PSEUDOPERONOSPORA CUBENSIS IS AN OBLIGATE, OOMYCETE, FOLIAR PATHOGEN OF CUCURBITS WITH TWO MATING TYPES. THE INTRODUCTION OF PSEUDOPERONOSPORA CUBENSIS MATING TYPE A1 IN 2004 LED TO THE BREAKDOWN OF CUCURBIT DOWNY MILDEW (CDM) RESISTANCE THAT CONTROLLED ONLY MATING TYPE A2. THIS ISSUE HAS BEEN ADDRESSED BY INCREASING FUNGICIDE APPLICATIONS IN CUCURBIT FIELDS, WHICH CAN BE COSTLY AND HAZARDOUS. THE PREDOMINANT MATING TYPE AFFLICTING MELON (CUCUMIS MELO) IN THE UNITED STATES IS UNKNOWN. A TWO-TIERED APPROACH WILL BE TAKEN TO RESEARCH AND ADDRESS ISSUES WITH CUCURBIT DOWNY MILDEW IN MELON. FIRST, A SURVEY OF AFFECTED MELON THAT COVERS THE ENTIRE EAST COAST OF THE U.S. WILL BE CONDUCTED TO IDENTIFY WHICH MATING TYPES ARE PREDOMINANT, WHILE ALSO CHARACTERIZING THE GENETIC DIVERSITY OF P. CUBENSIS ON THIS HOST. SECOND, A BREEDING LINE HAS BEEN CONSTRUCTED TO IDENTIFY GENETIC RESISTANCE TO BOTH MATING TYPES. THIS WOULD BE THE FIRST BREEDING PROJECT THAT A) ADDRESS BREEDING MELON TO SPECIFICMATING TYPES OF P. CUBENSIS AND B) UTILIZES THE RECENTLY PUBLISHED MELON GENOME. THE SURVEY COMPONENT WILL ALLOW SCIENTISTS AND PLANT BREEDERS TO ACCURATELY UNDERSTAND WHAT THE POPULATION OF THIS THREAT LOOKS LIKE, WHILE THE BREEDING COMPONENT WILL ALLOW FOR THE DEVELOPMENT OF GENETIC TOOLS FOR COMMERCIAL PLANT BREEDERS TO USE IN FUTURE CULTIVARS FOR DOWNY MILDEW RESISTANCE.