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IPM MANAGEMENT IN
COTTON FIELDS & FIELD CROPS
Transgenic Cotton & Corn with
Bt (Bacillus thuringiensis)
Bacillus thuringiensis
Bt was first discovered in 1901 by
Japanese biologist Ishiwatari.
 In Germany 1911, Bt was isolated
by Berliner in flour moth
caterpillars, as the cause of a disease
called Schlaffsucht
 In 1976, Zakharyan reported the
presence of a plasmid in a strain of
Bt involved in endospore insecticidal
and crystal formation, called crystal
proteins or Cry (proteins) toxins.
 Cry toxins belong to a large
family known as PFT
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PORE FORMING TOXINS (PFT)
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PFT are important virulence factors
produced by bacteria to kill eukaryotic
cells by forming holes in the cellular
membrane.
They represent a diverse group of
proteins with a wide range of target cells.
The mode of action of PFT involves:
(a) Receptor recognition.
(b) Activation by proteases (protein
enzymes).
(c) Aaggregation into oligomericstructures (molecule that consists of a few
monomer units).
(d) Insertion into the membrane to form
ionic pores.
BT CRY TOXIN – MOD OF ACTION
The toxin core travels across the
peritrophic matrix
Cry toxins interact with specific
receptors called cadherin, located
on the host cell surface, the brush
border membrane of the gut cells.
Activated by host proteases
following receptor binding .
A new pre-pore oligomeric structure
is formatted.
The new formation is insert into the
membrane to form ionic pores.
Pores lead to osmotic cell lysis.
Bt as an Insecticide
Bt is a naturally-occurring soilborne bacterium that is found
worldwide.
A unique feature of this bacterium: its production of
crystal-like proteins (Cry) and Cytolitic (Cyt) protein families,
that selectively kill specific groups of insects: Lepidoptera,
Coleoptera, Diptera and also other invertebrates such as
nematodes
Cry proteins are delta endotoxins, insect stomach poisons that
must be eaten to kill insects.
Once eaten, insects stop feeding within 2 hours of a first bite and,
if enough toxin is eaten, die within 2-3 days.
For more than 30 years, various formulations of Bt have been used
successfully against insect pests on a variety of crops.
Δ-ENDOTOXINS
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Historically, B.t. toxins have been divided into
two groups on the basis of target specificity:
(a) Insect-specific Cry (crystal) proteins
(b) Generally cytolytic Cyt proteins.
δ-endotoxins are a super family of proteins
that occur as crystalline inclusions in the
spore-forming bacterium Bacillus
thuringiensis.
Considered environmentally safe insecticides.
The Cry proteins are the group that is mostly
being used in commercial insecticide
preparations.
In 1981, scientists cloned the first Bt toxin
gene, which led quickly to the development of
the first transgenic Bt plants in the mid1980s.
There are several strains of Bt, each with
differing Cry proteins.
Scientists have identified more than 60 Cry
proteins.
Other Types of Bt Toxins
Other types of Bt toxins are called Vegetative
Insecticidal Proteins, or VIPs.
VIPs are also considered relatively safe for nonpest species.
Other classes of toxins produced by Bt have a
broader spectrum of toxicity.
Transgenic Bt Plants
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A transgenic Bt plant produces delta endotoxin or Vips controlled
by a single gene in the bacteria.
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A modified version of this gene can be placed in plants.
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Plants containing this gene can produce delta endotoxin or VIP and
therefore be toxic to insects that are susceptible to that form of the
protein.
Plant geneticists create Bt crops by inserting selected exotic DNA
into the corn plant's own DNA.
Seed companies select elite hybrids for the Bt transformation in
order to retain important agronomic qualities for yield, harvest
ability and disease resistance
The Essential Global Needs leading Towards
Production of Bt Crops
The need to increase food production to
meet the food and feed demands of
the world, requiring higher production,
particularly in developing countries in
Asia, Africa and Latin America.
This demand has to meet primarily
through yield increases on existing
cultivated lands in order to be
environmentally sustainable and cost
effective.
How safe is Bt and Bt Crops?
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The EPA U.S. (Environmental Protection
Agency), considered 20 years of human
and animal safety data before registering
Bt corn.
Bt proteins are not toxic to people,
domestic animals, fish, or wildlife; and
they have no negative impacts on the
environment.
The Food and Drug Administration (FDA)
exempts Bt Cry proteins from residue
analyses because of Bt's history of safety
and because these proteins degrade
rapidly.
Bt hybrids Genetic Package
Three primary components of the genetic
package inserted into the crop include:
A. Protein gene. Bt genes, modified for improved
expression in crops, produce Cry proteins.
B. Promoter. A DNA sequence that regulates
where, when, and to what degree, an associated
gene is expressed.
C. Genetic marker. The presence of a genetic
marker allows seed companies to identify
successful transformations.
The Promoter
Some promoters limit
protein production to
specific parts of the plant.
Example: Some
promoters produce
protein throughout
leaves, green tissue and
pollen, whereas others
produce protein
throughout the plant.
Genetic marker.
Current examples of markers
include genes for herbicide
resistance or antibiotic
resistance.
The genetic package is inserted
into plant through a variety of
plant transformation techniques
Successful transformations, called
"events," vary in the components
of the genetic package and where
this DNA is inserted into the corn
DNA.
 The insertion site may affect Bt
protein production and could
affect other plant functions.
Consequently, seed companies
carefully scrutinize
transformation events to ensure
adequate production of Bt protein
and no negative effects on
agronomic traits.

