2008 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.
Previously in 2007, sugarcane orange rust was detected for the first time in the Western Hemisphere in Florida. In order to determine its full distribution in the Western Hemisphere, sugarcane rust samples were obtained from several Caribbean Central American countries. In cooperation with scientists in Guatemala, Costa Rica and Nicaragua the presence of the orange rust pathogen was confirmed in their countries. The orange rust reactions of cultivars were determined in Guatemala and eleven resistant cultivars have been imported to the USDA-APHIS Quarantine for subsequent use as parental clones to assist in developing resistance. This research is in support of National Program 303 Plant Diseases, Component 3 Plant Disease Resistance, Problem Statement 3B Disease Resistance in New Germplasm and Varieties.
Evaluated artificial inoculation methodologies to determine sugarcane rust reactions: With the presence of brown rust and the introduction of orange rust to Florida sugarcane clones must be accurately evaluated for their disease reactions and reliance on natural infection may identify all susceptible clones. Sugarcane seedlings were artificially inoculated by spraying a spore suspension on their leaves and genotypes in the later stages of the Cultivar Development Program were inoculated by placing aliquot of a spore suspension in the whorl of the plant. Rust symptoms developed adequately for disease assessment using the whorl inoculation of field plantings and the methodology has been adapted in sugarcane disease screening. This research is in support of National Program 303 Plant Diseases, Component 3 Plant Disease Resistance, Problem Statement 3B Disease Resistance in New Germplasm and Varieties.
Identification of disease resistant cultivars: Disease susceptible cultivars must be identified to prevent yield losses if the sugar industry. Sugarcane clones in the variety development program were screened for their disease reaction and susceptible clones are discarded. Resistant cultivars will allow Florida to continue to produce approximately 20% of the sugar consumed in the United States. This research is in support of National Program 303 Plant Diseases, Component 3 Plant Disease Resistance, Problem Statement 3B Disease Resistance in New Germplasm and Varieties.
5.Significant Activities that Support Special Target Populations
|Number of the New MTAs (providing only)||1|
|Number of Non-Peer Reviewed Presentations and Proceedings||7|
Ovalle, W., Comstock, J.C., Glynn, N.C., Castlebury, L.A. 2008. First report of Puccinia kuehnii, causal agent of orange rust of sugarcane, in Guatemala. Plant Dis. 92:973
Comstock, J.C., Sood, S.G., Glynn, N.C., Shine, Jr., J.M., Mckemy, J.M., Castlebury, L.A. 2008. First report of Puccinia kuehnii, causal agent of orange rust of sugarcane, in the United States and Western Hemisphere. Plant Disease. 92:175.
Comstock, J.C., Milligan, S.B., 2007. Comparison of CL and CP germplasm reactions to sugarcane yellow leaf virus, Liefsonia xyli and Puccinia melancephala. American Society of Sugar Cane Technologists. 27:79-88 2007