Antagonistic effect of Trichoderma spp. against basidiospores
U Srinivasan, T L Highley, S C Croan, A Bruce
All screening of potential biocontrol agents of wood decay fungi have previously been used against basidiomycete mycelium. Similarly, experiments designed to evaluate the mechanisms involved in antagonism (soluble metabolites and volatile antibiotics) between biological control agents and target fungi have always been carried out on mycelial inoculum. Basidiospores are a primary source of infection leading to decay of wood exposed above ground and are the pathogenic form of the target fungus contact with a biocontrol antagonist. This paper examines the antagonistic responses of Trichoderma spp. against wood decay basidiospores. The paper also examines the influence of nutrient composition of growth media on the antagonistic responses by Trichoderma isolates. Assessment of individual modes of antagonism were carried out on two media types, a 3% malt extract agar and a nutritionally poorer minimal medium. The outcome of antagonism between Trichoderma isolates and wood decay basidiospores was often found to be dependent on the media type. Further studies were also carried out to evaluate the extent of inhibition of the basidiospores by concentrated soluble metabolites of Trichoderma isolates in vitro and in vivo i.e., in wood. The significance of using mycelial or spore inoculum with respect to antagonism for screening of biological control agents for wood protection is discussed.