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2.5.GM SOYBEAN
Soybean is the oil crop of greatest economic relevance in the world. Soybeans are
an important source of protein in many areas of the world. Its beans contain
proportionally more essential amino acids than meat. The extension of shelf-life and
improvement of technological qualities are aims of radiation processing of foods.
As a phytosanitary treatment irradiation is adopted in many countries. For insect
disinfestations in beans, irradiation offers an attractive alternative to chemicals. Until
now there is little information about the effect of irradiation alterations in the
composition of the compounds after irradiation of GMO soy. Since radiation was
employed for food disinfestations, half embryo test to identify irradiated foods and
viability of seeds are utilized.
Soya is currently one of the main sources of genetically-modified ingredients in
food, and can found in everything from chocolate to crisps, margarine to mayonnaise
and biscuits to bread.
First genetically modified soybean is developed resistant to herbicide (weed
killer) Roundup. This means Roundup can be sprayed on the so-called Roundup-Ready
Soybeans without killing the crop - only the weeds will be affected.
2.5.1. Herbicide-tolerant soybean
Herbicide-tolerant soybean varieties contain a gene that provides resistance to
one of two broad spectrum, environmentally bening herbicides.
This modified soybean provides beter weed control and reduces crop injury. It
also improves farm efficiency by optimizing yield, using arable land more efficiently,
saving time for the farmer, and increasing the flexibility of crop rotation. It also
encourages the adoption of notill farming-an important part of soil conservation
practice.
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2.5.2. Oleic acid soybean
This modified soybean contains high levels of oleic acid, a monounsaturated fat.
According to health nutritionists, monounsaturated fats are considered “good” fats
compared with saturated fats found in beef, pork, hard cheeses, and other dairy
products.
Oil processed from these varieties is similar to that of peanut and olive oils.
Conventional soybeans have an oleic acid content of 24%. These new varieties have an
oleic acid content that exceeds 80%.
2.5.2.1. Oleic Acid
Oleic acid is a fatty acid found in animal and vegetable oils. It is called a monounsaturated fatty acid because of the single double bond between the carbons. It's
physical properties are determined by the number, geometry, and position of this double
bond and the degreeofunsaturation.
Physical and Chemical Properties
appearance - pale yellow / brownish-yellow oily liquid
odor - lard like
solubility - insoluble in water
specific gravity - 0.895 at 25oC
boiling point - 360oC (680oF)
melting point - 16.3oC (61oF)
Structure of Oleic acid
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Oleic acid occurs naturally in greater quantities than any other fatty acid. It is
present as glycerides in most fats and oils. High concentrations of Oleic acid can lower
blood levels of cholesterol. It is used in the food industry to make synthetic butters and
cheeses. It is also used to flavor baked goods, candy, ice cream, and sodas
2.5.3. Compositional studies
2.5.3.1. Improvement of Soybean Protein
2.5.3.1.1. Lysine
Many grains are deficient in certain amino acids. Animal feed is sometimes
supplemented with crystalline amino acids produced by fermentative processes to meet
the dietary needs of animals. In addition, soybean seeds, which are rich in lysine and
other limiting amino acids, can be added to animal feeds, but may not always be costeffective to meet these dietary requirements.
Genetically engineered soybean seeds that have an increased lysine content
(1995). They bypassed the negative feedback mechanism in which lysine normally
would inhibit two enzymes of its biosynthetic pathway, aspartokinase (AK) and
dihydrodipicolinic acid synthase (DHDPS). Using DNA-coated particle bombardment,
they transformed soybean seeds with the Corynebacterium dapA gene and a mutant E.
coli lysC gene that were linked to a chloroplast transit peptide and expressed from the
phaseolin promoter, a seed-specific promoter. The Corynebacterium dapA and mutant
E. coli lysC genes encoded lysine-feedback-insensitive DHDPS and AK enzymes,
respectively.
L-Lysine is a basic, genetically coded amino acid It is essential in human nutrition
(probably most limited in the food chain).
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Symbol
lys k
Molecular formula
C6H14N2O2
Molecular weight
146.19
Isoelectric point (pH)
9.59
pKa values
2.20, 8.90, 10.28
CAS Registry Number
56-87-1
3D Molecular Model
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"Biosynthetic pathway for amino acids derived from aspartate illustrating end-product
feedback inhibition of dihydrodipicolinic acid synthase (DHDPS) and aspartokinase
(AK)"
They significantly improved the lysine content of the soybean seeds by
increasing the free lysine levels several hundred-fold while increasing the total lysine
content by as much as 5-fold. This substantial improvement may make soybean seeds a
more cost-effective animal feed supplement and may improve the quality and quantity
of animal products for human consumption, especially in underdeveloped countries.
Moreover, these transgenic soybeans may directly improve the nutrition of humans in
developing countries where soy is commonly eaten and where, coincidentally, diets lack
certain amino acids such as lysine that are particularly essential for the development of
children under the age of 2 years.
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P. aeruginosa Pathway: lysine, threonine and methionine biosynthesis
Locations of Mapped Genes:
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P. aeruginosa Pathway: lysine and diaminopimelate biosynthesis
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Locations of Mapped Genes:
2.5.3.1.2. Glycinin
One of the more important nutritional components of soya is glycinin which is
one of the predominant storage proteins of soybean. In the experiment "Improvement of
nutritional value and functional properties of soybean glycinin by protein engineering",
it is found that glycinin is a suitable target for genetic manipulation to improve the
nutritional and functional properties of soybean proteins. It is also concluded that the
functional properties exhibited by the genetically modified glycinin component of the
soybean was superior to those of the native glycinin which establishes the possibility of
creating glycinins with high food quality and high nutritional content.
The manipulation of glycinin has continued to be modified and enhanced as in
"A new approach to genetic alteration of soybean protein composition and quality".
Here the study focused on the manipulation of glycinin (11S) and B-conglycinin (7S)
contents, the principal components of soybean storage proteins. The study focused on
interspecific hybridization between cultivated and wild soybeans in order to improve the
protein quality of cultivated soybeans for animal feed.
Glycine is a non-essential, neutral, genetically coded amino acid. It is the only
protein-forming amino acid without a center of chirality.
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Symbol
gly g
Molecular formula
C2H5NO2
Molecular weight
75.07
Isoelectric point (pH)
5.97
pKa values
2.21, 9.15
CAS Registry Number
56-40-6
3D Molecular Model
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Amino Acids
Name
Alanine
Abbr.
