2006 Annual Report 4d.Progress report. This report serves to document research conducted under a Specific Cooperative agreement between ARS and the University of Idaho, Aberdeen. Additional details of research can be found in the report for the parent project, 5366-21000-023-00D, “Development of Potato Varieties and Germplasm with Improved Yield, Quality, Disease and Pest Resistance”. Research to be conducted by University of Idaho personnel entails the screening of a potato breeding population for resistance to green peach aphid (GPA) derived from wild potato species. Parameters of resistance examined include monitoring the survival and fecundity of. 1)first generation GPA nymphs, and. 2)nymphs subsequently produced by the first generation. In essence, two aphid generations are evaluated on host plants providing useful information concerning the mechanisms of resistance. Results of this research have shown segregation for resistance to GPA in the breeding population, with resistance detrimentally impacting both aphid generations. Clones previously screened in FY 2005 will again be screened in FY 2006 to generate two years of data. These results will be used for mapping GPA resistance in this unique germplasm.