Submitted to: Workshop Proceedings
Publication Type: Proceedings
Publication Acceptance Date: October 19, 2003
Publication Date: December 10, 2003
Citation: Jackson, M.A. 2003. Strategies for identifying fungal biocontrol agents suitable for commercial development and production by liquid culture fermentation. II Curso Internacional en Procesos Biotechnologicos [CD-ROM], Monterrey, MX, October 26-29, 2003. Technical Abstract: Numerous fungi show excellent potential for use as biocontrol agents due to their ability to selectively infect and kill a variety of weedy and insect pests or their ability to antagonize or exclude plant disease-causing organisms through parasitism or competitive exclusion. Many factors must be considered when selecting microbial biocontrol agents for commercial development, incuding need for non-chemical control measures, pathogen host range, economic importance of the target pest, potential of biocontrol organism to produce an effective propagule, and the availability of cost-effective production and stabilization technology for the required fungal propagule. All of these factors must be considered in selecting biological control agents (BCAs) for commercial development. The lack of suitable methods for economically producing stable and effective fungal propagules continues to impede the commercial use of these biocontrol agents. Selecting fungi for use as biocontrol agents and for concomitant amenability to liquid culture production requires an understanding of how the organism carries out its biocontrol function and in what environment it will be used. For use as a foliar spray or in post-harvest disease control applications, production of the fungal biocontrol agent as yeast or yeast-like propagules is advantageous. The potential to control soil-borne plant diseases with fungal biocontrol agents is greatly enhanced if the agent produces propagules such as chlamydospores or sclerotia that are capable of persisting in the soil environment. Our research focuses on developing media and processes for the liquid culture production of promising fungal biocontrol agents. To demonstrate how nutritional factors can be used to regulate propagule formation and propagule 'fitness' during liquid culture production, results from our studies with the mycoherbicides Colletotrichum truncatum and Mycoleptodiscus terrestris and the mycoinsecticide Paecilomyces fumosoroseus will be presented. High concentrations of desiccation-tolerant, yeast-like blastospores of the fungus P. fumosoroseus were produced in liquid culture when the supplied medium contained an appropriate concentration and source of nitrogen. Nutritional studies with C. truncatum cultures grown in liquid media demonstrated that sporulation or microsclerotia formation was regulated by the carbon concentration of the medium. High concentrations of desiccation-tolerant microsclerotia of C. truncatum were produced in liquid media that contained a high carbon concentration. Similarly, studies with M. terrestris showed that microsclerotia of this aquatic weed pathogen were produced under appropriate nutritional conditions. The use of fungal microsclerotia in aquatic environments for weed control or as a soil amendment for controlling weedy plants or soil-born plant diseases will be discussed.