ARS | Publication request: The first report of the Rye Smut, Tilletia secalis, from North America

Submitted to: North American Fungi
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 24, 2008
Publication Date: August 29, 2008
Citation: Carris, L.M., Castlebury, L.A. 2008. The first report of the Rye Smut, Tilletia secalis, from North America. North American Fungi. 3(7):147-159.

Interpretive Summary: Bunt fungi cause diseases on commercially important cereal crops including wheat and rye that have influenced global trade. Considerable confusion exists in distinguishing the fungi that cause these diseases because they may infect more than one kind of crop. This confusion has been partly resolved by the use of DNA sequencing. In this research a fungus on rye that appeared to be a wheat pathogen and could infect wheat was determined to be a distinct species based on sequencing three different genes. Based on this research the rye bunt fungus was determined to be different from three wheat bunt fungi and is reported for the first time from North America. This research will be useful to plant pathologists who work to control diseases of cereal crops and plant quarantine officials and policy makers who resolve disease issues when crops are imported or exported into or out of the United States.

Technical Abstract: A volunteer rye plant (Secale cereale) infected by a reticulately spored species of Tilletia was collected in a wheat field in southeastern Idaho in 1993 (WSP 71279). The smut was identified as Tilletia contraversa, the dwarf bunt pathogen of wheat, based on teliospore morphology and stunting of the host. Inoculation studies conducted in the greenhouse confirmed that the rye-infecting smut was able to infect wheat. A phylogenetic analysis based on the internal transcribed spacer region rDNA, eukaryotic translation elongation factor 1 alpha, and the second largest subunit of RNA polymerase II demonstrated that the rye-infecting smut was distinct from T. contraversa and the common bunt pathogens of wheat bunt, T. caries and T. laevis. The rye-infecting smut fits within the species concept of T. secalis, a pathogen of cultivated rye in Europe. The ability of T. contraversa, T. caries and T. laevis to infect rye, and of T. secalis to infect wheat has resulted in confusion over the identity of bunts found infecting rye. This study is the first demonstration that T. secalis is genetically distinct from the wheat bunt pathogens, and the first report of T. secalis in North America.