Sorosporium consanguineum: relation between variable nuclear condition and dissociation

Saprophytic development of Sorosporium consanguineum and its nuclear cycle were studied on laboratory media. During vegetative reproduction, the nuclei of the monokaryotic sporidia were shown to first migrate into developing bud cells where division occurs, one nucleus returning to the parent cell prior to completion of cell division. Following fusion of sporidia of opposite mating type and subsequent formation of infection hyphae, dikaryons eventually dissociated, giving rise to sporidia of both sex groups in the process. As a result of dissociation, shown to occur in several ways, "satellite" sporidial colonies characteristically formed in advance of the parent colony and fusions again occurred between sporidia of opposite mating type. Reports of variable nuclear condition of mycelia in other species of smut fungi in culture are discussed in light of these findings.