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Title: Description of a Distinctive Aflatoxin-Producing Strain of Aspergillus nomius that Produces Submerged Sclerotia

item DOSTER, MARK - University Of California
item Cotty, Peter
item MICHAILIDES, THEMIS - University Of California

Submitted to: Mycopathologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/14/2009
Publication Date: 5/31/2009
Citation: Doster, M.A., Cotty, P.J., Michailides, T.J. 2009. Description of a Distinctive Aflatoxin-Producing Strain of Aspergillus nomius that Produces Submerged Sclerotia. Mycopathologia. 168(4):193-201.

Interpretive Summary: Some members of the group of fungi called Aspergillus produce a poison called aflatoxin when they infect crops like cottonseed, pistachios, and figs. Crops that contain significant amounts of aflatoxins cannot be used as food or feed. Aflatoxin formation is difficult to prevent, in part because all the Aspergillus strains (strain is the fungal equivalent to breed) that contaminate crops with aflatoxins have not been identified. A unusual strain that produces aflatoxins was discovered on tree crops in California. This strain also looks and behaves different from other Aspergillus flavus strains. This new strain gives a broader view of which fungi produce aflatoxins and how aflatoxin-producing fungi may differ in behavior. It is hoped that the improved understanding of these aspects will provide scientists an opportunity to devise new methods for preventing aflatoxin formation.

Technical Abstract: Aspergillus nomius var. elaeosporus var. nov. is described from pistachio, pecan, and fig orchards in California. Similar to the typical variety of A. nomius, var. elaeosporus produced both B and G aflatoxins but not cyclopiazonic acid and grew poorly at 42 C. Furthermore, previous research using restriction fragment length polymorphism analysis indicated that this new variety is closely related to the typical variety of A. nomius. However, unlike the typical variety, which produces large elongated sclerotia on the surface of the medium, var. elaeosporus produced small (mean diameter less than 0.3 mm) spherical sclerotia submerged in the medium. Another difference is that var. elaeosporus has predominantly uniseriate heads, whereas the typical variety of A. nomius has predominantly biseriate heads. The colony color of var. elaeosporus on Czapek solution agar and on Czapek yeast extract agar was olive or grayish green, which is more yellowish in hue than the other aflatoxin-producing fungi. The conidium ornamentation for var. elaeosporus was intermediate between the almost smooth conidia of A. flavus and the rough conidia of A. parasiticus. Because the typical variety of A. nomius has never been found in California, the isolates of var. elaeosporus from orchards represent the first occurrence of A. nomius in California.