ULTRASTRUCTURE OF THE UNGERMINATED CONIDIUM OF BLUMERIA-GRAMINIS F-SPHORDEI

Ungerminated conidia of Blumeria graminis f.sp. hordei were prepared f or transmission electron microscopy using cryofixation and freeze-subs titution. Conidia were uninucleate, with the nucleus located in the ce ntral portion of the conidium, typically off to one side. The nucleus was spherical and contained a distinct nucleolus with an associated sa tellite. Conidia contained numerous large, spherical vacuoles that occ upied much of the spore volume. Vacuolar contents were mostly homogene ous with occasional electron-opaque inclusions. Much of the cytoplasm consisted of lightly staining aggregations of glycoprotein that could be labelled with Concanavalin A - gold and that stained darkly using a modified Thiery's reaction specific for carbohydrates containing vici nal hydroxyl groups. Mitochondria, strands of endoplasmic reticulum, G olgi body equivalents, multivesicular bodies, microbodies, Woronin bod ies, and microtubules were present in the conidium. Cuboidal, stacked, electron-translucent structures also were present in the cytoplasm. T he conidium was surrounded by a two-layered wall that labelled with go ld-conjugated wheat germ agglutinin-ovomucoid, indicating the presence of chitin. The wall between attached conidia contained areas that did not label with gold-conjugated wheat germ agglutinin-ovomucoid.