Teliospores of smut fungi - General aspects of teliospore walls and sporogenesis

The concept and nomenclature for the elements of teliospore walls in smut f ungi are presented and a survey of teliosporogenesis is given, as seen by l ight and transmission electron microscopy. Four developmental types are dis tinguished: the Ustilago, Microbotryum, Tilletia, and Entorrhiza type. Tn t he Ustilago type, sporogenous hyphae are completely segmented into teliospo re initials which are embedded in a hyaline matrix formed by gelatinised hy phal walls (found in species of Anthracoidea, Cintractia, Heterotolypospori um, Kuntzeomyces, Macalpinomyces, Melanopsichium, Sporisorium, Testicularia , Tolyposporium junci, Trichocintractia, and species of Ustilago infecting members of the family Poaceae). In the Microbotryum type, septate sporogeno us hyphae are also completely segmented into teliospore initials, however, they are not surrounded by a hyaline matrix (Microbotryum, Sphacelotheca, U stilago spp. infecting dicotyledons). A yeast-like budding of teliosporogen ic cells is observed for some species of Microbotryum, Sphacelotheca, and U stilago infecting dicotyledons. In the Tilletia type, teliospores different iate locally in the sporogenous hyphae, in an apical or intercalary positio n, without a hyaline matrix (Conidiosporomyces, Doassinga, Entyloma, Errato myces, Ingoldiomyces, Neovossia, Oberwinkleria, Rhamphospora, Tilletia). Tn all these types, the teliospore initials first develop a hyaline sheath un der which the ornamentation, the exosporium, sometimes a middle layer, and the endosporium are successively deposited by the fungal cell. In the Entor rhiza type, the teliospores develop inside vital host cells with the wall o f the sporogenous hypha included into the teliospore wall. The fungus devel ops a middle layer and an electron-transparent endosporium inside the hypha l wall while a layer forming the ornamentation is deposited onto the hyphal wall, probably by vesicles of dictyosomes of the host cell.