Linear structure formula
ala a
CH3-CH(NH2)-COOH
Arginine
arg r
Asparagine
asn n
H2N-CO-CH2-CH(NH2)-COOH
Aspartic acid
asp d
HOOC-CH2-CH(NH2)-COOH
Cysteine
cys c
HS-CH2-CH(NH2)-COOH
Glutamine
gln q
H2N-CO-(CH2)2-CH(NH2)-COOH
Glutamic acid
glu e
HOOC-(CH2)2-CH(NH2)-COOH
Glycine
gly g
Histidine
his h
HN=C(NH2)-NH-(CH2)3-CH(NH2)-COOH
NH2-CH2-COOH
NH-CH=N-CH=C-CH2-CH(NH2)-COOH
Isoleucine
ile i
CH3-CH2-CH(CH3)-CH(NH2)-COOH
Leucine
leu l
(CH3)2-CH-CH2-CH(NH2)-COOH
Lysine
lys k
H2N-(CH2)4-CH(NH2)-COOH
Methionine
met m
CH3-S-(CH2)2-CH(NH2)-COOH
Phenylalanine
phe f
Ph-CH2-CH(NH2)-COOH
Proline
pro p
NH-(CH2)3-CH-COOH
Serine
ser s
HO-CH2-CH(NH2)-COOH
Threonine
thr t
CH3-CH(OH)-CH(NH2)-COOH
Tryptophan
trp w
Ph-NH-CH=C-CH2-CH(NH2)-COOH
Tyrosine
tyr y
HO-p-Ph-CH2-CH(NH2)-COOH
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Valine
val v
(CH3)2-CH-CH(NH2)-COOH
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2.5.3.1.3. Isoflavones
2.5.3.1.3.1. Popularity of isoflavones
The importance of isoflavones is widely appreciated and is currently the subject
of intense research and discussions. Isoflavones appear to protect against hormonerelated disorders such as breast cancer and prostate cancers. The chemical structure of
isoflavones is very similar to that of our own estrogen. Because of this similarity in
structure, isoflavones can interfere with the action of our own estrogen. Sometimes
isoflavones will reduce the effects of estrogen because they compete with the same
receptor sites on our cells. Some of the risks of excess estrogen can be lowered in this
way.
Isoflavones can also increase the estrogen activity. If during menopause the
body's natural level of estrogen drops, isoflavones can compensate by binding to same
receptor sites thereby easing menopause symptoms as a result.
The best way to consume isoflavones is in the form soy, so you can benefit from
other healthy components of soy. Soy contains many types of isoflavones, but the most
beneficial are genistein (see picture) and daidzein. The highest amounts of isoflavones
can be found in soy nuts and tempeh. Isoflavones are fairly stable. Under normal
cooking methods, isoflavones are not destroyed.
2.5.3.1.3.2. Health benefits of isoflavones
Research in several areas of healthcare has shown that consumption of
isoflavones may play a role in lowering risk for disease. Isoflavones can fight disease on
several fronts. The following potential health benefits are attributed to isoflavones:
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
Ease menopause symptoms - The benefits of soy go beyond reducing long-term
cancer risk. Recent studies have found that soy isoflavones can reduce
menopause symptoms such as hot flushes and increase bone density in women.
Indeed, many menopausal and post-menopausal health problems may result
from a lack of isoflavones in the typical Western diet. Although study results are
not entirely consistent, isoflavones from soy or red clover may be helpful for
symptoms of menopause.

Reduce heart disease risk - Soy isoflavones also appear to reduce
cardiovascular disease risk via several distinct mechanisms. Isoflavones inhibit
the growth of cells that form artery clogging plaque. These arteries usually form
blood clots which can lead to a heart attack. A review of 38 controlled studies on
soy and heart disease concluded that soy is definitely effective for improving
cholesterol profile. There is some evidence that isoflavones are the active
ingredients in soy responsible for improving cholesterol profile.

Protect against prostate problems - Eating isoflavones rich products may
protect against enlargement of the male prostate gland. Studies show isoflavones
slowed prostate cancer growth and caused prostate cancer cells to die.
Isoflavones act against cancer cells in a way similar to many common cancertreating drugs.

Isoflavones improve bone health - Soy Isoflavones help in the preservation of
the bone substance and fight osteoporosis. This is the reason why people in
China and Japan very rarely have osteoporosis, despite their low consumption of
dairy products, whereas in Europe and North America the contrary happens.
Unlike estrogen, which helps prevent the destruction of bone, evidence suggests
that isoflavones may also assist in creating new bone. Other studies are not
entirely consistent, but evidence suggests that genistein and other soy
isoflavones can help prevent osteoporosis.

Reduce cancer risk - Isoflavones act against cancer cells in a way similar to
many common cancer-treating drugs. Population-based studies show a strong
association between consumption of isoflavones and a reduced risk of breast and
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endometrial cancer. Women who ate the most soy products and other foods rich
in isoflavones reduced their risk of endometrial cancer by 54%.
2.5.3.1.3.3. Isoflavones are natural plant hormones
Isoflavones can be found in many foods but the best known source of
isoflavones is the soybean (Glycine max). The soy isoflavones are responsible for most
of the soy health benefits. The Soybean is a plant cultivated as foodstuff whose health
properties have recently been discovered. Thorough studies have revealed that the
consumption of the soy beans or soy foods containing isoflavones have favourable
effects on people's health. Another source of isoflavones is red clover. As opposed to
soy beans, red clover is normally not eaten but the isoflavones are extracted and used to
make isoflavones supplements.
2.5.3.1.3.4. Isoflavones are natural antioxidants
A recent study has demonstrated that isoflavones have potent antioxidant
properties, comparable to that of vitamin E. The anti-oxidant powers of isoflavones can
reduce the long-term risk of cancer by preventing free radical damage to DNA.
Genistein is the most potent antioxidant among the soy isoflavones, followed by
daidzein.
2.5.3.1.3.5. What are isoflavones
Isoflavones are secondary vegetable substances, which can act as estrogens in
the body and have protective functions. The estrogen effects of isoflavones are much
less powerful than the estrogen hormones (it’s effectiveness represents around 1/1000 of
the estrogen hormones). This is why isoflavones and phyto-estrogens exercise a
balancing effect when the level of estrogens is low, such as during the menopause, and
cause less menopause symptoms. Isoflavones can also reduce the effect of the estrogen
on cells and skin layers when the hormone levels are high, and then essentially reduce
the risk of estrogen linked cancers.
As nutrition related observations have shown, diseases and troubles mentioned
above are uncommon in countries where a lot of soybeans are consumed, because
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soybeans bring to the organism isoflavones.Scientific literature contains data about the
synergy effects. Within the isoflavones we find daidzein and genistein.
2.5.3.1.3.6. Why is a good digestion so important
Isoflavones are transformed by bacteria in the intestinal flora during digestion. It
is only once this transformation has been completed that the isoflavones exercise their
beneficial effects in the body. Lower absorption in the intestine has been observed
following a lengthy intake of antibiotics or in the case of diarrhea. This can result in a
reduction of the protective functions of these substances for the body.
In order to obtain a regular absorption of isoflavones, the intake isoflavones rich
foods or isoflavones supplements must be spread during the day.
2.5.3.1.3.7. How do isoflavones work
In the eighties, scientists discovered the alpha- and beta-receptors for estrogens.
Estrogens, like all hormones, act by using receptors located on the cell, which provokes
some reaction. The alpha-receptors are linked with a risk of estrogen related cancers. On
the other hand, the beta-receptors initiate only favourable effects. The repartition of
these two types of receptors in the cells and organs is different. Different tissues appear
to have different ratios of each receptor type. This discovery allowed us to understand
why isoflavones can act differently than estrogens even though the structure of
isoflavones is similar to estrogens.
