Agriculture Reference
In-Depth Information
In the case of plants with input traits, the
gene products are functional proteins that
af ect a plant pest adversely or confer
herbicide tolerance. h ese genes are not
normally expected to af ect biochemical
pathways or cascades (Herman
et al
., 2009).
h erefore, some authors (e.g. Matten
et al
.,
2008; Herman
et al
., 2009; Giddings
et al
.,
2012) criticize the present regulations and
suggest that compositional assessment and
feeding studies with feed from i rst-
generation GM plants are no more necessary
for evaluating the safety of transgenic crops
than they are for plants bred traditionally.
2005). Maize plants that are less severely
weakened by the corn borer might be
expected to show better resistance to i eld
infections, particularly infection by
Fusarium
subspecies. As a consequence of the lower
level of fungal infection in the i eld, reduced
mycotoxin contamination is to be expected,
as summarized by Wu (2006a) and
demonstrated with respect to various
mycotoxins, but not in all cases (see Table
6.1). In studies made over several years,
Dowd (2000) and Wu (2006a) investigated
the inl uence of various levels of infestation
with corn borers on isogenic and Bt
hybrids
with respect to mycotoxin contamination
and came to the conclusion that, overall, a
lower level of mycotoxin contamination was
detected in the transgenic hybrids despite
the considerable geographical and temporal
variation observed.
Barros
et al
. (2009) compared the fungal
and mycotoxin contamination in Bt maize
and non-Bt maize grown in Argentina. h e
authors found signii cant lower total
fumonisin levels in Bt maize in all seven
locations in two harvest seasons compared
to non-Bt maize (see Table 6.1). h ere was
no signii cant dif erence in deoxynivalenol
levels between Bt and non-Bt maize.
Application of the fungicide Tebuconazole
did not alter either the infection or the toxin
levels in Bt and non-Bt maize hybrid. Wu
(2006b) and Brookes and Barfoot (2008)
analysed the impact of mycotoxin reduction
in Bt maize on economy, health, environ-
mental and socio-economic ef ects and
reported some important advantages for
both the consumer and the producer (see
Chapters 13 and 14).
Currently, the compositional equivalence of
GM plants with input traits is considered a
cornerstone of the case-by-case safety and
nutritional assessment of such plants in the
EU (see Chapter 4). Following this procedure,
the composition of a transgenic crop is
compared with that of non-transgenic
comparators with a history of safe use. When
compositional equivalence is established
between the endogenous components of
transgenic and non-transgenic plants, the
safety assessment can focus on the
properties of the products newly expressed
by the transgenes (Kuiper
et al
., 2001;
Chassy, 2002) and no additional feeding
studies seem to be needed. Such routine
feeding studies generally add nothing or
little to a nutritional assessment of feed
(ILSI, 2003; EFSA, 2006, 2008; Davis and
Kuiper, 2011). But, nevertheless, many
feeding studies have been done to compare
feed from a GM plant with its isogenic
counterpart and some commercial varieties.
However, there are some discrepancies
between transgenic plants and their isogenic
counterparts. For example, transgenic Bt
maize contains a gene from the soil
bacterium,
Bacillus thuringiensis
(Bt), which
encodes for the formation of a specii c
protein (Cry-protein) that is toxic to
common lepidopteran maize pests, such as
the European corn borer or corn rootworm
(Alston
et al
., 2002; Al-Deeb and Wilde,
2003; Magg
et al
., 2003; Siegfried
et al
.,
After determination of composition (see
Chapter 4) and various
in vitro
studies,
digestion experiments are the i rst step to
check substantial equivalence under
in vivo
conditions.
Some studies have been carried out at the
Institute of Animal Nutrition, Braunschweig,
Germany (Table 6.2), and also by further
authors as follows:
