2012 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.
The increased effort in the disease screening program for brown and orange rust has increased the proportion of resistant clones in the later stages of the development program.
Selection of brown rust resistance. Selection of brown rust resistance was conducted by rating plants with artificially and natural infected in multiple stages of the development program. Clones in Stage II were also tested for the major brown rust resistance gene, Bru1, approximately 30 % contain the gene. Because the brown rust incidence was higher this year and sufficient for evaluation all of the 14,434 clones in the Stage I were evaluated for their brown rust reaction. Eliminating the susceptible clones will improve subsequent control of brown rust when cultivars are released.