This award will support a two-year U.S.-Japan cooperative science research project between Professor Ralph Nicholson, Department of Botany and Plant Pathology, Purdue University, and Professor Hitoshi Kunoh, Laboratory of Plant Pathology, Mie University, Tsu, Japan. The project will also involve Professor Robert Hanau of Purdue and two co-investigators from Okayama University in Japan, Professors Tomonori Shiraishi and Tetsuji Yamada. These researchers have considerable expertise in diverse areas of plant pathology. The subject of this project is Erysiphe graminis, a fungal pathogen of barley. Understanding the molecular basis of disease interactions and its relationship to changes in plant physiology is important to both the United States and Japan. Plant diseases represent a significant problem in the production of all food and fiber crops. This collaborative research project will expand on previous work by the investigators to discern the molecular basis of the peptides released and their influence on the physiology of the host as well as their importance to the successful thigmodifferentiation of the fungus. Future research will be based on using the information obtained to elucidate logical control strategies based on the better understanding of the infection process and what specific sites in the process might be considered as targets in a control scheme. It is expected that researchers in both countries will benefit from this project because it will result in a new understanding of plant disease caused by obligate pathogens. It will also bring together researchers with considerable expertise in diverse areas of plant pathological research.