Antibiosis and Beyond:
Genetic Diversity, Microbial
Communities, and Biological Control
Jocelyn Milner, Laura Silo-Suh, Robert M. Goodman, and Jo Handelsman
Healthy plants grown in normal environments, such as the field or a greenhouse, are virtually never free of microbes. Anyone who has attempted to take plant tissues from the open environment into axenic culture, a technology commonly used in commercial horticulture, can attest to the perversity of microbial "contamination." Some of these organisms cause disease and some provide a known benefit to the plant. Many plant-associated microorganisms may have no effect on the plant or may influence plant health in important ways that have not yet been discovered. One goal of plant health management is to minimize the impacts of the detrimental microorganisms and maximize the effects of beneficial ones. A specific application of this concept is microbial biological control, which we define as the use of added microorganisms or organisms already in the soil as part of the crop production system to keep losses from disease and pests below economically acceptable thresholds. An extension of the concept of microbial biological control is the potential for managing communities of microorganisms to sustain plant health.
Conceptually, there are numerous possible approaches to developing microbial biological control strategies ( Campbell 1994; Jacobsen and Backman 1993; Gutterson 1990; Deacon and Barry 1993; Fravel 1988; Weller 1988; O'Sullivan and O'Gara 1992). Most biological control research has started with either a chance observation of, or a deliberate attempt to find, specific microorganisms that suppress a disease or exhibit antibiosis toward a pathogen. Although there are numerous examples of microorganisms that inhibit growth and development of pathogens in the laboratory,