Recovery and Detection of Deuteromycete Conidia from Soil

Abstract

The field ecology of Penicillium verrucosum (important Ochratoxin A producing storage fungus) is poorly understood. It is for example not known whether the fungus can survive, proliferate, and infect cereal plants in the field. For such studies, a sensitive method is needed to screen the presence of the fungus in naturally and artificially infested soils. Prior to experiments with deliberate release of P. verrucosum into the field environment, preliminary experiments were performed regarding four different media (V8, YES, DRYES, and DYSG). Only DYSG has selective and indicative properties that makes it suitable as a medium for recover and easy detection of P. verrucosum from a population of deuteromycete soil fungi. The recovery and detection level of P. verrucosum on DYSG was determined on Petri dishes, plated with mixtures from a suspension of a non-spiked soil and decreasing amounts of a suspension from a soil, spiked with conidia of P. verrucosum. Results showed a very high recovery (91% and 112%) of P. verrucosum and a detection level of 300 P. verrucosum CFU/g dry soil. In conclusion: given a good selective medium, classical microbiological methods may well be used for monitoring fungi deliberately released into the environment.