Copies of author's previously published articles inserted. Bibliography: leaves 128-143. This thesis describes the development of serological and nucleic acid based diagnostic methods for pea-seed borne mosaic virus (PSbMV), the isolation of specific effects on infected pea plants, the collection and biological comparison of new PSbMV isolates from Pakistan, the cloning and sequencing of specific parts of the genome of selected isolates, nucleotide and amino acid sequence comparisons between selected isolates, and the development of a ribonuclease protection assay (RPA) for identifying genomic differences among the PSbMV isolates. It is the first comparison of a range of geographically different isolates of PSbMV on the basis of both biological and molecular properties.

Pallidosis is a disease of strawberry identified in 1957 with an unknown etiology. Two previously uncharacterized viruses in strawberry, Strawberry pallidosis associated virus (SPaV) and Beet pseudo-yellows virus (BPYV), have been found associated with disease symptoms. The complete nucleotide sequence of both viruses was determined and molecular detection protocols developed. In addition, an immunological tissue blot assay was developed for SPaV. Phylogenetic analysis of SPaV placed it in the genus Crinivirus, family Closteroviridae, along with BPYV. Transmission studies identified Trialeuroides vaporariorum, the greenhouse whitefly, as a vector of SPaV, while the virus was not transmitted by pollen or seed. The geographic distribution of both SPaY and BPYV in the United States was examined. Two ilarviruses of strawberry were investigated. Tobacco streak virus (TSV) is the type member of the genus Ilarvirus, family Bromoviridae, and can cause severe yield losses in small fruit crops. Sequence and phylogenetic analysis of 15 "TSV" isolates from Fragaria and Rubus revealed that they are homogeneous and represent a new virus species designated as Strawberry necrotic shock virus (SNSV). Nucleic acid-based protocols failed to identify any plants of the study infected with TSV an indication that the virus may not be a pathogen of Fragaria and Rubus. Fragaria chiloensis latent virus (FC1LV) is the second member of the genus Ilarvirus that infects strawberry. Previously, the virus had been found only in Chile and although many plants have been tested in North America using a serological test, none was found infected with the virus. A molecular test has been developed and used to confirm the presence of the virus in strawberries along the west coast of North America. Phylogenetic analysis of the coat protein gene of the virus place it in subgroup 4 of the genus along Prune dwarf virus, while it was previously thought to be related most closely to Lilac ring mottle virus and Asparagus virus-2. The role of the newly identified viruses and other viruses infecting strawberry is discussed in association with the strawberry decline disease found to cause severe symptoms and yield losses in both California and British Columbia, Canada. The significance of the work presented in this publication includes: the identification of two viruses associated with strawberry pallidosis disease; the complete nucleotide sequence of two criniviruses, an emerging group of plant viruses adds to the limited knowledge we have about this diverse virus genus; the identification of FC1LV in North America; the identification of SNSV as a distinct virus species which demonstrates the need of further studies on TSV, a virus species that infect a wide range of plant species and may actually be a cluster of diverse species. The high incidence of the pallidosis associated viruses points to the significance of the disease and their role in strawberry decline. The development of fast, sensitive and reliable tests for four strawberry viruses will have an impact to the strawberry industry, since the need for high quality, virus-free plants is essential for a crop that is asexually propagated. / Graduation date: 2004

Raspberry bushy dwarf virus (RBDV) is the sole member of the idaeovirus genus of plant viruses. It is a pollen-borne virus that economically impacts both red and black raspberries worldwide. Three strains of the bipartite RBDV have been reported. The common strain found in North America, South America, Australia, New Zealand and Europe and the resistance breaking strain found only in Europe are serologically indistinguishable while the black raspberry strain from North America is distinct. Resistance to RBDV is conferred by a single dominant gene, Bu. The resistance breaking strain is able to infect all raspberry cultivars containing the Bu loci. The sequence of a full-length clone of the common strain was determined and compared to the previously published sequence of the resistance breaking strain. Nucleotide homology between the two isolates was 97.6% for RNA 1 and 97.6% for RNA 2. Comparison of the predicted RNA 1 protein product of the two strains showed 97.9% homology. The predicted amino acid sequence of the movement protein and the coat protein from RNA 2 demonstrated 98.6% and 98.5% identity respectively. The differential rate of virus spread under field conditions in the Pacific Northwest was also investigated. The possibility of higher temperatures inhibiting virus infected pollen was explored by using in vitro germination and enzymatic staining procedures. Results from a two year study of virus-infected and virus-free raspberry pollen viability from both the Oregon and southern Washington region and the northern Washington and southern British Columbia region suggest temperature does not affect pollen germination or viability. Further studies were conducted to determine if a virus-degrading agent could be present on bee-stored raspberry pollen that becomes active only at higher temperatures. RBDV infected pollen from hives in northern Washington was collected and tested by ELISA after receiving either no heating or 32 hours of heating at 20, 30 or 40 C. Preliminary results indicate no such agent exists in red raspberry pollen from hives in the Pacific Northwest. / Graduation date: 2000

Thesis (Ph. D.)--Ohio State University, 2003. / Title from OhioLINK abstract page. Abstract.

Thesis (Ph. D.)--York University, 2001. Graduate Programme in Biology. / Typescript. Includes bibliographical references. Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNQ67889.

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Copies of author's previously published articles inserted. / Bibliography: leaves 128-143. / xi, 143, [44] leaves, [36] 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. / This thesis describes the development of serological and nucleic acid based diagnostic methods for pea-seed borne mosaic virus (PSbMV), the isolation of specific effects on infected pea plants, the collection and biological comparison of new PSbMV isolates from Pakistan, the cloning and sequencing of specific parts of the genome of selected isolates, nucleotide and amino acid sequence comparisons between selected isolates, and the development of a ribonuclease protection assay (RPA) for identifying genomic differences among the PSbMV isolates. It is the first comparison of a range of geographically different isolates of PSbMV on the basis of both biological and molecular properties. / Thesis (Ph.D.)--University of Adelaide, Dept. of Crop Protection, 1999

Thesis (Ph. D.)--University of Adelaide, 1986. / Includes bibliographical references.