13.1 Introduction
Field testing is an important last step in the creation of transgenic plants. Two important and
interrelated aspects are discussed here: agronomical performance and biosafety. If a
company wants to commercialize a transgenic crop variety (and typically they do), it is
important to show that it performs as well as its parentorisogenicvariety under a
number of locations and types of fields. To be viable, it cannot have any genetic or pheno-
typic malformations. So, experiments must be performed to compare growth and yield, as
well as test for the durability and robustness of the transgenic trait in the field. For example,
an insect-resistant plant would be required to adequately express the transgene to kill target
insects. Robustness of expression under field conditions is needed to guarantee farmers
economic benefits. The second part of field testing,biosafety, is more complicated, and
it is important to show that a transgenic product is environmentally benign. This has
proved to be crucial for placement on the market since worldwide regulation requires a
number of tests to convince regulators to approve transgenic plants as safe (see Chapter
12). This chapter focuses on field testing to evaluate the environmental safety (exemplify-
ing any risks for nontarget butterfly caterpillars) and the economic benefit (on yield) posed
by genetically modified Bt maize. Thus, we will use this particular case as an example,
since it covers much of the ground that is needed for field testing. Some examples, such
as those for herbicide resistance, might be simpler, and there are, no doubt, more compli-
cated cases. We use Bt maize since there is a large body of knowledge that has been accu-
mulated over the past 10 or so years and it is a success story of sorts. Since the mid-1990s,
genes ofBacillus thuringiensis(Bt) that encode butterfly-specific toxins (Cry1Ab, Cry1Ac,
and Cry9) were engineered into maize for protection against the European corn borer
(Ostrinia nubilalis). Bt maize has been hailed as a success, having essentially passed all
the regulatory tests in the United States and the European Union (EU), and is grown
widely across North America, part of the EU, and other areas.
13.2 Environmental Risk Assessment (Era) Process
Environmental risk assessment (ERA) is particularly significant in the context of
genetically modified organisms (GMOs). There are some good reasons to be careful
when introducing new technologies, in particular when new biopesticides are introduced
into the environment. However, it is believed by some concerned people that any (as yet
unperceived) effects they have on the environment could be adverse, if not downright
“catastrophic.” Whatever the starting point is, a scientifically sound ERA factors in the
following aspects:
- Biological properties of the parental unmodified organism (maize in our example)
- Source of the introduced gene(s), expression, and nature of the gene product (“Bt”
protein kills pest caterpillars, but may also affect “lovely” nontarget butterflies) - Characteristics of the genetically modified organism, including its performance and
impact on the environment, taking into account the information of points 1 and 2 (above)
Environmental risk assessment has a conceptual framework consisting of four steps
described briefly below: evaluation of need for ERA, problem formulation, controlled
experiments and gathering of pertinent information, and finally the risk evaluation.
312 FIELD TESTING OF TRANSGENIC PLANTS