Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/1999
Publication Date: N/A
Interpretive Summary: 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. Karnal bunt of wheat, a major source of lost exports of U.S. wheat, has been confused with another bunt fungus on ryegrass that was recently described as a new species. This paper reports the results of a survey of bunt fungi of ryegrass in the southeastern United Sates and confirms that the fungus initially reported as karnal bunt is actually the new bunt fungus on ryegrass. No bunted kernels or teliospores of karnal bunt were found in the survey of wheat in the southeastern U.S. This paper ensures that karnal bunt does not occur in the southeastern U.S. and that wheat grown there is free of karnal bunt. This knowledge contributes to the increased export of wheat from the southeastern U.S. to countries outside of the U.S.
Technical Abstract: Annual ryegrass (Lolium multiflourm) is a common annual weed in wheat fields in the southeastern U.S. Between April and June 1997, ryegrass seed samples were collected from 190 fields of wheat (Triticum aestivum) in 47 counties in Georgia and from 26 fields in 17 counties in Alabama and south- central Tennessee. These are same regions where suspect teliospores of the eKarnal bunt fungus, Tilletia indica were found in USDA-APHIS surveys of wheat seed in 1996. In 1998, 70 samples were collected from 40 counties in the same regions of the three states. In 1997 teliospores were found in 13 samples from eight counties in central Georgia nd from one field in Tennessee. However, no bunted wheat seeds were found in the seed samples. In 1998 more teliospores and bunted seeds were found due to frequent rain in the region throughout the spring. Teliospores were found in 26 (37%) of the samples, and among these, only a small number of bunted seed were found din 13 of 70 (19%) (WHAT DOES THIS PERCENTAGE REFER TO? 13 of 70?) samples. One exception was seed from a wheat field in Morgan County, GA where about 50% of the ryegrass seed collected was partially bunted and a small percentage of completely bunted seeds were found.