Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/26/2012
Publication Date: 8/26/2012
Citation: Schisler, D.A., Dunlap, C.A., Slininger, P.J. 2012. Liquid cultivation techniques for enhancing the effectiveness of yeast biocontrol agents [abstract]. Thirteenth International Congress on Yeasts (ICY 2012), Madison, WI, August 26-30, 2012. p. 123.
Technical Abstract: Biocontrol agents will gain broader acceptance into integrated pest management programs if products with enhanced efficacy and consistency of performance are developed. Though given comparatively little research attention, liquid cultivation environments and protocols can and should be optimized to improve biocontrol products. Yeast Cryptococcus flavescens OH 182.9 (NRRL Y-30216) reduces Fusarium head blight (FHB) severity on wheat and deoxynivalenol in grain in field experiments but user acceptance will depend on maximizing product efficacy. Management of growth medium carbon:nitrogen ratio and carbon loading as well as reducing incubation temperatures to 15 C when cultures were between log- and stationary-growth resulted in cells of OH 182.9 with enhanced efficacy and storage stability when air-, freeze-, or fluidized bed- dried. Cold adaptation of biomass improved the liquid hyperosmotic shock tolerance of cells and altered the temperature dependence of their osmotic shock tolerance. Results of fluorescence anisotropy and atomic force microscopy suggested that cold adaptation significantly altered cell membranes of the yeast. Because co-cultivation of two or more biocontrol strains in a single vessel would provide the efficacy and consistency advantages of strain mixtures without incurring the cost disadvantages of multiple fermentors and processing protocols, cultivations containing two and three strains of yeast have been developed that reduce FHB in greenhouse and field trials to a greater extent than the component strains tested individually. Strain OH 182.9 has been successfully integrated with the fungicides tebuconazole and prothioconazole in field trials after first selecting for fungicide tolerant variants of strain OH 182.9 in liquid cultivation media incorporated with progressively higher concentrations of the fungicide. Co-cultures of C. flavescens and the bacterial strain Bacillus subtilis AS 43.3 are currently under development using variants of strain OH 182.9 selected for tolerance to fungitoxic lipopeptides produced by the bacterium.