Genetic Architecture of Water-Soluble Carbohydrates in Wheat

Benjamin Ovenden

Research output: ThesisDoctoral Thesis

89 Downloads (Pure)

Abstract

Water-soluble carbohydrates (WSC) accumulate in wheat when assimilatesupply is greater than assimilate demand from sinks. This characteristic has been identified as a potentially useful drought avoidance trait, as plants that accumulate carbohydrate reserves can remobilise that assimilate to contribute to grain filling under unfavourable growing conditions such as terminal drought. This study investigated a population of breeding germplasm constrained for maturity to explore the genetic control of WSC accumulation and the potential for genetic improvement of this trait.Experiments were conducted over two locations and two years with rainfed and irrigated treatments at each location to provide the multi-environment trial dataset.

The results of this study show that WSC accumulation involves complexinteractions with other traits and the environment. For both WSC concentration (WSCC) and total WSC per m2 (WSCA) strong environmental interactions were observed, with experiments clearly grouping into well-watered and water deficit environment clusters. Within these clusters, genetic correlations between experiments were high. Heritability for WSCC was higher than for WSCA, due to the difficulty in obtaining an accurate biomass measure, consequentially WSCC was used in the subsequent marker analysis. There was no correlation between grain yield and WSCC or WSCA, although significant correlations were observed in both well-watered and water deficit experiment clusters for reduced tillering, fewer grains per m2 and greater grain weight.

Genome-wide association studies for WSCC were performed in eachexperiment, by employing two different marker sets and two analysis pipelines, and using the identification of known flowering time loci via the same methodology as a vi positive control. Two quantitative trait loci (QTL) for WSCC were identified at multiple experiments and with both analysis pipelines. One of these markers has been previously associated with grain yield under water-limited conditions, and the other was located close to the Glu-1D locus controlling expression of glutenin grain storage proteins. Few loci for WSCC collocated with loci associated with flowering time.Notably, the association studies did not identify any major loci for WSCC that explained a large proportion of phenotypic variance.

The possible application of genomic selection was assessed by developingfactor analytic models. These were then used to generate genomic estimated breeding values (GEBVs) from the whole-genome marker profiles for both the well-watered and water deficit environment clusters of experiments. The GEBVs for each of these target populations of environments showed 65-70% relative accuracy compared to phenotypic predictions. This translates to an approximately 30-40% greater geneticgain for genomic selection per unit time when the duration of the breeding cycle is reduced by half at the same time. Interestingly, the additive GEBVs were correlated with the non-additive genetic variance component, indicating possible phenotypic epistasis or genetic correlation between underlying component traits. However, the nature of whole genome marker profiles needs to be taken into consideration when applying them to statistical genetics models, as statistical measures of additivity arenot necessarily additive genetic effects in the biological sense.

The empirical progression of methods used in this study highlight the nature of WSC genetic architecture as complex, polygenic, but ultimately a candidate for selection in breeding programs. This study demonstrates how some progress can be made towards genetic improvement of a complex trait even when the nature of inheritance is not completely understood.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Charles Sturt University
Supervisors/Advisors
  • Wade, Leonard, Co-Supervisor
  • Rebetzke, Greg J., Co-Supervisor, External person
  • Milgate, Andrew, Co-Supervisor
Award date07 Aug 2015
Place of PublicationAustralia
Publisher
Publication statusPublished - 2015

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