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Detection and estimation of conidial abundance of Penicillium verrucosum in soil by dilution plating on a selective and diagnostic agar medium (DYSG)

Published online by Cambridge University Press:  01 July 1999

SUSANNE ELMHOLT
Affiliation:
Department of Crop Physiology and Soil Science
RODRIGO LABOURIAU
Affiliation:
Biometry Research Unit, Danish Institute of Agricultural Sciences, Research Centre Foulum, P.O. Box 50, DK-8830 Tjele, Denmark
HELLE HESTBJERG
Affiliation:
Department of Crop Physiology and Soil Science
JØRGEN M. NIELSEN
Affiliation:
Department of Crop Physiology and Soil Science
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Abstract

Penicillium verrucosum is one of the main producers of ochratoxin A (OA) in agricultural commodities. To forecast the risk of OA contamination, there is a need to improve our knowledge on the ecology of P. verrucosum in the field. Dilution plating on ‘dichloran yeast extract sucrose 18% glycerol agar’ (DYSG) offers a simple and very sensitive method of detecting P. verrucosum propagules in soil. The properties of DYSG are illustrated in a suspension mixture experiment and confirmed in a soil mixture experiment. In the latter, P. verrucosum could be detected in conidial concentrations below 200 colony forming units (cfu) g−1 soil even when it constituted no more than 0·3% of the cfu. Furthermore, the DYSG method can be used to estimate the abundance of P. verrucosum propagules in soil with good precision. In some of the analysed cases, however, it was necessary to use appropriate mathematical models to treat results with high numbers of cfu on the Petri dishes.

Type
Research Article
Copyright
© The British Mycological Society 1999

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