Microbiological control of soil‐borne phytopathogenic fungi with special emphasis on wilt‐inducing Fusarium oxysporum

Contents   Summary  529 I. Biological control of plant diseases: state of the art  530 II. Main modes of action of biological control agents  530 III. The protective strains of F. oxysporum: an unexplored model  532 IV. Future directions for the study of the protective capacity of strains of F. oxysporum  539 V. How to make biological control successful in the field?  540   References  541 Summary Plant diseases induced by soil-borne plant pathogens are among the most difficult to control. In the absence of effective chemical control methods, there is renewed interest in biological control based on application of populations of antagonistic micro-organisms. In addition to Pseudomonas spp. and Trichoderma spp., which are the two most widely studied groups of biological control agents, the protective strains of Fusarium oxysporum represent an original model. These protective strains of F. oxysporum can be used to control wilt induced by pathogenic strains of the same species. Exploring the mechanisms involved in the protective capability of these strains is not only necessary for their development as commercial biocontrol agents but raises many basic questions related to the determinism of pathogenicity versus biocontrol capacity in the F. oxysporum species complex. In this paper, current knowledge regarding the interaction between the plant and the protective strains is reviewed in comparison with interactions between the plant and pathogenic strains. The success of biological control depends not only on plant–microbial interactions but also on the ecological fitness of the biological control agents.