The focus of my research is the genus Tilletia (Basidiomycota;  Ustilaginomycetes), a group of approximately 150 species that infect grasses (family Poaceae).   Most species of Tilletia form masses of dark, thick-walled teliospores in the ovaries of infected hosts (photo).   I am addressing questions on species limits and host specificity using population genetics and phylogenetic approaches.  A recent phylogenetic study (Castlebury, Carris and Vanky 2005) based on nuclear large subunit rDNA demonstrated that species infecting hosts in the grass subfamily Pooideae formed a well-supported lineage that includes all of the economically important pathogens of wheat—Tilletia caries (common bunt), T. controversa (dwarf bunt), T. indica (Karnal bunt) and T. laevis (common bunt).

Lori Carris holds a a blue chanterelle
collected during the Priest Lake Foray with
the Palouse Mycological Association in Fall 2005

Several Tilletia species have contributed to export problems with wheat and grass seed produced in Washington, Idaho and Oregon.  The best known of these is dwarf bunt, T. controversa, which was responsible for a quarantine by the People’s Republic of China on wheat from the Pacific Northwest that lasted nearly 30 years. A more recent problem is the rejection of grass seed shipments by Chinese quarantine officials due to the presence of bunted seed of Tilletia spp.  The cryptic nature of bunt fungi in commercial grass seed makes them almost impossible to detect in the field and contributes to the ease with which they are transported around the world.  Lack of knowledge of the diversity and distribution of these fungi also contributes to export problems. Chinese quarantine officials have intercepted species of Tilletia in alkali grass (Puccinellia distans) and red fescue (Festuca rubra) seed from the US and perennial ryegrass (Lolium perenne) seed from Australia.  Approximately 20-30% of the Kentucky bluegrass seed (Poa pratensis) shipments from the Pacific Northwest are rejected by Chinese quarantine officials because they contain spores and sori of Tilletia spp. (photo)  Most of the spores are probably T. bromi from cheatgrass (Bromus tectorum) that is growing as a weed in Kentucky bluegrass fields, but windgrass (Apera ventenata) and wiregrass (Ventenata dubia) are also important weeds in bluegrass seed fields, and both of these grasses are hosts of Tilletia spp. that are similar in appearance to T. bromi and T. controversa.  I am working with scientists at the Tianjin Entry-Exit Quarantine and Inspection Bureau on the identification of these fungi.  Scientists from the Tianjin quarantine bureau visited Washington State University in July 2004 (photo), and I have visited their bureau in December 2004 and 2005 (photo) to work on this problem. 

To learn more about Dr. Carris's research, see her current article in the 7 February 2006 issue of Annual Review of Phytopathology, "Nonsystemic Bunt Fungi--Tilletia indica and T. Horrida: A Review of History, Systematics, and Biology," co-authored with Dr. Lisa Castleburry and Dr. Blair Goates.