Hope Not Hype - Third World Network

56 Hope Not Hype
Comments such as Spielman’s above were criticized during the Assessment’s peerreview
process for understating the degree of environmental diversity that has been tested,
on the grounds that tests span the US and it is an environmentally diverse country. This
argument is fraught with difficulties, however, because it exposes a lack of easily compared
and comprehensive studies that are publicly available. For example:
There is an almost complete lack of peer-reviewed literature on the Cry1Ab [transgene] expression
of Mon810 [corn] at different plant growth stages, tissue types and seasons, despite
of the world-wide use of Mon810 varieties. Most of the published data on Cry1Ab expression
levels derived from a very few studies and are limited to a few tissue types, such as root, stalk
and anther (Nguyen and Jehle, 2007, p. 82).
This topic will be explored in more detail below. In any case, general yield benefit
claims even in US cropping systems are not consistent with the data.
Yields of [IR] cotton appear largely unchanged at most locations, and those of maize are
mostly unchanged (in 12 out of 18 regions), except where there has been high corn-borer
pressure. Where pressure was high, yields were 5-30% greater for GM maize. In Missouri,
however, no significant differences in yield under various corn-borer pressures across the
state were found and at the University of Purdue it has been concluded that farmers may not
benefit by adopting Bt [IR] technologies under average pest infestation levels, given that
economically-significant pest attack occurs only one [sic] in 4-8 years in most locations in
the USA (Pretty, 2001, pp. 255-256).
Researchers are now aware that GM crops in very uniform environments still display
variation in the expression of transgenes. To illustrate, a recent study found significant
differences in transgene expression levels between identical commercial varieties when
analyzed by growth phase and tissue and grown in two different locations just within
Germany (Nguyen and Jehle, 2007).
The monitoring of Cry1Ab expression showed that the Cry1Ab contents varied strongly
between different plant individuals (p. 82)…our analyses are the first large-scale expression
monitoring of Cry1Ab under European field conditions and provide a comprehensive data set
of the temporal distribution of Cry1Ab in transgenic maize Mon810. Cry1Ab expression was
lowest in pollen, very low in the stalks, low in roots, but highest in the leaves. Although our
studies corroborate the tendencies of reported Cry1Ab contents of Mon810, a considerable
variation in the expression levels of Cry1Ab was observed. The observed variation exceeds
variation levels reported previously and may be due to the large number of analysed samples
and different growing years (Nguyen and Jehle, 2007, p. 86).
Generally speaking, how variable the expression of any gene might be when the
plant is grown in different environments is not well surveyed. This is unfortunate because
the variation in the expression of these transgenes has benefit/harm-specific implications.
For insecticide-producing GM crops, individual variation could undermine long-term re-