Assignment of RFLP, RAPD and isoenzyme markers to Aspergillus nidulans chromosomes, using chromosome-substituted segregants of a hybrid of A. nidulans and A. quadrilineatus

Chromosome-substituted haploid segregants were selected from among the benomyl-induced progeny of an interspecific hybrid produced by polyethylene-glycol-induced fusion of protoplasts of an Aspergillus nidulans 'master strain' and an A. quadrilineatus auxotrophic mutant. These segregants were examined by RFLP, RAPD, and isoenzyme analysis. The A. nidulans ribosomal repeat unit was assigned to chromosome V, while the benA and the pyrG genes were assigned to linkage groups VIII and I, respectively, of A. nidulans. None of the other cloned genes tested (gdhA, amdS and 25 s rRNA) showed polymorphism between the two parents. The method was also used to assign RAPD markers and isoenzyme bands of β-arylesterase, phosphatases, NAD-dependent malate dehydrogenase, and cellulase, to A. nidulans chromosomes and/or to their A. quadrilineatus equivalents. The isoenzyme and DNA sequences assigned to chromosomes could be used to saturate the genetic map of A. nidulans, or could serve as starting points for the construction of a genetic map of A. quadrilineatus. No method affording the same possibilities has been described so far in Aspergilli. This chromosome-assay method may be a useful alternative to pulsed-field-gel electrophoretic procedures for the assignment of molecular markers to chromosomes.