Early infection of maize roots bySporisorium reilianum f. sp.zeae

Summary A cytological study was carried out to describe the initial steps of infection of maize roots by the soil fungusSporisorium reilianum f. sp.zeae. Morphogenetic changes of the fungal cells were induced in the presence of maize roots. Extensive hyphal growth led to the formation of a thick fungal layer colonising the maize root surface. This structure is original in interactions of members of the family Ustilaginaceae with plants. In the thick fungal layer, we observed fimbriae inserted into the host cell wall, suggesting a direct role of these fibrillar structures in cell adhesion and infection processes. During infection, no reaction of host cells was observed. In this way, the fungus acts as a biotrophic endophyte during the initial steps of infection.