** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** DESTRUCTIVE VINEYARD PATHOGENS WREAK HAVOC ON WINE, JUICE, AND TABLE GRAPE INDUSTRIES WORLD-WIDE AS THE PATHOGENS AND THE CULTIVATED GRAPE HOST (V. VINIFERA, V. LABRUSCA, AND HYBRIDS) CONTINUE IN AN EVOLUTIONARY-ARMS RACE. RESEARCHERS ACROSS THE GLOBE HAVE INVESTIGATED THE CRITICAL PATHOGENS IN THEIR AGRICULTURAL REGIONS TO BEST PROTECT THIS SPECIALTY CROP BUT ARE CHALLENGED WITH CHANGES IN FUNGICIDE RESISTANCE, IMPROVED PATHOGEN VIRULENCE, AND SPECIATION. THIS PROPOSAL FOCUSES ON BETTER UNDERSTANDING THE DYNAMICS OF THE PLASMOPARA VITICOLA (GRAPEVINE DOWNY MILDEW) CRYPTIC SPECIES COMPLEX TO AID AND IMPROVEDOWNY MILDEW MANAGEMENT.THE GOALS OF THIS STUDY ARE TO IDENTIFY GENETIC AND ENVIRONMENTAL DIFFERENCES IN THE THREE ECONOMICALLY RELEVANT CRYPTIC SPECIES TO SET THE FOUNDATION FOR MANAGEMENT RESEARCH INVOLVING THESE CRYPTIC SPECIES.THE TWO RESEARCH OBJECTIVES OF THIS NIFA PREDOCTORAL RESEARCH PROPOSAL ARE TO 1) DETERMINE DIFFERENCES IN GENE EXPRESSION AMONG P. VITICOLA CRYPTIC SPECIES BY PERFORMING AN INFECTION TIME-COURSE COMPARISON USING RNASEQ ANALYSIS AND 2) COMPARE THE EFFECTOR REPERTOIRE OF P. VITICOLA CLADES VINIFERA AND RIPARIA TO CLADE AESTIVALIS TO INCREASE UNDERSTANDING OF HOST-PATHOGEN INTERACTIONS AND HOW THESE INTERACTIONS MAY PLAY A ROLE IN INFORMING DISEASE MANAGEMENT AMONG THE RECENTLY IDENTIFIED CRYPTIC SPECIES. OBJECTIVE 1 AIMS TO FIND THE DIFFERENCES BETWEEN THE CRYPTIC SPECIES WHILE OBJECTIVE 2 AIMS TO COMPARE TO DISCUSS HOW THESE DIFFERENCES IMPACT PATHOGEN INFECTION AND SUCCESS.