Hermaphroditism Involving Self-Sterility and Cross-Fertility in the Ascomycete Pleurage Anserina

Abstract

SUMMARY In Pleurage anserina the mycelia derived from uninucleate ascospores are hermaphroditic, self-sterile but capable of cross- fertilization. All of the cultures from uninucleate ascospores fall into two classes, A and B, on the basis of compatibility; all cultures from single uninucleate spores belonging to class A are self-sterile and inter-sterile; all cultures from single uninucleate spores of class B are self-sterile and inter-sterile, but any one or all cultures derived from uninucleate spores of class A are reciprocally fertile with any one or all cultures derived from single uninucleate spores of class B. The cultures derived from the normal binucleate ascospores appear to be homothallic, i.e. hermaphroditic and self-fertile, as cultures from single ascospores readily develop perithecia; however, a study based upon hyphal tips shows that the individual nuclei differ from each other, not in sex but in compatibility, each nucleus retaining its individuality so that mycelia from a hyphal tip containing nuclei of the same compatibility class will give rise to both male and female organs, but will prove self-sterile. The mycelia arising from a normal binucleate ascospore therefore, although appearing to be homothallic, that is hermaphroditic and self-fertile, in reality comprise two hermaphroditic cultures growing intermingled as one, each giving rise to both male and female organs which are self-sterile but which are reciprocally fertile. It has previously been pointed out that cultures of class A and B are each hermaphroditic; but there is also evidence that within each nucleus contained in the male and female organs of each class are the genetical qualities of bisexuality. If we represent the difference of compatibility between class A and B by two factors S₁ and S₂ respectively we may assume, from experimental evidence, that factor S₁ and S₂ are allelomorphic and that associated with each are sex factors. The sexuality of the giant multinucleate ascospores is essentially like that described for the normal binucleate ascospores, except that there are more initial nuclei concerned; these nuclei belong to two classes, each of which gives rise to both male and female organs which are self-sterile but reciprocally fertile. Because it has been found that cultures from uninucleate ascospores of P. anserina are bisexual self-sterile and cross-fertile, it is no longer justifiable to conclude that a culture from a single spore is unisexual simply because it does not produce fruiting bodies when grown alone, or because it requires the mating of complementary mycelia; also it is no longer justifiable to conclude that a culture derived from a single spore is simply bisexual and self-fertile because it does produce fruiting bodies when grown by itself.