Browsing by Author "Dr. Larry Grand, Committee Member"

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    Fungal Degradation Properties of Young Small Diameter Genetically Modified Quaking Aspen (Populus tremuloides)
    (2008-10-31) Giles, Richard Lee; Dr. Perry Peralta, Committee Co-Chair; Dr. Ilona Peszlen, Committee Chair; Dr. Larry Grand, Committee Member; Dr. Hou-Min Chang, Committee Member
    Three studies were conducted to evaluate the fungal degradation properties of young transgenic aspen trees (Populus tremuloides). The first study focused on development of methods of decaying small diameter tree samples. The second and third studies focused on the mass loss differences and cellulose and lignin degradation between trees with different lignin types and contents. In the first study, two methods for rapid laboratory fungal decay tests of very young small diameter (5-15 mm) hybrid poplar (Populus nigra x Populus maximowiczii), yellow poplar (Liliodendron tulipifera), and willow (Salix sp.) trees were examined using the white rot fungi Trametes versicolor and Ceriporiopsis subvermispora. An agar plate method and a modified soil-agar block method were compared using non-standard size stem parts. The agar plate method did not prove to be suitable for testing materials when limited numbers of samples are available because of the extremely high variation of mass loss values. Mass loss using the modified soil-agar block technique was comparable to established methods for small and large blocks using extended colonization periods. In the second study, one-year old quaking aspen (Populus tremuloides) trees including a control wild type aspen and three lines of transgenic trees were analyzed for resistance to lignin selective white rot fungal decay. The transgenics had reduced lignin content through transfer of an antisense -4CL gene, changed syringly/guaiacyl ratio through insertion of a sense CAld5H gene, and modified lignin content and syringyl/guaiacyl through simultaneous insertion of -4CL and CAld5H genes. Mass loss was used to examine differences between genetic lines. The small diameter transgenic trees were decayed using lignin selective white rot fungus Ceriporiopsis subvermispora. A modified soil-agar block method was used with a forty day colonization time. The transgenic lines with higher S/G lignin ratio exhibited a higher mass loss percentage compared to the wild type and other transgenic lines. In the third study, the transgenic lines were analyzed for resistance to three types of fungal decay. The small diameter transgenic trees were tested using simultaneous white rot fungus Trametes versicolor, lignin selective white rot fungus Ceriporiopsis subvermispora and a brown rot fungus Poria placenta. A modified soil-agar block method was used to decay the samples. Near infrared spectroscopy and chemical analysis determined loss of cellulose and lignin variations between transgenic genotypes. Near infrared transmittance was successful in predicting the cellulose and lignin percentages of the decayed material. The reduced lignin content lines did not affect the rate of lignin decay for all fungi tested. Lignin decay rates were reduced by the increased S/G ratio lines for all fungi tested.
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    Interactions Between Phytophthora spp. and Castanea spp. and the Creation of a Genetic Linkage Map for the F1 Parent in a First-Generation Backcross Family of Castanea spp.
    (2006-09-13) Bowles, Mollie Ellen; Dr. John Frampton, Committee Chair; Dr. Henry Amerson, Committee Member; Dr. Larry Grand, Committee Member
    Efforts are underway to restore the American chestnut, Castanea dentata (Marsh.) Borkh, to its original range within the United States. The American Chestnut Foundation has traditionally focused on introducing blight resistance of the Chinese chestnut, C. mollissima Blume, into their breeding stock. Now, however, they are encountering problems with a root rot caused by Phytophthora cinnamomi Rands, and the threat of a potential disease caused by Phytophthora ramorum Werres, De Cock, and Man in't Venld. In order for the Foundation to breed for resistance against the effects of these pathogens, much more needs to be discovered regarding their interactions within Castanea. This thesis is part of the effort to understand these interactions. The first chapter provides a literature review of interactions for two Phytophthora species and Castanea spp. The second chapter presents experiments investigating the mode of inheritance and number of loci controlling resistance to each of these Phytophthora species. Initial experimentation appears to suggest that resistance to P. cinnamomi may be controlled by a single dominant gene in chestnut, but conclusive evidence from subsequent experiments was not found; possible causes are discussed. A series of screening assays based on leaf disk assays using P. ramorum also failed to provide conclusive evidence that a single locus controls the degree of response, but statistically significant differences were noted among seedlots in each trial, suggesting some level of genetic control. The third chapter presents a genetic linkage map developed from amplified fragment length polymorphic (AFLP) markers for the F1 parent in a backcross family ((C. mollissima 'Mahogany' x C. dentata 'RCF1' = 'KY115') x C. dentata 'WB348'). This purpose of this map is to correlate future resistance segregation patterns from controlled P. cinnamomi inoculation trials with specific marker loci. This would provide a foundation for future genetic research regarding the number of loci controlling resistance to root rot caused by P. cinnamomi and its relationship with other traits of interest in chestnuts.