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2.5.3.1.3.8. The isoflavones mechanism
When the natural levels of estrogens are low, isoflavones can help the estrogens
by activating the beta-receptors.
When the natural levels of estrogen are high, for example during Adolescence ,
the isoflavones bind with the alpha-receptors and prevent the natural estrogens from
binding with these receptors.
2.5.3.1.3.8.1. How do isoflavones influence health
Isoflavones activate the beta-receptor and reinforce the favourable estrogenic
properties. On the other hand, isoflavones protect the estrogen alpha-receptors.
Consequently the proneness to estrogen-related cancers is lower.
The beta-receptors, which exercise favourable effects for health, can be found
mainly in the blood cells, the lungs, the prostate, the bladder, bones and thymus.
Isoflavones stimulate their function even after the level of estrogens has decreased.
The alpha-receptor can be mainly found in the breast tissue, the uterus, the
ovaries, the testicles and the liver. In those places, isoflavones protect the receptor
against estrogens and help reduce the proneness to tumors.
2.5.3.1.3.8.2. Regulation of the hormonal balance during menopause
Isoflavones regulate the estrogen levels in the body. Isoflavones play a role
when the estrogen level is low. The typical symptoms of the menopause, such as hot
flushes and night sweat become less severe.
When taking daily 40-50mg of isoflavones, the symptoms of menopause will
decrease after 2 to 3. This treatment will also reduce the risk of hormones related
tumors, osteoporosis and arterio-sclerosis. In the long term the health benefits are really
high.
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2.5.3.1.3.8.3. Other isoflavones actions
Most interest in isoflavones has been generated by their potential hormonal
effects. But isoflavones have other physiological effects. There are indications that
isoflavones can stop the growth of cancer cells through inhibition of DNA replication
and reduction in the activity of various enzymes. Isoflavones also have antioxidant
effects and inhibit the actions of various growth factors.
2.5.3.1.3.9. Metabolism of isoflavones
2.5.3.1.3.9.1. Formation of aglycones
Isoflavones occur in foods in the form of glucosides which means that the
isoflavones are bound to sugar (conjugated isoflavones). These glycosides are very
water soluble. These conjugated isoflavones have to undergo further changes. When
ingested, these conjugated isoflavones undergo hydrolysis by ß-glucosidases in the
intestine, releasing the principal bioactive aglycones (daidzein, genistein and glycitein).
These aglycones may be absorbed and further metabolized to many specific metabolites
such as equol.
2.5.3.1.3.9.2. Influence of diet on isoflavones metabolism
Further metabolism of aglycones seems to be strongly influenced by the diet. A
high carbohydrate environment, which causes increased intestinal fermentation, results
in more phytoestrogens being transformed in equol. This may be relevant because the
potency of equol is higher than that of its plant precursor, daidzein. Also, the intestinal
microflora has an effect on the metabolism of isoflavones. When intestinal flora is low
(antibiotics, germfree animals, newborn babies) metabolism falls down too. When the
dietary intake of fat is high, intestinal microflora has difficulty in synthesizing equol
from isoflavones.
Like endogenous estrogens (estradiol), isoflavones are metabolized in the
intestines and liver. Absorption happens along the entire length of the intestine and they
are secreted in bile and urine. Excretion of isoflavones metabolites can vary strongly
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between individuals. This may be influenced by the fact that each person has his own
specific intestinal microflora population.
Once absorbed equol shows less affinity to be bound to serum proteins and
therefore has a greater availability than estradiol. When soy is consumed on a regular
basis (50 mg isoflavones/day), plasma isoflavone levels far exceed normal estradiol
concentrations. This observation led to the hypothesis that isoflavone would be
biologically active, conferring health benefits that could explain the relatively low
incidence of hormone-dependent diseases in countries in which soy is a dietary staple
2.5.3.1.3.10. Sources of isoflavones
There are several natural sources of isoflavones but the most important ones are
soy and red clover.
2.5.3.1.3.10.1. Red clover
Red clover is a perennial plant with trifoliate leaves and pink to red flowers. The
plant derives its name in part from its flowers, which are fragrant and can range in color
from white to a dark red. Red clover is a member of the legume family and has been
used worldwide as a source of hay for cattle, horses and sheep and by humans as a
source of protein in the leaves and young sprouts. Red clover is also medicinal plant for
human use.
The beneficial effect of red clover isoflavones are very similar to that found with
soy isoflavones. Isoflavones from red clover will reduce menopausal symptoms. Red
clover isoflavones help maintain the density of the bones in both menopausal and perimenopausal women. Red clover isoflavones have not shown a cholesterol reducing
effect, probably because soy proteins take an important role for the cholesterol reducing
effect.
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2.5.3.1.3.10.2. Soybeans
Isoflavones are present in relatively large amounts in virtually all soybean
products, with the exception of soy-protein concentrate. Whole soybeans contain about
200 mg isoflavones per 100g. Soybeans contain three types of isoflavones in four
chemical structures.
2.5.3.1.3.11. Isoflavones supplements
There are a lot of isoflavones supplements on the market. Most of these
supplements contain isoflavones which are extracted from soy beans or red clover. They
can be considered as natural products.
Some supplements and medicines contain a synthetic form of isoflavones, called
ipriflavone. It was chemically designed to have only the bone-stimulating effect of
isoflavones but lack other estrogen-like effects. Ipriflavone is not used for the treatment
of menopausal symptoms, but is not believed to adversely affect estrogen receptorpositive breast cancer
2.5.3.1.3.12. Isoflavones - the Active Ingredients in Soybean
Soybean is becoming a popular food ingredient. More and more consumers are
looking for products that contain soybean, and fortunately the grocery stores have many
soy-based foods. Food manufacturers have been happy to find that alternatives to
replace traditional meat and milk products using soy have been relatively easy to
produce. Foods containing textured soy have the same taste and mouth feel as
equivalent meat products. Soy beverages abound and, although the flavoured varieties
are popular, the natural soy drinks have lost the bean flavour that initially turned many
consumers off. Soy products include soy-meat paddies, soy cheese, soy ice cream soy
yogurt - the list keeps growing.
glycine max
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Isoflvones are the active ingredients in soybeans. Interest in soy has grown
because it has been shown that the isoflavones in soybean have weak estrogen-like
properties. Women who question hormone replacement therapy and are looking for
natural ways to reduce the effects of menopause have turned to soybean.
There are three major isoflavones in soybean - daidzein, genistein, and glycitein.
Tofu, soybean sprouts, miso and tempeh all have high isoflavone levels. Soy sauce is a
poor source of soy isoflavones.
Asians are known to consume high levels of soybean and, therefore, isoflavones.
Typically Asians consume 20-80 mg of isoflavones per day. At the present time food
labels do not contain information about isoflavone levels..
Chemical Structure of Daidzein, Genistein, and Glycitein
R1
R2
R3
Isoflavone
H
H
OH
Daidzein
OH
H
OH
Genistein
H
OCH3
OH
2.5.3.1.3.13. Nutritional Composition of Glyphosate-Tolerant Soybeans
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One of the main concerns from a nutritional and health aspect of genetic
modification of soybean has dealt with glyphosate-tolerant soybeans (GTS), which is
mainly incorporated in animal feed for commercially grown animals.
