An evaluation was made of the genotypic diversity
(DNA fingerprinting) of 269 A. flavus strains,
including subpopulations isolated
from grain sampled at harvest (91 unique
‘fingerprints’ or genotypes/128 strains),
field soil (26 genotypes/31 strains), maize insects
(49 genotypes/52 strains) and air-spora (56 genotypes/58
strains), from a maize field near Kilbourne, Illinois. Eight
A. flavus genotypes were isolated from grain samples
harvested in different years (1988–1991). Genotype 36,
isolated from three maize
samples, matched the DNA fingerprint of a K. E. Papa strain
NRRL 19997, isolated from maize grown in Georgia.
Ninety-eight percent of the A. flavus genotypes
produced sclerotia and 53% produced aflatoxin. Contrasts of
DNA fingerprints revealed two
matches involving subpopulations from grain and soil, one
match for grain and maize insects, and no matches for grain
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.