed are more resistant to seedling diseases caused by Pythium aphanidermatum and R. solani under certain environmental conditions. No endophyte-mediated resistance occurred to Magnaporthe poae. A laboratory assay was developed to study resistance mechanisms to R. zeae. Laboratory experiments were also conducted to determine resistance mechanisms. Exudates from E+ seedlings had no influence on the growth of R. zeae. Endophyte-infected seedlings also did not produce zones of inhibition to R. zeae in vitro. Endophyte infection of seedlings had no influence on emergence rate of seedlings. Seed lots of Kentucky 31 tall fescue are more resistant to some soilborne pathogens, but at the present time resistance mechanisms are unknown.

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