To make soybeans herbicide resistant, the gene of 5-enolpyruvylshikimate-3phosphate synthase from Agrobacterium was used. Safety tests claim the GM variety to
be "substantially equivalent" to conventional soybeans. The same was claimed for GTS
(glyphosate-resistant soybeans) sprayed with this herbicide. However, several
significant differences between the GM and control lines were recorded and the
statistical method used was flawed because:

Instead of comparing the amounts of components in a large number of
samples of each individual GTS with its appropriate parent line grown side-byside and harvested at the same time, samples from different locations and
harvest times are compared.
There were also differences in the contents of natural isoflavones (genistein, etc.)
with potential importance for health.

Additionally, the trypsin inhibitor (a major allergen) content was
significantly increased in GTS.
Because of this, and the large variability (± 10% or more), the lines could not be
regarded as "substantially equivalent."
It was found that "The feeding value of soybeans fed to rats, chickens, catfish,
and dairy cattle is not altered by genetic incorporation of glyphosate tolerance." The
weight and body composition of these animals did not differ significantly when fed
GTS instead of the parental line of soybean. The cows milk did not differ in
composition or production. Furthermore, compositional analysis of the GTS seeds
showed no meaningful differences between the parental and GTS lines in the
concentrations of important nutrients and antinutrients.
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Confirming this, another study tested macronutrients by proximate analyses
(protein, amino acids, fat, fatty acids, carbohydrates, fibre and ash), as well as
antinutrients (trypsin inhibitor, lectins, isoflavones, stachyose, raffinose, phytate and
urease). They also found that the GTS lines were equivalent to the parental.
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Thus, the nutritional value of GTS soybeans is comparable with that of the
parental cultivar and is consistent with the established ranges for soybeans. Feeding
trials revealed that the growth and composition of the animals fed is GTS soybeans was
not significantly different with control soybeans.
2.5.3.1.3.13.1. Analysis of the Environmental, Ecological, and Health Effects
of Genetically Engineered, Glyphosate-Resistant Soybeans
The very concept of Genetic Engineering has for so long been the stuff of
science fiction that its approach in reality has been greeted with mixed reactions by
scientists and laypeople alike. Particularly as the new technology begins to work its way
into consumer products, a wave of negative publicity has developed surrounding its use,
with the depth to prevent in many cases its acceptance in general market productions. In
1994, Calgene's "Flavr Savr" tomato became "the first genetically engineered whole
food to hit grocery stores," but was soon pulled from the market after an unfavorable
reception by consumers.There are some that hope that reluctance on the part of
consumers to accept genetically altered food will similarly prevent market acceptance of
a new line of genetically altered crops scheduled to appear in the fields within the year
Roundup Ready™ Soybeans, or the new line of Monsanto soybeans that have been
genetically altered to be resistant to glyphosate, the active ingredient in its most popular
herbicide, Roundup™. As a result, many liberal and consumer oriented groups have
been working to spread opposition to the product, often through articles aimed at
alarming consumers with suggestions of potential hazards this product might carry for
them or their environment. When the claims of many of these groups are examined and
compared to the actual evidence available regarding Roundup Ready™ soybeans,
however, many of the fears prove to be based more in embellishment and rhetorical
overstatement than in reality, and often fail to take into account the degree to which all
modern farming techniques already involve an unprecedented degree of environmental
disruption and experimentation.
A determination of the potential impacts of RRS on the environment and human
health must consider:

whether ecological effects may arise through the unrestricted release and use of
genetically engineered soybean containing 'foreign' genes
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
how the pattern of use of the herbicide glyphosate could change and the effects
of such a change on human health and the environment

potential for harm to human consumers as a result of the changes to the soybean
When these specific concerns are compared directly to the scientific and
chemical realities of the alterations involved, it becomes clear that while the basic
concerns - regarding the degree to which the ecological implication of the changes
being made are not thoroughly understood - are significant, most of the substance of the
particulars focused on by the accusations do not themselves constitute sufficient reason
to shun the products in question as suggested.
The first and most obviously refutable set of accusations voiced are those
regarding the potential for harm to human consumers as a result of the changes to the
soybean. The basic concern in this area is that the genetic alterations will result in
phenotypical differences in the consumable portion of the plant, which would have the
potential to negatively affect those consuming the beans. The only case discussed or to
be found as a concrete example,however, is one that took place last year, when the
addition of Brazil nut genes to soya plants in order to increase production of a protein
rich in the important amino acid methionine, previously produced in only small
quantities by soy, was determined to cause the newly developed soy to elicit an allergic
reaction in people previously allergic to Brazil nuts.The genetic alterations that led to
this incident, however, differ in qualitatively important ways from the those undergone
by the Roundup Ready™ soybeans.
To understand the differences in alterations, and the effect these differences have
on the potential hazards for consumers, the actual process of the genetic alterations and
the resulting structural changes to the DNA of the plant itself must be examined. When
this is done, two basic differences arise between the comparison example cited and the
situation involving Roundup Ready™ soybeans. The first involves the nature of the
genes that are being added. In the case where Brazil nut genes were added to Soya
plants, the specific aim was to increase their production of a protein in such a way that
the nutritional value of the consumable portion of the plant is significantly altered. This
means that the genes added were such that they led to the production of a protein
designed specifically to accumulate in large quantities in the bean.
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In the Roundup Ready™ soybeans, however, the purpose of the genetic
alterations was not to change in any way the final nutritional value of the product.
Instead, the purpose was to induce resistance to the nonselective herbicide glyphosate
(HO3PCH2NHCH2COOH; see fig.1). This chemical binds to and blocks the activity of
5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) - an enzyme responsible for
catalyzing the reaction of shikimate-3-phosphate (S3P) and phosphoenolpyruvate (PEP)
into 5-enolpyruvylshikimate-3-phosphate (EPSP) and phosphate. The introduction of
resistance to this chemical was accomplished principally by the insertion through use of
a plasmid vector of a glyphosate-tolerant EPSPS enzyme, taken from Agrobacterium sp.
Strain CP4 (CP4 EPSPS), into the experimental soybean line (line 40-3-2).
As experimentation demonstrated, however, in order for high levels of resistance
to be achieved, the glyphosate tolerant EPSPSs had to be targeted directly to the
chloroplast, where the aromatic amino acid biosynthetic pathways that produce EPSP
are located. This was achieved by the fusing of a chloroplast transit peptide sequence
derived from petunia EPSPS to the 5´ end of the CP4 EPSPS gene inserted into the soya
line.The transit peptide consists of 72 amino acids, and has been shown both to deliver
bacterial EPSPSs to the chloroplasts of higher plants in general, and deliver CP4 EPSPS
to the chloroplasts of soya plants in particular. It then, in both petunias as well as in the
presence of other chloroplast samples, appears to serve as a recognition site by the
appropriate receptor on the chloroplast membrane, ensuring that the enzyme is delivered
to the specific site in the chloroplast where aromatic amino acid biosynthesis is
localized. This holds significance for the potential effects of the genetic alterations
because it means that the newly introduced proteins are directed specifically to the
25
chloroplasts of the plants - and to a lesser degree the root plastids and cytosol (ie, the
matrix in which the chloroplasts are suspended)- which are located in either the roots or
the leaves and other green organs of plants, and thus not the beans themselves. As a
result, CP4 EPSPS is present in soybean seed at levels of approximately 0.03% of the
fresh weight of the seed, and 0.08% of the total protein, whereas most allergens must be
present as major protein components in the consumable portion of the plant before they
can have an effect. So while the altered proteins in the case with Brazil nut genes were
able to have a large potential effect on those consuming the beans, this would not be the
case with glyphosate-tolerant soybeans (GTS).
