2009 Annual Report 1a.Objectives (from AD-416) To screen public spinach germplasm for new sources of resistance to downy mildew race 10. 1b.Approach (from AD-416) The entire USDA spinach germplasm collection will be screened for downy mildew resistance in inoculated greenhouse tests. Documents Trust with California Leafy Greens Research Board. Log 37163. 3.Progress Report Downy mildew caused by Peronospora farinose f. sp. Spinaciae is the most important disease for California spinach growers. Along with the rapid increase of spinach consumption and production in recent years, many new downy mildew races have emerged including the latest Races 10 and 11. Genetic resistance continues to be an important component in the management of the threat. We have conducted several increases of pathogen isolates and identified their races through differential host tests. An initial screening of 135 USDA spinach germplasm accessions plus 9 commercial cultivars for resistance to Race 10 is in progress. Seeds of commercial cultivars and Race 11 isolates have been collected for resistance screening.