Contents - Faperta

344 Biotechnological Approaches for Pest Management and Ecological Sustainability
TABLE 11.3
Protocols for Assessment of Biosafety of Transgenic Plants to Nontarget Organisms
Test Effect Action
Tier I: Host/prey ingests the toxin
Yes
No No need for further tests
Tier I: Host/prey sensitive to toxin
Yes
No No need for further tests
Tier II: Parasitoid/predator ingest the toxin
Yes
No Host prey-mediated effects expected; need to be
assessed in transgenic plants
Tier II: Parasitoid/predator sensitive to toxin
Yes
No Host prey-mediated effects expected; need to be
assessed in transgenic plants
Tier III: Direct and prey-mediated effects
Direct and prey-mediated effects need to be assessed
expected, but not separable
in transgenic plants under contained and open fi eld
trials for a long period, and outcomes compared
with current pest control practices
The risk posed by transgenic plants to entomophagous arthropods also depends on
exposure and their sensitivity to the insecticidal protein. It is therefore essential to determine
if and at what level the organisms are exposed to the transgene (Dutton, Romeis, and
Bigler, 2003b). Exposure is associated with the feeding behavior of phytophagous and entomophagous
arthropods and temporal and spatial expression of the insecticidal protein. For
organisms that are potentially exposed to the insecticidal protein, sensitivity tests should
be performed to assess the toxicity. The route of exposure (fed directly or via herbivorous
prey) and the origin of the Bt (from transgenic plants or incorporated into artifi cial diet)
strongly infl uence the degree of mortality (Hilbeck, 2001). In choice feeding trials where
Chrysoperla carnea (Stephan) could choose between nontransgenic maize- and transgenic
Bt-maize-fed Spodoptera littoralis (Boisd.), the later instars showed a signifi cant preference for
nontransgenic maize-fed S. littoralis, while this was not the case when the choice was between
Bt- and isogenic maize-fed aphids. Partially or moderately resistant plants expressing
quantitative rather than single gene traits and affecting the target pest sublethally may
provide a more meaningful assessment of the effects of transgenic plants on nontarget
organisms. Transgenic plants with less severe nontarget effects may allow for better
incorporation of such plants in integrated pest management or biological control programs
using multiple control strategies, and thus reducing the selection pressure for development
of resistance to the transgene in pest populations (Hilbeck, 2001). Cowgill and Atkinson
(2003) suggested a sequential approach for testing the effects of protease inhibitor-expressing
crops on nontarget herbivorous insects. For the fi rst four tiers of the approach, potatoes
expressing cystatins (cysteine proteinase inhibitors) were used as an example. Although
the plants had high levels of resistance to potato cyst nematodes, Globodera pallida (Stone)
and Globodera rostochiensis (Wollen.), the results showed that they have negligible impact
on the nontarget herbivorous insect, Eupteryx aurata (L.) Skar. The approach consisted of
fi ve tiers: (1) conduct fi eld surveys to characterize nontarget invertebrate fauna of a crop,
(2) perform histochemical assays to identify a subset of herbivores with a particular type
of digestive proteolytic enzymes, (3) conduct controlled environment or small-scale fi eld
trials, (4) evaluate the impact of the protease inhibitor-expressing plants on the selected