ULTRASTRUCTURE OF PRIMARY SPORIDIA OF A WHEAT-BUNT FUNGUS, TILLETIA-CARIES, DURING ONTOGENY AND MATING

Primary sporidia of Tilletia caries (DC.) Tul. are borne on denticles at the tips of promycelia. The promycelia contain many small vacuoles and mitochondria and numerous lipid bodies. As the primary sporidia develop, the promycelial cytoplasm passes into the nascent cells. Septa develop between the bases of mature sporidia and the tips of the denticles. Sporidia that abscise from the denticles commonly have prominent birth scars at their bases. The sporidia have very thin walls, few vacuoles, attenuated mitochondria, and numerous lipid bodies. Conjugation pegs are generally produced by both members of a conjugating pair of sporidia and there are bud scars where they emerge from the sporidia. The sporidial walls are apparently hydrolyzed during emergence of the pegs. Vesicles are sometimes present at the tips of the conjugation pegs and, before fusion, electron-dense accumulations are sometimes observed between the tips of adjacent pegs. The approaching conjugation pegs are precisely aligned prior to fusion, suggesting polar communication. The walls of the conjugation pegs fuse and then are hydrolyzed. Fused sporidia are relatively homogeneous in content. The nucleus in a sporidum is often close to the conjugation tube and occasionally is partly within the fusion tube. © 1979 Springer-Verlag.