Flax (Linum usitatissimum L.) is one of the richest plant sources of omega-3 fatty acids praised for their health benefits. In this study, the extent of the genetic variability for genes encoding stearoyl-ACP desaturase (SAD), fatty acid desaturase 2 (FAD2) and 3 (FAD3) was determined by sequencing the six paralogous genes from 120 flax accessions representing a broad range of germplasm including some EMS mutant lines. A total of 6 alleles for sad1 and sad2, 21 for fad2a, 5 for fad2b, 15 for fad3a and 18 for fad3b were identified. Deduced amino acid sequences of the alleles predicted 4, 2, 3, 4, 6, and 7 isoforms, respectively. Allele frequencies varied greatly across genes. Fad3a, with 110 SNPs and 19 indels, and fad3b, with 50 SNPs and 5 indels, showed the highest levels of genetic variation. While most of the SNPs and all the indels were silent mutations, both genes carried non-sense SNP mutations resulting in premature stop codons, a feature not observed in sad and fad2 genes. Some alleles and isoforms discovered in induced mutant lines were absent in the natural germplasm. Correlation of these genotypic data with fatty acid composition data of 120 flax accessions phenotyped in six field experiments revealed statistically significant correlations of some of the SAD and FAD isoforms on fatty acid composition, oil content and iodine value. The novel allelic variants and isoforms identified for the six desaturases will be a resource for the development of oilseed flax with unique and useful fatty acid profiles. / October 2015

No description available.

No description available.

The corresponding isoperoxidases from the flax genotrophs L and S have different molecular weights. Since further structural analysis will rely on knowledge of the primary structures of these molecules, the isolation of a molecular clone of this enzyme was attempted. Probing a cDNA library with a synthetic oligonucleotide was not successful, but a partial cDNA sequence was isolated by probing an S genotroph stem $ lambda$gt11 library with polyclonal antibodies raised against anionic plant peroxidases. Its longest reading frame sequence is divergent from those of other peroxidases, but contains some related segments. Genomic Southern analysis of the clone is presented, along with a study of the expression of its corresponding mRNA in plant tissues. A study on the effects of IAA, ABA and kinetin levels on the expression of peroxidase and of the putative peroxidase cloned mRNA is also presented.

The potential of using fibre flax cultivars; developed in Europe for production in Quebec and Eastern Ontario was investigated in 1997 and 1998, in field trials at Macdonald Campus, McGill University, Ste. Anne-de-Bellevue, Quebec and at Winchester and Kemptville, Ontario. A total of 11 cultivars were evaluated based on parameters pertinent to successful production. The French cultivar 'Ariane' stood out as the cultivar whose performance was most consistent across a variety of soil types and locations. The best method of establishing fibre flax (c.v. Ariane) in terms of seeding depth (zero, one, two, four or six centimeters), with soil compaction prior to vs. after seeding, or not at all, was also investigated during 1997 and 1998 at Macdonald Campus. Results were somewhat contingent on soil type at a specific site, but generally, a shallow seeding depth of one or two centimeters is best, with soil compaction prior to seeding more effective in lighter soils, and the same shallow seeding depth with no soil compaction in heavier soils. Preliminary investigations at Macdonald Campus in 1998 indicate good potential for the production of fibre flax (cv. Ariane) in minimum and zero tillage systems compared with conventional tillage. There were no significant differences between treatments in fresh straw yield, and minimum tillage plots produced significantly taller plants in one of the two sites. Overall, findings from this research indicate that fibre flax can successfully be produced in Eastern Canada using cultivars; of European origin and in a variety of tillage systems.

A series of investigations was undertaken regarding the biorefining of biomass for the recovery of multiple high-value products. The overall objective was to develop a simple, selective breakdown approach for flax shive, addressing three specific research areas: material properties; extraction processing; and product purification. This thesis includes five published papers and additional research all related to the topic. Flax shive represents the woody residue left over after removing fibre from flax straw. It is composed of lignified xylem tissue. Flax shive is readily available in large quantities, at low cost, and with relatively consistent particle-size and composition characteristics. Frictional behaviour investigations of bulk flax shive showed differing effects for addition of alcohols versus water. Adding any liquid significantly increased internal friction. The wall friction effects, however, depended on the liquid. Friction was increased significantly by water, but not as much by alcohols. Absorptive behaviour of flax shive, specifically liquid-holding capacity, was assessed using five liquids and compared to three other biomass materials. Flax shive was found to be a comparatively poor absorbent, a desirable behaviour for a feedstock used in aqueous- or alcohol-based processing. The first step extraction employed sodium ethoxide catalyst in anhydrous ethanol. Yield of solvent-soluble organics varied linearly with catalyst concentration. At 1.0 M the yield was 54.5 ± 14.5 mg/g dry basis (db). Analyses using 1H NMR consistently showed extracts to be phenolic in nature, and to contain no carbohydrate constituents. The second step extraction of hemicellulose polysaccharides was done using aqueous 1.0 M sodium hydroxide. The yield of carbohydrate precipitates was consistent, 99.4 ± 5.1 mg/g (db), and was unaffected by pretreatment. Analyses of polysaccharide backbone monomers showed consistently high molar ratios of xylose-to-glucose, i.e., 25.5 ± 3.4, with no mannose present. These results suggested a high concentration of glucuronoxylan polymer, likely greater than 90% by mass, with no glucomannan present. Economic evaluation showed two-stage extraction of high-value products to be a potentially viable business. Such processing also tied directly to government polices aimed at increasing value-add from agricultural materials. Overall, flax shive was found to be a desirable feedstock for recovery of high-value bio-products.

