Contents - Faperta

306 Biotechnological Approaches for Pest Management and Ecological Sustainability
accidental release of transgenic insects in the environment. Extreme mobility, small size,
and large numbers of insects that exist in laboratories the world over have a high probability
of accidental escape of transgenic insects into the environment. Scant attention has
been paid to monitoring and actual impact of accidental escapes.
In general, transgenic insects have a reduced fi tness, but it may not be true in all cases.
There are no established procedures in place to conduct risk assessment for transgenic
insects, as the goal is to spread them as far as possible (Hoy, 2000). Insects with insecticide
resistance traits might pose a threat to public health (Hoy et al., 1997). Each transgenic species
should be evaluated on a case-by-case basis depending on whether an insect species
is a pest or a benefi cial arthropod. Host/prey specifi city is usually important to ensure that
arthropod biological control agents control the target pests. Changes in host specifi city of
a vector insect or agricultural pest should be carefully evaluated. Host range or preference
should be documented through laboratory or greenhouse no-choice tests. Temperature
and relative humidity tolerances and diapause attributes often restrict geographical distribution
of arthropods. Changes in responses to abiotic factors should be demonstrable with
growth chamber and laboratory tests by comparing the responses of transgenic with those
of the unmanipulated strains. Laboratory tests should also determine whether the trait is
transmitted to the progeny. Likewise, genetic evaluations should determine whether the
inserted gene(s) are maintained in their original insertion site. For this reason, it may be a
good idea to avoid the use of transformation methods, such as transposable-element
vectors, that could result in movement of the inserted DNA. Even a transposable-element
vector lacking the transposase gene could possibly move if a transposase were supplied by
a helper transposable element that was native to the engineered species. Likewise, it may
be important to determine that the inserted gene cannot be transmitted to the pest species,
particularly if it confers resistance to pesticides (Tiedje et al., 1989; Hoy, 1992b).
Concerns have also been raised about the safety of classical biological control agents.
The environmentalists are particularly concerned about the preservation of native fl ora
and fauna (Howarth, 1991). The era of accepting classic biological control as environmentally
risk free appears to have passed (Harris, 1985; Ehler, 1990; Hoy, 1992b). Protocols for
evaluating the risks associated with releasing parasitoids and predators that have been
manipulated with rDNA techniques do not currently exist, but will probably include, as a
minimum, the questions or principles governing the release of genetically modifi ed living
organisms (Tiedje et al., 1989; Hoy, 1990b, 1992b, 1995). Some of the concerns that need to be
addressed are discussed below.
Genetic Exchange with Natural Populations
Genetic variation, in general, is much greater in natural populations than in transgenic
insects. Mating between transgenic and wild populations would expose the transgenic
insects to a range of genetic backgrounds that would allow for broad nonadditive effects.
These interactions may alter vector competence and host range, and infl uence life history
parameters by affecting survival and reproduction (Gubler, 1993). Novel traits may spread
to a large geographical area in a short span of time (Daborn et al., 2002). The risks associated
with accidental release of a transgene are largely associated with the nature of the
transgene, the marker gene, and their expression patterns. Interspecifi c transfer of the
transposable element mariner has been suggested for Drosophila and Zaprionus (Maruyama
and Hartl, 1991), and the lepidopteran, H. cecropia (Lidholm, Gudmundsson, and Boman,
1992). While the interspecifi c transfer of mariner is suspected only on the basis of DNA
sequence similarities and no specifi c vector has been identifi ed, the data are consistent