Errata attached to inside front cover. Bibliography: leaves [156-188]

Pyrenophora teres, the causal agent of net blotch of barley (Hordeum vulgare L.), exists in two forms; P. teres f. teres and P. teres f. maculata. Both forms induce a combination of brown necrotic spots and extensive chlorosis in susceptible barley cultivars. Although a number of low molecular weight compounds (LMWCs) have been previously isolated from P. teres culture filtrates, they only induced certain components of symptoms. Fungal metabolites were extracted from culture filtrates of both forms of the pathogen and separated into low (<3kDa) and high molecular weight compounds (HMWCs, >10 kDa) with each fraction inducing a component of the net blotch symptoms in a barley leaf toxicity assay. Inactivation of both LMWCs (<1kDa) and HMWCs resulted in loss of activity confirming their potential role in symptom development. Low molecular weight compounds induced chlorosis and water soaking but not the brown necrotic spots or lesions usually seen during the infection of barley by P. teres. The high molecular weight compounds (>10 kDa) induced the brown necrotic spots or lesions with no chlorosis evident. Further characterisation of LMWCs showed that they are not host specific while HMWCs exhibited host specificity. LMWCs were purified and further analysed using high voltage paper electrophoresis, staining and mass spectrometry. Electrophoretic properties and staining of the LMWCs with ninhydrin indicated that both forms of P. teres produced similar LMWCs in the conditions grown. Each form produced eight ninhydrin-positive compounds with the samerelative mobilities. Each individual compound was shown to induce chlorosis in excised barley leaves. All compounds except the one isolated in this study appear to be derivatives of or are the previously described compounds; N-(2-amino-2carboxyethyl) aspartic acid (Toxin A), aspergillomarasmine A, anhydroaspergillomarasmine A and aspergillomarasmine B. The exception is a bioactive UV absorbing LMWC which appears to be a reductive conjugation of the α-keto acid of phenylalanine with Toxin A. The HMWCs (>10kDa) were proteinaceous since they were identifiable using Coomassie staining. Additionally, the loss of activity that occurred with incubation at 40, 60, and 80 °C for 30 and 60 min followed a pattern fairly typical for protein denaturation. Further, treatment with protease decreased their phytotoxicity in proportion to the amount of enzyme used. Enzyme and heat treatment of proteins extracted from each form showed that proteins of P. teres f. teres are more resistant to heat and enzyme treatment compared with those of P. teres f. maculata. This suggests the protein(s) involved in symptom induction by P. teres f. teres and P. teres f. maculata are different which contributes to the difference in the symptom expression during the interaction between the pathogens and barley. Proteinaceous metabolites extracted from P. teres f. teres and P. teres f. maculata ranged from 10 to 100 kDa. Fractions purified using gel filtration had biological activity when they contained eight proteins when extracted from P. teres f. maculata (90, 80, 75, 55, 48, 35, 14 and 12 kDa) and six proteins when extracted from P. teres f. teres (90, 80, 55, 48, 14 and 12 kDa). Additionally, intercellular washing fluids (IWF) extracted from barley plants inoculated with both forms of P. teres, contained proteins of the same size as those in the biologically active fractions extracted from culture filtrates of P. teres f. maculata (80, 14 and 12 kDa) and P. teres f. teres (80, 48 and 14 kDa). Automated MS/MS sequencing of the biologically active proteins showed no resemblance to the sequences or conserved domain information available in public databases and as a consequence, these proteins were considered as novel proteins for P. teres. However, exact short matches with fragments resulting from the 80, 48 and 14 kDa proteins, showed considerable homology with ATP-binding cassette (ABC) transporters and their components, cellulases, serine proteinases as well as some hypothetical proteins isolated from different fungal species. Reaction of six plant species including one susceptible barley cultivar (Sloop) and one resistant line (CI9214) to P. teres showed that partially purified proteins induce the symptoms selectively in barley cultivars where the proteinaceous metabolites only induced brown necrotic spot/lesions in barley with a greater response seen on the susceptible cultivar Sloop when compared to the resistant line CI9214. No symptoms were seen on other plant species employed in this study suggesting that the proteinaceous metabolites isolated in this study are host specific phytotoxins. This research has allowed the first isolation of proteinaceous host-specific toxins from P. teres as well as the identification of a UV-sensitive LMWC phytotoxin not previously described. Proteinaceous toxins induced brown necrotic spots/lesions specific to the host while the LMWCs induced chlorosis in a number of different plant species. This contributes significantly to the body of knowledge defining how symptoms are caused during the pathogenicity process in the interaction between P. teres and barley. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1297672 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2007

"August, 2003" / Includes bibliographical references (leaves 260-292) / v, 294 leaves : ill. (some col.), plates (col.), maps (col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, School of Agriculture and Wine, 2003

Bibliography: leaves 118-132. This thesis examines the structure and gene expression of barley yellow dwarf viruses (BYDVs)-PAV in order to gain a better understanding of the interaction between the virus and the Yd2 resistance gene. The protein products of open reading frame (ORF)3, ORF4 and ORF5 are expressed in bacterial cells, in order to characterise the BYDV-PAV virion-associated proteins. The effect of the Yd2 resistance gene on the expression of the BYDV-PAV viral proteins in infected cells is also studied.

