Isolation, characterization, and genetic analysis of osmotic mutants of Neurospora crassa.

O S M O T I C (os) mutants of N . crassa are those whose growth is inhibited by high osmolalities. The usual operational definition is inhibition of growth of the mutant strains by the addition of 4% NaCl to the growth medium (PERKINS 1959). Prior to the present investigation, a group of os mutants had been mapped on linkage group IR, at approximately 90 map units from the centromere (PERKINS 1959; ST. LAWRENCE 1956; EMERSON 1963). These mutants will be designated os-1. Another mutant, called cut, had been mapped on the same linkage group at about 8.5 map units from the centromere (KUWANA 1960) and was shown to be inhibited by high concentrations of sucrose added to the growth medium ( KUWANA 1953). This paper presents data defining three other os loci on linkage group I and characterizing cut and flame-2 (flm-2) as additional osmotic loci on linkage group I.