Karnal Bunt Update for June 1998 I attended the IXth Biennial Workshop on Smut Fungi in Moscow, Idaho June 3-5. Most of one day of the meeting was devoted to papers and discussion of Karnal bunt and the ryegrass smut that was incorrectly identified as Karnal bunt in the Southeast in 1996. A major area of research since December, 1996 has been the taxonomic and biological relationship of the ryegrass smut and Karnal bunt. Studies from Washington State University and USDA-APHIS and a study from Alberta, Canada using various molecular techniques to compare the two fungi each showed that there are distinct genetic differences between them. The U.S. studies included isolates of the ryegrass smut from Oregon and the Southeast. The USDA study included isolates from Georgia. The Alberta study used ryegrass smut isolates from Canada only. Isolates of the ryegrass smut from all locations within each study were closely related. I reported on my collection of smut from ryegrass in the Southeast in 1997. Samples of the smut spores I found were examined by USDA expert mycologists at Beltsville, MD. Four samples from Georgia and one from Tennessee were verified to be the ryegrass smut. USDA mycologists have also examined numerous collections of the ryegrass smut and have submitted a paper for publication describing it as a new species of Tilletia based on morphological and genetic characters. All of these studies, using traditional and molecular techniques, show clearly that the ryegrass smut is biologically distinct from Tilletia indica, the cause of Karnal bunt. All evidence to date demonstrates that the smut spores found on wheat in the Southeast in the past two years are from the ryegrass smut. All studies in Oregon, Canada, and my own show that the ryegrass smut is a cryptic disease. It occurs at very low levels and diseased flowers and seed are very difficult to identify because the infected area is minute in most cases. Collection of fourteen wheat samples in Georgia by APHIS as part of the 1998 national survey is in progress. I am also repeating my survey of ryegrass in the region to collect additional isolates of the fungus for ongoing comparisons of the two fungi. A continuing point of discussion on the Karnal bunt issue is progress by USDA to withdraw its quarantine regulations. Unfortunately, it appears that very little progress has been made since last year. Ongoing discussions with international trading partners is a long term process and linked to overall negotiations on trade issues related to GATT and other trade agreements. An APHIS representative stated that eradication is no longer the primary issue for Karnal bunt regulations, but that deregulation is still 1-2 years away, the same estimate made a year ago. This still means that if a single bunted wheat kernel is found, quarantine measures will be implemented. Barry Cunfer
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Georgia Invasive Species Task Force |
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