Submitted to: International Congress of Plant Pathology Abstracts and Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 2/7/2003
Publication Date: 2/7/2003
Citation: SCHISLER, D.A., KHAN, N.I., BOEHM, M.J., VAN CAUWENBERGE, J.E., SLININGER, P.J. DISCOVERY, PILOT-PLANT PRODUCTION, AND EFFICACY OF ANTAGONISTS OF FUSARIUM HEAD BLIGHT (SCAB) OF WHEAT. 8TH INTERNATIONAL CONGRESS OF PLANT PATHOLOGY. ABSTRACT PAPER NUMBER 3.85. Interpretive Summary:
Technical Abstract: A serious impediment to the commercialization of biocontrol agents is the lack of adequate methodologies for selecting biocontrol agents that have both high efficacy and amenability to the stresses of commercial-scale biomass production. Seven microbial strains were obtained from wheat anthers and were effective against three different isolates of Gibberella zeae in greenhouse tests. Bacillus subtilis strains AS 43.3, AS 43.4, and Cryptococcus nodaensis OH 182.9 reduced disease severity by >77%, 93%, and 56%, respectively. Yeasts Cryptococcus nodaensis OH 182.9 and Cryptococcus sp. OH 181.1 reduced disease severity by as much as 60% in a series of field experiments on winter and durum wheats. To test the amenability of these yeasts to withstand pilot-plant scale production procedures, biomass was produced in 30-liter and 100-liter bioreactors. Cells were harvested after 48 h, dewatered using a continuous flow centrifuge, resuspended to 1/5 original volume using buffer or spent broth and frozen at -18 C. Preharvest yields were 4 x 10(8) CFU/ml and 1 x 10(9) CFU/ml for OH 181.1 and OH 182.9, respectively. Frozen, washed cells of both yeasts maintained over 10(8) CFU/ml after 10 weeks but less than 10(5) CFU/m1 if resuspended and frozen in spent broth. Melezitose, a previously undescribed cryoprotectant, significantly increased the survival of freeze-dried OH 182.9 but product efficacy was compromised by melezitose stimulating the development of disease. Alternative drying methodologies such as air, fluidized-bed or spray-drying may be required to produce a dried OH 182.9 biocontrol product that maintains biocontrol efficacy.