Genetics of Sordaria Fimicola. VIII. Nitrosoguanidine Mutagenesis and Isolation of Protoperithecial Mutants

SUMMARY

An effective mutagenic method for obtaining auxotrophic and self-sterile mutants in the homothallic pyrenomycete Sordaria fimicola consists of treating mycelium grown on a dialysis membrane with nitrosoguanidine, followed by the isolation of random ascospores from perithecia that later appear on the mycelium. Self-sterile and colonial-growth mutants can be recognized on complete medium containing sorbose. A 4-hr treatment with 100 μM solution of the mutagen yields approximately 5–6% ascospores with auxotrophic and selected morphological mutations. A number of selfsterile mutants with blocks at the protoperithecial stage produce hybrid perithecia in crosses. Those which show no selling in such crosses would be especially suitable in the the search for complementing alleles that demonstrate the synthesis of balanced heterothallism. One protoperithecial mutant is linked to the ascospore-color locus g₁ on linkage group I.