Transgenic Bt Crops, Advantages
Non-toxic to vertebrates unlike synthetic
pesticides
Very specific to particular insect pests.
Reduction in sprays per season, with synthetic
pesticides
Very specific to particular insect pests.
Suitable for small-scale farmers, no equipment
and pesticide knowledge are needed
Benefits both the environment and labourers’
health,
Increase incomes through higher yields of
healthier grain.
Global Area of Biotech Crops, 1996 to 2010
(Million Hectares)
Bt Issues There is some evidence that
the prolonged use of Bt crops can create
emergence of resistant insect strains or
elevation in populations of insects that
are naturally resistant; these would
likely have emerged with the use of Bt
alone.
How does resistance develop?
Many factors contribute to the development
of resistance:
 Widespread
use of Bt crops

High season-long mortality

Two or more generations per year.
 The
lack of “refuges” – small crop areas that
are not GM.
Insect resistance management (IRM) high dose and refuge strategy assumes
resistance is recessive. Many susceptible moths (SS) are produced in refuge
maize that mate with rare resistant (RR) moths. Mating of resistant (RR) and
susceptible (SS) moths produces heterozygous (RS) moths that die when they
feed on high-dose Bt maize. This strategy dilutes resistance genes and delays
or prevents the evolution of resistance to Bt maize.
© 2012 Nature Education All rights reserved.
Avoiding/Delaying appearance of resistance
Farmers who plant crops with Bt trait(s) must
also plant a refuge area - a block or strip of crops
without the Bt gene.
 Insects who feed on that crop remain susceptible
to Bt technology.
 When they then mate with the rare insects that
survive after feeding on Bt corn, they produce
offspring that is susceptible to the technology.
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Refuge Configurations
Farmers Can Use
Different Refuge
Requirements
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The EPA requires a corn field that contains
insect-protected (or Bt) crops with a single modeof-action against corn rootworm to be planted
with 20% non-Bt corn in corn-growing areas (the
U.S. Corn Belt) and 50% non-Bt in cotton-growing
areas (the U.S. Cotton Belt).
New seed technologies that have multiple Bt
genes, or modes-of-action, provide additional
protection.
This enabled the EPA to reduce the size of
structured.
The right amount
of refuge seed is
included in the
bag
Farmers simply
put the
complete seed
bag in the
planter and
plant both the
Bt crop and the
refuge
For cotton growers,
there was a lot of
pressure from pests
before the introduction
of Bt cotton in 1996.
Due to synthetic
pesticide resistance,
farmers were losing
much of their cotton to
tobacco budworms,
cotton bollworms, and
pink bollworms.
Tobacco Budworm,
Heliothis virescens
Cotton Ballworm
Helicoverpa armigera
Cotton Ballworm
Helicoverpa zea
The Pink Bollworm
Pectinophora gossypiella
Benefits of Bt Cotton
China , 2007
Green bolls (100/field) were sampled from the
uppermost internodes within adjacent fields of Bt
(Deltapine 33B) and non-Bt (Hyperformer HS 44)
cotton experiencing severe pink bollworm pressure
late in the growing season.
 Average top crop lint yield reductions ranging
from 30 to 70% were observed in the uppermost
bolls of the non-Bt cotton variety. Average top crop
lint yield reductions ranging from 0 to 40% were
observed in the uppermost bolls of the transgenic
Bt cotton variety.
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.
YI E L D S
O F BT C O T T O N V E R S U S
CONVENTIONAL COTTON IN CHINA (KG/HA)
.
Benefits of Bt Cotton in India, 2011
Pesticide use has been cut by at
least half, a new study shows.
 The use of Bt cotton helps to
avoid at least 2.4 million cases of
pesticide poisoning in Indian
farmers each year, saving US$14
million in annual health costs.
(The current study, published online in the

