Contents - Faperta

Transgenic Resistance to Insects: Nature of Risk and Risk Management 439
biosafety committee should have the responsibility for monitoring the site after release for
risk assessment to enhance accountability. All the unexpected events should be documented
and reported. The national biosafety committee should look into the proposal, and recommend
any additional information that may be necessary. The oversight responsibility of
the national biosafety committee should also involve interaction with the fi eld experimentation
staff, and the release team or institution. Finally, the release proposal may be examined
by regional or international agencies as appropriate to ensure a proper and transparent
release process.
It is diffi cult to conclude that release of a transgenic plant would or would not pose a risk
to the environment or human health. And it is not possible to put a value on the degree of
risk. The essential point is to determine whether and how the transgene might alter the
risk compared to the nontransgenic counterpart. There will certainly be questions that
cannot be answered fully. Not much can be said about the nature and extent of gene fl ow.
In situations where enough knowledge is not available, it is important to use the knowledge
available through conventional plant breeding to aid in risk assessment. Plant breeding
has been carried out for several thousand years, and many of the genes that are being
inserted through the recombinant technology fall into the same classes as those manipulated
by conventional plant breeding.
Once the transgenic plants are released for commercial cultivation, measures such as
prevention of fl ower production and destroying all plant parts are not possible (Sharma
et al., 2002a, 2002b). Therefore, the risk assessment should take into account pollen transfer
between the nontransgenic crop and wild relatives. There may also be possibilities for
taking the transgenic plants into areas where the sexually compatible wild relatives of the
crop are present in large numbers. Transgene instability may be another cause of concern
when the transgenic crops are grown on a large scale. Strategies for introducing herbicide
resistance into several crops or different toxins against the prevalent pests and diseases
have to be properly devised. The options for containment after large-scale cultivation of a
transgenic plant are limited. Therefore, risk assessment must take these factors into
account, and consider all information available from small-scale experiments. To overcome
such problems, it may be useful to use tissue- specifi c expression (target site for insect
feeding or infection by the pathogen) or use of male-sterile lines to limit the dispersal of
pollen, as is the case with hybrids produced by conventional plant breeding. The cultivation
of genetically modifi ed crops may be stopped if there is a risk to human health and
the environment.
Many agricultural practices are in place for risk management. The risk of gene transfer
by outcrossing from a herbicide-resistant crop to a weed, for example, from canola to
weedy mustard, can be managed by spraying a herbicide with a different mode of action.
Crop rotations can also be used to control such weeds (Sharma et al., 2002b). The risk of
introducing a fertile hybrid between the transgenic plants and weedy relatives can be
managed by seeds grown under strict certifi cation procedures to identify crop weed
hybrids in the seed production plots. Gene transfer within the same species can be avoided
by keeping a safe distance between the adjacent plots. Such information to avoid outcrossing
is available for most of the cultivated crops. In areas where there is a greater
chance of gene transfer, for example, in the center of origin of a crop plant, serious thought
should be given before introducing a transgenic crop with certain genes. Varieties
or crops that are likely to be carried to the next crop season or contaminate the same
crop next season can be replaced by crop varieties with less or no carryover of seed to the
next season.