Sunday, August 10, 2008
P73

Toxigenic and atoxigenic Aspergillus section Flavi isolates from corn producing areas in Thailand

Khanchai Danmek1, Kenneth E. Damann2, and Hunsa Punnapayak1. (1) Plant Biomass Utilization Research Unit, Department of Botany, Faculty of Science,, Chulalongkorn University, Bangkok, 10330, Thailand, (2) Department of Plant Pathology and Crop Physiology, 302 Life Science Building,, Louisiana State University, Baton Rouge, LA 70803

 Aspergillus section Flavi including Aspergillus flavus and parasiticus are nomally considered as prominent aflatoxin producers in corn producing areas.  We have screened Aspergillus section Flavi from corn producing areas in Thailand. Soil samples from the major corn producing areas of Thailand were collected and plated in aspergillus flavus and parasiticus agar (AFPA) to select for Aspergillus section Flavi. We found 55 isolates of Aspergillus flavus, 18 isolates of A. tamarii, 8 isolates of A. parasiticus, 4 isolates of A. sojae, and 12 isolates of A. nomius. Typically A. flavus and A. parasiticus produced orange color when viewing from the reversed side of the AFPA plate. However these isolates of Aspergillus section Flavi from Thailand showed different color on the reversed side of colony including deep orange color (A. flavus), pale orange color (A. parasiticus, A. sojae, and A. nomius), and deep brown color (A. tamarii). All fungal isolates were cultivated in modified yeast extracted medium for the characterization aflatoxins. All A. tamarii did not have ability to produce aflatoxin B1 and B2. All A. parasiticus had high ability to produce 4 groups of aflatoxins (B1, B2, G1, and G2), with aflatoxin type B1 more than type G1 in the medium. A. nomius produced 4 groups of aflatoxin similar to A. parasiticus but 7 of 12 strains of isolates produced aflatoxin type G1 more than type B1 in mYES. Interestingly, 4 isolates of A. flavus did not show ability to produce aflatoxin and were considered as atoxigenic fungi.

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