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PRECISION OF ESTIMATORS OF GENETIC VARIABILITY WITH APPLICATIONS IN SORGHUM POPULATION IMPROVEMENT (NEBRASKA)
Abstract
Variance components and ratios of variance components (heritabilities) are frequently estimated in recurrent selection experiments. Estimates of these parameters are often interpreted without reference to precision, or else inaccurate measures of precision are used. One objective of this research was to identify or develop accurate measures of precision for variance component and heritability estimators. An exact confidence interval was developed for heritability (H) on a progeny mean basis. This interval was derived using the fact that 1-H was distributed as F (df(,1),df(,2)). An exact confidence interval for phenotypic variance estimates and an accurate approximate confidence interval for family variance component estimates were identified. These confidence intervals were applied to estimates of genetic parameters obtained from 200 families each from NP3R cycle-three S(,1), full-sib, and half-sib families, and 200 S(,1) families from NP5R random-mating sorghum {Sorghum bicolor (L.) Moench} populations grown in two replications in a replications-in-blocks experimental design in 1981 and 1982 at Mead, Nebraska. Yield, height, days to flower, protein percentage, 100-seed weight, and culms/plant were measured among families in each population. The precision of family variance component estimates was exceedingly low. Ratios of confidence interval widths to point estimates ranged from 0.35 to 1.12. Heritability estimates ranged from 0.323 to 0.824 with confidence interval widths from 0.304 to 0.079. The level of precision of heritability estimates was uniformly higher relative to the precision of the variance component estimates. Another objective of this research was to conduct an empirical study of the precision of heritability estimates. Precision was a function of the magnitude of genetic variation relative to phenotypic variation. For a given experimental design and sample size, precision increased as heritability increased. Precision was also a function of sample size, experimental design, and the confidence coefficient. It was empirically demonstrated that more efficient experimental designs are obtained with unbalanced experimental designs.
Subject Area
Agronomy
Recommended Citation
KNAPP, STEVEN JOHN, "PRECISION OF ESTIMATORS OF GENETIC VARIABILITY WITH APPLICATIONS IN SORGHUM POPULATION IMPROVEMENT (NEBRASKA)" (1983). ETD collection for University of Nebraska-Lincoln. AAI8328177.
https://digitalcommons.unl.edu/dissertations/AAI8328177