Value of a plant growth retardant for isolating soil fungi

Abstract

Various concentrations of 42 dyes, alkaloids, plant-growth regulators, and miscellaneous chemicals were tested as substitutes for rose bengal in peptone–dextrose–streptomycin agar for isolating soil fungi by the dilution-plate method. Most of the chemicals did not compare favorably with rose bengal, but a plant growth retardant 2,4-dichlorobenzyltributylphosfonium chloride (phosfon) used at 500 μg/ml significantly increased numbers of fungal colonies per plate and suppressed fast-growing fungi. The value of phosfon persisted even in the presence of gibrel, which alone induced rapid overgrowth of plates by Trichoderma and the Mucoraceae.