Preliminary evaluations of a small wafer assay for screening potential biological control agents
C M Freitag, J J Morrell
Screening potential biological agents for controlling wood decay fungi poses a dilemma. The ideal test would eliminate as many variables as possible. Most tests utilize pure cultures of the test organism on an artificial media which in no way resembles wood. The use of sawdust improves this approach, but the sawdust increases fungal access to the lignocellulose matrix, potentially inflating the importance of fungi which might not compete in the normal wood system. This report describes a simple wafer sandwich assay in which small test wafers colonized by the potential biocontrol agent and a Basidiomycete are placed above and below a sterile test wafer on moist soil in a glass petri dish. Weight loss of the middle wafer is used as a measure of biocontrol potential. Preliminary trials indicate that several previously identified biocontrol agents performed well in this test, inhibiting wood weight losses by both white and brown rot fungi. Because the wood structure is not disturbed, this method could also be used to screen wood treatments which might enhance colonization by the biological control agent.