Bibliography: leaves 118-132. / iv, 132 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis examines the structure and gene expression of barley yellow dwarf viruses (BYDVs)-PAV in order to gain a better understanding of the interaction between the virus and the Yd2 resistance gene. The protein products of open reading frame (ORF)3, ORF4 and ORF5 are expressed in bacterial cells, in order to characterise the BYDV-PAV virion-associated proteins. The effect of the Yd2 resistance gene on the expression of the BYDV-PAV viral proteins in infected cells is also studied. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 1997

One-irrigation barleys were bred to be grown with only a single irrigation near planting time. To further our understanding of how to manage these new cultivars, one-irrigation barleys were grown at 4 seeding rates (20, 40, 60, and 80 lbs seed /A), 4 nitrogen rates (0, 50, 100, and 150 lbs/A), and 3 planting dates (Nov. 17, Dec. 15, and Jan. 22). Seeding rates 01 40 to 60 lbs seed/A resulted in the highest yields at the Dec. 15 planting date, comparing all planting dates combined. However, in individual analyses of the Nov. 17 and Jan. 22 planting dates, no significant differences in yield due to seeding rate were detected. Grain yield increased linearly with nitrogen rate at the Nov. 17 planting date, but was not influenced by nitrogen rate at the other planting dates. Yields were similar for the Nov. 17 and Dec. 15 planting dates, but decreased considerably in the Jan. 22 planting date due partially to lower head number. Grain yields of 2-22-9 were consistently higher than Seco this year.

A series of experimental plots was planted because ranchers, conservationists, farmers and homeowners in southeastern Arizona were interested in knowing more about one -irrigation barleys. The results of these observations are contained in this paper.

This study was initiated to determine how barley cultivars perform outside the environment for which they were selected. Also, a comparison was made of water use by a one-irrigation barley with water use of a commercial cultivar selected for high yield conditions. Six barley cultivars bred for differing growing conditions (Westbred Gustoe and Westbred Barcott - high input; Arivat and Prato - medium input; and, Seco and 2-22-9 - low input) were compared under 12 water regimes delivered by a line -source sprinkler system. Water use of Seco, a one-irrigation barley, and Westbred Gustoe, a commercial barley, was monitored with a neutron probe. The barley cultivars bred for high, medium, and low input conditions performed best in their respective optimum water levels with the exceptions of Westbred Barcott and Prato. Westbred Barcott (high input) yielded relatively well over all water levels, and Prato (medium input), performed similar to a high input barley. Seco (low input) used slightly less water than Westbred Gustoe (high input), primarily due to its earlier maturity. The water extraction pattern with depth was similar for both cultivars due to the frequent shallow irrigations applied in this study. The water extraction pattern of Seco needs to be investigated under one- irrigation conditions.

