Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 6, 2000
Publication Date: N/A
Interpretive Summary: Biological control of plant diseases remains a favorable alternative to pesticide control since biological control promises reduced risk to agricultural workers, consumers, and the environment. Yet, observations of biological control in research laboratories sometimes do not make the transition from laboratory phenomenon to commercial product. Using a model lsystem of biologically controlling Fusarium dry rot with patented microbes from our previous research, we proposed that strategies used to select biological control microbes are inadequate when they do not consider the breadth of pathogen types and host plant cultivars that a biocontrol agent must perform on. Additionally, strategies used to select biocontrol agents often do not consider how the agent will perform when mass produced in a manner similar to what occurs in the commercial production of biocontrol agents. In this study, we showed that the effectiveness ranking of a group pof five biocontrol agents varied greatly depending on the type of host plant and type of pathogen used in the experiment. The type of medium used to grow the biocontrol microbe also made a difference in the effectiveness ranking of the biocontrol microbes. By drawing the attention of biocontrol researchers to the critical importance of these factors in accurately selecting the best candidate biocontrol microbe, it is expected that a greater percentage of biocontrol agents discovered to be successful in the laboratory will make the transition to successful commercial biological control product.
Technical Abstract: The process of selecting biological control agents for further development frequently does not entail conducting bioassays of strain effectiveness on a range of pathogen isolates or host cultivars. Additionally, though previous studies have demonstrated that the medium used to produce antagonist biomass can alter its efficacy, this factor is also rarely considered when selecting for the most effective antagonist. In this study, host cultivar, pathogen isolate, and the cultivation medium used to produce antagonist biomass were examined as factors of potential importance for accurately assessing the relative effectiveness of bacterial biocontrol strains. Five antagonists that biologically control Fusarium dry rot on stored potato tubers were assayed for effectiveness against 10 isolates of Gibberella pulicaris. All antagonists reduced disease severity (35-81%) regardless of the specific assays conducted. However, when antagonist biomass was produced on two media that differed both in nutrient composition and phase, the efficacy ranking of antagonist Enterobacter sp. S11:P:08 varied from first to fourth most effective. For the antagonists studied, the phase of a nutritionally identical medium had little impact on the efficacy ranking of the five antagonists. Four of the five antagonists had efficacy rankings that ranged from first to last depending on the isolate of the pathogen used to conduct the bioassay. The cultivar of the host also caused variations in the efficacy ranking of the antagonists. These results indicate that bioassays should be conducted using a range of liquid culture production media, pathogen isolates, and host cultivars in order to choose a biocontrol strain that has the highest likelihood for commercial development as an effective biological control product.