Inheritance of Sex in Fungi

Abstract

The fungus Hypomyces solani f. curcurbitae is normally hermaphroditic, but when it mutates to [male] or [female] the progeny of the crosses with the normal hermaphrodite occur in the ratio of 1:1 indicating that the factors for [male] and [female] are alleles of the factor for hermaphrodite. However, when 200 single-ascospore thalli from the cross [male] [female] were tested, 4 sex types appeared: 84 [male]" [male], 64 [female] [female] , 24 hermaphrodites and 28 neuters. The factors for [male] X [female] are thus not alleles but occupy loci some distance apart in homologous chromosomes. Crossing over between the loci occurs and is responsible for the appearance of hermaphrodites and neuters in the [male] X [female] cross.