The occurrence of Boron (B) toxicity in Australian soils is recognised as a limiting factor for cereal productivity. A number of loci conferring tolerance to B toxicity have been identified in barley and chromosomally mapped. However, a lack of knowledge relating to the physiological and molecular events that occur under B toxicity and the molecular basis for B stress tolerance has been a bottleneck in harnessing available genetic diversity in barley and wheat. The recent advances in functional genomics provided an opportunity to examine B stress in barley in more detail. The aim of this project was to analyse genes differentially expressed under B stress in tolerant and intolerant barley to identify candidate genes involved in B toxicity tolerance. Two experimental approaches, Suppression Subtractive Hybridization (SSH) and microarray were adopted. Firstly, SSH was performed to examine gene expression in roots of selected tolerant and intolerant doubled haploid lines from a Clipper (B intolerant) X Sahara 3771 (B tolerant) mapping population, grown under moderate B stress. The SSH experiment aimed to investigate the early transcriptional response of B tolerant barley lines to B stress in order to identify the basis for B toxicity tolerance in roots. Differential screening of the subtracted library generated from B treated plants identified a total of 111 non-redundant clones up-regulated in bulked tolerant lines. On the other hand 94 clones were differentially expressed under non-treated conditions. Among the clones identified from subtracted library generated from B treated plants, metabolism was the largest functional category, representing 21% of the clones. The largest functional category in the subtracted library generated from non treated plants was cellular transport, representing 19% of the clones. Based on sequence similarity, about 170 transcripts identified in this experiment were assigned to chromosomal segments (bins) on the three homoeologous genomes of bread wheat. In total, 36 clones from the subtracted library generated from B treated plants were analysed as candidates. Nine were genetically mapped within the region of B tolerance QTL on three chromosomes (2H, 4H and 6H). The genes mapped to 4H and 6H QTL have the highest association with these loci in the Clipper X Sahara 3771 doubled haploid mapping population. A 4H B tolerance QTL candidate gene was identified as a B transporter gene with similarity to the Arabidopsis BOR1 gene. Genes identified to be differentially expressed in the tolerant lines from SSH suggest activation of a diverse defence response in the roots of barley plants under B stress. Data from SSH experiment indicate that cell wall-plasma membrane cytoskeleton continuum constitute the first action site against B toxicity and the influence of toxic B on K+ uptake could be the key initiating factor. In the second approach, the Affymetrix 22K Barley1 GeneChip(TM) was used to investigate B stress adaptation processes in barley. Gene expression was profiled in leaves of Sahara 3771 and Clipper plants grown under various B concentrations. The results show that the two genotypes respond differently to B toxicity. The B intolerance of Clipper is expressed through the induction of a high number of probe sets (2310) even at a low B concentration of 100 µM. In contrast, Sahara 3771 responded to a high B concentration (2000 µM) through the induction of only a few hundred (266) probe sets. In Sahara 3771 no change in the expression level of any probe sets was observed at 100 µM B. Altogether 286 probe sets showed differential expression in Sahara 3771 under three levels of B treatment (500, 1000 and 2000 µM). About 30% of these were down-regulated and about 70% were up-regulated in Sahara 3771 in response to B treatment. Most of the probe sets (59%) up-regulated in Sahara 3771 did not respond to B treatment in Clipper. These genes are either salt stress responsive or related to plant defense and thus could play a key role in protecting barley plants from the toxic effects of B. Two differentially expressed probe sets annotated as B transporters were identified between Sahara 3771 and Clipper under control condition. These two B transporter probe sets did not respond to B treatment but showed opposing expression patterns in the two varieties. One of these probe sets (Contig21126_at) is similar to the B transporter gene isolated from the SSH experiment that maps to the 4H tolerance locus. The map location and expression of this B transporter gene suggest that it could be the borate anion efflux transporter predicted by the proposed efflux model of B tolerance in Sahara 3771 barley. The other B transporter gene (Contig14139_at) showed over expression in Clipper under control condition and could be contributing to high B accumulation in Clipper which needs further investigation. Data from both experiments have indicated that B toxicity triggers oxidative stress and that jasmonate-based signaling plays a key role in B toxicity tolerance. SSH data indicate that Sahara 3771 which evolved in the harsh environment of Africa is more efficient in osmoregulation and ROS scavenging than Clipper. This trait is likely to give Sahara 3771 an edge over Clipper in tolerating toxic the effect of B. In addition to the efflux mechanism, which becomes less efficient with increasing B supply, Sahara 3771 appears to apply a number of other mechanisms for alleviating or withstanding toxic B induced stress to sustain growth. Some of these mechanisms are already known to be used by plants to cope with a number of stresses. / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2008

Fall-sown barley will be increasingly important in the era of climate change due to higher yield potential and efficient use of water resources. Resistance/tolerance to biotic and abiotic stresses will be critical. Low temperature is an abiotic stress of great importance. Resistance to barley stripe rust (incited by Puccinia striifomis f. sp. hordei) and scald (incited by Rhynchosporium secalis) will be important in higher rainfall areas. Simultaneous gene discovery and breeding will accelerate the development of agronomically relevant germplasm. The role of FR-H1 and FR-H2 in low temperature tolerance (LTT) has been well documented. However the question still remains: is LTT due only to FR-H1 and FR-H2 or are there other, undiscovered, determinants of this critical trait? We developed two doubled haploid mapping populations using two lines from the University of Nebraska (NE) with superior cold tolerance and one line from Oregon State University (OR) with good malting quality and disease resistance: NB3437f/OR71 (facultative x facultative) and NB713/OR71 (winter x facultative). Both were genotyped with a custom 384 oligonucleotide pool assay (OPA). QTL analyses were performed for LTT, vernalization sensitivity (VS), and resistance to barley stripe rust and scald. Disease resistance QTL were identified with favorable alleles from both NE and OR germplasm. The role of VRN-H2 in VS was confirmed and a novel alternative winter allele at VRN-H3 was discovered in the Nebraska germplasm. FR-H2 was identified as a determinant of LTT and a new QTL, FR-H3, was discovered on chromosome 1H that accounted for up to 48% of the phenotypic variation in field survival at St. Paul, Minnesota, USA. The discovery of FR-H3 is a significant advancement in barley LTT genetics and will assist in developing the next generation of fall-sown varieties. / Graduation date: 2012