Genetic Analysis of an Insertional Translocation in an Osmotic-Sensitive Mutant of \u3cem\u3eNeurospora crassa\u3c/em\u3e

Mutant strains which have translocations provide valuable research tools for use in cytogenetic analyses in N. crassa. Mutants which produce more than 10% white ascospores are examined for the presence of a translocation. SS-656, an osmoticsensitive mutant on N. crassaisolated in the Georgia Southern Neurospora Genetics Laboratory, was found to produce 21% white ascospores when it was crossed to the tester strain fluff/ (OR). This finding supported the presence of a translocation in SS- 656. Further analysis of 160 unordered tetrads from the same cross produced black to white ascospore ratios of 8:0 (41.5%); 6:2 (12.3%); 4:4 (32.1%); 2:6 (4.7%); 0:8 (9.4%) which further supported the presence of a translocation which appeared to be insertional. When the progeny were crossed to wild type, half the progeny were fertile. The other half produced perithecia but did not produce ascospores. Three of the fertile progeny produced white ascospores at the same frequency as the parent strain. Thus the translocation was shown to go through the cross. Growth tests of the three progeny which contained the translocation indicated that one was osmotic sensitive but that the other two were not osmotic sensitive. The observed segregation of osmotic sensitivity from the translocation indicated that the translocation was not responsible for the osmotic-sensitive trait of SS-656. Crosses of SS-656 to multicent-1, a tester strain useful for mapping translocations, indicated the insertional translocation occurred between linkage groups II and III. The osmotic sensitivity in SS-656 was found to be linked to the cut locus in linkage group IV