Teliospores of smut fungi - Teliospore connections, appendages, and germ pores studied by electron microscopy; phylogenetic discussion of characteristics of teliospores

Special features of teliospores in smut fungi are described, including teli ospore connections, appendages, and germ pores. Balls of teliospores in spe cies of many different genera cohere by remnants of hyphal walls, sheaths, and sometimes interlocking ornamentation. Teliospores are connected in pair s in species of Mycosyrinx and Geminago by special local structures. Append ages can be formed locally by persistent material from the sheath (Cintract ia, Anthracoidea, Sphacelotheca), thickened parts of the spore wall (e.g., Georgefischeria, Jamesdicksonia, Rhamphospora, Tolyposporella), or persiste nt walls of sporogenous hyphae (Rhamphospora, genera of the Tilletia relati onship). Species of Georgefischeria,Jamesdicksonia, and Tolyposporella have teliospore walls composed of more than three layers of different electron density. "Germ areas" corresponding to thinner parts of the spore wall are known, e.g., for species of Anthracoidea, Cintractia, and Ustilago infectin g members of the family Poaceae, while distinct germ pores, one per teliosp ore, are found in some species of Thecaphora, "Tolyposporium", and Sporisor ium. Teliospores of Mycosyrinx cissi have a germination ring. Characteristi cs of teliospores are used to discuss the phylogeny of smut fungi. A phylog enetic tree in accordance with teliospore characteristics is compared to th ose obtained from ultrastructural characteristics of host-parasite interact ion, of septal pores, and from sequence data. Aspects of teliospore develop ment help to define taxa at a high systematic level (Entorrhizales, Ustilag inales, Tilletiales/Entylomatales, Microbotryaceae), while details of ornam entation ontogeny delimit groups of genera (e.g., genera related to Ustilag o on members of the Poaceae and Sporisorium, Cintractia and Anthracoidea, T illetia) or single genera (e.g., Melanopsichium, Dermatosorus, Mycosyrinx, Doassinga, Rhamphospora). Types of ornamentation (warty, reticulate), middl e layers, teliospore balls, and germ pores evolved repeatedly by convergenc e. The smut teliospore itself probably evolved independently at least twice , or perhaps three (or more) times, in the Microbotryales, in the Entorrhiz ales, and in a common ancestor of the remainder of the Ustilaginomycetes.