The other significant difference between the two cases involves the relation of the
modified protein to those proteins originally present in the plant before modification. In
the case of the soybeans containing Brazil nut genes, the purpose of the modification
was to initiate the production of proteins unlike any found in significant quantities
previous to the alteration. In the GTS plants, however, the aim was to introduce an
EPSP synthase that serves the same function as the original EPSPS, but just does so
even in the presence of glyphosate. This would indicate that the CP4 EPSPS protein
developed would be functionally similar to the original EPSPS in non-GTS plants, and
thus less likely to react differently within a living organism. While the EPSPS
chloroplast transit peptide sequence was also added, the peptide produced from this
sequence is cleaved and degraded when the pre-CP4 EPSPS protein reaches the
chloroplast, just as other naturally occurring chloroplast transit peptides are, meaning
that only the mature CP4 EPSPS - with no chloroplast transit peptide sequences retained
- is left as the CP4 EPSPS species present in planta, and thus the only possible allergen
related difference between GTS plants and non-GTS plants results from the difference
between the two functionally similar EPSPSs. While this is far from conclusive
evidence for determining the allergenic potential of GTS - CP4 EPSPS is only 26%
identical to soybean EPSPS - when combined with the knowledge that
1) the divergence among food EPSPSs is on the same order (30% between soybean
EPSPS and Bacillus subtilis EPSPS) as the 26% divergence observed between CP4
EPSPS and soybean EPSPS;
2) CP4 EPSPS shows no meaningful homology with any known "toxins" in the
SwissProt, Pir and Genpept sequence databanks;
26
3) CP4 EPSPS is significantly degraded both by the protease present in the mammalian
digestive system - as well as the amount of heat applied in the processing and toasting
procedure - and hence unlikely to survive the peptic and tryptic conditions of the
digestive system and reach and pass through the intestinal mucosa, as is necessary for a
protein to become an allergen; it both strongly supports the suggestion that the
allergenic potential is low, and - as does the first comparison discussed - makes it clear
that the case involving the addition of Brazil nut genes to soya plants, which is being
trumpeted as an example of the dangers of genetic engineering, is not a comparable
situation, and serves little use as a tool for understanding the threat posed by GTS plants
other than that of stirring up concern among those without sufficient information.
The second set of criticisms that can be dealt with are those pertaining to how
the pattern of use of the herbicide glyphosate could change with the development of
Roundup Ready™ soybeans, and what the direct effects of such a change on human
health and the environment might be. These concerns center around the possibility that,
whether or not Roundup Ready™ soybeans increase or decrease herbicide use overall,
they very well may increase the use of glyphosate in particular, and that this increase
may have direct negative effects on people and the immediate environment.
Much of this critique, however, fails to be impregnable if compared to the actual
chemically functional properties of glyphosate. The toxicity of the compound comes
from its ability to function as an noncompetitive inhibitor versus S3P in the synthesis of
EPSP from S3P and PEP. Although it has not been completely determined whether the
uninhibited synthesis of ESPS occurs through the random, synergistic binding of the
substrates, or requires a compulsory ordered, sequential binding process, the reaction is
prevented in the presence of glyphosate by the formation of a tight ternary complex
between glyphosate, S3P, and the enzyme thus preventing the standard synthesis
reaction. Analysis of occurrences where glyphosate can be made to bind to the free
enzyme alone indicate, by the similarity between observed entropy loss (see chart 1)
and the "theoretical limit of 35 cal/mol K normally attributed to the complete restriction
in motional freedom of a bound ligand," that there is a significant degree of
complimentarity between glyphosate and EPSPS. While the failure of the
thermodynamic binding parameters demonstrated by the interaction between glyphosate
and EPSP to align with those demonstrated by PEP and EPSP make it unlikely that
27
glyphosate functions as an actual ground state analog inhibitor of PEP, this still
provides good evidence for the limited nature of glyphosate's toxicity. Finally,
comparisons of glyphosate bonding to the free enzyme versus the observed EPSPS S3P
complex reveal that the involvement of S3P enhances glyphosate binding by a factor of
almost 80,000, while similar examinations of PEP show that S3P enhances PEP binding
by only a factor of 20.This strong synergistic interaction between glyphosate, EPSPS,
and S3P, as compared to that between PEP, EPSPS, and S3P, then, helps to explain
glyphosate's high specificity and selectivity for EPSPS versus other PEP-dependent
enzymes, providing a final indication of the specificity of glyphosate's toxicity towards
only those organisms that rely on the use of EPSPS in their metabolism.
Chart 1: Characterization of PEP and Glyphosate ESPS
|=========================================|
|
Complex
|
dH
|
dS
|
|=========================================|
| EPSPS + S3P | -5.2+-0.1 |
5.4+-0.6 |
|-----------------------------------------|
| EPSPS + PEP | -4.9+-0.3 | -0.6+-0.8 |
|-----------------------------------------|
| EPSPS + GLY | -13.7+-1.6 | -36.7+-5.5 |
|-----------------------------------------|
| EPSPS+S3P+GLY | -19.0+-0.4 | -31.9+-1.8 |
|=========================================|
The significance of this limitation on glyphosate's toxicity lies in the limited
number of organisms in which EPSPS is present. The purpose of this enzyme is to
catalyze the transfer of a carboxyvinyl group from PEP regiospecifically to the 5alcohol group of S3P, resulting in EPSP and inorganic phosphate. The EPSP is then
used in the production of the aromatic amino acids necessary for the synthesis of
proteins and some secondary metabolites. While EPSPS is present in all plants, bacteria,
and fungi, however, it is not found in animals, for animals do not produce their own
aromatic amino acids, but receive them only from plant, microbial, or other animal
foods. Hence the inhibition of the production of EPSP will, in plants at least, results in
death or severe growth reduction; in animals, it will have no effect. Thus, while the fear
that glyphosate may harm beneficial soil micro-organisms is a reasonable one, it holds
little direct threat for animal life, particularly human life; suggestions otherwise appear
to constitute more hyperbole than real analysis or evidence.
