ABSTRACT
Cephalosporium acremonium is a commercially important filamentous fungus used in the production of cephalosporin antibiotics, most commercial strains being derived from the Brotzu isolate. When fused protoplasts from complementing auxotrophs are regenerated on a medium selecting for prototrophic growth two types of product may be recovered: Heterokaryons formed from protoplasts undergoing cytoplasmic but not nuclear fusion and Diploids, aneuploids, or haploid recombinants formed from protoplasts undergoing cytoplasmic and nuclear fusion. Genetical analysis may proceed along two lines: either by highly unstable heterozygotes and their breakdown products or through the direct selection of haploid recombinants. In the selectant analysis approach, one marker is chosen from each strain to provide a positive selection for the isolation of recombinants, and the others are allowed to segregate in a neutral manner. Both the heterozygote and the selectant technique can be used to allocate new markers to linkage groups. The construction of suitably marked “master strains” would facilitate this task.