journal Ecological Economics)
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India is now the world’s biggest
producer of Bt cotton with an
estimated 23.2 million acres
planting in 2010.
Insects Evolving Resistance
 Scientists
have confirmed incidents of
insects evolving resistance to Bt toxins in
the field to date: Bt cotton in India (2010)
and US (2008).
 Field
monitoring in parts of Gujarat has
discovered that the Bt crop is no longer
effective against the pink bollworm pest
there.
GM Cotton May Affect Biomass
A study concluded
in India 2011,
concluded:
 A decade of
planting with GM
cotton, or any GM
crop with Bt genes
could lead to total
destruction of soil
organisms, “leaving
dead soil unable to
produce food.”
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GM Cotton May Affect Biomass
Bacteria overall were reduced by 14 percent,
while the total microbial biomass was reduced by
8.9 percent.
 Vital soil enzymes, which make nutrients
available to plants, have also been drastically
reduced.
 Acid phosphatase which contributes to the
uptake of phosphates was lowered by 26.6
percent.
 Nitrogenase enzymes, which help fix nitrogen,
were diminished by 22.6 percent.
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Bt Cotton Led Agri-revolution, 2009
Bt cotton adversely affected the
farmers leading to suicides being
committed, and loss of biodiversity.
 There are studies, which show that
yields do not rise necessarily due to
growing of Bt cotton.
 The quality of the cotton grown is
poor in the case of Bt cotton.
 It provides little resistance to Pink
bollworm.
 The economic advantage of growing
Bt cotton is over-exaggerated. The
seed companies are extracting huge
royalties by selling the genetically
modified seeds at higher prices to
farmers.

European corn borer
Ostrinia nubilalis
Southwestern Corn Borer, Diatraea grandiosella,
Corn Earworm Helicoverpa zea
Fall Armyworm Spodoptera exigua
Black Cutworm Peridroma saucia
Western corn rootworm
(Diabrotica virgifera)
The diamondback moth (Plutella
xylostella),
sometimes called cabbage moth
Company
Bt gene
Dow Chemical CryIF +
Cry34Ab1 +
Co. +
Cry35Ab1 +
Monsanto
C0ry3Bb1 +
Cry1A.105+
Cry2Ab
Syngenta
Seeds Inc
VIP and
CryIAb
Trade
name
Pests controlled
or
suppressed
SmartStax European and
southwestern
corn borers,
corn earworm,
fall armyworm
and corn
rootworms
Agrisure
Viptera
3110
Corn borers,
corn
earworm, fall
armyworm,
black
cutworm
Refuge
requirement
5% non-Bt
refuge in , or
immediately
adjacent to Bt
field
20% non-Bt
refuge
needed within
1/4 to
1/2 mile
Resistance of Rootworm in Bt Cron
Severe lodging
caused by western
corn rootworm
larvae to Bt corn
expressing the
Cry3Bb1 protein
(northwestern
Illinois, August 16
2011).
It is said that the Western
corn rootworm (Diabrotica
virgifera) causes one billion
dollars worth of damage
annually in the maizegrowing areas of the USA.
The soil-dwelling larvae of
the beetle eat the aerial
roots, which quickly die back.
Older larvae then penetrate
the heart of the root and from
there move further into the
maize plants. Many infested
plants collapse before harvest
as a result of the root
damage.
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If rootworms do become
resistant to Bt corn, it
“could become the most
economically damaging
example of insect
resistance to a
genetically modified
crop in the U.S.,” said
Bruce Tabashnik, an
entomologist at the
University of Arizona.
“It’s a pest of great
economic significance —
a billion-dollar pest.”
FIELD-EVOLVED INSECT RESISTANCE
BT CROPS: A REVIEW
TO
After more than a decade since initial commercialization of
Bt crops, most target pest populations remain susceptible,
field-evolved resistance has been documented in some
populations of three noctuid moth species:
 Spodoptera frugiperda (Armyworm) , Bt corn ,Puerto Rico,
 Busseola fusca (stem borer) to Cry1Ab in Bt corn in South
Africa,
 Helicoverpa zea (Corn Earworm ) to Cry1Ac and Cry2Ab in
Bt cotton in the southeastern United States.
Factors delaying resistance include:
 Recessive inheritance of resistance,
 Abundant refuges of non-Bt host plants,
 Two-toxin Bt crops deployed separately from one-toxin Bt
crops.
Journal of Economic Entomology- 2009
BT TOXINS
Scientists have modified the
molecular structure of two Bt
toxins, Cry1Ab and Cry1Ac, in
order to overcome resistance. The
novel toxins, Cry1AbMod and
Cry1AcMod, are effective against
five resistant insect species, such
as the diamondback moth, the
cotton bollworm, and the European
corn borer. Cry1AbMod and
Cry1AcMod can be used alone or
in combination with other Bt toxins
for plant protection
New Bacteria Toxins
Against Resistant Insect Pests
Scientists have
developed Bt toxins for
the management of Bt
resistance in European
corn borer and other
crop pests.
B.t. VIP Toxins
In addition to the endotoxins, B. thuringiensis also
produces secreted insecticidal proteins during its
vegetative growth stage, namely, vegetative
insecticidal proteins (Vip).
Vip toxins include two major groups :
Vip1 and Vip2 The combination of Vip1 and Vip2
is highly insecticidal to an agriculturally
important insect, the western corn rootworm
(Diabrotica virgifera), but does not show any
insecticidal activity for any lepidopteran insects
VIP3 TOXIN
The first-identified Vip3 toxin,
Vip3Aa1, is highly insecticidal to
several major lepidopteran pests of
maize and cotton, including the fall
armyworm Spodoptera frugiperda
and the cotton bollworm Helicoverpa
zea, but shows no activity against the
European corn borer Ostrinia
nubilalis, a major pest of maize.
Vip3 contributes to the overall
toxicity of B. t strains
STRATEGIES TO IMPROVE THE INSECTICIDAL
ACTIVITY OF CRY TOXINS FROM BACILLUS
THURINGIENSIS
(i) Chitinase that improves accessibility of the
toxin to the epithelial membrane.
 (ii) Serine protease inhibitors that reduce
degradation of Cry or of toxin-receptors.
 (iii) Introduction of intramolecular cleavage sites
in the toxin that improves binding interaction.
 (iv) Introduction of more binding sites such as the
CR12-MPE-peptide from cadherin receptor or the
Cyt1A toxin.
 (v) Deletion of helix α-1 that induces toxinoligomerization and skip cadherin interaction.