28
The other primary concern for a mechanism by which an increase in the usage of
glyphosate could directly harm non-targeted plant or animal life is if it were to remain
in the soil long enough to either leach into the ground water, or prevent future croprotation or diversification in a field after treatment. Once again, however, the chemistry
behind the matter tends to diminish the degree to which these matters become serious
concerns. As long ago as 1978 it was demonstrated that glyphosate chelated with metals
associated with soil;since then it has been determined that glyphosate/metal complexes,
most likely composed of a water bridge between the carboxylic and phosphonic acid
groups and the exchangeable cations on clay particles, were formed within the inner
layer of the clays studied. This chelating effect serves to rapidly bind the glyphosate to
the soil, not only preventing leaching and protecting groundwater supplies, but
preventing as well the movement of glyphosate from an area of application to nearby
areas. A measure of this nonleachability is provided by the observation that although
glyphosate has been widely used for more than 20 years now, there are no reports of its
ever having been found in groundwater. Finally, the strength of the interactions between
glyphosate and the soil molecules also serve to prevent its interaction, in most soils,
with any future plant life, thus preventing the possibility of the chemical remaining in
the soil and harming the growth of subsequent plant life in the area.
Once in the soil, glyphosate is readily degraded by soil microflora. This process
takes place without a lag phase under both aerobic and anaerobic conditions, and results
in a primary metabolite of aminomethylphosphonic acid (AMPA; see figure) This
product itself undergoes degradation to CO2 at an only slightly slower rate than that of
glyphosate, and in the end, the primary products of the degradation of glyphosate are
CO2 and NH4+.While the exact rates of metabolism for these processes can vary
29
considerably depending on the soil and microbial activity levels in the soil, they
generally range from less than a week to several months. In addition, the facts that
glyphosate binds tightly to soil particles, has a short average half-life and degrades over
time in soil mean that it is highly unlikely to move from the site of its application;" a
claim reasonably well supported by the evidence thus far examined, at least to the
degree that it diminishes the concerns about increased Roundup™ use to the level
where it becomes an issue primarily of comparing the potential for danger still present
in the use of Roundup™, versus the known hazards of the alternatives available.
The final concern regarding direct hazards of increased Roundup™ usage is the
fear that it will lead to an increase in the rate at which glyphosate resistant strains of
weeds develop. However, while there is always the danger that increased usage of one
pesticide over another will increase its chances of developing resistant strains while
decreasing the chances of developing resistant strains of the other pesticide, there is no
indication that this would be any more likely with glyphosate than with any other
chemical herbicide it might for the time being be replacing. This claim is not only
supported empirically by the observation that while glyposate has been used for nearly
20 years now, there has still been observed no problems related to development weed
resistance, but by the recognition that the selectivity of glyphosate's mode of action, its
instability in the soil, and its lack of carryover from one year to the next can all be seen
to stem from the chemical nature of glyphosate itself, as discussed above. Glyphosate,
30
then, carries no guaranties of being risk-free; however, the specific attacks offered
against the possibility of increased usage do not seem to be based in any dangers
directly related to the development and use of the Roundup Ready™ soybean.
The final area in which criticism has been leveled against the promotion of GTS
plants is that concerning the more general fears of genetic pollution and the knowledge
that the long term impacts on an ecosystem of even minute, well-regulated changes in
population can have unpredictable and dangerous, unexpected impacts. The first of
these two fears, that of genetic pollution, is based in the idea that the introduction of an
expressive gene not normally present in a particular genus of plants carries the
possibility that that gene may spread throughout that genus, changing in unexpected
ways both the metabolic processes within individual plants and the long term natural
ecosystem.
One of the main issues in the environmental risk assessment of genetically
engineered crops is whether the introduced, foreign gene can be transferred through
outcrossing to native, related species and cause genetic pollution. Although cultivated
soybean is mainly self-pollinating, pollen can also be carried by bees to other soybeans
and related wild or weed plants.
In additional, crosses between the two plants are unlikely because soybeans are
99% self-pollinated and because soybeans are not a plant preferred by insects, which
carry pollen. Glyphosate tolerance does not provide any competitive advantage beyond
its intended effect, and volunteer soybeans can be controlled by a variety of commonly
available and used agronomic techniques.
Both sides of this conflict are difficult to asses due to the lack of empirical data
on the subject; a difficulty that serves itself to highlight both the generality and
theoretical nature of the attacks against the GTS product, as well as the degree to which
their arguments regarding the amount which is still as of yet unknown about possible
impacts are accurate and significant.
A very similar difficulty is encountered when the long term impacts of the
increase of glyphosate use on the ecosystem in general are examined. The protestations
31
that these impacts cannot be accurately predicted clearly contain a significant degree of
validity; not only does the past usage of glyphosate as a means of purposefully altering
the basic floral elements of local ecosystems provide an indication of the power
glyphosate has to drastically affect an ecosystem at the most basic level, thus rendering
the claim that Roundup™ poses no threat to animal life somewhat shortsighted, but it is
not hard to see that once one starts changing even minor elements of an ecosystem at a
basic level, the results are going to be unpredictable. It is important to keep in mind,
however, that these concerns are in no way specific to either Roundup Ready™
products, or the use of glyphosate in general.
Thus, identification of concerns regarding ecological implications of herbicide
use should not be viewed as sufficient cause to dismiss exploration of a new product.
Instead, it should be remembered that each product must be evaluated not in terms of its
risk as an isolated venture, but in terms of its risk as compared to the alternatives that
would otherwise be used, the alternatives being any number herbicides with
environmental implications which are similar to but slightly more dangerous than that
of glyphosate.
The variety of commercial, agricultural herbicides often used in place of or in
conjunction with glyphosate display, on the whole, comparable levels of toxicity in
humans and laboratory animals, thus the discerning factor between glyphosate and the
alternatives is the degree to which these alternative persist in the water and soil. The
benign nature of glyphosate once it has entered the soil, and it's properties therein, are
central to the argument that glyphosate is the least destructive herbicide, as this quality
of swift binding and nonleachability are unique to glyphosate as demonstrated by field
studies as much as 15 years ago. Examples of these studied alternatives are: atrazine (2chloro-4-ethylamino-6-isopropylamino-s-triazine), used primarily to control certain
grasses; amitrole (3-amino-1,2,4-triazole) which is often combined with ammonium
thiocyanate liquid to form amitrol-T and used as a broad spectrum herbicide; dicamba
(2 Methyl-2, 6-dichlorobenzoic acid), an herbicide specific to certain plant species;
dalapon or dalapon sodium salt, depending upon the application (2,2-dichloropropionic
acid, sodium salt), used against grasses and some annual weeds; and picloram (4-amino3,5,6,-trichloropicolinic acid), a wide-range herbicide which is seldom used in
agricultural practices.
32
Of these herbicides, atrazine, amitrole, dicamba, and dalapon are significantly
more environmentally detrimental than glyphosate. Atrazine is somewhat persistent in
soils, though there is minimal breakdown by microorganisms and some leaching into
local groundwater, the result of which is that, under the correct conditions, crops
planted in atrazine-treated soils the following year may be negatively effected by the
residues. There have also been some indications of damage to bottom fauna in
waterways with atrazine residues.
