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Barley (Hordeum vulgare L.) is the preferred cereal for malting. Its suitability for malting depends on many criteria, including the size, shape and uniformity of the kernels. Malting quality is affected by many quantitative trait loci (QTL). Such loci have been mapped using phenotypic and genotypic information on all members of mapping populations. It may also be possible to detect marker-QTL associations using selective genotyping, in which only the progeny with high or low phenotypic values for a trait are genotyped with available markers. Information on marker-QTL associations may be used in marker-assisted selection. Marker-assisted selection could be particularly useful for barley malting quality traits, some of which are costly to assess. Here, three studies were conducted related to QTL for barley grain and malt quality characteristics. In the first study, QTL were mapped using kernel size and shape data obtained by image analysis on samples from a two-rowed by six-rowed barley cross. QTL were detected near vrs1 on chromosome 2(2H) and near int-c on chromosome 4(4H). Some QTL affected the within-sample variability without affecting the mean of kernel characteristics. QTL alleles that made kernels larger and/or rounder also tended to improve malt quality. Those that increased the variability of kernel size were associated with poor malt quality. In the second study, marker genotype data and grain and malt quality phenotype data from three mapping populations were used to investigate the feasibility of selective genotyping for QTL mapping. Almost all previously mapped QTL were detected often with only 10% of the population genotyped. Additional, possibly spurious, QTL were detected in regions of the genome where no significant QTL had been mapped. The results indicated that simultaneous investigation of two or more traits by selective genotyping could be worthwhile. In the third study, Morex alleles at a QTL on chromosome 7(5H) affecting alpha-amylase activ

Bibliography: leaves 114-141. / vi, 141, [42] leaves, [19] leaves of plates : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Using RFLP, STS-PCR and isoenzyme techniques, maps the structural genes of hydrolytic enzymes important in seed germination processes, and determines the contribution of each gene to the activity of the enzyme. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 1998

Understanding complex traits is a fundamental challenge in plant genetics and a prerequisite for molecular breeding. Tools for trait dissection are markers, maps, and quantitative trait locus (QTL) analysis. Marker-assisted selection (MAS) is an application that integrates these tools. In this thesis research, a new sequence-based marker was evaluated, maps were constructed and used, and QTLs were detected using two types of populations. Marker-assisted selection was used to develop a novel class of barley. Restriction-site Associated DNA (RAD), a sequence based-marker technology, allows for simultaneous high-density single nucleotide polymorphism (SNP) discovery and genotyping. We assessed the value of RAD markers for linkage map construction using the Oregon Wolfe Barley (OWB) mapping population. We compared a RAD-based map to a map generated using Illumina GoldenGate Assay (EST-based SNPs). The RAD markers generated a high quality map with complete genome coverage. We then used the RAD map to locate QTL for agronomic fitness traits. A paper describing this research was published (Chutimanitsakun et al., 2011). Marker-assisted selection was used to rapidly develop fall-sown barley germplasm for human food uses. The target traits were high grain β-glucan, vernalization sensitivity (VS) and low temperature tolerance (LTT). The target loci were WX and VRN-H2. Marker-assisted selection was effective in fixing target alleles at both loci and waxy starch led to increase in grain β-glucan. Unexpected segregation at VRN-H1 and VRN-H3, revealed by genome-wide association mapping (GW-AM), led to unanticipated phenotypic variation in VS and LTT. We found that GW-AM is an efficient and powerful method for identifying the genome coordinates of genes determining target traits. Precise information is obtained with perfect markers; additional research may be needed when multiple alleles are segregating at target loci and significant associations are with markers in linkage disequilibrium (LD) with the target loci. A paper describing this research will be submitted for publication. / Graduation date: 2012