Biocontrol of soilborne plant pathogens with fungi

Abstract

The mechanisms of biocontrol of soilborne pathogens are discussed. They include competition, parasitism and antibiosis, all of which function in the rhizosphere. Competition may be the mechanism most prevalent in natural systems, but it is often difficult to observe experimentally. Parasitism can be an efficient control mechanism and has the potential to be very target specific, as in control of Sclerotinia spp. by Sporidesmium. Although antibiosis has not been definitively demonstrated to be the sole control mechanism of any biocontrol fungus, there is evidence for involvement of antibiotics, antibiotic-like compounds, or enzymes in control mediated by numerous fungi including isolates of Trichoderma, Gliocladium and Talaromyces. In general, these mechanisms are not mutually exclusive; different mechanisms may act in combination to produce biocontrol. Knowledge of mechanisms can be used to design screening procedures for potential antagonists, evaluate management practices which favour antagonists, select genetically improved antagonists and assist in registration of antagonists. This paper was presented at a symposium held at the Beltsville Agricultural Research Center (BARC), Beltsville, MD, USA, on 8-11 May, 1989.