Contents - Faperta

410 Biotechnological Approaches for Pest Management and Ecological Sustainability
This will allow the evaluation of issues such as contribution of the transgene to the weediness
and fi tness of the host plant. For each transgene, a “transgene fi le” with all relevant
information should be put together, and encompass all aspects of a “transgene-centered
approach to bio-safety” (Metz, Stiekema, and Nap, 1998). Assessing ecological impact of
the transgene in a given crop in a region is an important component of risk assessment.
Where the transgenic crops are used as food for human beings, then there is also a need
to include food profi le, in which all nutritional and food safety aspects of a given plant
product should be evaluated and classifi ed. There is a need to provide information to the
consumers in a way that is equivalent to current labeling of the presence of food additives,
and defi ne a unique key for each product (OECD, 2002).
Introgression of transgenes into the crop plants and wild relatives is of potential concern
(Gregorius and Steiner, 1993; Serratos, Willcox, and Castillo-Gonzalez, 1997). Transgenes
conferring resistance to insect pests, diseases, and herbicides may result in enhanced fi tness,
survival, and spread of weeds (Ellstrand, 2001). This may add to farmers’ weed management
burden, and/or result in invasion of natural habitats and compromise the
biodiversity of these habitats. The potential for a crop plant to hybridize with a weed
depends on sexual compatibility and relatedness between the species. The opportunity for
natural hybridization between two species depends on many pre- and post-zygotic factors.
While plant breeders have repeatedly crossed crops with wild relatives to introgress a
wide range of benefi cial traits (Harlan, 1976), many of the hybrid combinations developed
in this manner would not occur in nature because of the barriers within the plants to
prevent normal embryo or endosperm development. The occurrence of interspecifi c and
intergeneric hybrids as a result of manual hybridization only gives a possible indication of
sexual compatibility and potential for hybridization in nature. If an interspecifi c or intergeneric
hybrid develops in nature, the success of such hybrids and their progeny depends
on a number of factors. Gene introgression from one species to another or from a crop to a
weed requires repeated backcrossing to effect the incorporation of alleles from one gene
pool to another. The possibility of repeated hybridization leading to allele introgression
from cultivated crops to weedy relatives has been recognized for a long time (Anderson,
1949), and is considered to have played an important role in both the domestication
of crops and the evolution of weeds (de Wet and Harlan, 1975). These events occur where
the distribution of a wild species overlaps with the cultivation of the related crop, and are
especially common in the centers of diversity for a specifi c crop.
The characteristics infl uencing gene transfer between species are complex and will not, in
general, change as a consequence of transgene expression. Changes in fl ower color as a result
of genetic transformation may have either a positive or negative infl uence on insect pollinators.
Depending on crop management, male sterility may remove pollen competition and
provide a better opportunity for hybridization. For a majority of transgenic traits, transgenic
crops are no more likely to transfer either their transgenes or any other gene to other species
than through crop cultivars developed by conventional methods in the past. If gene introgression
from a crop to natural populations does occur, the key issue to consider is whether
the impact is any different for cultivars derived from genetic modifi cation as compared to
those derived through traditional breeding. When considering the ecological concerns about
transfer of transgenes to weedy species, it is the phenotype conferred by a gene that is
important, not whether it was derived by genetic engineering or traditional plant breeding
(Metz and Nap, 1997). However, extension of the botanical profi le approach to include a
description of the transgene to assess the ecological impact of a gene is quite important.
If transgenes conferring resistance to insect pests, diseases, and environmental stress
are introgressed into weedy relatives of crops, there is a concern that they may enhance