CORVALLIS - Field tests at two sites in Oregon have demonstrated the successful genetic engineering of valuable new traits into hybrid poplar trees, in work that could further boost an already fast-growing industry.
The research, done by scientists at Oregon State University, is confirming that resistance to a common herbicide has been attained in engineered seedlings that evolved from single plant cells in a test tube.
The new possibilities this opens for weed control in poplar tree plantations is the most significant advance to date for genetic engineering in forestry, said Steven Strauss, an OSU professor of forest science.
"These tests have been even more successful than we expected," Strauss said. "When we address environmental concerns and finalize the selection of plant strains we want to propagate, this technology could be widely applied."
The development of hybrid poplar and cottonwood plantations is rapid in the Pacific Northwest and elsewhere. These extraordinarily fast-growing trees can shoot up to a height of almost 100 feet just six to eight years after planting, and be grown almost like an agricultural crop for pulp, lumber or composite wood products.
The problems of early weed control, however, are a constraint to even greater use of poplar plantations, which are now planted on more than 80,000 acres in the Pacific Northwest. These studies may solve that problem.
The findings were an outgrowth of years of work at OSU with two genes discovered by scientists at Monsanto, Inc. In other crop plants, including soybeans and maize, these two genes have also provided natural resistance to the herbicide glyphosate, commonly known by the trademark name Roundup.
Glyphosate is a desirable herbicide because it kills grasses and weeds while posing few risks - it degrades over time, is very unlikely to move into groundwater, is considered almost non-toxic by the World Health Organization, and the EPA says it shows "no evidence of being a human carcinogen."
Using genetic engineering, the new genes were successfully incorporated into cells of poplar trees, which in turn grew into complete, living trees.
And laboratory tests during the past two years showed that at least some of the transgenic trees now had a new trait - high resistance to glyphosate.
"In our lab tests, the normal poplar trees died immediately after exposure to glyphosate," Strauss said. "The engineered trees thrived. And now, in the field, we're seeing basically the same results."
In field tests begun in 1995 near Corvallis, Clatskanie and Boardman, Ore., 40 hybrid cottonwoods and 39 hybrid aspen trees - all engineered for glyphosate resistance - are showing they can survive, thrive and grow normally when exposed to glyphosate. Normal trees without the genetic resistance die.
Other studies are continuing at OSU that may further enhance the value of genetically-engineered poplar, Strauss said. One project is trying to give the plants the ability to naturally produce the pesticide "Bt," which could ward off a key insect pest of poplars, the cottonwood leaf beetle.
Another project will try to genetically engineer sterility into these trees, so they can't spread their new characteristics in a field environment.
"Although we're furthest along with the engineering of herbicide resistance, it's very possible that commercial use of this work may wait until we can provide sterile trees with both insect and herbicide resistance," Strauss said. "That isn't far away, and it would make a very nice package which farmers and foresters would love to have as an option."
Aside from providing dependable, cost-effective weed control, Strauss said, the development of herbicide resistance in these plants does not necessarily mean the use of more chemicals in plantation forestry.
It could mean the use of the preferred chemical at an ideal time in the lowest possible dose to actually lessen the overall usage of herbicides.
The technology could also allow more "no-till" agriculture, less soil erosion and nutrient loss, fewer non-target herbicide impacts, and reduce pressure on marginal and wild lands for food and fiber production.
This and other advances with genetic engineering in forestry are one outgrowth of the Tree Genetic Engineering Research Cooperative based at OSU, a collaboration of the university and 13 private companies or other agencies.
Findings on this research, as well as an analysis of the various risks and benefits involved, will be analyzed by Strauss and two other scientists in the May, 1997, publication of the professional Journal of Forestry.