Cyanogenic glucosides (CGs) are bioactive plant secondary metabolites that can release toxic hydrocyanic acid when hydrolyzed. The accumulation of CGs in flax seed is a safety issue as a feed component and may contravene international trade restrictions. Here, we report the identification of major effect quantitative trait loci (QTL) for linustatin and neolinustatin, the two most abundant CGs in the mature flax seed. Current methods of CG analysis for screening and quality control are prohibitively expensive. Here, we also report on the development of a low cost, high throughput method of analysis using near infrared spectroscopy (NIRS) to estimate individual CGs and total hydrocyanic acid equivalent based on a regression of reference data obtained by gas chromatography. The genetic and physical mapping of the QTL and the NIRS calibration hold direct applications in the development of a flax breeding strategy for developing germplasm and cultivars with reduced CG content.

A series of investigations was undertaken regarding the biorefining of biomass for the recovery of multiple high-value products. The overall objective was to develop a simple, selective breakdown approach for flax shive, addressing three specific research areas: material properties; extraction processing; and product purification. This thesis includes five published papers and additional research all related to the topic. Flax shive represents the woody residue left over after removing fibre from flax straw. It is composed of lignified xylem tissue. Flax shive is readily available in large quantities, at low cost, and with relatively consistent particle-size and composition characteristics. Frictional behaviour investigations of bulk flax shive showed differing effects for addition of alcohols versus water. Adding any liquid significantly increased internal friction. The wall friction effects, however, depended on the liquid. Friction was increased significantly by water, but not as much by alcohols. Absorptive behaviour of flax shive, specifically liquid-holding capacity, was assessed using five liquids and compared to three other biomass materials. Flax shive was found to be a comparatively poor absorbent, a desirable behaviour for a feedstock used in aqueous- or alcohol-based processing. The first step extraction employed sodium ethoxide catalyst in anhydrous ethanol. Yield of solvent-soluble organics varied linearly with catalyst concentration. At 1.0 M the yield was 54.5 ± 14.5 mg/g dry basis (db). Analyses using 1H NMR consistently showed extracts to be phenolic in nature, and to contain no carbohydrate constituents. The second step extraction of hemicellulose polysaccharides was done using aqueous 1.0 M sodium hydroxide. The yield of carbohydrate precipitates was consistent, 99.4 ± 5.1 mg/g (db), and was unaffected by pretreatment. Analyses of polysaccharide backbone monomers showed consistently high molar ratios of xylose-to-glucose, i.e., 25.5 ± 3.4, with no mannose present. These results suggested a high concentration of glucuronoxylan polymer, likely greater than 90% by mass, with no glucomannan present. Economic evaluation showed two-stage extraction of high-value products to be a potentially viable business. Such processing also tied directly to government polices aimed at increasing value-add from agricultural materials. Overall, flax shive was found to be a desirable feedstock for recovery of high-value bio-products.

Bibliography: leaves 106-132. / 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 project investigated the role of VAM fungi in the growth and nutrition of Linum usitatissimum L. in agricultural soils in southern Australia. It had two general aims: (1) to examine the role of indigenous VAM fungi in the growth and nutrition of linseed in field soil collected near Clare, South Australia; and (2) to examine the effect of VAM fungi on the Zn nutrition of Linola. / Thesis (Ph.D.)--University of Adelaide, Dept. of Soil and Water, 2001

The possible biochemical mechanisms of varietal and species specificity of obligate fungal parasites are considered in relation to the established genetics and biochemistry of host-parasite systems. The two general theories of specificity which have been put forward are identified. One invokes the induction of successful pathogenesis as a primary determinant in specificity while the other predicts that recognition of avirulent pathogens by the host leads to induced resistance which acts as the determinant in specificity. The former theory is supported by evidence for the appearance of novel host enzymes during disease development. The latter is supported by observations of host gene derepression and phytoalexin accumulation which occur in resistance responses at times prior to any significant response in susceptible combinations. These theories are examined experimentally in the flax/flax rust system. The molecular origin of ribonuclease with altered catalytic properties, which arises during disease development, is examined. Rigorous purification reveals that the altered catalytic properties can be accounted for by altered proportions of ribonuclease I isozymes. These changes are similar during resistant and susceptible reactions until sporulation occurs. Induced resistance is characterized and compared to primary changes during susceptibility through a detailed study of RNA and protein synthesis. Enhanced RNA synthesis occurs in the resistant reaction at times prior to any measurable response in the susceptible combination, although both combinations exhibit higher rates of RNA synthesis at later times. RNA was fractionated by electrophoresis and affinity chromatography and messenger activity assessed by in vitro translation. Enhanced RNA synthesis is characterized by decreased messenger polyadenylation. However, polyadenylated and non-polyadenylated messenger RNA were shown to encode many common polypeptides; this provides an explanation for the fact that few changes in iri vivo protein synthesis can be detected by one or two dimensional electrophoresis. The only marked changes in protein synthesis occur in the susceptible combination and include a dramatic decline in the synthesis of the large subunit of ribulose-1,5-bisphosphate carboxylase. It is concluded that incompatibility of an avirulent race of rust with the flax variety Bombay is determined by induced resistance resulting from recognition of the avirulent pathogen prior to the initiation of pathogenesis. However, specific biochemical events in the host, particularly those involving chloroplast function, may be necessary for successful pathogen development. / Land and Food Systems, Faculty of / Graduate