Some aspects of the life histories of certain smut fungi

Abstract

Accounts of the sporidial stages of members of the genus Entyloma are very confusing, and the role of the sporidia in the life cycles of these fungi is uncertain. A sporidial stage described by Stempell (1935) for E.calendulae has been stated by Derx (1948) and Olive (1952) to represent a fungus, Itersonilia perplaxans, independent of the life cycle of the Entyloma, and present on the lesions as a contaminant. The accounts of Derx (1930) and Hyland (1950) of the widespread occurrence of Tilletiopsis spp. on the leaves of "healthy" plants suggests that members of this genus may likewise have been occasionally assigned to Entyloma. Exploratory work on nine species of Entyloma revealed that "sporidia" approximating to Derx's and Olive's descriptions of Itersonilia perplexans are prevalent on lesions of Entyloma, but are also widespread on lesions of other fungal pathogens and occasionally present on "healthy" leaves. Fungi approximating to Nyland's descriptions of Tilletiopsis washingtonensis and T.minor are present on most leaves, whether or not attacked by Entyloma. A detailed investigation of E.calendulae and E.dahliae showed that needle-shaped and allantoid sporidia are formed when the chlamydospore germinates, and are discharged at the surface of the lesions of the smut. Inoculation experiments proved that the disease Is reproduced by the needle-shaped sporidia; all other Inoculation experiments had negative results. The allantoid sporidia superficially resemble the ballistospores of Tilletiopsis washingtonensis, but the two kinds of spore can be distinguished when they germinate. No connection was established between the life cycle of Entyloma and I.perplexans or T.washingtonensis, and it is highly probable that the latter fungi are present on the lesions as contaminants.