Submitted to: XII Biennial Workshop on Smut Fungi Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 8/15/2000
Publication Date: 8/15/2000
Interpretive Summary: Knowledge of the occurrence of bunt fungi on grass crops such as wheat, rice, and millet around the world is extremely important for the risk-free export and import of these commodities throughout the world. Presence of a previously unknown species of bunt fungi in the United States recently caused a plant quarantine crisis in the export of wheat from that country. The newly described species on ryegrass is known from both the United States and Australia. This paper expands the knowledge of the distribution of this fungus in Australia based on an extensive collecting trip. The new species of bunt fungus was found in 17% of the seed washes of ryegrass samples. Several other species of bunt fungi were found and identified. This paper will be used by plant pathologists and plant quarantine officials to identify bunt fungi found in shipments of grain crops as well as in developing plant quarantine regulations concerning these commodities.
Technical Abstract: During the summer of 1996, tuberculate teliospores similar to those of the quarantined plant pathogen Tilletia indica (Karnal bunt of wheat) were found in wheat seed samples from Alabama, Florida, Georgia and Tennessee in the southeastern U.S. (Cunfer and Castlebury, 1999). These spores tested positive for T. indica using the available PCR-based method of Smith et al. (1996). Similar spores were found in November 1996 in pasture seed mixtures from the Willamette Valley, Oregon (Palm, 1999). The T. indica-like teliospores were later shown to come from infected annual ryegrass (Lolium multiflorum). The ryegrass smut was characterized and described as a new species, Tilletia walkeri, by Castlebury and Carris (1999). During a search for T. walkeri in Australian ryegrass during 1996-1997, sori belonging to a Tilletia species with reticulately ornamented teliospores were found in two seed lots of perennial ryegrass that had been sent to the Oregon Department of Agriculture's Seed Testing Laboratory. In 1999, we spent three weeks in Australia to gather information on the distribution and incidence of T. walkeri, the reticulate-spored species, and other smut fungi associated with perennial ryegrass. The trip was funded by grants from the Research and Scientific Exchanges Division (RSED) and the Animal and Plant Health Inspection Service (APHIS) of the U.S. Department of Agriculture. The objective of the trip was to screen collections of perennial ryegrass seed for Tilletia species and obtain germinable collections of these fungi for further characterization.