Analysis of two additional loci in Neurospora crassa related to Spore killer-2

Two new loci found in one strain of Neurospora crassa (P2604) collected in Malaya are related to the meiotic drive system Spore killer Sk-2. Sk-2 was found in Neurospora intermedia and introgressed into N. crassa. P2604 showed high resistance to killing when crossed to Sk-2. This resistance was found to be linked to, but not allelic to, resistance locus r(Sk-2) on LGIIIL. Analysis showed that the high resistance phenotype of P2604 requires resistance alleles at two different loci on LGIIIR. Strains carrying a resistance allele at only the proximal or the distal locus, respectively, were obtained and intercrossed. Highly resistant strains were obtained by rejoining the two genes. The proximal locus alone confers a low level of resistance. This locus was named pr(Sk-2) for partial resistance to Sk-2. The distal locus was named mod(pr) because its only known phenotype is to modify pr(Sk-2).