2009 Annual Report 1a.Objectives (from AD-416) Screen potato germplasm resistance for resistance to major pests and pathogens. Test management strategies and their interaction with different levels of host resistance. 1b.Approach (from AD-416) Plant various genotypes of potato in affected fields infested with major pests and pathogens. Score resistance reactions. Where appropriate find linkages between resistance and molecular markers. Test management strategies and study interactions with different levels of resistance in potato breeding lines and cultivars. Documents SCA with WSU. Formerly 5354-21220-002-24S (5/08). 3.Progress Report C. coccodes expands linearly from an inoculum source and that for multiple disease foci to develop on roots, multiple primary infections must occur from over wintering sclerotia in the soil. The lack of secondary infections from a single inoculum source also suggests that overwintering inoculum in the soil or seed is exclusively responsible for disease of roots in the field and that management tactics that reduce the effects of overwintering inoculum or inhibit the rate of disease development on plants should be emphasized. Aboveground stem severity differed significantly among seed lots in two of four fields (but differences were not related to the incidence of C. coccodes-infection in seed lots. Both fields where differences were noted were in common (potato is grown every fouth year) rotation. Black dot severity of roots differed significantly among seed lots (P < 0.05) and a higher incidence of C. coccodes infection in seed lots was related to increased disease severity on roots in both fields in 2008 (P < 0.01, R2 = .89 and .94). Relationships were not found between progeny tuber infection and the percentage of seed lot infected with black dot. Oversight of the Specific Cooperative Agreement was carried out by telephone conversations, in-person meetings, and sharing of data by email between the ADODR and the lead researcher.