2010 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.
The detection of sugarcane orange rust in Florida in 2007 (first confirmed report in the western hemisphere) impacted the pathology program. To determine the extent and possible source of the introduction sugarcane rust samples were obtained from Central American and African countries. Sugarcane orange rust was confirmed in Belize and in Cameroon and the Ivory Coast in western Africa. Molecular comparisons of the samples from these countries are being made to samples obtained previously in Florida and Central America (reported in 2008 and 2009).
The brown rust reaction of clones in the sugarcane cultivar development program was determined using an artificial whorl inoculation and natural infection. The clones were similarly evaluated for their orange rust reaction using natural infection. With the introduction of orange determining the rust reaction of clones for resistance to both brown and orange rust pathogens is required to develop adequate resistance.
Identification of disease resistant cultivars of sugarcane: Disease susceptible cultivars must be identified to prevent yield losses in the sugarcane industry. Sugarcane clones in the variety development program were screened for their disease reaction and susceptible clones were discarded. Resistant cultivars will allow Florida to continue to produce approximately 20% of the sugar consumed in the United States.
Flores, C., Loyo, R., Ojeda, A., Rangel, C.A., Ceron, F., Marquez, W., Guerra-Moreno, A.S., Hernandez, H.M., Gonzalez, R.E., Castlebury, L.A., Dixon, L.J., Glynn, N.C., Comstock, J.C., Flynn, J., Amador, J. 2009. First Report of Orange Rust of Sugarcane Caused by Puccinia kuehnii in Mexico, El Salvador and Panama. Plant Dis. 93:1347
Sood, S.G., Comstock, J.C., Glynn, N.C. 2009. LEAF WHORL INOCULATION METHOD FOR SCREENING SUGARCANE RUST RESISTANCE. Plant Disease. 93:1335-1340.
Dixon, L.J., Castlebury, L.A., Aime, M., Glynn, N.C., Comstock, J.C. 2010. Phylogenetic relationships of sugarcane fungi. Mycological Progress. 9(4):459-468.