Molecular tools, coupled with unique germplasm stocks and rigorous phenotyping, are useful for developing a better understanding of qualitative and quantitative disease resistance genes in plants. The identification of molecular markers linked to all types of resistance genes provides opportunities for implementing a range of resistance breeding strategies, ranging from gene pyramiding to gene deployment. This thesis consists of two chapters. The first describes a disease resistance gene mapping effort and the second describes a disease resistance gene introgression effort. The number, location, and effects of genes determining resistance to stripe rust, leaf rust and Barley Yellow Dwarf Virus were determined using a population of doubled haploid (DH) lines from the cross of Shyri x Galena. Resistance to leaf rust was qualitatively inherited, and the locus was mapped to the long arm of chromosome 1. Resistance to stripe rust and BYDV was quantitatively inherited. Multiple QTLs were detected for each type of resistance. The principal stripe rust resistance QTL was on the short arm of chromosome 5 and the principal BYDV resistance QTL was on the long arm of chromosome 1, linked in repulsion phase with the leaf rust resistance gene. Additional QTLs and QTL x QTL interactions were detected. The majority of the qualitative and quantitative resistance loci detected in the Shyri x Galena population coincided with Resistance Gene Analog Polymorphisms (RGAPs) mapped in the same population. These RGAPs were based on degenerate primers derived from cloned resistance gene sequence motifs. These associations should be useful for efficient resistance gene mapping and provide an approach for ultimately isolating and describing quantitative and qualitative resistance genes. The second chapter describes a molecular marker assisted selection (MMAS) effort to introgress stripe rust resistance QTLs on chromosomes 4 and 7 into susceptible germplasm. DH lines were derived form a MMAS backcross-one (BC-1) population, extensively phenotyped for stripe rust resistance, and genotyped for the introgressed QTLs and background genome. The resistance QTLs that were introgressed were significant determinants of resistance in the new genetic background. Additional resistance QTLs were also detected. Together, these chapters describe an integrated approach to disease resistance gene characterization and utilization. / Graduation date: 1999

A genome sequence can be conceptualized as a 'book' written with four nucleotide 'letters' in oligonucleotide (oligo) 'words'. These words can be used in genomics, bioinformatics and the development of molecular markers. The whole-genome sequence for rice (Oryza sativa L.) is almost finished and has been assembled into pseudomolecules. For barley ( Hordeum vulgare L.) expressed sequence tags (ESTs) have been assembled into 21,981 tentative consensus sequences (TCs). The availability of such sequence information provides opportunities to investigate oligo usage within and between genomes. For the first of three studies reported in this thesis, a C++ program was written to automatically design oligos that are conserved between two sets of sequence information. In silico mapping between rice coding sequences (CDS) and barley TCs indicated that oligos between 18 and 24 bp provide good specificity and sensitivity (83% and 86%, respectively, for 20mers). Conserved oligos used as PCR primers had a high (91%) success rate on barley lines. Sequencing of PCR products revealed conservation in exon sequence, size and order between barley and rice. Introns were not conserved in sequence but were relatively stable in size. Map locations of eight new markers in barley revealed both genome colinearity and rearrangements between barley and rice. The second study reported in this thesis examined word frequency within the rice genome. A non-random landscape composed of high-frequency and low-frequency zones was observed. Interestingly, high-frequency words seemed to be rice specific while single-copy words were gene specific and conserved across species. As in the first study, oligos of 12 bp or less were not specific, and 18 bp seemed to be a critical length for the specificity of oligos. The third study reported in this thesis involved the development of molecular markers for known genes using public sequence information. Six new polymorphic markers were d

A modification of bulked segregant analysis was used to raise the density of markers in a 34.5 cM region between Ugp2 and Ugp1, on chromosome 3 of the Harrington x TR306 barley Hordeum vulgare L.) cross. A computer program was used to select pools contrasting for parental alleles at the target site. Of 257 RAPD primers tested on DNA pools, one, UBC 508, detected a polymorphic DNA fragment (UBC508(C)). It mapped 10.2 cM distal to Ugp2. Two additional DNA polymorphisms, (UBC508(A) and UBC508(B)), mapped on chromosome 2. An additional marker, BCD 1796B, mapped 4.9 cM proximal to Ugp1. Both strands of the UBC508(C) fragment were sequenced. They were 588 bp long and had some homology to a region of the DNA that regulates transcription of the H. vulgare pazx gene encoding protein Zx. The effect of adding new marker(s) on the QTL analysis of agronomic and quality traits of barley, was investigated. For extract beta-glucan, a new peak was identified in the analysis when only UBC508(C) or when both UBC508(C) and BCD1796B were added. For fine-coarse difference a QTL x E interaction peak was detected when only BCD 1796B was added or when both UBC508(C) and BCD 1796B were added.

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Bibliography: leaves 93-114. / 114, [43] leaves, [30] leaves of plates : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis investigates genome analysis of wheat, rye and barley. The objective is to evaluate the feasibility of using polymerase chain reaction (PCR) as a tool for studying cereal genomes. Results are compared for PCR and RFLP (restriction fragment length polymorphism) / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 1994

Bibliography: leaves 93-114. This thesis investigates genome analysis of wheat, rye and barley. The objective is to evaluate the feasibility of using polymerase chain reaction (PCR) as a tool for studying cereal genomes. Results are compared for PCR and RFLP (restriction fragment length polymorphism)

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