Contents - Faperta

424 Biotechnological Approaches for Pest Management and Ecological Sustainability
fi eld borders after fl owering, rather than by leaving a surrounding gap, which would
need to occupy up to threefold as much fi eld surface to achieve the same level of containment
(Reboud, 2003).
Use of Cytoplasmic Male Sterility
Cytoplasmic male sterility (CMS) can also be used to restrict pollen fl ow (Feil and Stamp,
2002; Feil, Weingartner, and Stamp, 2003). Such a system can produce grain yields as high
as or even higher than those produced by pure male-fertile maize crops, especially when
the male-sterile component is pollinated nonisogenically. Growing 80%:20% mixtures
of CMS-transgenic hybrids and male-fertile nontransgenic hybrids, whereby the latter
component acts as pollen donor for the entire stand, can be used for pollen management.
Since the CMS-transgenic plants release no pollen, the transgenes cannot escape from the
transgenic maize fi eld (Feil and Stamp, 2002). Blends of male-sterile Bt maize and malefertile
nontransgenic maize will help in delaying the development of Bt toxin-resistant
insect populations. The A3 CMS system can be used in sorghum to control transgene fl ow
(Pedersen, Marx, and Funnell, 2003). Seed set on A1F2 individuals averaged 74%, and on
A3F2 individuals averaged 0.04%. Upper confi dence limits for seed set were 1.32% or less
for all A3 hybrids. PCR analysis detected four individuals with outcrossing (from a population
of 1007) in A3 cytoplasm.
Conclusions
The use of crop protection traits through transgenic plants for pest management will
continue to expand in the future and, therefore, there will be a continuing need to understand
the degree of gene fl ow and the likely consequences of such a phenomenon. The
consequences of gene transfer to and between bacteria and viruses will be a major concern,
particularly in relation to use of antibiotic and herbicide resistance genes as selection
markers. Efforts would have to be made to devise appropriate measures to contain gene
fl ow where its likely consequences may be deleterious to the environment. There is considerable
evidence that current transgenic crops in conjunction with conventional agricultural
practices offer a suffi ciently safe and effective technology that may contribute to a
better, cost-effective, sustainable, and productive agriculture. Experience has shown that
the promise of transgenic crops has met the expectations of large and small farmers, in
both industrialized and developing countries, and established an appreciable market
share. The risk of not using transgenic crops, particularly in developing countries where
the technology may have most to offer, should also be considered more explicitly.
Governments, supported by the global scientifi c and development community, must
ensure continued safe and effective testing, and implement harmonized regulatory programs
that inspire public confi dence. Many of the crop traits being modifi ed through
genetic modifi cation are the same as those targeted through conventional plant breeding
for many years. The impact of transgenic crops would therefore be similar to the impact of
cultivars derived through traditional breeding, which have been an integral part of agriculture
for many years. Consequently, the risks of growing most transgenic crops on the
environment or ecosystems will be similar to the effects of growing new cultivars from
traditional breeding. Whenever unresolved questions arise concerning undesirable effect