Rapid differentiation of four related species of Koji molds by agarose gel electrophoresis of genomic DNA digested with SmaI restriction enzyme.

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Abstract
We describe a simple and rapid procedure for differentiating the koji molds, Aspergillus oryzae and A. sojae, from the closely related species, A. flavus and A. parasiticus. Total DNA from the Aspergillus strains was digested with the restriction enzyme SmaI and was separated by electrophoresis on an agrose gel. The size of the bands, ranging from 3 to 5 kb strongly stained with ethidium bromide, was intraspecifically consistent but was interspecifically different. The difference in the size of the bands seemed to be due to the divergence in the nucleotide sequence of nuclear ribosomal DNA. The restriction enzyme cleavage patterns can be readily distinguished on agarose gel, so they will provide a useful tool for identifying koji molds and other related species.