Submitted to: Aflatoxin Elimination Workshop Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: December 17, 1996
Publication Date: N/A
Technical Abstract: An evaluation was made of the sclerotium- and aflatoxin- producing abilities of 259 strains of Aspergillus flavus isolated from soil samples collected (1988-1990) in 39 crop fields in eastern Iowa that were the source of corn that tested higher than 20 ppb aflatoxin at harvest in 1988 and 347 strains of A. flavus from soil samples collected (1989-1990) from corn rotation plots at three Iowa State Agricultural Experiment Stations. Sclerotia were produced by 95% of the A. flavus isolates from Iowa soils. Aflatoxin was produced by 49% of the A. flavus strains from 39 crop fields but only 20% of the A. flavus strains from the experimental corn rotation plots. The prevalence of non-aflatoxigenic strains in Iowa experiment stations may function naturally in reducing the severity of an aflatoxin outbreak. DNA fingerprinting was performed on 83 of the aflatoxin-producing A. flavus strains from Iowa crop fields. Pst1 digests of total genomic DNA from each isolate were probed using the pAF28 repetitive sequence. Fifty-four (65%) distinct genotypes (each genotype with less than 100% pAF28 band similarity) were identified. Genotype 36 was the most frequently recorded genotype from Iowa crop fields and matches the DNA fingerprint of A. flavus strains isolated from corn grown in a field in central Illinois as well as NRRL 19997 (= K. E. Papa h-c group 21) isolated from corn grown in Georgia. Eight of ten genotypes recorded from crop fields in two or more Iowa counties, were previously isolated from the University of Illinois River Valley Sand Field, Kilbourne, IL.