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Ecological Section

Clement, Suzette [1], Nelson, David L. [1], Meyer, Susan E. [1].

Susceptibility of Perennial Grass Species to Ustilago bullata Races from Bromus tectorum.

Ustilago bullata induces a head smut of Bromus tectorum (cheatgrass) and is being studied as a biocontrol agent for this important weed. Pathogenicity of U. bullata races from B. tectorum on non-target species was investigated using native and exotic perennial grass species. Seeds of the perennial species were inoculated with teliospores or sporidia of U. bullata, planted in individual containers, and grown in greenhouse and lath house culture. Of the thirteen grasses inoculated, three did not develop smut symptoms, two species failed to head, and the rest had low to intermediate levels of infection. A subset of non-headed and of smutted plants was transplanted to field conditions to induce more uniform heading and study further smut development. Plants of three of the species that exhibited smut in greenhouse conditions produced only unsmutted heads when transferred to the field. The other species that had some smutted plants remained smutted in the field. Except for Elymus canadensis, plants that did not head in the greenhouse headed but developed no signs of smut in the field. In the greenhouse 9% of the E. canadensis plants had detectable infection initially but 14% had distorted heads and many did not head. After being transplanted to field conditions 53% showed smutting and an additional 12% had distorted heads. Results suggest that with marginally susceptible species, smut development may be abnormal, resulting in distorted heads and bullae. Overall, E. canadensis was the only species that showed persistent smutting at more than very low levels. The risk to non-target grass hosts involved in use of U. bullata for biocontrol of cheatgrass therefore appears to be minimal.

1 - USDA Forest Service, Rocky Mountain Research Station, Shrub Sciences Laboratory, 735 N 500 E, Provo, Utah, 84606, USA

plant pathology
Ustilago bullata
Bromus tectorum
risk assessment.

Presentation Type: Paper
Session: 40-6
Location: Wasatch (Cliff Lodge)
Date: Tuesday, August 3rd, 2004
Time: 3:45 PM
Abstract ID:181

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