Naturally occurring diploid isolates of Aspergillus nidulans.

Six wild isolates belonging to heterokaryon compatibility group A of the Birmingham Aspergillus nidulans collection were shown to be diploid. Five were proven heterozygous for a naturally occurring conditional lethal haploid genotype. It is considered unlikely that these diploids arose by mutation in storage. Consequently, somatic diploidy is a regular occurrence in the natural population of this saprophytic species.