Family evaluation for quality traits in sugarcane
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Date
2019-01
Authors
Mishasha, Tondani
Journal Title
Journal ISSN
Volume Title
Publisher
University of the Free State
Abstract
Family evaluation and selection has the potential to increase the selection efficiency, thereby
improving breeding for quality traits at early stages of sugarcane breeding. Data from family
evaluation trials can also be useful for quantifying the performance of parental genotypes that
were used to produce families. The objectives of this study were to compare family to individual
genotype evaluation and determine optimum sample size for estimating sucrose content; to
determine family evaluation breeding parameters and phenotypic correlations for quality traits;
to determine the proportions of families and parents producing significantly higher trait values
compared to the trial mean for the coastal short cycle mini-line breeding programme. Data were
collected from 20 genotypes within each family plot for hand held refractometer Brix %cane
data (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 individual
genotype variances were significant (P<0.01) suggesting selection for individual genotypes
within 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 individual
genotypes (2.42 to 5.47%). The higher H and %Gs indicated superiority of family selection
compared to individual genotype evaluation. Response surface graphs showed four replications
and 10 genotypes produced H values of 0.77 to 0.80 compared to 0.74 to 0.77 with sample size
of 20 genotypes in three replications. Reducing the sample size from 20 to 10 genotypes will
reduce 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 showed
strong associations among sucrose related traits (ERC %cane, Pol %cane and Brix %cane) with
correlation coefficient values ranging from 0.80 to 0.99. The significant (P<0.05) negative
correlation between sucrose related traits and fibre %cane (r>0.07) showed a decrease in
sucrose content with an increase in fibre content. Results showed that Brix %cane had a high
H, 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 measured
easily in the field using a hand held refractometer, providing data to quantify within family
variability in early stages of sugarcane breeding. Results showed highly significant family,
female and male variances, highlighting the existence of genetic differences and control among
families. Results showed a lower proportion of families producing significantly higher best linear unbiased prediction (BLUP) values compared to the population mean. Results suggested
the need to use breeding values to guide parent selection for breeding programmes.
Description
Keywords
Dissertation (MSc. (Plant Breeding))--University of the Free State, 2019, Sugarcane, Family and parent evaluation, Broad-sense heritability, Predicted selection gains