Identify if one or more pathogens cause the unusual symptoms occurring mid- to late-season in potato fields in the Columbia Basin. Objective 1: Grafting diseased plant tissue. Objective 2. Molecular diagnostics of diseased plants. Sub-objective A: Established molecular diagnostic tools will be used to determine if known fungal, bacterial, and/or viral pathogens are present in the symptomatic plant materials. Sub-objective B: Molecular diagnostic tools designed to identify unknown pathogens will be used to determine if fungal and/or bacterial pathogens are present in the symptomatic plant material. Objective 3. Fulfill Koch?s postulate for pathogens identified in field samples.