Highlights 1996-1997

• Four new federal grants will extend and accelerate TGERC-associated projects. Grants were received from the Department of Energy (Agenda 2020/NCASI) for genetic engineering of sterility, the U.S. Forest Service for disease resistance, the EPA for genetic risk of transgenic plantations, and USDA for the genetics of Bt resistance in the cottonwood leaf beetle.

 

• MARs (matrix attachment regions) substantially increase the level and uniformity of transgene expression in regenerated poplars. Flanking the GUS reporter gene with a MAR element from a tobacco genomic clone doubled expression and reduced variation among lines in a section Leuce (aspen) hybrid, and in two P. trichocarpa x P. deltoides (TD) cottonwood hybrids. MARs will facilitate the generation of valuable transgenic trees from modest gene transfer efforts.

 

• Diagnostic molecular markers are developed for detecting gene flow from hybrid poplar plantations. Several RAPD-DNA markers specific to Populus deltoides, but absent in wild P. trichocarpa, have been identified. This facilitates studies of gene movement from plantations to wild populations, important for predicting the environmental risks of transgenic plantations.

 

• Glyphosate-tolerant poplars continue to show high levels of resistance to applications of Roundup® herbicide in their second growing season. Several transgenic lines of section Leuce and cottonwood hybrids have shown rapid growth and little herbicide damage even after their fourth spraying. Use of glyphosate-tolerant trees may increase efficiency, and reduce the costs and environmental impacts, of weed control in plantations.

 

• Transgenic poplars are produced with high resistance to the cottonwood leaf beetle. High toxicity of several transgenic lines of section Leuce and cottonwood hybrids containing a MAR-cry3-Bacillus thuringiensis (Bt) gene construct was found after 24-hour laboratory trials on leaves of greenhouse plants. Use of insect-resistant trees may improve plantation growth and reduce management costs and pesticide applications.