Bull Long & Medium-Term Research: The Role of Pyoluteorin Production by Pseudomonas fluorescens in Biological Control of Plant Pathogens This award is made under the Program for Long & Medium-Term Research at Foreign Centers of Excellence, which enables U.S. scientists and engineers to conduct three to twelve months abroad at research centers of proven excellence. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad. This award, sponsored by Dr. Joyce E. Loper of Oregon State University, will support a twelve-month postdoctoral research visit by Dr. Carolee T. Bull with Dr. Dieter Haas of Eidgen ssische Technische Hochschule (ETH), Z rich, Switzerland. Certain strains of Pseudomonas fluorescens, when applied to seeds of agricultural plants, control plant diseases caused by soilborne fungi. P. fluorescens strains CHAO and Pf-5 control a seedling disease of cucumber caused by the fungal phytopathogen, Pythium ultimum, and produce the antifungal metabolite, pyoluteorin. Pyoluteorin production is implicated in the biocontrol activity of strain Pf-5 but the role of pyoluteorin produced by strain CHAO in disease suppression is unknown. A cosmid clone, pME3090, obtained from a genomic library of CHAO, confers to strain CHAO an enhanced biocontrol activity, and enhanced production of pyoluteorin and of a second antifungal compound, 2,4-diacetylphloroglucinol production to the enhanced biocontrol activity of CHAO/pME3090 will be elucidated through a combination of molecular and agronomic approaches. The proposed research will use organisms and techniques developed in the United States and Switzerland to determine the role of pyoluteorin production in biological control by CHAO. The specific objectives are to: (1) Identify genes involved in pyoluteorin production; (2) Generate mutants in strain CHAO that are defective specifi- cally in the production of pyoluteorin (Plt); (3) Determine the relative ability of pyoluteorin mutants, 2, 4-diacetylph- loroglucinol mutants (Phl) and of wildtype CHAO to control plant diseases. The proposed research will provide critical information describing fundamental mechanisms in the biocontrol of plant diseases. The award recommendation provides funds to cover international travel and a flat administrative allowance of $250 for the U.S. home institution.
