Elad, Y., Department of Plant Pathology, ARO, The Volcani Center, Bet Dagan, 50520, Israel

Mechanisms involved in the biological suppression of infection and inoculum potential of Botrytis cinerea are numerous and variable and the involvement of two or more mechanisms has been demonstrated in several systems. Reported combinations include antibiosis with enzyme degradation of B. cinerea cell walls; competition for nutrients followed by interference with pathogenicity enzymes of the pathogen or with induced resistance; and alteration of plant surface wettability combined with antibiosis. Since germinating B. cinerea conidia are dependent on the presence of nutrients, competition for nutrients is regarded as important in systems where biocontrol is involved. Conidial viability and germination capacity are also potentially affected by the presence of antibiotics produced by biocontrol agents and present in the phyllosphere. Slower in action are mechanisms involving induced resistance in the host plant and production of hydrolytic enzymes that degrade B. cinerea cell walls. The latter has been demonstrated much more convincingly in vitro than in the phyllosphere. Biocontrol in established lesions and reduction of sporulation on necrotic plant tissues is a means to minimize the pathogen inoculum. © 1996 Kluwer Academic Publishers.