The Political Economy of Regulation of Biotechnology in Agriculture - The Oxford Topic of Food, Politics, and Society - page 697

Another highly publicized example of human-facilitated gene flow was reported by
Quist and Chapela (2001), who found that DNA from transgenic Bt maize had intro-
gressed into traditional maize landraces in Mexico. They used a polymerase chain reac-
tion protocol to detect the presence of the 35S promoter (p-35S) from the cauliflower
mosaic virus (CMV), a common element in transgenic constructs. They obtained a pos-
itive PCR signal in five of the seven pooled maize seed samples they tested. Maize seed
imported from the United States as food, which was not approved for planting, was the
likely source of the transgenic maize detected by Quist and Chapela (2001). Their results
led to a six-year de facto moratorium on the planting of transgenic crops in Mexico.
The results of Quist and Chapela (2001) were challenged by the findings of Ortiz-Garcia
et al. (2005). Ortiz-Garcia et al. (2005) sampled maize seeds from 870 plants in 125 fields
in eighteen locations in Oaxaca, Mexico, in 2003 and 2004. They tested 153,746 seeds
for the presence of the 35 S promoter of the CMV and the nopaline synthase gene from
Agrobacterium tumefaciens ; one or both of these transgenic elements are present in all
commercial varieties of transgenic maize. They detected no transgenic sequences in
any of the samples tested. While not contesting the report of Quist and Chapela (2001),
they suggested that the negative results they obtained were likely a result of reduced GM
maize imports and education of local farmers.
Unauthorized herbicide tolerant wheat was found recently in non-GM wheat fields in
Oregon.32 It has been difficult and time-consuming to determine where (which industry
test plots) the rogue GM wheat came from, which is still unknown. The industry pro-
posed that anti-GM activists (human vector) might be responsible in that seed could
have been purposefully put into the field to stir up the gene flow issue. Until the source
is identified, we will not know if it was a human vector or other events that led to both its
presence and its discovery.
Gene flow from GM to non-GM crops can have cultural and biodiversity implica-
tions. Conventional breeding has already led to wholesale replacement of landraces
with elite line monocultures, thereby reducing biodiversity. Such a result is no more, nor
less, a concern with transgenic crops. Other expressed concerns are: (1) could transgenic
traits, such as drought or pest resistance, lead to an expansion in the niche of transgenic
crops that might lead to reduced biodiversity in the surrounding areas? (2) could the
widespread adoption of stress-tolerant plants, for example, increase pressure on frag-
ile, marginal lands, thus potentially destroying valuable natural ecosystems? (3) could
transgenes confer increased plant fitness that might enhance the invasiveness of weedy
species? and (4) could plants carrying transgenic traits have other, unintended effects
on non-target species or trophic interactions? The answers to all these pressing ques-
tions will depend on the nature of the gene involved and on the biology and ecology
of the recipient, and they may be case specific. Research is underway, but the answers
are not well known as yet (Newell-McGloughlin, this volume). The need for research to
enhance the potential for co-existence between GM and non-GM farmers was identified
during a USDA Risk Assessment Stakeholder Workshop in 2003. Research needs that
were cited included: (1) identifying factors controlling the rate of flow and fate of genes
in wild populations as well as the spatial dimensions; (2) developing means to detect