Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/17/1998
Publication Date: N/A
Interpretive Summary: Each year billions of dollars of agricultural losses are caused by fungal diseases of crop plants. Bunt and smut diseases of wheat and other grass crops have resulted in an estimated $2 billion loss in crop yield and lost export markets in 1996 and 1997 alone. The discovery of karnal bunt on wheat in the United States precipitated a crisis particularly in the wheat export market due to the strict quarantine that had been placed on this fungus. This situation was exacerbated by the mistaken identification as karnal bunt of a bunt fungus on ryegrass occurring as a contaminant in wheat seed. Teliospores of the new bunt fungus on ryegrass from the United States and Australia were carefully compared with fungus causing karnal bunt on wheat using light, fluorescent, and scanning electron microscopy. With close observations it is possible to differentiate the ryegrass bunt fungus from karnal bunt. In this paper the ryegrass bunt fungus is formally described as a new species known from both the United States and Australia. Differences in teliospore morphology and germination characteristics between the bunt fungus on ryegrass and the karnal bunt fungus on wheat are discussed and illustrated. These results will be useful to seed technologists and wheat and grass pathologist working to certify wheat in order to maintain and open international markets for U.S. wheat.
Technical Abstract: Tilletia walkeri (Ustilaginales: Tilletiaceae) is described as a new species of partial bunt infecting Lolium multiflorum, annual ryegrass, and L. perenne, perennial ryegrass in the United States and Australia, respectively. The new species is characterized by large, tuberculate teliospores with the exospore ornamentation comprised of incompletely cerebriform ridges in surface view. Teliospores of T. walkeri are compare with those of T. indica and other similar species of Tilletia, and the issue of Neovossia versus Tilletia is discussed. A key is provided to smuts known to occur on species of Lolium.