CHARACTERIZATION OF THE ASPERGILLUS-FLAVUS POPULATION WITHIN AN ILLINOIS MAIZE FIELD

An evaluation was made of the genotypic diversity (DNA fingerprinting) of 269 A. flavus strains, including subpopulations isolated from grai n sampled at harvest (91 unique 'fingerprints' or genotypes/128 strain s), field soil (26 genotypes/31 strains), maize insects (49 genotypes/ 52 strains) and air-spora (56 genotypes/58 strains), from a maize fiel d near Kilbourne, Illinois. Eight A. flavus genotypes were isolated fr om 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. Ni nety-eight percent of the A. flavus genotypes produced sclerotia and 5 3 % produced aflatoxin. Contrasts of DNA fingerprints revealed two mat ches involving subpopulations from grain and soil, one match for grain and maize insects, and no matches for grain and air-spora. The high g enotypic diversity recorded for each subpopulation, in addition to a l imited sample size, precluded any assessment of the relative importanc e of these subpopulations as sources of A. flavus infective inoculum. Aspergillus parasiticus was routinely isolated from soil samples.