APS Homepage

Poster: Biology & Disease Mgmt: Biological Control


Switchgrass Extractives Inhibit Plant Pathogenic Fungi
A. BRUCE (1), B. Ownley (1), J. Tao (1), N. Labbe (1), K. Gwinn (1), D. D'Souza (1), N. Moustaid-Moussa (2) (1) University of Tennessee, U.S.A.; (2) Texas Tech University, U.S.A.

Switchgrass is a leading contender for biofuel production. Cellulosic ethanol yield is reduced by a phenolic-rich, nonstructural portion of switchgrass, called extractives. Switchgrass extractives hinder enzyme activity and microorganism growth utilized during the biofuel conversion process. Switchgrass would be a more cost-effective feedstock if the extractives portion was developed for use as a biopesticide. The aim of this study was to assess different concentrations of switchgrass extracts for inhibition of Fusarium oxysporum, Fusarium graminearum, Alternaria alternata, Botrytis cinerea, and Bipolaris oryzae. Crude ethanol extracts were evaluated for inhibition of fungal plant pathogens with disk diffusion and spore germination assays. Colony growth was measured in disk diffusion assays on water agar; treatments were disks treated with 60X and 75X concentrations of extracts, and a ‘no extracts’ control. Inhibition of mycelial growth was greatest in disk diffusion assays with A. alternata and F. graminearum at 75X, and F. oxysporum at 60X. Spore germination was tested by incubating spores in a water control, or in extracts concentrated at 10X and 15X for 24 h, followed by repeated sampling over a 4-hour period. Germ tube growth was observed microscopically. Spore germination of all fungi was significantly inhibited by both extracts concentrations at all time points. Results indicate that switchgrass extracts have biopesticide potential.