2005 Annual Report 4d.Progress report. This report documents research conducted under a Specific Cooperative Agreement between USDA ARS and Washington State University, CRIS 5358-21000-035-01S. Additional details may be found in the report of the parent project: Genetics, Genomics and Germplasm Development of Hops, CRIS 5358-21000-035-00D. Washington State has the need of publicly developed hop varieties that perform well under dry and hot conditions. The major accomplishments of the WSU Specific Cooperative Agreement include creating hop germplasm for evaluation as high-yield, high-quality hop cultivars adapted to arid hop growing regions, testing advanced selections from USDA-ARS in an arid environment thereby expanding the range of environments in which to test these selections, and identifying heritable sources of resistance to hop powdery mildew. An active and continuous hop breeding program under dry and hot conditions that compliments germplasm development performed by the USDA-ARS hop geneticist is required to maintain USA’s position as a top world producer of hop. Numerous crosses were performed to produce new germplasm possessing traits of interest to USA breweries and offspring from previous crosses (2000 to 2004) were grown out in field plots with advanced selections (17 aroma lines and one bittering line: USDA 9725-082) replicated in off-station large-scale plots. In crop year 2005, advanced selections, seven from the USDA-ARS project and ten from the WSU project, were harvested and provided to Anheuser Busch for pilot brewing tests—12 of these lines proved resistant to powdery mildew. Sixty-two new advanced selections from USDA-ARS, representing crosses made in 2000, were established in the field in early May. Finally, we determined WSU 9216-022 as having a single dominant gene for powdery mildew resistance. The results of this project are important as they enable further development of hop varieties and germplasm that perform well under arid conditions and will ultimately benefit growers, merchants and breweries in the USA.