Field pea (Pisum sativum L.) is highly susceptible to ascochyta blight, primarily caused by the pathogen Mycosphaerella pinodes (Berk. & Blox.) Vestergr. Grasspea (Lathyrus sativus L.) has been reported to possess a moderate level of resistance to ascochyta blight caused by M. pinodes. The work reported in this thesis aimed to develop the various techniques that would be required to transfer ascochyta blight resistance from grasspea into field pea via somatic hybridisation. This thesis also assesses the feasibility of achieving this goal. Field pea shoot cultures were established on hormone-free MS medium, and a protoplast isolation protocol developed for both species. Grasspea shoot cultures were established on both RL and SSB8 medium. Friable grasspea callus was achieved on media supplemented with 2,4-D in the range 4.523 µM, whereas kinetin tested at any concentration did not appear to influence callus growth. A suspension culture of grasspea was developed for the first time, in B5 medium supplemented with 4.5 µM 2,4-D and 0.5 µM kinetin. Grasspea protoplasts were isolated from both in vitro seedlings and suspension cultures. Protocols for hybrid shoot culture on KM8p medium were developed via organogenesis and somatic embryogenesis.

Copies of author's previously published articles inserted. Bibliography :leaves 65-80 Ice nucleation active (INA) bacteria were detected in a pea field in South Australia. They were identified as strains of Pseudomonas syringae and Pseudomonas flourescens biotype 1. Some chemical agents were tested on the two ice nucleating species, as cryoprotectants.

Bibliography: leaves 182-217. This study was conducted to determine the etiology of a blight disease of chickpea in south-eastern Australia and the factors affecting disease development. The disease had previously been identified as phoma blight. Pathogenicity testing revealed two isolates subsequently identified as Asochyta rabiei, the first conclusive identification in the southern hemisphere. Greenhouse screening of chickpea varieties identified types resistant to ascochyta blight. The effects of plant age and environmental conditions on disease development were investigated under controlled conditions in growth rooms. Seedlings were more susceptible than older plants. The optimum conditions for ascochyta blight were 20° C and a 48-96 h period of leaf wetness. Through field trials it was found that disease intensity increased over time, especially in cv. Desavic. The means of penetration of the chickpea host was established in histological studies. This study provided advance warning of this disease for the expanding chickpea industry, and has allowed the implementation of appropriate disease management strategies. It is recommended that cv. Desavic should not be grown where ascochyta blight is likely to be a problem.

Successful chickpea production in western Canada typically requires multiple applications of fungicides to minimize the severity of Ascochyta blight (AB) caused by <i>Ascochyta rabiei</i>. Although planting resistant cultivars could be economical and environmentally safer than fungicide usage, varieties with a high level of resistance are not available. The objectives of this research were i) to determine the effect of different seeding arrangement treatments on ascochyta blight severity and seed yield of two cultivars (moderately resistant and susceptible) of kabuli chickpea; ii) to compare one and four fungicide applications at recommended and reduced rates and their impact on disease severity and cost; and iii) to assess organ-specific reaction to AB in chickpea in leaves, stems and pods of 12 desi and 12 kabuli varieties that are of economic significance to western Canada. <p>Treatments significantly influenced AB severity on both moderately resistant and susceptible cultivars in a season with a severe epidemic. Seed yield was significantly influenced by treatments for both varieties in both years. Contrast analyses revealed that four fungicide applications significantly reduced the AB severity for both varieties in a season with a severe epidemic and for the susceptible variety in a season with a moderate epidemic. Seed yield of both varieties was significantly higher under four fungicide applications compared to a single application. Solid seeding and paired row arrangements did not differ in their effect on seed yield and AB severity for both varieties in both years, except that the susceptible variety benefited from paired row planting with respect to seed yield and reduced AB severity in the season with a severe epidemic. Reducing fungicide rates and seeding rate could reduce the cost of cultivation without significantly affecting disease control and yield. Economic assessment revealed that in a severe epidemic season, the gross returns were high for the moderately resistant variety under four fungicide applications than one fungicide application. Gross returns for the susceptible variety were higher under four fungicide applications in both years.<p>There were differences among varieties for AB severity on leaves, stems and pods, seed yield and 1000 seed weight at all site-years tested. The variation was greater in kabuli varieties than desi varieties. AB severity on leaves, stems and pods was lower under high fungicide regimes, with few exceptions. Varieties with a fern leaf type had lower AB severity than those with unifoliate leaves. There was a positive correlation among AB severity on leaves, stems and pods. No differences in organ-specific reaction were observed.

