Variable electrophoretic karyotypes of members of Aspergillus Section Flavi

Summary

Contour-clamped homogeneous electric field gel electrophoresis was used to establish karyotypes for fungi of Aspergillus Section Flavi. Under identical electrophoretic conditions, five to eight chromosomal bands were separated in Aspergillus flavus isolates and five to seven chromosomal bands in A. parasiticus isolates. Each distinct chromosomal band contained one or more chromosomes. Other members of Aspergillus Section Flavi (A. oryzae, A. sojae, and A. tamarii) had similar karyotypes to those of A. flavus and A. parasiticus. A related species, A. versicolor, showed six chromosomal bands. With the exception of small chromosomes present in some isolates, the estimated sizes of chromosomes for all six species range from approximately 3.0 to ≥7.0 Mb. It is likely that all isolates of these species contain the same number of large (>3 Mb) chromosomes; however, not all of the chromosomal bands could be resolved into separate chromosomes for each isolate due to chromosome length polymorphisms. This variability, observed in A. flavus and A. parasiticus, generated unique chromosomal band patterns within these species. The total genome sizes of these fungi were at least as large as those reported for A. nidulans and A. niger (31–38.5 Mb). Conserved genes were mapped to analogous chromosomes of A. flavus and A. parasiticus by gene hybridization.