Significance of ecology in the development of biocontrol agents against soil‐borne plant pathogens

Abstract

Approaches to the development of inoculant biocontrol agents (BCAs) of soil‐borne pathogens are discussed. Based on an analysis of the success of Peniophora (Phlebia) gigantea and Agrobacterium radiobacter it is argued that most subsequent attempts to develop inoculant BCAs have failed because the organisms were selected for in vitro antagonism but were ecologically unsuited to the environments where pathogens grow. The reported modes of action of BCAs are reviewed and in some cases reinterpreted. It is argued that antibiosis and some types of mycoparasitism have not been shown to be direct mechanisms of biocontrol in vivo; they might, instead, facilitate competition for substrates or sites as the primary mechanism of control. The ecology of BCAs in general is reviewed, with emphasis on interactions in microsites and the design of appropriate screening strategies. Specific examples are used to illustrate these points.