The document discusses transgenic and herbicide resistant crops. It defines transgenic crops as plants modified through genetic engineering by transferring genes between organisms. Herbicide resistant crops are made resistant to herbicides either through genetic engineering or cell/tissue culture mutations. The document discusses how glyphosate and glufosinate herbicides work, mechanisms of resistance in crops, benefits and risks of herbicide resistant crops, and management strategies to address herbicide resistant weeds.

1. By
Khushi Maniktala
A005116520017

2. WHAT IS A TRANSGENIC CROP?
• A transgenic plant is a modified organism where genes are transferred
from one organism to another through genetic engineering techniques”.
The purpose of producing a transgenic plant is to obtain a species that
has ideal traits, high yield and quality.
WHAT IS A HERBICIDE RESISTANT CROP?
• The term 'herbicide-resistant crop' (HRC) describes crops made
resistant to herbicides by either transgene technology or by selection in
cell or tissue culture for mutations that confer herbicide resistance.
HRCs are also referred to as herbicide-tolerant crops
• Herbicide-resistant crops (HRC) have been available since the mid-
1980s; these crops enable effective chemical control of weeds, since
only the HRC plants can survive in fields treated with the
corresponding herbicide

3. • Weeds are unwanted & useless plants that grow along
with the crop plants .
• Weeds compete with the crops for light & nutrients,
besides harboring various pathogens .
• So it is estimated that the worlds crop yield is reduced by
10 – 15 % due to the presence of weeds.
• To tackle the problem of weeds , modern agriculture has
developed a wide range of weed killers : herbicides

4. • An ideal herbicide is to posses the following characters : -
1. Capable of killing weeds with out affecting crop plants
2. Not toxic to animals & microorganisms
3. Rapidly trans located with in the target plant
4. Rapidly degraded in the soil
EXAMPLE:
• 2, 4-D ( 2,4-Dichloropnenoxy Acetic Acid): It is selective translocated herbicide and most widely
used to control dicot weeds
• Glyphosate
• Tornado
• Cornex

5. HOW DO THESE HERBICIDES WORK?
Such herbicides interfere with plant agricultural production and inevitably cause
the plant to die by targeting important enzymes in the biological process.
WHY DEVELOP HT CROPS?
A newly developed capability to develop some resistance to broad spectrum
herbicides, especially glufosinate and glyphosate, which will control the majority
of other green plants. These two herbicides are effective in controlling weeds,
have a negligible effect on animal life directly, and are non-persistent. They are
among the safest agrochemicals to use and quite effective.
They are, regrettably, equally potent against plants used for agriculture. In order
to some degree tolerate these pesticides, HT crops are created.

6. DEGRADATION
OF HERBICIDE IN
PLANT
CHANGES IN
TARGET PROTEIN
USE OF
HERBICIDE
RESISTANT GENE
OVEREXPRESSION
OF TARGET
PROTEIN
• Glyphosate oxidoreductase gene
It cleaves the C-N bond in glyphosate
hence no activity
• Glyphosate N-acetyl transferase
acetylation of glyphosate hence it gets
deactivated
• CP4-EPSPS Gene
Isolated from agrobacterium ,since it is
mutated form it wont be able to bind to
and hence pathway remains unaffected

7. • Glyphosate is an herbicide. It is applied to the leaves of plants to kill both broadleaf
plants and grasses
• Glyphosate is a non-selective herbicide, meaning it will kill most plants. It prevents
the plants from making certain proteins that are needed for plant growth.
Glyphosate stops a specific enzyme pathway, the shikimic acid pathway. The
shikimic acid pathway is necessary for plants and some microorganisms.
• It is a glycine derivative , that affects the synthesis of aromatic amino acid (
phenylalanine , tyrosine and tryptophan )pathway occurring in chloroplast
• Favorable physicochemical characteristics, low cost, tight soil sorption, application
flexibility, low mammalian toxicity, and availability of GR crops have helped make
glyphosate the most widely used herbicide in the world

8. MECHANISM :
Glyphosate is a broad
spectrum herbicide ,
effective against 76 of
worlds worst 78 weeds
Shikimic acid pathway results
in the formation of aa, phenols
, metabolites . Glyphosate
binds with EPSPS & blocks
metabolism . Thus
biosynthesis of aa & other
products are inhibited
it works on EPSP synthase
enzyme and act as a
COMPETITIVE INHIBITOR
which stops the process
So cell division & plant
growth are blocked

