CONSTRUCTION AND CHARACTERIZATION OF A DNA-PROBE FOR DISTINGUISHING STRAINS OF ASPERGILLUS-FLAVUS

Repetitive DNA sequences have proven useful and reliable characters in evaluating genetic relatedness of strains at different levels of taxo nomic classification. A DNA probe was constructed to distinguish among strains of Aspergillus flavus by DNA fingerprinting techniques. Chrom osomal DNA of A. flavus var. flavus NRRL, 6541 was partially digested with EcoRI and ligated to a Lambda Dash bacteriophage vector. Four lam bda clones were identified which displayed multiple and distinct bands when hybridized with chromosomal DNA from seven strains of A. flavus var. flavus digested with either EcoRI or PstI. One of these clones wa s chosen for further analysis and was subcloned Into pUC19. The subclo ne, pAF28, contained a 6.2-kb chromosomal DNA insert and was able to d istinguish among strains characterized by and E. Papa (Mycologia 78:98 -101, 1986) as belonging to 22 different vegetative compatibility grou ps. The subclone identified unique banding patterns when hybridized to genomic DNA digested with PstI. The cloned probe may be species speci fic as it hybridized with the DNA of all isolates of A. flavus tested in addition to strains recognized as varieties of A. flavus (e.g., A. flavus var, oryzae, A. flavus var. parasiticus, and A. flavus var. soj ae). pAF28 hybridized to a single band on a Southern blot with Aspergi llus nomius DNA but did not hybridize with the DNA of other fungal spe cies tested including Aspergillus ochraceus, Aspergillus auricomus, As pergillus alliaceus, Fusarium moniliforme, and Penicillium thomii.