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A Coconut-Agar Medium for Rapid Detection of Aflatoxin Production by Aspergillus spp.. M. T. Lin, Associate Professor, Dept. of Plant Biology, University of Brasilia, Brasilia, 70.000 DF, Brazil; J. C. Dianese, Associate Professor, Dept. of Plant Biology, University of Brasilia, Brasilia, 70.000 DF, Brazil. Phytopathology 66:1466-1469. Accepted for publication 15 June 1976. Copyright © 1976 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-66-1466.

An agar medium containing commercial coconut extract and with pH adjusted to 6.9 was developed for detection of aflatoxin production by Aspergillus spp. On this medium, aflatoxin-positive, but not -negative, isolates showed a characteristic blue or blue-green fluorescence in agar surrounding the colonies when observed under ultra-violet light. The fluorescence produced by strong aflatoxin producers began to appear within 32 hours after transfer to the medium. The intensity of fluorescence increased with prolonged incubation. An incubation time of 3 days was sufficient for detection of even very weak aflatoxin production. Several known aflatoxin promoters either had no effect or decreased the production of fluorescence. Incubation at 20 C slightly reduced the intensity of fluorescence, whereas no difference was observed at 24, 28, or 32 C. Seven of 27 Brazilian isolates of the A. flavus group that were tested on the medium were aflatoxin-positive; this was confirmed by thin-layer chromatographic assay of culture broths. An orange-yellow pigmentation on the coconut-agar medium consistently was associated with the production of fluorescence and the aflatoxin-producing ability of Aspergillus spp. The pigmentation can be used to identify aflatoxin-positive isolates without the use of ultra-violet light. The medium is easy to prepare and aflatoxin detection is rapid and simple with only minimal equipment.