Amitrole, though it appears to be quickly removed from the soil and is thought
to participate in some complex metal binding similar to glyphosate, still leaches to some
degree into surrounding water supplies and there is suspected to interfere with the
nitification of river water. Aside from this, the use of amitrole presents a hazard as it is a
known anti-thyroid agent and, though relatively nontoxic, has shown evidence of
leading to thyroid tumors in rats, and amitrol-T, as it contains the fairly poisonous
substance ammonium thiocyanate, is considered toxic. Dicamba, while it is
experimentally noted as being almost four times as toxic to rats than Glyphosate, is very
mobile in soils and is highly soluble in water, thus any application of this particular
herbicide will have direct repercussions on the local groundwater; though there are not
any documented hazards associated with dicamba in the water supply. Finally, dalapon,
though it is rapidly broken down in soils due to the microorganisms present, there is
also experimental evidence of a reduction of soil nematodes and nitrate content in the
surface inch of soil treated with dalapon. The breakdown of this herbicide is much
slower in water and it is not metabolized by plants, presenting an issue of the degree to
which the presence of this herbicide in plant-foods is dangerous.
33
The
last
mentioned herbicide, picloram, is
believed to decompose rapidly in soils and is so powerful against most annual broadleaf
weeds, even in low concentrations, that it is often used in conjunction with other
34
herbicides, the only drawback being that it appears to be experimentally more toxic than
glyphosate, as it is two times more toxic in laboratory rats than glyphosate. This
particular herbicide illustrates the reality that, in practice, the specificity of many of
these herbicides dictates the need for combinations of herbicides in order to attain the
desired result, where as glyphosate is determined to be effective when used singularly.
The practice of creating herbicide "cocktails", leads to an increase in the variety of
hazards presented by the herbicides as each has specific drawbacks which render
glyphosate as the safer option.
This leads to the final aspect that must be taken into account before any coherent
examination of the issues surrounding the use of Roundup Ready™ soybeans can be
completed - the question of how the Roundup Ready™ system compares to alternative
herbicide packages.
When combined with the understanding that however many hidden dangers
glyphosate might posses, it is still widely accepted to be far more benign an herbicide
than any commonly used alternative, the evidence indicating that use of the Roundup
Ready™ system actually decreases overall herbicide use leads to the conclusion that its
benefits may very well outweigh the costs.
2.5.3.1.3.13.2. A Study About Yield Suppressions of Glyphosate-Resistant
(Roundup Ready) Soybeans
Glyphosate is a popular postemergence herbicide. However, potential yield
suppression from either genetic differences among varieties, the glyphosate-resistant
gene/gene insertion process, or glyphosate is a concern. The first of these could
contribute to a yield lag; the latter two could contribute to a yield drag.
Lag Versus Drag
Yield lag is the potential yield suppression due to the age of the variety in which
the gene is inserted. Yield drag is the potential yield suppression due to glyphosate or
the insertion of the gene itself.
Yield suppression (if it exists) = Yield drag (due to herbicide or glyphosate-resistant
gene) + Yield lag (due to the variety containing the glyphosate-resistant gene)
35
Data from University soybean variety performance trials in Nebraska and other
states suggest a yield suppression may exist. Figure 15 shows data from the 1998
variety trials at Lancaster County. Conventional varieties (nonglyphosate-resistant)
were included in either the early-maturing or late-maturing performance trials. All but
the lowest yielding conventional varieties yielded more than the glyphosate-resistant
varieties. No one else has reported the effects of glyphosate on a diverse group of
commercially available glyphosate-resistant soybean varieties or whether the
glyphosate-resistant gene/gene insertion process suppresses soybean yield.
Figure 15. 'Early-maturing' and 'late-maturing' performance trials compared
conventional varieties in Lancaster County, Nebraska, in 1998. Data from university
soybean variety performance trials in Nebraska and other states suggest a yield
suppression may exist.
Research Goals
Experiments are designed to test for both elements of yield drag: the effect of
glyphosate herbicide application and the effect of the glyphosate-resistant gene. Since it
36
could not be distinguished between yield drag associated with the glyphosate-resistant
gene or effects of its insertion, reference to this gene in the following could mean either
or both of these possibilities. Two experiments were conducted at each of four Nebraska
locations for two years with the intent to:

investigate the glyphosate herbicide effect on 12-13 varieties; and

look at the effect of the glyphosate-resistant (glyphosate-resistant) gene on five
pairs of glyphosate- resistant, nonglyphosate-resistant sister cultivars (eight
other cultivars were included as checks).
1. Glyphosate Herbicide Effect
Thirteen glyphosate-resistant varieties (Table 7) were grown to determine the
effect of glyphosate, ammonium sulfate (AMS), and water application (herbicide
effect). Direct comparisons were made within the same glyphosate-resistant variety
planted in side-by-side plots with one plot sprayed with glyphosate with 2 percent AMS
and the other plot sprayed only with 2 percent AMS in the first year. In the second year
a water-only treatment also was included. All plots were maintained weed-free by using
hand weeding and preemergence application of metolachlor and metribuzin. Crop
growth and development were monitored. Both glyphosate applications were at standard
rates (32 oz/acre of Roundup Ultra) and timing for soybean production (21 and 42 days
after soybean emergence).
Table 7. Glyphosate-resistant varieties included in the glyphosate
herbicide effect study. These were all either Maturity Group II or III
varieties adapted to the locations.
Golden Harvest H1280RR
Northrup King S23F5
37
Golden Harvest H1357RR
Pioneer 92B25
Pioneer 92B51
NU Pride Excel 8355
Dyna Grow 187
Asgrow A3601STS/RR
Asgrow AG2702
Asgrow AG3002
Northrup King S28V8
NC+ 32RR
Stine 3203-4 (1999 only)
Glyphosate did not adversely affect growth and development of glyphosateresistant soybeans. Flowering date was affected by neither glyphosate nor AMS (Table
8). However, plant height at physiological maturity in 1999 was reduced by 0.3 to 0.4
inches with glyphosate (Table 8). This finding was consistent across all locations but
was not significant in the two-year analysis. Physiological maturity of most of the
varieties was likewise not generally affected by the spray treatments.
Table 8. Spray treatment effects on plant characteristics. University of Nebraska,
1998-1999.
Physiological
Mature Plant
Maturity
Height
1998-99 1999 1998-99 1999 1998-99 1999
6 Env†. 4 Env. 7 Env. 4 Env. 8 Env. 4 Env.
Spray Treatment Flowering Date
Glyphosate
Ammonium
sulfate
Water
-days from May -days from May
313157*
54
112
112
---inches---
Seed
Weight
1999
2 Env.
-g/100-
37.9a
38.8b
14.6a
57
54
112
112
38.1a
39.1a
14.4b
-
54
-
112
-
39.2a
14.6a
†Env = Number of environments
*Means followed by the same letter within a column are similar (P < or equal to
0.05).
Did glyphosate affect grain yield of glyphosate-resistant soybeans? No. Grain
yield of glyphosate-resistant varieties was neither affected by glyphosate at any location
nor affected when averaged across locations (Figure 16). Two-year average grain yield
38
of varieties treated with glyphosate, AMS, and water was 55.7 bushels per acre; this was
not different than 56.5 bushels per acre with AMS and water treatment.
Figure 16. Comparisons of glyphosate-resistant soybeans with: 1) glyphosate,
AMS, and water (GLY); 2) AMS and water (AMS); and 3) water. Treatment
yields within the same year groupings were similar (P < or equal to 0.05).
