Rice, the staple food crop for more than half the worlds
population, among them the poorest, is the current target of genetic
modification, an activity that has greatly intensified after the rice genome
was announced two years ago (see "Rice is life" series,
SiS 15, Summer 2002).
Since then, all major biotech giants are investing in rice research.
At the same time, a low-input cultivation system that really benefits
small farmers worldwide has been spreading, but is dismissed by the scientific
establishment as "unscientific". This is one among several recent innovations
that increase yields and ward off disease without costly and harmful inputs,
all enthusiastically and widely adopted by farmers.
A war is building up between the corporate establishment and the peoples
of the world for the possession of rice. The food security of billions is at
stake, as is their right to grow the varieties of rice they have created and
continue to create, and in the manner they choose.
This extended series will not be appearing all at once, so look out for
Rice, the food crop for half the worlds population is the
current target of genetic modification. What are the health and environmental
consequences?Prof. Joe Cummins
version of this article, the fifth in "Rice wars" series, is posted on ISIS
members website. Details here.
Rice a target for corporate control?
Rice is the primary food for half the people in the world, providing
more calories than any other single food. It supplies an average of 889
calories per day per person in China, as opposed to only 82 calories in the
United States. Rice is a nutritious food, providing about 90 percent of
calories from carbohydrates and as much as 13 percent of calories from protein
. Such a crop of immense global importance is a certain target for control
by multinational corporations, especially since the rice genome was announced
two years ago (see "Rice is life" series,
SiS 15, 2002).
Only one GM rice trait tolerance to the herbicide glufosinate -
is currently available on the market. The rice varieties under development
include resistance to insects, microbial pests and tolerance to high salt
levels. Pharmaceutical products and multiple transgenic traits are being
pyramided into a single strain of rice. It is likely that the next GM rice to
be approved for commercial release will contain an insect toxin gene from the
bacterium, Bacillus thuringiensis (Bt), but that will be followed by a
range of modifications, including insect resistance based on lectins and
protease inhibitors. Because rice has a huge impact on the worlds food
supply, we should at least make sure it is safe.
Herbicide tolerance and insect resistance
Two glufosinate-tolerant GM rice events, LLRICE06 and LLRICE62, have
been approved for commercial production. They have been inserted into the rice
varieties M202 and Bengal, consisting of the bar gene encoding the
phosphoinothricin-N-acetyltransferase (PAT) enzyme.
Safety testing of the bar gene and PAT enzyme was done using the
bacterial gene and protein, not the synthetic gene and its product in the rice
crop. Despite this obvious flaw, the United States Department of Agriculture
determined that the GM rice strains were suitable for commercial release, and
these are marketed by Bayer as Liberty Link rice. In 2002, Aventis (later
purchased by Bayer) destroyed 5 million pounds of Liberty Link rice because
they feared rejection by the international market, but efforts are continuing
to promote and disseminate the transgenic crop. Bayer is currently seeking
approval for the import of LLRICE62 for food, feed and industrial uses into
Synthetic analogues of the Bt Cry toxin genes have been used
extensively to construct experimental rice varieties. Indica Basmati
rice was transformed by a synthetic Cry1Ab gene in several different
constructs. These transgenic rice plants contained up to 0.15% of their total
protein as synthetic toxin. Such high levels of toxin are preferred because it
discourages insect resistance, but it also means that the synthetic toxin
protein makes a significant contribution to peoples diet and to the rice
straw fed to animals.
Rice lines containing Cry1Ab and Cry1Ab/Cry1Ac fusion
protein genes were reported to have no effect on the fitness of non-target
Rice with Cry1Ab toxin gene and resistance genes for the
antibiotics hygromycin and neomycin was reported to be resistant to rice
leafhopper insects. However, elite Indica rice with a synthetic
Cry1Ac toxin gene, although resistant to the yellow stem borer insect,
had high toxin levels in all of the plant tissues.
European rice cultivars were transformed with synthetic Cry1Aa or
synthetic Cry1B toxin genes under a constitutive ubiquitin promoter,
which turns on the gene in all the tissues all of the time, or synthetic
Cry1B gene under a wound inducible maize promoter, which responds to
stresses such as insect predation. The constitutive promoter-driven toxin genes
produced high toxin levels that prevented striped stem borer predation but left
toxin in all the rice tissues and seeds, while the wound inducible strain
produced toxin mainly at the site of insect attack.
Research has established that Bt toxin was introduced into soil by root
exudates of transgenic rice. The toxin released into the soil affected the
enzymes of soil microbes, increasing soil acid phosphatase and decreasing soil
The benefit of insect protection from Bt rice is offset by the
potential harmful effects of high levels of toxin protein in the rice grain. As
rice is such an important food crop, the safety of Bt rice must be concretely
established. It has been found that food irradiation improved the "quality" of
GM rice modified with the Cry1Ab toxin, by selectively removing the toxin
protein. However, study of the radiation products and adducts created during
destruction of the toxin is essential. Furthermore, it is clear that food
irradiation may be used to disguise GM rice.
