SCREENING GRASSES FOR SUSCEPTIBILITY TO USTILAGO PHRYGICA, A POTENTIAL BIOLOGICAL CONTROL PATHOGEN FOR MEDUSAHEAD

Authors: Berner, Dana; Dubin, Harvey; Smallwood, Emily

Submitted to: American Phytopathological Society Abstracts
Publication Type: Other
Publication Acceptance Date: 7/30/2005
Publication Date: 8/1/2005
Citation: Phytopathology 95:S8

Interpretive Summary:

Technical Abstract: Medusahead ( Taeniatherum caput-medusae) is an introduced invasive grass in much of the western U.S. It is a target of biological control efforts. Isolates of the systemic ovary smut fungus Ustilago phrygica were collected from medusahead in Turkey and are being screened for possible use in classical biological control of the weed. Because the smut is an exotic pathogen, screening in the U.S. is done in quarantine in a BSL-3 facility of the Foreign Disease-Weed Science Research Unit, USDA, ARS, Ft. Detrick, MD. The focus of screening is determination of host range of the fungus among related native and agriculturally important grasses in the U.S. A procedure was developed to consistently, and quickly, produce high levels of disease on medusahead and other grasses. Without vernalization, plants inoculated with U. phrygica will not produce smutted seed heads. Teliospores of the fungus were vacuum inoculated onto medusahead seeds, which were then placed on moist germination paper in a petri dish (25 seeds per dish). The dishes were sealed with parafilm and placed in a refrigerator at 4 C. After 6 weeks the seedlings were transplanted into pots on a greenhouse bench at 22-25 C and 14 h light (620 'mol m EE-2 sec EE-1). After 4 weeks, the plants began to flower and produce smutted seed heads. Tests were repeated with compatible sporidia cultures and germinated seedlings.