Using GS corn as a platform would be
a quicker way of enhancing the number of transgenes in a single crop
The trademarked Genuity-SmartStax corn (GS corn)
containing eight transgenes-six for pest control and two for weed
control-developed through collaboration between Monsanto and Dow
AgroSciences, introduced few months ago, is an amazing development in
crop genetic engineering (GE). Incorporated into the best of corn
varieties, this event is expected to provide the most comprehensive
pest and weed control system available, leading to an impressive crop
health and increase of whole farm crop yields. The development of
Genuity SmartStax corn from the shaky origins of genetic engineering is
a fascinating reading.
Genuity SmartStax corn
GS corn takes care of the major pests, such as the European and
southwestern corn borer, northern and western corn rootworm, western
bean cutworm, black cutworm, corn earworm, and fall armyworm and also
imparts tolerance to both glyphosate and glufosinate herbicides. In
addition, the coming together of two giants in the seed industry will
encourage other private-private partnerships to further this initiative.
Eight transgenes in GS corn
- Tolerance to aerial pests (three Bt genes): Cry 1A.105
(Monsanto), Cry 2Ab2 (Monsanto) and Cry 1F (Dow).
- Tolerance to subsoil pests (three Bt genes): Cry 3Bb1 (Monsanto),
Cry 34Ab1 (Dow) and Cry 35Ab1 (Dow).
- Tolerance to herbicides (two genes): Glyphosate (Roundup Ready,
Monsanto) and Glufosinate (LibertyLink, Dow, under license from Bayer).
Transgenic crops are evaluated for product efficacy and biosecurity in
the laboratory, green house and in the field for over 10 years before
commercialization. The GS corn is in phase-IV of regulatory evaluation,
the final step prior to the product's planned commercial release in
2010. This phase includes development and testing of best trait and
germplasm combinations for commercial launch.
All the genes involved in the GS corn were approved in the US in single
gene transgenic varieties and are being commercialized in different
countries. Each of these eight traits has also been individually
approved by the Canadian Food Inspection Agency (CFIA).
A refugium is a non-Bt buffer zone in a transgenic crop field to retard
the development of pest resistance to the Bt proteins. Earlier a 20
percent refugium was mandatory. In June 2008, Monsanto requested the US
Environment Protection Agency (EPA) for a reduction of refugium
requirement to five percent for GS corn in the northern corn belt and
20 percent in southern states where cotton is planted. The EPA has now
approved a five percent refugium for the product's aerial pest
protection. The CFIA has evaluated the potential impact and risk to the
environment, by using a five percent non-Bt refugium strategy for the
GS corn, and has concluded that 'a conditional authorization until
December 31, 2012, for the use of this reduced volume of refugium poses
minimal risk to the environment'. Thus both the US and Canada
have given short-term approvals for GS corn.
There has been a protracted and persistent activism against GE crops
stemming mostly from Europe for over 15 years. It is not surprising
that the activist groups were disappointed when an eight gene product
is approved by both the US and Canadian regulatory authorities. Some
Canadian farmer and environmental groups said that Canada rushed the
approval process ignoring environmental risks and even without making
public the basis of their decision. They charged that the CFIA has
substantially weakened a critical environmental stewardship rule just
for the introduction of SmartStax.
Committee for Independent
Research and Information on Genetic Engineering (CRIIGEN) alleged that
humans are used as guinea pigs for the 'second generation' of
genetically modified (GM) crops. The Canadian Biotechnology
Action Network, chose the World Food Day (October 16, 2009) as the
first 'International Day of Action Against Multinational
Corporations'. Some activist groups argue that there might
be unintended consequences when so many traits are combined. It
should not surprise any one if the opposition to GS corn gains momentum
in the coming months.
Notwithstanding activist noises, GS corn is being planned to be grown
on 30 to 40 lakh acres in the US and Canada in 2010, both for internal
consumption and export. With regulatory approvals for import, GS corn
will now be exported to Japan, Korea, Taiwan, Mexico, Australia and New
Zealand, under the trade names such as Mycogen, Dairyland, Renze,
Brodbeck, Triumph, Pfister and Hyland.
Certainly there would be several other products similar to GS corn, but
using GS corn as a platform would be a quicker way of enhancing the
number of transgenes in a single crop variety, not as a gene game but
to compound several benefits into a single product.
