Ultrastructure of infection of Cokeromyces recurvatus by Piptocephalis unispora (Mucorales)

Infection of the mucoraceous host Cokeromyces recurvatus by Piptocephalis unispora was studied ultrastructurally, using a new technique involving yeast-phase cells of the host to obtain large numbers of infection sites for thin-sectioning. Morphologically, the haustorial apparatus was similar to that of fungi parasitic on higher plants, and comprised an appressorium, a neck region with a collar and a neck ring, and a lobed region surrounded by a sheath matrix enclosed in an extra-haustorial membrane. Penetration of the host by the infection peg probably involved both enzymatic degradation and physical pressure. Reaction of the host to infection is described and the results related to the theory of host infection by haustorial fungal parasites.