Submitted to: American Society of Sugar Cane Technologists
Publication Type: Abstract Only
Publication Acceptance Date: 5/3/2013
Publication Date: 6/13/2013
Citation: Comstock, J.C., Sood, S.G. 2013. Developing Disease Resistance in CP-Cultivars. American Society of Sugar Cane Technologists. pp3.
Technical Abstract: Disease resistance is an important selection criterion in the Canal Point (CP) Sugarcane Cultivar Development Program. Ratoon stunt (RSD, caused by Leifsonia xyli subsp. Xyli Evtsuhenko et al.), leaf scald (caused by Xanthomonas albilineans Ashby, Dowson), mosaic (caused by Sugarcane mosaic virus strain E), smut (caused by Sporisorium scitamineum (Syd.) M. Piepenbr., M. Stoll & Oberw.), brown rust (caused by Puccinia melanocephala H. & P. Sydow) and orange rust (caused by Puccinia kuehnii E.J. Butler), are economically important diseases in Florida. Reactions to natural infection to all diseases except RSD begin in the Seedling (first) selection stage and continue in subsequent stages. Artificial inoculations begin in the third selection stage (Stage 2, with 1500 clones) and Stage 3 (135 clones) for RSD, brown rust, and orange rust. Artificial inoculations for leaf scald, mosaic, and smut are applied to the most promising clones in the final year of Stage 3 (40 clones) and continued on all clones in Stage 4 (18 clones). Selections of clones for disease resistance and tolerance are based on both natural infections and artificial inoculations. For most diseases, only resistant and moderately resistant clones are advanced to the next stage, except that sometimes clones with high sucrose yields and moderately susceptible ratings for RSD and other diseases with no natural infection in the fields are also selected. Also, there is an increased willingness among growers to advance clones that are moderately susceptible to brown or orange rust from Stage 3 to Stage 4 and Stage 4 to release, because growers have fungicides to control the spread of these two diseases. Data of artificial inoculations for different diseases from several years are compiled and compared to determine if inoculations techniques and/or selection practices require improvements. Data for RSD show that the CP 06 series in Stage 4 had more resistant clones than the CP 07 and CP 08 series. However, the CP 08 series in Stage 4 had more moderately resistant clones and less susceptible clones than the CP 06 and CP07 series. The CP 08 series in Stage 4 had a total of 70% resistant and moderately resistant clones compared to 50% in the CP 06 series and 47% in the CP 07 series. These variations could be results of escapes. All the series in Stage 4 had improved resistance to leaf scald than in Stage 3. The percentage of mosaic and smut resistant clones in Stage 3 increase and Stage 4 had no significant (P = 0.05) difference. This complex program of disease evaluation enables the CP program to continuously monitor the disease status of its new cultivars and to breed for improved disease resistance and tolerance while maintaining high yields.