ABSTRACT
Studies on hybridization in Aspergilli are of interest from several points of view. The finding that heterokaryon-incompatible strains of Aspergillus nidulans could be hybridized by protoplast fusion and that somatic diploids could be isolated has allowed the investigation of the genetic background of the incompatibility system to proceed. The introduction of protoplast fusion techniques has presented an opportunity to consider the prospect of interspecies hybridization in the Aspergilli. Where closely related species are involved, events parallel parasexual processes, i.e., the formation of a heterokaryon and subsequently a “hybrid” phenotype, or allodiploid, which is a consequence of nuclear fusion. Fusion of protoplasts from nutritionally complementing strains, using polyethylene glycol, resulted in recovery of heterokaryons after plating in osmotically stabilized minimal medium. Interspecies hybrid formation could also aid our understanding of the taxonomy of the genus. As the range of hybridization between species is extended, so a genetic basis for taxonomy may prove to be possible as an adjunct to existing approach.
