| Genes modifying traits affecting agronomic performance and grain quality have been characterized using the techniques of quantitative trait locus (QTL) analysis. These have been most generally attempted in model plant and animal populations which are most often characterized by parents which are genetically quite different. Plant breeders improve crops most efficiently using parents which are more closely related, but which differ for a few important genes. In this project, three populations derived from a single relatively narrow plant breeding cross were developed and evaluated to determine whether QTL analysis could be productively utilized within the context of a practically-oriented plant improvement program.; There are several problems associated with narrow parental divergence and genome-wide genetic analysis. Generating a representative linkage map is challenging and may indeed be impossible. Measuring and interpreting the actions of genes with relatively small effects, especially linked genes, is problematic as well. One of the three populations was used to generate a linkage map comprising 50 anchor markers and 191 AFLP markers. The map covered all seven barley chromosomes with an average distance between markers of 12cM.; QTL analysis was based on results gathered from three years' replicated field experiments and initially the map constructed in the ‘Fiber-2’ mapping population. A substantial proportion of the variance for grain yield, β-glucan content, flowering date and plant height was accounted for by a few, relatively well-marked genes. Composite interval mapping provided a clearer picture of the impacts of these genes on phenotype than did simple interval mapping, and strongly supported the contention that the n and lk2 genes both impacted grain glucan content.; A search for digenic, interactions suggested that the waxy gene acted as a controller of gene expression for flowering date and plant height, a result not previously noted. |
