A practical method for the early assessment of the value of sugar cane crosses in generating potentially elite genotypes for selection
| MSI07P4237 | |
| Ramdoyal, K. Badaloo, M. G. H. | |
| A practical method for the early assessment of the value of sugar cane crosses in generating potentially elite genotypes for selection | |
| Abstract Book. 8th ISSCT Breeding and Germplasm Workshop, Guayaquil, Ecuador, 1-5 May 2006 | |
| 8th ISSCT Breeding and Germplasm Workshop, Guayaquil, Ecuador, 1-5 May 2006 | |
| book chapter | |
| 2006 | |
| p. 16 | |
| Abstract only | |
| En | |
| En | |
| Replicated cross evaluation trials have traditionally been laid down with potted seedlings that are transplanted in the fields. Since 2004, the policy of transplanting 50 per cent of the total seedlings produced each year directly in the field at high density, without prior potting, was implemented as a means to reduce on resources. This study investigates the feasibility of applying cross evaluation techniques on seedlings transplanted in this way based on random samples of 81 seedlings from 26 crosses in order to derive quick information on the value of crosses and parents in producing elite genotypes. Seedlings were planted in three replicates on raised beds of size 8m x 1.5m, in three rows and spaced at 0.40m between seedlings. Ten months after planting, stalk number, stalk diameter and stalk height were measured on five stalks per 20 progeny within each replicate. Genotypes selected from each family were evaluated at the 1st clonal stage and selection rate was appraised on field Brix, vigour and visual grade. Three univariate cross prediction methods were examined, the predicted proportion of genotypes that transgress set target values (PROB), the observed proportion of genotypes that transgress the target (OBS) and the mean of family (MEAN). Multivariate methods were based on the sum of ranks (RANK) and the frequency of genotypes that transgress set targets simultaneously (FREQ). Families differed significantly for all characters and between family variance was much more important than the within family variance. Narrow-sense heritability estimates, were very low for stalk number (0.11) and moderately low for stalk diameter (0.25) and stalk height (0.27), implying high environmental variation. The three univariate predictive statistics were equally robust in identifying the best crosses for all three characters with significant correlation between PROB and OBS (r = 0.90 - 0.96), MEAN and PROB (r = 0.97 - 0.99) and MEAN and OBS (r = 0.89 - 0.95). Highly significant correlation between the RANK and FREQ statistics were obtained for multivariate combinations of characters (r = -0.58 to -0.70). In general, the "better" crosses (top 50 per cent), based on frequency ( per cent) of elite genotypes and ranking, gave significantly higher selection rates (28 per cent to 50 per cent) at the seedling stage compared with lower potential ones. In general, crosses that gave the highest selection rates at the seedling stage also produced high selection rates at the 1st clonal stage. The MEAN and RANK methods are simple and reliable statistics that could be used in determining the best crosses even when seedlings are transplanted densely in the fields. A scenario for evaluating a large number of crosses quickly within the routine selection programme is discussed. | |
| sugarcane breeding crossing selection varieties cross prediction heritability univariate statistics multivariate statistics genotypes assessment method | |
| MAURITIUS | |
| Cane breeding and genetic improvement | |
| Breeding: Crossing | |
| 2007-01-31 | |
| En | |
| CAT | |
| PB |