9. • Glufosinate is a nonselective, broad-spectrum foliar
herbicide with no soil residual soil activity that inhibits
glutamine synthetase an enzyme that catalyses the
conversion of glutamate plus ammonium to glutamine as
part of nitrogen metabolism
• However, glufosinate is used at higher rates and has
historically been more expensive than glyphosate. Cost and
more restrictive application timing relative to weed size are
probably its greatest disadvantages compared to glyphosate
• Glufosinate is faster acting and controls key broadleaf
weeds such as morningglories (Ipomoea spp.), hemp
sesbania (Sesbania herbacea (P. Mill.) McVaugh),

11. • Roundup Ready is the Monsanto trademark for its patented line of genetically modified crop seeds
that are resistant to its glyphosate-based herbicide.
• In 1996, genetically modified Roundup Ready soybeans resistant to Roundup became
commercially available, followed by Roundup Ready corn in 1998. Current Roundup Ready crops
include soyabean , maize (corn), canola, sugar beets, cotton, and alfalfa, with wheat still under
development.
• The first Roundup Ready crops were developed in 1996, with the introduction of genetically
modified soybeans that are resistant to Roundup. These crops were developed to help farmers
control weeds. Because the new crops are resistant to Roundup, the herbicide can be used in the
fields to eliminate unwanted foliage
HOW ARE THEY MADE?
• Roundup Ready crop lines contain a gene derived from Agrobacterium sp. strain CP4, encoding a
glyphosate-tolerant enzyme, the so-called CP4 EPSP synthase
• Expression of CP4 EPSP synthase results in glyphosate-tolerant crops, enabling more effective
weed control by allowing post emergent herbicide application

12. TABLE: Herbicide Types Commonly Used in Corn, Soybeans, and Cotton and Their Application Method, Preemergence
(PRE) or Postemergence (POST), with Respect to Crop
herbicide type corn soybean cotton
glyphosate (G) PRE and POST PRE and POST PRE and POST
glufosinate (H) POST POST POST
ALS inhibitor (B) PRE and POST PRE and POST PRE and POST
synthetic auxin (O) PRE and POST PRE and POST PRE and POST

13. • Superior weed control, which results in increased crop yields
• Flexibility: Weeds may be controlled at a later stage of the plant's
development.
• Fewer sprays used throughout a season
• Fewer fuels used (because of less spraying)
• Reduced soil compactness (because of less need to go on the land
to spray)
• Use of low-toxicity substances that are inactive in soil
• Utilizing no-till or conservation-till methods, which helps soil
organisms and structure.

14. • Issues with contaminated grain
• Segregation and spread of characteristics
that resist herbicides
• Adoption in the market and a greater
reliance on herbicides to manage weeds.
• Cross-pollination risk

15. Tactic Benefit risk Potential impact
herbicide rotation reduced selection pressure,
control HR weeds
lack of different MOAs,
phytotoxicity, cost, limited
weed spectrum of
alternatives
Excellent
herbicide mixtures reduced selection pressure,
improved control, broader
weed spectrum
poor activity on HR weed
species, increased cost;
potential phytotoxicity
Excellent
mechanical weed control
strategies
decreases selection
pressure; consistent
efficacy, relatively
inexpensive
increased time required,
high level of management
skill needed, additional
tactics needed, potential
for crop injury
Poor to fair
TABLE: Assessment of Commonly Used Tactics for Herbicide-Resistant Weed Management

16. crop resistance trait trait gene first sales
cotton Glyphosate
glufosinate
cp4 epsps
bar
1996
2005
corn Glyphosate
glufosinate
two cp4 epsps
Fat
2001
1996
soybean Glyphosate
glufosinate
cp4 epsps
Fat
1996
2005
 Weed management dramatically changed with the widespread adoption of GR crops. Using glyphosate in
GR crops made weed management too simple and convenient

18. • https://catalog.extension.oregonstate.edu/pnw437/html
• https://pubs.acs.org/doi/10.1021/jf101286h
• https://www.beyondpesticides.org/resources/genetic-
engineering/herbicide-tolerance
• https://www.britannica.com/science/herbicide-resistant-crop
• https://www.ars.usda.gov/ARSUserFiles/60663500/publications/redd
y/reddy%20and%20nandula_2-12_ija_57-1-7.pdf