Observation 63970: Aspergillus flavus Link

This fungus was first isolated from almond mummies, infested with Naval Orange Worm, remaining on the tree after harvest at the USDA Wolfskill Germplasm Repository near Winters, Ca.

The morphology and appearance of A.parasiticus and A. flavus are very similar so it is difficult to distinguish them without an oil immersion microscope lens to view the spores. The spores of A. parasiticus are more echinulated (spiny) than A. flavus. Chemotaxonomy is a more reliable way of distinguishing the two species. First run a thin layer chromatography plate to separate the toxins and then view it under a black light. A. parasiticus always makes 2 green spots indicating aflatoxins G1 & G2 plus two 2 blue-green spots indicating aflatoxins B1 & B2. Aspergillus flavus may or may not produce B1 & B2 spots and no G spots because less than half of A. flavus isolates found are atoxigenic which has led to the development of a biocontrol method by USDA researcher, Peter Cotty, of finding very aggressive strains of atoxigenic A. flavus to grow in mass culture and spread over field crops with toxigenic strain problems. He has found good results from the aggressive atoxigenic strains out competing the toxigenic ones in field trials thus reducing the levels of aflatoxin contamination in the crop.


The S strain of A flavus indicated by the mat of small white (immature) and black (mature) sclerotia. The S strain always makes the B1 and B2 toxins.

Proposed Names

84% (1)
Used references: The Genus Aspergillus Rapier KB & Fennel DI
Based on chemical features: Thin layer chromatography plates had spots of Aflatoxins B1 & B2 viewed under UV light 365 nm and no Aflatoxin G present.

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Created: 2011-02-28 03:21:11 CST (-0500)
Last modified: 2017-07-24 02:17:17 CDT (-0400)
Viewed: 462 times, last viewed: 2019-10-28 02:07:29 CDT (-0400)
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