Submitted to: Plant Pathology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2011
Publication Date: 12/12/2011
Publication URL: http://handle.nal.usda.gov/10113/53952
Citation: Schisler, D.A., Slininger, P.J., Boehm, M.J., Paul, P.A. 2011. Co-culture of yeast antagonists of Fusarium head blight and their effect on disease development in wheat. Plant Pathology Journal. 10:128-137. DOI: 10.3923/ppj.2011.128.137. Interpretive Summary: This research demonstrated that two and three strains of yeasts that reduce Fusarium head blight (FHB) of wheat can be cultured in the same fermentation vessel to produce an effective biocontrol product. Fusarium head blight disease frequently causes severe losses of grain yield and quality in wheat and barley and has proven to be very difficult to control using conventional disease control methods. Multistrain mixtures of biocontrol agents, which can reduce plant disease to a greater extent than individual biocontrol strains and could be used to enhance FHB control, commonly are prepared by blending separately produced fermentation products. By discovering a way to co-cultivate multiple strains of yeast biocontrol agents to equivalent biomass yields in a single fermentation reactor, we have succeeded in producing a product with the advantages of a microbial mixture without incurring the cost disadvantages of conducting multiple fermentation and processing protocols. Continued research on optimizing mixtures of yeast biocontrol agents produced in co-cultures could provide another new disease management tool, for use alone or in combination with certain fungicides, to reduce the negative impact of FHB on United States' producers, millers and consumers of wheat and barley products.
Technical Abstract: Discovery, fermentation, and formulation represent key steps in the development of biological control products, with each step linked to final product performance. By managing the fermentation environment, the quality, quantity, and efficacy of biomass and bioactive products of biocontrol strains can be improved. Multistrain mixtures of biocontrol agents, which can reduce plant disease to a greater extent than individual biocontrol strains, commonly are prepared by blending separately produced fermentation products. Co-cultivation of strains to equivalent biomass yields in a single fermentation reactor would provide mixture advantages without incurring the cost disadvantages of multiple fermentation and processing protocols. Cryptococcus flavescens OH 182.9 (NRRL Y-30216), C. aureus OH 71.4 (NRRL Y-30213), and C. aureus OH 181.1 (NRRL Y-30215), which have demonstrated individual efficacy against Fusarium head blight, were grown in two- and three- strain co-cultures to assess the feasibility of this cultivation method and the quality and efficacy of the fermentation end products. Final cell counts of component strains of all co-cultures produced were equivalent when plated on a medium that contained the trisaccharide melezitose as a sole carbon source and produced colonies of strain-distinguishable sizes. After 48 h, co-cultures of C. flavescens OH 182.9 and C. aureus OH 71.4 had near equivalent cell counts and represented the only treatment that significantly reduced FHB disease severity (32%, P=0.05, Dunnett’s t-test) when averaged across four greenhouse studies. In wheat field trials, biomass from co-cultures of these two strains reduced FHB incidence in some cases but rarely other FHB disease parameters (P=0.05, Bonferoni mean separation). Relative performance index (RPI) analysis of the overall effect of treatments at both field sites revealed that treatment with the OH 71.4 and OH 182.9 co-culture significantly reduced FHB, as evidence by a higher RPI value than for the control, while the individual strains did not (P=0.05, Bonferoni mean separation). The potential for obtaining superior efficacy and cost benefits with multistrain cultures of biocontrol agents justifies additional research effort on this concept.