Comparison of malt agar with malt agar plus orthophenylphenol for isolating Armillariamellea and other fungi from conifer roots

Abstract

Armillariamellea isolations from the roots of dead and dying conifer saplings increased by 40% when o-phenylphenol (OPP) was added to malt agar compared with isolations on malt agar alone; they were similar on the two media from the roots of larger, healthy trees. This is attributed largely to the inhibiting effect of the additive on fast-growing Hyphomycetes and other fungi which are far more abundant in the roots of dead or dying saplings than in the roots of healthy older trees. Decay-causing Basidiomycetes other than A. mellea were isolated less frequently, whereas bacteria and yeasts were isolated more frequently, when OPP was added to the malt agar medium. This suggests that the additive must be used with discretion.