Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2001
Publication Date: N/A
Interpretive Summary: Karnal bunt of wheat, a major source of threatened loss of U.S. wheat export markets, has been confused with another bunt fungus on ryegrass that has recently been described as a new species. The ability to differentiate these species resulted in saving of the U.S. wheat export market. Evidence for the differentiation of these species was based primarily on morphological characteristics but was not backed by molecular data. This paper reports the results of molecular studies using DNA sequencing and restriction digest that confirm the differences between these two species of bunt fungi. This knowledge contributes to the increased confidence in the purity of U.S. wheat and helps to stabilize the U.S. wheat export market.
Technical Abstract: A PCR-RFLP assay to distinguish T. walkeri, a ryegrass bunt fungus that occurs in the southeastern U.S. and Oregon, from Tilletia indica, the Karnal bunt fungus, is described. The internal transcribed spacer region of the ribosomal DNA repeat unit was amplified and sequenced for isolates of T. indica, T. walkeri, T. horrida, and a number of other taxa in the genus Tilletia. A unique restriction digest site in the ITS1 region of T. walkeri was identified that distinguishes it from the other taxa in the genus. Phylogenetic analysis of the taxa based on ITS sequence data revealed a close relationship between T. indica and T. walkeri, but more distant relationships between these two species and other morphologically similar taxa.