Role of Antibiosis in the Biocontrol of Plant Diseases*

Abstract

Understanding the mechanisms through which the biocontrol of plant diseases occurs is critical to the eventual improvement and wider use of biocontrol methods. These mechanisms are generally classified as competition, parasitism/predation, and antibiosis (6). This classification should provide a framework to aid our understanding of biocontrol, but should not circum­ scribe our thinking. These mechanisms have been discussed and reviewed in several papers (6, 10, 30, 39, 64, 76, 79, 82, 109, 110, 116) and books (14, 16, 23, 75, 83, 84, 92). While evidence for the role of competition and parasitism has been convincing, definitive evidence establishing the im­ portance of antibiosis has been more elusive. The lack of methods to evaluate in a meaningful way the production and function of compounds mediating antibiosis has been the major stumbling block to acquisition of basic informa­ tion on antibiosis. Recently developed methodologies have provided the means to look at the mechanisms of biocontrol. For this review, I consider antibiosis as antagonism mediated by specific or nonspecific metabolites of microbial origin, by lytic agents, enzymes, volatile compounds, or other toxic substances (47). Although the relative importance of antibiosis is still conjectural, new evidence obtained with the modem tools of microbial genetics, recombinant-DNA technology, and new detection techniques make a review of the literature appropriate.