Masters Theses

Date of Award

12-1993

Degree Type

Thesis

Degree Name

Master of Science

Major

Entomology and Plant Pathology

Major Professor

Charles D. Pless

Committee Members

Kimberly Gwinn, Reid Gerhardt

Abstract

Toxicity was compared among four tall fescue clone pairs. Seasonal comparisons were made by measuring development of fruit flies, Drosophila melanogaster Meigen, in diets prepared with endophyte-infected (E+) and endophyte-free (E-) tall fescue leaf powder. Toxicity was also evaluated by observing the behavior of the corn flea beetle, Chaetocnema pulicaria Melsheimer, on E+ and E- tall fescue leaf segments.

Clone pairs developed at The University of Tennessee were designated as 31, 38, 39 and 48. Diets containing 38E+ tall fescue had less fruit flies than other diets during most of the year. Diets containing 39E+ tall fescue had fewer fruit flies than other diets in summer. Diets containing 31E+ had more fruit flies than other E+ diets in spring. Toxic effects of all E+ diets diminished in winter.

In no-choice bioassays, corn flea beetles were found on E- tillers more often than all E+ tillers except 39E+. Amount of feeding was similar on E+ and E- tillers of clone pair 39; whereas, E+ tillers of other clones had less feeding than the respective E- tillers.

Since contrasting levels of toxicity occur in E+ plants, a variety of phenotypes may be expected in a pasture. Results of this study show the importance of evaluating several clone pairs before a particular variety is selected for livestock forage.

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