Random amplified polymorphic DNA (RAPD) markers were used in three genetic studies in lentil (<i>Lens culinaris</i> Medikus). The first study involved development of RAPD markers linked with genes for resistance to ascochyta blight, caused by <i>Ascochyta fabae</i> f. sp. lentis Gossen et al. Seventy F₂-derived F₃ (F_2:3) lines were field screened for ascochyta blight reaction in each of two hybrid populations, Indianhead x Eston and ILL 5588 x Eston, that were segregating for resistance to ascochyta blight. Resistance to ascochyta blight in ILL 5588 lentil was conferred by a single dominant gene (<i>Ral₁</i>), whereas resistance in Indianhead lentil was conferred by a single recessive gene (<i>ral₂</i>). An efficient DNA extraction procedure and a PCR protocol that yielded RAPD markers with high resolution were developed for lentil. Bulked segregant analysis was used to produce four bulks of DNA from resistant vs. susceptible F₂ plants in each of these two populations which were then screened for RAPD markers using 400 random oligonucleotide primers. One RAPD marker, UBC227₁₂₉₀, was linked to the recessive gene, <i>ral₂</i>, in Indianhead lentil in repulsion phase with a map distance of 14.1 ± 4.5 cM. No RAPD marker was linked with the <i>Ral₁</i> gene in ILL 5588 lentil. In the second study, RAPD markers were used to study phylogeny of the genus Lens. DNA, extracted from 23 accessions of all five taxa of the genus Lens (culinaris, orientalis, nigricans, odemensis and ervoides), was screened for RAPD polymorphisms, using 11 random oligonucleotide primers. Two accessions of the differentiated cytotype of L. nigricans were also included. One hundred and forty eight polymorphic RAPD markers were resolved. A dendrogram for these RAPD markers, using the unweighted pair group method, clearly separated all accessions into their supposedly related taxa. Lens orientalis was the undisputed progenitor of the cultivated lentil, <i>Lens culinaris</i>. A low level of RAPD polymorphism was observed in <i>Lens culinaris</i> and L. ervoides. The differentiated cytotype of L. nigricans was well separated from the normal cytotype of L. nigricans and was closely associated with the L. odemensis accessions, indicating its close genetic similarity to L. odemensis. Principal component analysis (PCA) also indicated a similar relationship among these accessions, but resulted in a better resolution of the groupings. In the third study, the genetic polymorphism of seven Canadian lentil cultivars were studied using RAPD markers. Four lentil cultivars, CDC Gold, CDC Matador, Eston and Indianhead each had a unique, cultivar-specific RAPD marker, allowing their identification.