A number of projects have studied the use of snowdrop lectin,
Galanthus nivalis agglutinin (GNA) alone or in conjunction with other
genes to control rice pests. Lectins are proteins that interact with human
blood cells (agglutinin) and also act as anti-predator chemicals in plants or
microbes. A GNA gene was driven by a phloem specific promoter
accompanied by a hygromycin antibiotic resistance gene and was used to
transform japonica rice strains. The modified rice controlled sap-sucking
insects that spread rice viruses. However, Ewen and Pusztai showed that
potatoes modified with GNA affected different parts of the rat digestive
system. Similar research on the in vivo effects of rice genetically
engineered with GNA has not been reported.
Rice plants containing both the GNA gene and the unlinked
Cry1Ac gene were reported to be resistant to the major rice insect
pests, striped stem borer and brown leaf hopper (rice with only Cry1Ac resisted
striped stem borer while rice with GNA resisted brown leaf hopper). Rice
transformed with a single vector containing Cry1Ab along with GNA
and the bar gene for herbicide tolerance was intended to be resistant to
yellow stem borer and three sap sucking insects, and also tolerant to the
herbicide glufosinate. This huge package of genes was integrated at a single
chromosomal site. No account has been taken of the interaction of the various
toxins in the human food supply and in the environment.
Basmati rice was co-transformed with three plasmids carrying four genes
including GNA, synthetic Cry1Ac, synthetic Cry2A and
resistance to the antibiotic hygromycin. As in the previous construction, care
must be taken to evaluate the toxicity of the toxin products and their
interaction in the human diet and in the environment.
Elite Chinese rice cultivars were transformed with a gene for bacterial
blight and a GNA gene. The transformed rice was resistant to sap sucking
insects and to bacterial blight.
Insect and bacterial disease resistant lines have been pyramided
(pyramiding is combining transgenes by genetic crosses). A strain with a fused
Cry1Ab/Cry1Ac gene was combined with a gene derived from a wild rice for
resistance to bacterial blight, in a male sterile restorer line of rice. The
pyramided line was resistant to bacterial blight and to stem borer insects. In
the pyramided lines, regulators must consider and evaluate the toxicity of each
transgenic toxin and the combination of toxins brought about by crossing.
Resistance to the rice stem borer was produced using a synthetic
trypsin inhibitor that interferes with insect food digestion. The synthetic
gene was roughly based on a winged bean chymotrypsin inhibitor. A synthetic
copy of a gene product that interferes with digestion surely requires extensive
Salt tolerance & enhancement of biomass
Increasing the transcription level of a rice sodium antiporter (a pump
that moves sodium ion into a vacuole) gene, called OsNHX1, is reported
to improve the salt tolerance of rice, with the potential of opening large
tracks of land to rice cultivation. Over expression of barley aquaporin gene in
rice led to increased carbon dioxide conductance and assimilation. Such
modifications are potentially able to enhance biomass production in rice.
Rice has also been the target of genetic modifications that
nutritionally enrich food crops. Golden Rice genetically engineered
to produce pro-vitamin A has been discussed extensively elsewhere. Although
much touted as a cure for vitamin A deficiency in developing countries, it has
yet to be commercialized and its effectiveness in addressing vitamin A
deficiency has been called into question.
Production of pharmaceutical proteins in rice crops poses potent threats
to the food supply. Recent efforts to test and produce rice modified to produce
the human gene products lactoferrin and lysozyme have been temporarily
thwarted. However, rice producing human growth hormone has been developed
despite the likelihood that the GM rice could cause cancer in those consuming
it. Rice is not a suitable cross for producing pharmaceutical products because
of the high likelihood that the products will pollute the food supply.
The genetic modifications being used or promoted for rice pose a
significant threat to the environment if they contaminate conventional rice
fields or spread transgenes to weedy relatives such as red rice. Pollen
mediated gene flow was substantial from Mediterranean GM rice bearing a gene
for herbicide tolerance to conventional rice and to the weed, red rice. Gene
flow from herbicide tolerant to cultivated rice was also substantial in another
study of Mediterranean rice. Rice pollen was spread from a test plot up to 110
meters from the boundary of the test plot. It is very clear that transgenic
rice will pollute any nearby conventional rice.
GM rice may soon be approved for commercial production in a number of
countries. Safety testing of the currently described products has not yet been
published. GM rice cannot be presumed to be substantially equivalent to
conventional rice, but that may not hamper approval in the United States of
many such constructions. For the most part, GM rice is formed from synthetic
genes that should require much fuller safety testing than has been done in the
In North America, regulators have allowed substitution of genes and
proteins produced in bacterial surrogates for the actual genes and proteins
produced in crop plants in toxicity tests of human and environmental safety.
The use of the bacterial surrogates is allowed, to save corporations the cost
of preparing genes and proteins from the crop plants, even though the genes and
proteins tested differ significantly from the genes and proteins produced in
the crop plants . The public should insist that the actual genes and
proteins produced in the crops be tested.
The worlds leading food crop should be treated with more care than
has been done with maize, soy and canola.
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