Thesis (Ph. D.)--University of Wisconsin--Madison, 1948. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 59-61).

Thesis (Ph.D.)--University of Western Australia, 2005.

Diss. (sammanfattning) Alnarp : Sveriges lantbruksuniv., 2001. / Härtill 4 uppsatser.

Thesis--K. Technischen Hochschule zu München, 1906.

No description available.

Wild Hordeum species, from the four genome groups of X, H, I and Y, were assessed for physiological traits associated with tolerance to salinity and waterlogging. When grown in saline conditions, a number of wild Hordeum species had exceptional ‘exclusion’ of Na+ and Cl- from the young leaves, and also maintained tissue K+ concentrations, compared with Hordum vulgare ssp. vulgare (cv. ‘Golf’). For example, at 150 mol m-3 NaCl, the K+:Na+ in youngest, fully expanded leaf blades of wild Hordeum species averaged 5.2, compared with 0.8 in H. vulgare. H. marinum was more salt tolerant than H. vulgare, with a relative growth rate 30% higher than H. vulgare at 150 mol m-3 NaCl. At 300 mol m-3 NaCl, glycinebetaine plus proline contributed to 15% of πsap in expanding leaf blades of H. marinum, compared with 8% in H. vulgare. When grown in stagnant conditions, 16 accessions (approximately half of those evaluated) formed a barrier to radial O2 loss (ROL) in basal zones of adventitious roots. In the Triticeae, this trait had previously only been described in one species, H. marinum. The barrier to ROL occurred only in accessions from wetland or intermediate habitats, and was also related to genome type, being present in accessions with the X or the H genome (Hordeum vulgare has the I genome). In stagnant conditions, aerenchyma formed was, on average; 22% in accessions with the X genome; 19% in those with the H genome; and 15 and 16% in those with the I or the Y genomes, respectively. The combination of a barrier to ROL and aerenchyma enhances longitudinal O2 movement in adventitious roots, permitting roots to penetrate deeper into anaerobic substrates. In H. marinum, induction of the barrier to ROL was associated with a 97% reduction in apparent O2 diffusivity across the external layers of the basal zones of roots, compared with near the root tip. The barrier results from physical resistance to radial O2 movement, although when roots were cooled to suppress respiration some additional leakage of O2 was detected, indicating respiration also contributes to the low rates of ROL from the basal regions of roots. Low radial O2 permeability in the roots of stagnantly-treated H. marinum was associated with secondary thickening, putatively lignin or suberin deposits, in the hypodermis. These changes in root structure, however, did not influence root hydraulic conductivity, assessed for individual adventitious roots and whole root systems. Thus, diversity amongst Hordeum species in expression of traits for tolerance to waterlogging (an inducible barrier to ROL and aerenchyma) and salinity (Na+ and Cl- ‘exclusion’) were documented in this study. Traits for root aeration did not compromise the capacity of roots to take up water, presumably being of importance for growth in soils with fluctuating water levels (i.e. wet/dry cycles). The high degree of salinity tolerance in several Hordeum species, and especially in H. marinum, is consistent with field observations that these species occur in salt affected areas

In plants, P450 enzymes encoded by P450 genes play a central role in numerous biosynthetic pathways, such as the production of secondary metabolites, stress responses and disease resistance. This thesis reports upon the utilization of molecular biology techniques to study P450 gene(s) in barley (Hordeum vulgare L.).Using several combinations of degenerate primers, a large number of barley P450 gene fragments were cloned and sequenced from two commercial varieties, Chebec and Harrington. Among 247 isolated sequences, twenty six percent were homologous to genes of known function. The abundance of these sequences differed between the two cultivars. Variations in the motif sequences of the cloned genes were also found between these two cultivars. In addition to the cloned fragments, twenty-two putative barley P450 encoding genes were identified from 24,000 cereal sequences in the International Triticeae EST Cooperative (ITEC) database by homology search. Among these Expressed Sequence Tag (EST) sequences, a full-length P450 sequence was selected for further investigation in this study.This novel P450 gene, CYP72A39, was expressed at a very early vegetative stage, but no expression was detected at the reproductive stage. Comparison of expression profiles of this gene and "digital expression" databases confirmed that this gene was homologous to several cereal EST clones with tissue-specific transcripts responding to various environmental stimuli, such as stresses and disease. Among these, many transcripts in barley were obtained from stressed tissues at the vegetative stage, and two transcripts in wheat (Triticum aestivum L.) were expressed after being challenged by barley powdery mildew pathogen (Blumeria graminis f. sp. hordei L.). This suggested that CYP72A39 may play a defence role in the barley seedling.The secondary structure of CYP72A39 was investigated in a comparative analysis using a computational approach. However, attempts to express CYP72A39 in a heterologous system and functional assays of the native protein in barley did not give decisive results, due to the disordered structure of the native protein and limitations of the current method. Screening the 3' UnTranslated Region (3'UTR) of this gene in 158 genotypes of domesticated, landrace and wild barley revealed two haplotypes, which differed by a 12 base indel positioned between two transversions. The presence of both haplotypes in wild and cultivated barley suggests this polymorphism predates the domestication of barley. This indel was mapped to the long arm of chromosome 6H, less than 10 centi-Morgans (cM) from the gene encoding resistance to powdery mildew in barley (B. graminis). A comparison between haplotype diversity and powdery mildew resistance data for over 102 genotypes showed a weak link between the 'long' haplotype and resistance, while the 'short' haplotype was associated with susceptibility. There was no evidence for a strong correlation between haplotype and quality type (malt or feed); however, more malting varieties had the long haplotype, suggesting a possible association with some attributes in modern malting barley. There was no evidence for association with other characteristics such as geographic origin, growth habit or row number. Phylogenetic relationship of the CYP72A39 to other CYP72 members was also investigated.

Four experiments were conducted with the objectives of (i) comparing the suitability of various H. bulbosum clones for haploid production, (ii) determining the parental effects of H. bulbosum and barley genotypes on percentage of pollinated florets yielding caryopses with rescuable embryos and on embryo viability, (iii) comparing different stages for embryo culture and caryopsis culture, and (iv) attempting to produce barley haploids directly from cultured immature caryopses. The results demonstrated: that reproductive characteristics of H. bulbosum clones varied with environmental conditions; that the hybrid H. bulbosum clones MBC-3 and MBC-4 were superior to their parents Cb2920 and Cb2929 as pollen donors; that both parental genotypes and date of harvesting after pollination had large effects on percentage of pollinated florets yielding caryopses with rescuable embryos and on embryo viability; that haploid plantlets can be generated from haploid caryopsis culture without embryo rescue, but only at a low frequency and with a slow rate of germination.

Diss. (sammanfattning)--Uppsala : Sveriges lantbruksUniversity. / Härtill 4 uppsatser.

No description available.