2012 Annual Report 1a.Objectives (from AD-416): Screen potato varieties for zebra chip disease resistance and assess risk of the disease developing in stored potatoes resulting from late liberibacter infection. 1b.Approach (from AD-416): Conduct controlled insect exposure experiments under field cage conditions to determine whether potato varieties and advanced breeding lines are resistant to zebra chip potato disease. Conduct controlled insect exposure experiments under field cage conditions late in the season to determine whether symptomless potato tubers produced by late liberibacter infected plants will develop zebra chip symptoms in storage. 3.Progress Report: As a continuation of the research projects #5352-22000-018-22R and 5352-22000-018-23R, a further screening trial of the promising tolerant or resistant potato breeding lines identified earlier is currently underway at the ARS Wapato location. In addition, a dozen of selected lines are being evaluated for potato psyllid feeding and plant metabolites to assess potential source of insect and disease resistance. Furthermore, little is known on the risk of zebra chip developing in potato tubers while in storage. This is especially a major concern for potatoes produced in the Pacific Northwest, majority of which go into storage and where potato fields are subjected to zebra chip late infection because of the late psyllid arrival into the region. Preliminary research conducted at the ARS Wapato location determined that asymptomatic tubers produced by Atlantic (a very susceptible chipping) potato plants infected with zebra chip pathogen late in the season could develop the disease symptoms in storage. Information from this research will help potato producers make informed decisions on the management of the potato psyllid and on whether to store tubers from fields impacted by zebra chip. The work reported here addresses objective 3 of the parent project plan.