Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/24/2004
Publication Date: 11/1/2004
Citation: Schisler, D.A., Slininger, P.J., Behle, R.W., Jackson, M.A. 2004. Formulation of Bacillus spp. for biological control of plant diseases. Phytopathology. 94(11):1267-1271.
Interpretive Summary: Biological control of plant pathogens is an environmentally friendly method for reducing plant diseases. Developing methods for producing cells of biocontrol agents that are effective and can be successfully incorporated into a biological control product requires considerable research effort. Bacillus is a bacterial genus that contains many good candidates for the biological control of plant diseases. In this paper, we describe important factors to consider when producing and formulating cells of Bacillus and other biocontrol agents. We also discuss a technique that we developed for experimentally evaluating multiple cell production and formulation variables in a small scale assay that permits many more factors to be evaluated simultaneously than was possible previously. Using this technique, we discovered that adding a lignin compound or an optical brightener to cells of our patented Bacillus strain OH 131.1 for reducing Fusarium head blight (FHB) of wheat reduced the amount of damage done to the Bacillus cells when they were exposed to levels of ultraviolet light similar to that in sunlight. This work will provide researchers in the field of formulating microbial cells with new ideas for conducting such work. Additionally, the discovery of compounds that protect Bacillus strain OH 131.1 from ultraviolet light should advance the progress of this strain toward becoming a commercial product active against FHB.
Technical Abstract: Maximizing the potential for successfully developing and deploying a biological control product begins with a carefully crafted microbial screening procedure, proceeds with developing mass production protocols that optimize product quantity and quality, and ends with devising a product formulation that preserves shelf-life, aids product delivery and enhances bioactivity. Microbial selection procedures that require prospective biocontrol agents to possess both efficacy and amenability to production in liquid culture enhance the likelihood of selecting agents with enhanced commercial development potential. Scale-up of biomass production procedures must optimize product quantity without compromise of product efficacy or amenability to stabilization and formulation. Formulation of Bacillus spp. for use against plant pathogens is an enormous topic in general terms but limited in published specifics regarding formulations used in commercially available products. Types of formulations include dry products such as wettable powders, dusts and granules, and liquid products including cell suspensions in water, oils, and emulsions. Cells can also be microencapsulated. Considerations critical to designing successful formulations of microbial biomass are discussed and include preserving biomass viability during stabilization, drying, and rehydration; aiding biomass delivery, target coverage, and target adhesion; and enhancing biomass survival and efficacy after delivery to the target. Solutions to these formulation considerations will not necessarily be compatible. Data from several biocontrol systems including the use of B. subtilis OH 131.1 (NRRL B-30212) to reduce Fusarium head blight of wheat is used to illustrate many of these issues. Using our recently described assay for efficiently evaluating biomass production and formulation protocols, we demonstrate the effectiveness, in vitro, of UV protectant compounds lignin (PC 1307) and Blankophor BBH in reducing OH 131.1 morbidity when cells were exposed to UV light from artificial sunlight.