|Del Blanco, Isabel|
|GILBERT, ROBERT - University Of Florida|
|DAVIDSON, WAYNE - Florida Sugarcane League|
Submitted to: Journal of Crop Improvement
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/2011
Publication Date: 1/17/2012
Citation: Zhao, D., Comstock, J.C., Glaz, B.S., Edme, S.J., Glynn, N.C., Del Blanco, I.A., Gilbert, R., Davidson, W., Chen, C.Y. 2012. Vigor rating and brix for first clonal selection stage of the Canal Point Cultivar Development Program. Journal of Crop Improvement. 26:60-75.
Interpretive Summary: Sugarcane is an important crop in Florida with annual economic impact of more than $440 million. Cane and sugar yields increased linearly in south Florida from 1968 to 2000, in which the Canal Point (CP) cultivar improvement contributed 69% of yield gain. Consistent and continuous development of high-yielding sugarcane cultivars with disease resistance/tolerance is critical to commercial sugarcane production in the region. The CP sugarcane cultivar development program consists of Crossing, Seedlings, and Stages I, II, III, and IV. In this paper, the Stage I selection was emphasized. Approximately 10,000 clones from more than 450 crosses are individually selected from the Seedling stage currently and planted in Stage I annually. A better understanding of genetic variation in agronomic performance both among- and within-families is essential for optimizing breeding and selection strategies. The specific objective of this study was to quantify genotype variability and influences of parents and families on plant vigor (an indicator of cane yield) and Brix (reflecting stalk sugar content). Data were collected from the 2009 and 2010 Stage I clones of the CP program. Stage I selection was based on major disease resistance and on the product of vigor and Brix. Vigor scores from all clones and Brix of clones with vigor >= 6 were collected in the Stage I in September and November, respectively, and analyzed for relationships between vigor and Brix, for selection rate in each family, and for their coefficients of variation within and among families. There was no tradeoff between vigor and Brix and it was feasible to select for sugarcane cultivars with both high cane yield and high sugar content in Stage I. Variability was high for number of clones and for percentage of selection among families with a coefficient of variation of 59% for both parameters. The coefficient of variation for vigor (7.2%) was greater than that for Brix (5.4%). The within-family coefficients of variation (9.3 and 6.3%) were greater than the among-family coefficients of variation (6.3 and 4.7%) for both vigor and Brix, respectively, averaged across years. These results should provide useful information about efficient use of parents in the future crossing and help improve our ability for early stage selection.
Technical Abstract: A better understanding of sugarcane (Saccharum spp.) genetic variability in agronomic performance will help optimize breeding and selection strategies. Vigor ratings and Brix data were collected from the 2009 and 2010 clones in the first clonal selection stage (Stage I) of the Canal Point (CP) sugarcane cultivar development program. Stage I individual selection was based on disease resistance and on the product of vigor and Brix. Vigor ratings (from 1 to 9) from all clones and Brix of any clones with a vigor rating ' 6 were collected in the Stage I fields and analyzed for relationships between vigor and Brix, for selection rate in each family (i.e., cross), and for their coefficients of variation (CV) within and among families. There was no correlation between vigor and Brix, suggesting that it would be feasible in Stage I to select sugarcane clones with both high vigor and high Brix. Variability was high (CV = 59%) for both the number of planted clones and selection rates among families, and vigor (7.2%) had greater CV than Brix (5.4%). Averaged across years, the within-family CVs (9.3% for vigor and 6.3% for Brix) were greater than the among-family CVs (6.3% for vigor and 4.7% for Brix). Results indicated that greater emphasis on family-based than on individual selection in Stage I should be avoided as it would result in the loss of potentially productive clones. However, use of individual selection data on vigor and Brix for analyzing family performance should improve parental selection and optimize crosses.