2013 Annual Report
1a.Objectives (from AD-416):
Duplicate critical stem rust isolates for backup and off-site storage, and establish and maintain stem rust sentinel plots in Arizona and California for Ug99 surveillance in the United States.
1b.Approach (from AD-416):
A part-time technical position will be established to duplicate critical stem rust isolates to be stored at an off-site location for backup and long-term storage. This involves reviving stem rust isolates currently housed in the USDA, ARS, Cereal Disease Laboratory liquid nitrogen storage, increasing to adequate amounts, assigning proper race names by testing differentials of new North American stem rust nomenclature, and moving to a long-term storage space. Stem rust sentinel plots in Arizona and California will be established in conjunction with the winter nursery increase of wheat by co-operators. Universal susceptible varieties, as well as critical resistant lines to be planted, and maintained during crop season, rust infections will be recorded during the growing season, and samples will be collected and forwarded to USDA, ARS, Cereal Disease Laboratory for race analysis. Regular communications will be maintained via conference calls and e-mail.
A rust increasing system has been developed to eliminate potential cross-contamination by using cellophane bags to contain inoculated plants and collecting rust under bio-safety hood. A storage system using foil-bags has been developed. Bar-code system is being used to maintain passport information on the increased isolates. Culture increase will begin from the most recent collections. Thirty cultures from the 2012 surveys have been increased and race-typed. Currently, increased cultures are stored in -80C at ARS, Cereal Disease Lab. Once a backup location is identified, the cultures will be moved in bulk in an annual basis.
In the 2013 field season, stem rust sentinel plots were planted in Yuma, Arizona and Imperial Valley, CA. The plots were visited by the PI in March, by a collaborator in April, and nearly daily by farm management crew. Stem rust was not detected on the entries of sentinel plots, breeding lines planted at the same location, or nearby wheat fields. Thus, we conclude that stem rust was absent at this location in the 2013 season.