Date of Award
Master of Science
Forestry (Forest Biology)
The genus Populus L., which includes the aspens, has many important uses such as paper production. Aspens are also attacked by many pests and are particularly susceptible to crown gall disease. A genetically engineered Populus grandidentata x P. sieboldii clone with sense and anti-sense constructs of crown gall oncogenes was field-tested to determine differences in long-term crown gall resistance and overall performance of the parental clone and sublines. Because the use of transgenics raises concern with the public, we added an objective to analyze the ethical implications of outplanting genetically engineered aspen. The field test included a total of 336 trees divided among seven transgenic sublines and the parental clone. Trees were arranged in a Latin square surrounded by 16-tree block plantings of the single genotypes in a randomized design. Heights and diameters were measured and stem volumes estimated at the end of four years of growth. The number of frost cracks per stem and their length were measured in the fifth year. Data were analyzed by a completely randomized model and then by a spatial model to correct for site variation. Dormant hardwood cuttings were subjected to nutrient solution and IBA treatments to produce greenhouse plants for Agrobacterium tumefaciens inoculations. Stored bacterial inoculum was re-cultured and tested for virulence on tomato plants. Ethical implications were examined through an analysis and summary of the forestry and philosophy literature. Four-year heights and volumes were significantly different (P<.O1) with the parental clone and one anti-sense subline having the best heights (5.1 m) and volume (2500 cm3). Frost crack occurrence was not significantly different. No propagation technique gave better than 1.7% success in establishing greenhouse plants. All inoculations failed, probably because of inoculum age, appropriateness of culture medium, or inoculation technique. I conclude that the research to date is consistent with the Forestry Code of Ethics because gene flow can be prevented in small, closely monitored research plantations that are not allowed to flower. However, the risk of transgene escape is still too great to allow commercialization.
Thomas RaShad Easley
Easley, Thomas RaShad, "Growth, propagation, and ethical considerations with using aspens genetically engineered for crown gall resistance" (2002). Retrospective Theses and Dissertations. 19838.