DYES AS FUNGAL INHIBITORS - EFFECT ON COLONY ENUMERATION

The effects of three dyes on the colony enumeration of nine fungal str ains (including members of the Deuteromycetes and Zygomycetes) in pure and mixed cultures were investigated. Using malt extract agar as basa l and control medium, the following dyes and concentrations were assay ed: auramine (25 ppm), gentian violet (5 ppm) and malachite green (1 p pm). The chemicals commonly used in commercial media dichloran (2 ppm) and rose bengal (50 ppm) were included in the study as reference moul d-spreading inhibitors. Higher counts were usually obtained in the med ia containing dichloran, rose bengal or auramine, including the contro l medium in the absence of chemical when the mixed-conidium inocula di d not include a spreading mould. Nevertheless in most cases no signifi cant differences were observed between them. Malachite green (1 ppm) p erformed mainly as a strong inhibitor of spreading moulds, only allowi ng adequate colony development and recoveries of both Fusarium and Asp ergillus strains tested.