The concepts of 'biotechnology' (Karl Erkey1919) and 'genetic
engineering' (Justin, 1941) came into use long before Watson and Crick
(1953) proposed their model of the structure of DNA, the genetic
material. It took 20 years of basic research before Stanley Cohen and
Herbert Boyer (1973) perfected the recombinant DNA (rDNA)
technology. They cut genes of the African clawed toad using
restriction enzymes and incorporated them in the genome (total genetic
complement) of the experimental bacterium Escherichia coli (E.
coli) using the enzyme DNA ligase and demonstrated the expression of
the transferred genes in the new environment, a major breakthrough in
Genesis of GE crops
In 1982, the first transgenic plant, an antibiotic resistant tobacco,
was developed. In January 1983, three different teams reported success
in using the bacterium, Agrobacterium tumefaciens, a natural genetic
engineer, to produce transgenic plants. Soon, using Agrobacterium
tumefaciens to carry new genes into plant cells became the most common
means of producing transgenic plants. Field tests for GE crops
resistant to pests and pathogens were first conducted in the US in 1985
and the first GE tobacco was approved for commercial release in
1986. After getting the approval from the Food and Drug
Administration, Flavor Saver, the first GE tomato, with a longer shelf
life, reached the US markets in 1994. Between 1995 and 1996, GE
soybean, corn and cotton were approved for commercialization in the US.
GE crops with several different beneficial traits are now commercially
cultivated in 25 countries and imported into five others. Global
transgenic acreage has increased from 17 lakh hectares in 1996 to 12.5
crore hectares in 2008. This impressive growth indicates farmer
and consumer acceptance of GE crops and products for their benefits.
Over 35 crore Americans have consumed GE foods for over 13 years
without any discernible untoward health effects showing that GE food
crops and their products are safe for human consumption.
The most widely used trait in the commercialized GE crops is tolerance
to the most important pest in each of such crops as cotton, potato,
tomato, and corn, with genes from the universally occurring soil
bacterium, bacillus thuringinesis. The other important trait is
tolerance to herbicides, to achieve an easier and efficient weed
control that facilitates no-tillage farming. There is also a GE
papaya with tolerance to the ring spot virus disease in commercial
An array of GE crops
A number of grain, oil seed and vegetable crops with diverse traits for
pest, disease (bacterial and viral) and herbicide tolerance have joined
the array of GE crops, many of them in very advanced stages of
development. Produced through gene silencing, a protocol different from
rDNA technology, a variety of coffee without caffeine and a variety of
tearless onion are interesting products.
GE crops with a number of traits for nutritional enhancement and
production of pharmaceuticals are also in advanced stages of
development. Golden Rice, rice with genes for â-carotene, the precursor
of vitamin A, is a very promising means to alleviate vitamin A
deficiency in the developing countries. GE rice with human milk
proteins is designed to provide an efficient infant feed. Rice
with higher iron content, a carrot variety with very high levels of
calcium and a purple tomato with high levels of anthocyanins that
function as antioxidants to prevent several diseases, are fascinating
developments in the year 2008.
Among the non-food GE crops, genes for number of pharmaceutically
active chemicals, vaccines and antibodies have been introduced into
crop plants for an inexpensive and large scale production of these
therapeutic aids, an area called biopharming. A GE tobacco plant that
synthesizes human haemoglobin and another that detoxifies soils
contaminated by explosive residues have been demonstrated. A GE blue
rose is now available in the Japanese market.
GE food grains that withstand drought, flood and salinity are high
priority research, and so are those for high yield. Due to the
complexity of inheritance of these traits a successful development of
these crops would take some years to become a reality.
Genes of transgenic crop
In all these products only a single gene is involved. For quite
long it was an open question as to how many different genes can be
genetically engineered into a single crop variety, a process called
gene stacking or gene pyramiding, to derive their cumulative benefits.
A significant development was Monsanto's Bollgard II, a GE cotton with
two stacked Bt genes, Cry 1 Ac and Cry 2 Ab, which provides a better
pest control, than with a single gene. In several other crop varieties
two genes for pest or viral or herbicide tolerance were stacked.
Monsanto announced a triple-stack corn for release in the US in
2009. DuPont stacked five genes in corn to make it both pest and
The April 2009 announcement of a transgenic corn with five different
genes to synthesize very high quantities of vitamin A, vitamin C and
vitamin B9 precursors, was a welcome news, from the points of view of
both scientific accomplishment and product benefits. But the GS
corn announced in July 2009, caps it all.
- C Kameswara Rao,
Foundation for Biotechnology, Awareness and Education, Bangalore