2007 Annual Report 1a.Objectives (from AD-416) 1. Screen sugarcane clones in the breeding pipeline and germplasm for resistance to ratoon stunt, leaf scald, mosaic, smut, eye spot and yellow leaf using proven techniques. 2. Improve assessment of brown rust resistance. a. Characterize pathogenic variation of brown rust in Florida. b. Evaluate seedlings screening methodology to identify rust resistant families. c. Determine the rust reaction of clones using improved natural infection and artificial inoculation methodologies. 3. Develop and associate molecular markers with disease resistance genes for use in marker-assisted selection. 1b.Approach (from AD-416) 1. Sugarcane clones in the cultivar development program will be screened for their disease reaction to the major diseases (ratoon stunt, leaf scald, mosaic, smut and eye spot) using established artificial inoculation tests. 2. a. Pathogenic variation to rust will be determined by inoculating cultivars that have known reactions with rust collected in locations in Florida to determine differences in reaction patterns. b. Sugarcane seedlings inoculation procedures will be evaluated using various rust spore concentrations and rating the reaction of individuals. c. The rust reaction of clones will be evaluated based on natural infection by produced by rust infected susceptible plants grown adjacent to them and also by artificially inoculating the plants either by whorl or spray inoculations. 3. Previously selected polymorphic SSR’s, developed RGA primers and AFLPs will be used to identify markers by bulk segregation analysis that are associated to brown rust, yellow leaf and ratoon stunt resistance using characterized populations of sugarcane. 4.Accomplishments Detection of Orange Rust of New Disease in the Western Hemisphere Indentification of a new sugarcane disease in Florida: Reports from growers of unusual brown rust symptoms in the South Florida growing area were investigated during the spring of 2007. Identified sugarcane orange rust caused by Puccinia kuehnii and it is the first reported incidence of this disease in the Western Hemisphere. Although its impact in Florida is unknown; in Australia it caused substantial yield losses in 2000. Further, ARS scientists who develop new high-yielding sugarcane cultivars will need to identify cultivars that are resistant to orange rust as well as several other major diseases. This research is in support of ARS NP 303 Component 3: Plant Disease Resistance. Problem Statement 1B, Detection, Identification, Characterization, and Classification of Pathogens. 6.Technology Transfer Number of non-peer reviewed presentations and proceedings 1