2. Glyphosate Resistant Gene Effect
In the second study, five backcross-derived pairs of glyphosate-resistant and
nonglyphosate-resistant soybean sister lines were compared along with three high-yield,
nonherbicide-resistant varieties and five other herbicide-resistant varieties (Table 9).
Weeds were controlled with metolachlor and metribuzin combined with hand weeding.
This study allowed us to compare glyphosate-resistant varieties and their
nonglyphosate-resistant sister lines to monitor yield drag and also to obtain a measure of
yield lag by comparing glyphosate-resistant to conventional varieties. Glyphosate was
not applied to the soybeans in this study.
Table 9. Varieties and lines included in the glyphosate gene effect study.
These were all either Maturity Group II or III varieties adapted to the
locations of the trials.
39
1
2
3
4
5
6
Asgrow 2704-LL
Pioneer 9323-STS
Golden Harvest H1359-STS
Hoegemeyer 232
Desoy 2343
M/W Genetics 2711
7
Pioneer 92B51
8
9
10
11
12
13
14
15
16
17
18
Asgrow AG3002
NC+ 2.4N
NC+ 2.5RR
NC+ 3.2N
NC+ 3.2RR
Stine EX25N
Stine EX25RR
Stine 2170
Stine 2174
Stine 2250
Stine 2254
Liberty/STS resistant
STS resistant
STS resistant
Normal-high yield
Normal-high yield
Normal-high yield
GR (Glyphosate Resistant) also in other
study
GR also in other study
Non-GR sister of #10
GR resistant
Non-GR sister of #12
GR resistant
Non-GR sister of #14
GR resistant
Non-GR sister of #16
GR resistant
Non-GR sister of #18
GR resistant
The glyphosate gene or its insertion affect soybean growth or development.
Weight of 100 seed of the nonglyphosate-resistant sister lines was 0.6 grams heavier (in
1999) and the plants were 0.7 inches shorter than the glyphosate-resistant sisters (Table
10). Other variables monitored were similar between the two variety groups.
Table 10. Seed weights and plant heights of nonglyphosate-resistant sister lines and
their glyphosate-resistant sisters differed. Other growth and development characteristics
of these two variety groups were similar.
40
Variety
Group
(Entry
numbers
in each
group)
Flowering
Plant
days
1999 Lodging height
from May Seed wt at R7† at Mat.
31
(R7)
-g/100Non-GR Sisters
(9, 11, 15,
43.6a*
14.7a
17)
GR Sisters
(10, 12, 16,
43.7a
14.1 b
18)
No. of locations reporting
data
1998/1999
2/4
0/3
Maturity
Maturity
(R7)
(R8)
days
days from
from
May 31
May 31
-inches-
Grain
moisture
-%-
1.6 a
33.9 b
111.9a
120.4a
10.0a
1.4a
34.6a
112.7a
121.7a
10.0a
4/4
4/4
3/4
3/1
4/4
†1 to 5 scale with 1 = erect and 5 = prostrate; R7 = Physiological maturity
*Means followed by the same letter within a column are similar (P < or equal to 0.05).
Did the glyphosate gene or its insertion affect soybean yield? Yes. On average,
nonglyphosate-resistant sister lines yielded 5 percent (3 bushels per acre) more than the
glyphosate-resistant sisters when averaged over all locations and both years (Figure 17).
Nonglyphosate-resistant sister grain yields were greater than those of their associated
glyphosate-resistant sisters in two of the five pairs. This 5 percent difference is a yield
drag. Results were similar in the single-year analyses (data not shown). Grain yields of
sister-line pairs are shown in Figure 18. The greater number of data points below the 1:1
ratio line indicates that the nonglyphosate-resistant sisters yielded more on the average
than their glyphosate-resistant sister counterparts.
41
Figure 17. Comparisons of herbicide-resistant (HR) and nonherbicide-resistant soybeans,
University of Nebraska, 1998-1999. Non-GR sis = nonglyphosate-resistant sister lines; GR =
Glyphosate-resistant sister lines; LL = Liberty Link cultivars; STS = cultivars resistant to
STS. Columns with the same letters on tops are similar (P < or equal to 0.05).
Figure 18. Yield of glyphosate-resistant sisters compared to their respective nonglyphosateresistant sisters at four locations in two years. Each of the 132 markers represents yield data
of sister line pairs from the same replicate, location, and year. Markers below the line
indicate that the nonglyphosate-resistant sister yielded better than its glyphosate-resistant
sister (r = correlation coefficient). University of Nebraska, 1998 and 1999.
42
The high-yield, nonherbicide-resistant varieties yielded 5 percent more (57.7
bu/a) than the nonglyphosate-resistant sisters (54.8 bu/a) (Figure 17). This 5 percent
difference is a yield lag. The glyphosate-resistant gene in the glyphosate-resistant sisters
therefore reduced soybean yield 5 percent compared to the nonglyphosate-resistant
sisters. This 5 percent is a yield drag. When this is added to the 5 percent yield lag, the
glyphosate-resistant sisters yielded 10 percent less than the high-yield, non-herbicideresistant varieties.
As conclusion; yields were suppressed with glyphosate-resistant soybean
varieties relative to their sister lines, but we found no effect of spraying glyphosate on
glyphosate-resistant varieties. The research reported here demonstrates that a 5 percent
yield suppression was related to the gene or its insertion process and another 5 percent
suppression was due to variety genetic difference. Producers should consider the
potential for 5 percent to 10 percent yield differentials between glyphosate-resistant and
nonglyphosate-resistant varieties as they evaluate the overall profitability of producing
soybean. However, producers should consider that yields are often reduced far more
than 5 percent or 10 percent if weeds are not controlled.
Variety choices are best based on:
1. previous weed pressure and success of control measures in specific fields,
2. the availability and cost of herbicides,
3. availability and cost of herbicide-resistant varieties, and
4. yield.
Variety choices should not be made solely on whether varieties are herbicide
resistant. Based on our results from this study, the yield suppression appears associated
with the glyphosate-resistant gene or its insertion process rather than glyphosate damage
to the soybeans.
Two interrelated concerns are worth discussion. First, since the demand for
glyphosate-resistant soybeans is high, breeding efforts on nonglyphosate-resistant
cultivars by commercial seed firms will likely decrease proportionately. Thus, yield
potential gains of nonglyphosate-resistant cultivars over time may be less than those of
glyphosate-resistant cultivars. Second, and as result of this and the reported 5 percent
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yield suppression associated with the glyphosate-resistant gene, long-range yield
potentials are also less than if soybean breeder efforts and associated gains in yield
potential of nonglyphosate-resistant soybeans were maintained. If the trend continues,
we may look back on this time and likely see little or no gain in genetic yield potentials
at the beginning of the 21st century.
2.5.4. Soy Derivatives
most miso
soy sauce
teriyaki marinades
tofu
Tempeh
shoyu
Bread
pastry
textured vegetable protein
(usually soy)
soy protein isolate
soy beverages
or protein isolate
many non-stick sprays
lecithin or soy lecithin
rely on soy lecithin
tamari
margarine
Mayonnaise and salad dressings also may include lecithin.
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