The development and practical application of microbial pesticides for the control of bacterial and fungal pests has been severely limited by the variable efficacy observed in field trials. This project will improve our understanding of the molecular basis for an observed biological control phenomenon, from both a genetic and ecological perspective. The key genetic elements in the biosynthetic pathway of an antifungal (Afu) compound, produced by a rhizosphere Pseudomonas, have been identified. The Afu compound is potentially a valuable biocontrol agent for pathogens of cotton. Fusion of the regulatory operons involved in the synthesis of this antibiotic to strong promoters may create root colonizing bacteria that produce the compound in far larger amounts than occurs naturally. Efficacy may also be improved by determining the environmental conditions which optimize expresion of Afu genes. The influence of pH, soil temperature, moisture, C-N source, cotton cultivar, and selective nutrients on antibiotic biosynthesis will be ascertained. These and related efforts in this research will make possible the selection and design of biological pesticides for possible use in crop management after appropriate testing to assure environmental safety. The investigators have the expertise to assure completion of the laboratory aspects of this project. Facilities at Advanced Genetic Sciences, Berkeley, California, are excellent. This project does not include field trials; these must await approval through regulatory channels. The Ecology Program recommends funding of this Phase II project which stems from a Phase I funded via the 1985 SBIR solicitation.