Family evaluation for quality traits in sugarcane

[摘要] Family evaluation and selection has the potential to increase the selection efficiency, therebyimproving breeding for quality traits at early stages of sugarcane breeding. Data from familyevaluation trials can also be useful for quantifying the performance of parental genotypes thatwere used to produce families. The objectives of this study were to compare family to individualgenotype evaluation and determine optimum sample size for estimating sucrose content; todetermine family evaluation breeding parameters and phenotypic correlations for quality traits;to determine the proportions of families and parents producing significantly higher trait valuescompared to the trial mean for the coastal short cycle mini-line breeding programme. Data werecollected from 20 genotypes within each family plot for hand held refractometer Brix %canedata (surrogate for sucrose content), estimated recoverable crystal (ERC) %cane, polarisation(Pol) %cane, Brix %cane, Brix dry matter (DM) %cane, purity %, fibre %cane and DM %cane.Data were analysed using statistical analysis system software (SAS). Both family and individualgenotype variances were significant (P<0.01) suggesting selection for individual genotypeswithin selected superior families will increase efficiency of selection. Broad-sense heritability(H) values ranged from 0.74 to 0.77 for families and from 0.14 to 0.17 for individual genotypes.Families (7.06 to 12.72%) produced higher predicted selection gains (%Gs) than individualgenotypes (2.42 to 5.47%). The higher H and %Gs indicated superiority of family selectioncompared to individual genotype evaluation. Response surface graphs showed four replicationsand 10 genotypes produced H values of 0.77 to 0.80 compared to 0.74 to 0.77 with sample sizeof 20 genotypes in three replications. Reducing the sample size from 20 to 10 genotypes willreduce data collection costs. ERC %cane, Pol %cane and fibre %cane had the largest H and%Gs values, suggesting that family evaluation was effective for these traits. Results showedstrong associations among sucrose related traits (ERC %cane, Pol %cane and Brix %cane) withcorrelation coefficient values ranging from 0.80 to 0.99. The significant (P<0.05) negativecorrelation between sucrose related traits and fibre %cane (r>0.07) showed a decrease insucrose content with an increase in fibre content. Results showed that Brix %cane had a highH, high %Gs and significant positive correlations with both ERC %cane and Pol %cane,suggesting that Brix %cane is a suitable trait for family evaluation. Brix %cane can be measuredeasily in the field using a hand held refractometer, providing data to quantify within familyvariability in early stages of sugarcane breeding. Results showed highly significant family,female and male variances, highlighting the existence of genetic differences and control amongfamilies. Results showed a lower proportion of families producing significantly higher best linear unbiased prediction (BLUP) values compared to the population mean. Results suggestedthe need to use breeding values to guide parent selection for breeding programmes.

[发布机构] University of the Free State