Location: Sugarcane Field Station2014 Annual Report
1a. Objectives (from AD-416):
1. Optimize assessment technologies for evaluating sugarcane disease resistance. 2. Characterize biological and molecular variation of endemic and emerging sugarcane pathogens. 3. Evaluate sugarcane and energy cane clones to identify resistant germplasm to diseases that are economically important and threatening in the varietal development programs. 4. Identify parental clones and characterize populations that will enhance the development of resistant cultivars for commercial release.
1b. Approach (from AD-416):
1. For brown rust, seedlings of three crosses that vary in the proportion of brown rust susceptible progeny will be in inoculation experiments to evaluate conditions that have promoted infection using older plants. 2. Sentinel plots of susceptible cultivars that were previously rated resistant and resistant commercial cultivars will be planted with two replications in each of the ten Stage IV locations annually (the test has a three crop cycle). Spores will be collected separately from each variety of this test and inoculated to a duplicate set of standard cultivars (of all cultivars that spores were collected from plus B4362). Differences in rust reaction based on sporulation between the isolates on each cultivar will be recorded and verified by repeating the inoculation test. For orange rust, similar experiments as described above will be conducted once handling procedures are developed that eliminate problems with spore viability. For other diseases/pathogens, clones will be surveyed at two month intervals on the Sugarcane Field Station and in 6 growers’ fields for outbreaks of both exotic and endemic diseases. Once something new is suspected the pathogen (pathogenic race) will be identified and similar experiments as that described for brown rust above will be conducted. 3. Sugarcane clones in the cultivar development programs for sucrose and bio-energy will be screened for their disease reactions to the major pathogens in artificial inoculation tests and ratings will be determined based on incidence and severity of disease. 4. Sugarcane progeny of selected families, parental clones in the Canal Point (CP) Cultivar Development Program and clones in other populations will be inoculated using standard procedures and disease resistant individuals will be identified.
3. Progress Report:
Because diseases of sugarcane are a major economic threat, there has been an increased screening and evaluation of germplasm in the Cultivar Development Program that includes clones being developed for organic soils and sand soils. This entails rating clones based on both natural infection and artificially inoculating clones in the program. Susceptible clones have been eliminated at each stage of the program because of susceptibility to diseases: brown and orange rust, leaf scald, mosaic and smut. There has been an improvement in resistance on clones in the later stages of the program.
1. Identification of disease resistant cultivars of sugarcane is essential. In order to prevent yield losses due to diseases susceptible cultivars should not be released; all disease susceptible clones must be identified in the cultivar development program. Sugarcane clones in Stage II (1500) Stage III (135) and Stage IV (18) in the variety development program for organic soil (muck) were screened for their disease reactions to ratoon stunt, smut, brown rust, orange rust, leaf scald and mosaic and similarly clones for sand soil were screened. Clones with unacceptable susceptibility levels were discarded. Resistant cultivars will allow Florida sugarcane growers to continue to produce approximately 20% of the sugar consumed in the United States. Resistant sugarcane cultivars will provide growers with an effective means of controlling diseases.
2. Yellow leaf is caused by Sugar Cane Yellow Leaf Virus and little resistance is present in the breeding population. In order to identify new sources of resistance approximately 1,100 clones in the World Collection of Sugarcane and Related Grasses were screened for the presence of the virus and 57% were resistant. These clones will be used for breeding and for molecular research to associate markers with yellow leaf resistance.
Garcés, F.F., Fiallos, F.F., Silva, E., Martinez, F., Aime, M.C., Comstock, J.C., Glynn, N.C., Castlebury, L.A. 2014. First Report of Orange Rust of Sugarcane caused by Puccinia kuehnii in Ecuador. Plant Disease. 89:842.