Submitted to: Book Chapter
Publication Type: Book / chapter
Publication Acceptance Date: 12/26/2006
Publication Date: 6/20/2007
Citation: Thomashow, L.S., Weller, D.M., Mavrodi, O.V., Mavrodi, D.V. 2007. Selecting, monitoring, and enhancing the performance of bacterial biocontrol agents: principles, pitfalls, and progress.p.87-105. In M. Vurro and J. Gressel (eds.) Novel Biotechnologies for Biocontrol Agent Enhancement and Management. Springer. Interpretive Summary: Root diseases caused by soilborne pathogens are major yield-limiting factors in the production of food, fiber and ornamental crops. Trends in agriculture toward greater sustainability and less dependence on synthetic fungicides have created a need for more ecologically sound methods of disease control. Biological control, which exploits the natural antagonistic activity of certain root-colonizing bacteria against fungal pathogens, is one such approach. However, commercial development of biological control agents has been slow because of the perception that biological control agents do not perform consistently. This paper reviews methods for isolating effective biological control agents, techniques for monitoring the persistence and activity of biocontrol strains in the environment, and the construction and environmental safety of genetically modified strains with enhanced biocontrol activity.
Technical Abstract: Genetic resistance to root diseases of plants is rare, and agriculture controls these diseases by practices such as crop rotation and soil fumigation. However, plants have evolved a strategy of stimulating and supporting specific groups of antagonistic rhizosphere microorganisms as a defense against diseases caused by soilborne pathogens. Antibiotic production plays a significant role in plant defense by many of these bacteria, and detailed information is now available about the genetics, biochemistry, and regulation of synthesis of several commonly-produced antibiotics. Similarly, many genes that contribute to the ability of these strains to colonize roots have been identified, and studies of naturally suppressive soils have provided evidence of preferential interactions between plant hosts and biocontrol bacteria, revealing the existence of functional diversity in protective populations of very closely related strains. Here, we consider how this knowledge can be applied to better manage the indigenous rhizosphere microflora, aid in the selection of more effective microbial amendments, and guide the tailoring of microflora through directed genetic manipulation to enhance crop health and productivity.