Survey of Vietnamese peanuts, corn and soil for the presence of Aspergillus flavus and Aspergillus parasiticus.

Aspergillus flavus and Aspergillus parasiticus cause perennial infection of agriculturally important crops in tropical and subtropical areas. Invasion of crops by these fungi may result in contamination of food and feed by potent carcinogenic aflatoxins. Consumption of aflatoxin contaminated foods is a recognised risk factor for human hepatocellular carcinoma (HCC) and may contribute to the high incidence of HCC in Southeast Asia. This study conducted a survey of Vietnamese crops (peanuts and corn) and soil for the presence of aflatoxigenic fungi and used microsatellite markers to investigate the genetic diversity of Vietnamese Aspergillus strains. From a total of 85 samples comprising peanut (25), corn (45) and soil (15), 106 strains were isolated. Identification of strains by colony morphology and aflatoxin production found all Vietnamese strains to be A. flavus with no A. parasiticus isolated. A. flavus was present in 36.0% of peanut samples, 31.1% of corn samples, 27.3% of farmed soil samples and was not found in virgin soil samples. Twenty-five per cent of the strains produced aflatoxins. Microsatellite analysis revealed a high level of genetic diversity in the Vietnamese A. flavus population. Clustering, based on microsatellite genotype, was unrelated to aflatoxin production, geographic origin or substrate origin.