PHYTOPHTHORA STEM AND ROOT ROT (PSR), CAUSED BY THE OOMYCETEPHYTOPHTHORA SOJAE, CAUSES SIGNIFICANT LOSSES IN SOYBEAN.P. SOJAESECRETES EFFECTOR PROTEINS CODED BY AVIRULENCE (AVR) GENES TO SUCCESSFULLY INFECT SOYBEAN. PSR IS PRIMARILY MANAGED BY PLANTING VARIETIES WITH RESISTANT GENES (RPS) THAT PREVENT INFECTION. HOWEVER, THE DURABILITY OF THESE GENES IS LIMITED TO 8-15 YEARS BECAUSE NEW VIRULENT PATHOTYPES EVOLVE TO BECOME VIRULENT AGAINST THERPSGENE. CONSEQUENTLY, NOVEL WAYS TO MANAGE THIS PSR ARE NEEDED.P. SOJAEIS ATTRACTED TO THE SOYBEAN RHIZOSPHERE BY ROOT EXUDATES. ROOT EXUDES ALSO TO ATTRACT BENEFICIAL MICROBES TO THE RHIZOSPHERE AND THESE MICROBES MAY SUPPRESS SOIL-BORNE PATHOGENS LIKEP. SOJAE. WE HYPOTHESIZE THATP. SOJAEUSES ITS EFFECTOR PROTEINS TOMANIPULATE THE HOST ROOT MICROBIOME FOR SUCCESSFUL INFECTION.STUDYING THE INTERACTION OF EFFECTOR PROTEINS WITH THE RHIZOSPHERE MICROBIOME MAY HELP US DISCOVER NOVEL BIO-BASED MATERIALS FOR BIOCONTROL OF PSR AND CONTRIBUTE TOTHE LONG-RANGE IMPROVEMENT IN AND SUSTAINABILITY OF US AGRICULTURE AND FOOD SYSTEMS. IN THE PROPOSED STUDY, WE WILL INVESTIGATE CHANGES IN ABUNDANCE, DIVERSITY, AND FUNCTION OF THE SOYBEAN ROOT MICROBIOME OVER TIME DURING COMPATIBLE AND INCOMPATIBLE SOYBEAN-P. SOJAEINTERACTIONS WITH TWO SOYBEAN GENOTYPES. THIS AIM ALIGNS WELL WITH THE PROGRAM AREA PRIORITY OF STUDYING FUNCTIONS OFAGRICULTURAL MICROBIOMES IN PLANT SYSTEMS AND NATURAL RESOURCES. THE OUTCOME OF THIS PROJECT WILL STRENGTHEN OUR RESEARCH PROGRAM BY CONTRIBUTING TO OUR UNDERSTANDING OF HOWP. SOJAEALTERS THE SOYBEAN ROOT MICROBIOME FOR INFECTION AND COLONIZATION. IN ADDITION, THIS STUDY WILL BUILD RESOURCES AND EXPERTISE FOR US TO BE MORE COMPETITIVE FOR EXTERNAL GRANT APPLICATIONS (NSF/USDA) TO STUDY BENEFICIAL AND PATHOGENIC MICROBE INTERACTIONS.