Successful chickpea production in western Canada typically requires multiple applications of fungicides to minimize the severity of Ascochyta blight (AB) caused by <i>Ascochyta rabiei</i>. Although planting resistant cultivars could be economical and environmentally safer than fungicide usage, varieties with a high level of resistance are not available. The objectives of this research were i) to determine the effect of different seeding arrangement treatments on ascochyta blight severity and seed yield of two cultivars (moderately resistant and susceptible) of kabuli chickpea; ii) to compare one and four fungicide applications at recommended and reduced rates and their impact on disease severity and cost; and iii) to assess organ-specific reaction to AB in chickpea in leaves, stems and pods of 12 desi and 12 kabuli varieties that are of economic significance to western Canada. <p>Treatments significantly influenced AB severity on both moderately resistant and susceptible cultivars in a season with a severe epidemic. Seed yield was significantly influenced by treatments for both varieties in both years. Contrast analyses revealed that four fungicide applications significantly reduced the AB severity for both varieties in a season with a severe epidemic and for the susceptible variety in a season with a moderate epidemic. Seed yield of both varieties was significantly higher under four fungicide applications compared to a single application. Solid seeding and paired row arrangements did not differ in their effect on seed yield and AB severity for both varieties in both years, except that the susceptible variety benefited from paired row planting with respect to seed yield and reduced AB severity in the season with a severe epidemic. Reducing fungicide rates and seeding rate could reduce the cost of cultivation without significantly affecting disease control and yield. Economic assessment revealed that in a severe epidemic season, the gross returns were high for the moderately resistant variety under four fungicide applications than one fungicide application. Gross returns for the susceptible variety were higher under four fungicide applications in both years.<p>There were differences among varieties for AB severity on leaves, stems and pods, seed yield and 1000 seed weight at all site-years tested. The variation was greater in kabuli varieties than desi varieties. AB severity on leaves, stems and pods was lower under high fungicide regimes, with few exceptions. Varieties with a fern leaf type had lower AB severity than those with unifoliate leaves. There was a positive correlation among AB severity on leaves, stems and pods. No differences in organ-specific reaction were observed.

Fusarium head blight (FHB) caused by Fusarium graminearum and Septoria tritici blotch (STB) caused by Septoria tritici are economically important wheat diseases in Ontario. Both reduce yield, FHB is associated with mycotoxin accumulation including deoxynivalenol (DON). Different F. graminearum chemotypes produce either DON/15-acetyldeoxynvialenol (ADON) or DON/3-ADON. The majority (97.5%) of F. graminearum isolates collected from commercial fields across Ontario were 15-ADON chemotype, the remaining were 3-ADON. In inoculated field experiments 3-ADON chemotypes were more aggressive and toxic compared with 15-ADON chemotypes as measured by FHB symptoms and DON content. In inoculated field experiments with a population derived from ‘RCATL33’ and ‘RC Strategy’ soft red winter wheat parents, genetic resistance was more effective than fungicide application at controlling FHB. Field trials with the hard red winter wheat population derived from ‘Maxine’ and ‘FTHP Redeemer’ parents revealed that STB and FHB phenotypic resistance had no negative impact on grain yield in the absence of disease.

No description available.

Bibliography: leaves 182-217. / xx, 217, [18] leaves, [17] leaves of plates : ill. (chiefly col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This study was conducted to determine the etiology of a blight disease of chickpea in south-eastern Australia and the factors affecting disease development. The disease had previously been identified as phoma blight. Pathogenicity testing revealed two isolates subsequently identified as Asochyta rabiei, the first conclusive identification in the southern hemisphere. Greenhouse screening of chickpea varieties identified types resistant to ascochyta blight. The effects of plant age and environmental conditions on disease development were investigated under controlled conditions in growth rooms. Seedlings were more susceptible than older plants. The optimum conditions for ascochyta blight were 20C and a 48-96 h period of leaf wetness. Through field trials it was found that disease intensity increased over time, especially in cv. Desavic. The means of penetration of the chickpea host was established in histological studies. This study provided advance warning of this disease for the expanding chickpea industry, and has allowed the implementation of appropriate disease management strategies. It is recommended that cv. Desavic should not be grown where ascochyta blight is likely to be a problem. / Thesis (Ph.D.)--University of Adelaide, Dept. of Applied and Molecular Ecology, 1999

Copies of author's previously published articles inserted. / Bibliography :leaves 65-80 / x, 80, [64] leaves, [24] leaves of plates : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Ice nucleation active (INA) bacteria were detected in a pea field in South Australia. They were identified as strains of Pseudomonas syringae and Pseudomonas flourescens biotype 1. Some chemical agents were tested on the two ice nucleating species, as cryoprotectants. / Thesis (Ph.D.)--University of Adelaide, Dept. of Crop Protection, 1991