The expression and inheritance of stem strength in irrigation wheat

[摘要] English: The aim of this study was to determine the inheritance and environmental factors that regulate stem strength in irrigation wheat. The strength of the stem is defined by its length and as an index of the function of the pressure which it takes to break the stem, the pith thickness of the stem wall at breaking point and the length of the internodes. In the first experiment a set of parents was evaluated to determine the differences amongst parents for stem strength and its components. The parents significantly differed in stem length and strength. Some parental genotypes had shorter and more solid stems. For the second experiment the same parental genotypes were used to create a diallel set of progeny. The progeny and the parents were planted in pots in the tunnel in a replicated experiment to evaluate plant height and stem strength. It was found that the variances for all characteristics were significant, but the additive component (general combining ability) was higher than the dominance component. The parents differed significantly in their ability to produce F1 progeny with stronger stems. The calculated heritability was high and significant, which showed that the best way to select for improved stem strength is to select amongst plants in the progeny of the parents with the highest combining ability for the desirable traits. The third experiment was done to determine the interaction of higher plant density and higher N fertilisation on the expression of stem strength. This experiment (parents and progeny) was planted in pots in a tunnel. It was found that genotype, plant density and N fertilisation had a highly significant effect on stem strength. The ability of the parents to produce progeny with strong stems differed. The parents with the solid stem phenotype and shorter stems generally produced progeny with stronger stems. The variance for general combining ability (additive genetic variance) is significant. The heritability for all characteristics was high, but higher in increased plant density or increased nitrogen application but with the highest expression where both plant density and nitrogen application were increased. This indicates that selection for stem strength should be more successful in populations with a higher plant density under high N conditions.

[发布机构] University of the Free State