Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 18, 1997
Publication Date: N/A
Interpretive Summary: Aflatoxin contamination of maize grain by the mold Aspergillus flavus often results in serious health problems for humans and livestock. We wanted to determine if the molds infecting corn originate from soil, corn insects, or airborne spores. DNA fingerprinting revealed that the A. flavus molds from each of these sources are genetically distinct from one another and produced only three matches among 128 A. flavus molds from corn grain. These results show that the A. flavus molds in corn grain do not represent a single pathogenic race(s) originating exclusively from soil, corn insects, or airborne spores. This information is important in considering strategies aimed at preventing aflatoxin contamination by eliminating naturally occurring mold populations.
Technical Abstract: An evaluation was made of the genetic diversity (DNA fingerprinting) of 265 A. flavus strains, including subpopulations isolated from grain sampled at harvest (91 unique 'fingerprints' or genotypes/128 strains), field soil (26 genotypes/31 strains), corn insects (49 genotypes/52 strains) and air-spora (56 genotypes/ 58 strains), from a corn field near Kilbourne, Illinois. Eight A. flavus genotypes were isolated from grain samples harvested in different years (1988- 1991). Genotype #36, isolated from three corn samples, matched the DNA fingerprint of a K.E. Papa strain NRRL 19997, isolated from corn grown in Georgia. Ninety eight percent of the A. flavus genotypes produced sclerotia and 53% of the genotypes produced aflatoxin. Contrasts of DNA fingerprints revealed two (2) matches involving subpopulations from grain and soil, one (1) match for grain and corn insects, and no matches for corn and air-spora. The high genotypic diversity recorded for each subpopulation, in addition to a limited sample size, precluded any assessment of the relative importance of these subpopulations as sources of A. flavus infective inoculum. Aspergillus parasiticus was routinely isolated from soil samples.