GENOTYPIC DIVERSITY OF ASPERGILLUS-PARASITICUS IN AN ILLINOIS CORN FIELD

Aspergillus parasiticus was isolated from direct platings of soil from a corn field near Kilbourne, Illinois. Soil contained 0.2 to 4.0 CFU of Aspergillus flavus and/or A. parasiticus per g of soil. Sixty isola tes of A. parasiticus, each from a separately collected soil sample, w ere examined for ability to produce sclerotia and aflatoxins, and were subjected to DNA fingerprinting. PstI digests of total genomic DNA fr om each isolate were probed using the pAF28 repetitive sequence. Among 60 isolates analyzed, 33 (55%) distinct DNA fingerprint groups were i dentified (each group sharing less than 80% pAF28 band similarity), in cluding 50 distinct genotypes (83%) with less than 100% pAF28 band sim ilarity A single A. parasiticus fingerprint group represented 13% of t he sample population. The 83% genotypic diversity of the A. parasiticu s population was equivalent to the 81% genotypic diversity recorded ea rlier for a population of 31 A. flavus isolates from the same field so il. Sclerotia were produced by 82% of the 50 A. parasiticus genotypes during dark incubation at 25 degrees C. All isolates of A. parasiticus produced aflatoxin B1B2 and G(1)G(2), whereas only 36% of the 31 A. f lavus isolates from these soils produced aflatoxins.