Page 373 - Biosystems Engineering

350 Cha pte r T w e l v e

12.2.2 Challenges for Evaluation and Safety
Because the ability to transform forest-tree species is becoming a real-
ity, the release and use of transgenic wood has not been exempt from
criticism, generally due to activist groups. Unlike annual crops, a for-
est tree has a long perennial life, needs a large field size, and requires
stability of the transgenes over several years. A forest tree must adapt
to seasonal climatic changes; has resistance to pests, diseases or her-
bicides, and enhanced stress tolerance. All of these raised a fear of the
generation of “superplants” that could displace the natural ecosys-
tem or the occurrence of pollen-mediated transfer of undesired trans-
genic traits into unexpected hosts.
James et al. (1998) have described potential impacts from the
escape of transgenic forest trees, outlined some potential avenues to
decrease the possibility for such escapes, and encouraged increased
field testing and monitoring. Many of their suggestions were incor-
porated into a position statement on the benefits and risks of trans-
genic tree plantations adopted by the IUFRO Working Party on
Molecular Biology of Forest Trees (2.04.06) in September 1999 (Strauss
et al. 1999; Merkle and Dean 2000). There are many options to
mitigate their impacts. Strauss et al. (1999) listed the following prior-
ity research areas: (1) isolation, modification, and testing of additional
genes, and systems for gene regulation, to impart traits without unde-
sired effects on tree development or ecosystem function; (2) studies to
support resistance-management programs for use of pest-resistant
trees; (3) efficient transformation methods so that genetic diversity is
not unintentionally impaired as result of the inability to produce
large numbers of useful transgenic genotypes; and (4) methods to
modify flowering to allow reliable containment of transgenes within
plantations when ecologically prudent. Field trials are crucial for all
of these research objectives and can be done with a high degree of
environmental safety.
Rendering transgenic trees sexually sterile is one means of mini-
mizing, if not avoiding, the presence of foreign genes to natural pop-
ulations (Dinus et al. 2001). Genetic constructs for sterility in poplars
should be available in 5 to 10 years. Useful side effects may also
accrue, such as eliminating reproductive structures to channel more
energy, water, and nutrients into wood production. Concern might be
eased further by using genetic markers to monitor the potential gene
flow. Confidence and acceptance can also be built by responsible,
transparent testing along with clear, consistent communication of
both risks and benefits.
Agencies primarily responsible for regulating biotechnology in
the United States are the U.S. Department of Agriculture (USDA), the
Environmental Protection Agency (EPA), and the Food and Drug
Administration (FDA) (Tang and Newton 2003). Products from trans-
genic organisms are regulated according to their intended use, with some