Peptides Vol: 30 589-595 2009
STRATEGIES TO IMPROVE THE INSECTICIDAL
ACTIVITY OF CRY TOXINS FROM B.T
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Monsanto's GMO
sweet corn is
engineered to
tolerate the herbicide
Roundup, and to
produce the insectkilling toxin Bt.
These modifications
have been shown to lead
to some serious health
problems in animals
who eat them.
How can genetically modified
(GM) corn and its attributed
changes in agricultural
practices affect the agroecosystem’s biodiversity and
the economic status and social
life of the farmers?
Philippines 2013
GMO IMPACT ON HUMANITY
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Genetic engineering may disrupt the precise
sequence of a food's genetic code.
Disturbs the functions of neighboring genes,
Can give rise to potentially toxic or allergenic
molecules or even alter the nutritional value of
food produced.
The Bt toxin used in GMO
corn, was recently (2013),
detected in the blood of
pregnant women and their
babies, with possibly
harmful consequences.
GMO Impact on livestock– Philippines 2013
Livestock, especially goats and
cattle that eat GM corn leaves
and stalks, become sickly,
suffering from diarrhea.
Carabaos and cows have been
observed to lose weight and are
sickly.
In Caquilingan, Cordon, Isabela
for example, five carabaos died in
2011. Farmers examined the
carabaos’ stomachs, these were
filled with undigested corn
fodder.
GMO May Cause Genetic Contamination
A GMO crop, once released in
the open, reproduces via
pollination and interacts
genetically with natural
varieties of the same crop.
A GMO crop produces
‘genetic contamination’.
According to a study
published in Nature, one of the
world's leading scientific
journals, Bt corn has
contaminated indigenous
varieties of corn tested in
Oaxaca, Mexico.
GMO Impact on Biodiversity
GMO brought into natural
surroundings may have a toxic
or lethal impact on other living
organisms.
Bt corn destroyed the larvae
of the monarch butterfly.
Many other natural plant and
animal life may be impacted in
the same way.
GMO Impact on Environment – Philippines 2013
Scarce vegetation, acidic soil,
Silted rivers, only few fishes
remain;
Papaya fruits are deformed
Soil is easily eroded especially
during the rainy season.
Stones protrude out from the
soil
and the soil turns red and
clayish.
Corn leaves turn violet.
Published 2013 by
Magsasaka at
Siyentipiko para sa Pagunlad ng Agrikultura
MASIPAG
The
benefits of
GMOs
have been
oversold by
the
companies,
like
Monsanto
and
Syngenta,
that peddle
them.
It has been shown, however, that
insects are fast developing
resistance to Bt as well as to
herbicides, resulting in even
more massive infestation by the
new superbugs.
No substantial evidence exists
that GM crops yield more than
conventional crops.
What genetically engineered
crops definitely do lead to is
greater use of pesticide, which is
harmful both to humans and the
environment.
Public
debates
about
transgenic
crops should
focus more
on the health
and
environment
al benefits
which can be
substantial.

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