2011 Annual Report 1a.Objectives (from AD-416) To determine the population genetic structure of Pythium irregulare, P. sylvaticum, and P. ultimum. 1b.Approach (from AD-416) Survey three forest tree nurseries for P. irregulare, P. sylvaticum, and P. ultimum; and investigate the population genetic structure of the three Pythium species by SSR and ISSR analyses for similarities. 3.Progress Report Pythium species cause mortality of conifer seedlings in forest nurseries. We are trying to determine whether nursery-to-nursery movement of Pythium has occurred. This is being evaluated by examining the genetics of Pythium species isolated from three forest nurseries. If the genetics of the Pythium isolates are similar at all three nurseries, this will provide evidence that movement from nursery to nursery has occurred. If the genetics of the Pythium isolates are different at each of the three nurseries, this will provide evidence that movement from nursery to nursery has not occurred. The genetics of one of the Pythium species isolated, P. irregulare, have been characterized from all three nurseries, however, work continues on P. sylvaticum and P. ultimum isolates. Analyses to compare the genetics of P. irregulare at the three nurseries are also in progress. Methods of project monitoring included meetings, e-mail, and phone calls.