This document discusses weed management and biotechnological interventions for weed control. It begins by defining a weed and outlining the problems caused by weeds, including crop yield losses. It then discusses conventional weed control methods like mechanical, cultural, chemical and biological control. The document focuses on developing herbicide-resistant crops through biotechnology by introducing genes that confer resistance to herbicides like glyphosate and glufosinate. It also discusses improving biocontrol agents and using transgenic allelopathy in crops to better compete with weeds. The advantages and disadvantages of transgenic herbicide resistance are outlined.

1. JUNE 5TH
WORLD ENVIRONMENT
DAY

3. WEED
A weed is a plant considered undesirable in a
particular situation, "a plant in the wrong place”.
It causes
•Yield losses
•Low output efficiency
•Extra Labor costs
•Environmental issues through herbicide usage etc.

4. THE TIME A WEED SPENDS IN CONTACT WITH A CROP
PLANT CAN HAVE A DRAMATIC EFFECT ON YIELD.

5. ALL WEED PLANTS IN CULTIVATED
FIELD GIVING HARM RATHER THAN
BENEFIT
CROP TYPE PRODUCTION LOSSES
CEREALS 433.903 54.349
VEGETABLES 201.691 23.718
FRUITS 66.567 2.462
WINEYARD 50.697 7.909
World wide Production and Losses due to Weeds (Million tons) (Duke et al.
2013)

6. BIOTECHNOLOGICAL
INTERVENTIONS ON WEED
MANAGEMENTSHELVY S
2011-09-123

7. INTRODUTION
oTransgene technology has been used to generate
herbicide-resistant crops, which have profound effects on
the herbicide market.
oSame technology has the potential to make crops better
competitors with weeds through improving competitive
traits or making the crop more allelopathic. And has wide
application in agronomy and horticulture by transgenic bio
control agents.
oMolecular Systematics helps to provide information on
weed identification and characterisation.

8. Chemical Method Mechanical Method
Cultural Method Biological Method
C
O
N
V
E
N
T
I
O
N
A
L
W
E
E
D
C
O
N
T
R
O
L

9. CONVENTIONAL WEED
MANAGEMENT
Mechanical
All common tillage practices before and after planting
crops, including frequent cultivation at precise times
using specialized implements, deep plowing to bury
weed seed banks, hand plucking etc.
Cultural
Includes fallowing land, stale seedbeds, adjusting
seeding dates, transplanting instead of seeding,
mowing, and smother cover crops, etc.

10. Chemical
 Use of Chemical Herbicides
Biological
 Introduction of a living organism to control a weed species.
(Bio control agents )

11. WHY BIOTECHNOLOGY
A national Research Council report acknowledge “GE
Crop technology has produced substantial net
environmental and economic benefits to farmers
growing GE products over using non GE varieties in
conventional production system.
Because of concerns of health, safety, and
sustainability, there is a growing interest in reducing
chemical weed control measures.

12. BIOTECHNOLOGICAL APPROACHES
FOR WEED MANAGEMENT
 Development of Herbicide resistant crops
 Improvement of Biocontrol Agents
 Development of Transgenic Allelopathy in crops
 Characterization of weeds using Molecular
systematics

13. DEVELOPMENT OF
HERBICIDE RESISTANT
CROPS

14. TYPES OF HERBICIDES BY CHEMICAL
FAMILIESChemical Family Affected System Target Proteins Spectrum
Triazines (atrazine,
ametryne, cyanazine,
prometryn, simazine
Photosystem II, electron
transport from QA to QB
D-1 protein, product of
psbA gene
Total
Sulfonylurease,
imidazolinones,
triazolopyrimidines
Amino acid synthesis Acetolactate synthetase
(ALS)
Selective
Aryloxypenoxypropiona
tes (AOPP),
cyclohexanediones
Lipid Synthesis Acetyl coenzyme
Acarboxylase (ACCase)
Selective
Glyphosate (N-
phosphonomethyl)glyci
ne
Amino acid Synthesis 5-enolpyruvyl-
shikimate-3-phosphate
synthetase (EPSPS)
Total
Bromoxynil Photosystem II D-1 protein Total
Phenoxycarboxylic
acids (eg: 2,4-D)
Unknown Unknown Selective
Glufosinate
(Phosphinothricin, PPT)
Amino acid synthesis Glutamine synthetase Total

15. BIOTIC RESISTANCE DEVELOPMENT IN
CULTIVATED CROPS IN INDIA
Acharya N. G. Ranga Agricultural
University

16. PROBLEMS IN APPLICATION OF
HERBICIDES
•Lack of tolerance to the chemical by one or more of the
major world crops, e.g. Rice, Maize, Soybean, Wheat etc.
•Use of multiple types of herbicides to broaden the spectrum
of the affected weeds, which in turn increase the possibility
that the crop is injured also.
•Continuous use of one herbicides leads to the development
of super weed.

17. HERBICIDE RESISTANCE IN PLANTS
Herbicide resistance is the ability, trait or
quality of a population of plants within a
species or larger taxon, to withstand a
particular herbicide at a dosage that is
substantially greater than the wild type of that
plant is able to withstand.

19. Normal Crop
Herbicide resistant Crop

20. WHY HERBICIDE RESISTANT
PLANTS ?
Total herbicides, when applied, kills all the plants in
the field including culture plant
Selectivity of a herbicide is an important criteria.
Increase selectivity
• Maximum effect on herbs
• Minimum effect on culture plant

21. HERBICIDE RESISTANT CROPS
Gene for herbicide resistance can be inserted into crop plant’s
chromosomal DNA.

22. GLYPHOSATE
Glyphosate (N-(phosphonomethyl)glycine) is a broad-spectrum
systemic herbicide used to kill weeds. Such as broad leaf weeds and
grasses.
It was discovered to be an herbicide by Monsanto chemist John E.
Franz in 1970.
Monsanto brought it to market in the 1970s under the trade name
Roundup and Monsanto's last commercially relevant United States
patent.
Glyphosate's mode of action is to inhibit a plant enzyme involved in
the synthesis of the aromatic amino acids.
It inhibits a critical enzyme of the shikimate pathway, 5-
enolpyruvylshikimate-3-phosphate synthase (EPSPS).

24. GLYPHOSATE RESISTANT CROPS
Presently, glyphosate-resistant and glufosinate-resistant crops are
the only two transgenic HRCs commercially grown.
Glyphosate-resistant (GR) crops represent more than 80% of the 120
million ha of transgenic crops grown annually worldwide. (Duke et al.
2012)
One to two timely applications of glyphosate, pre-emergence
herbicides can provide effective control of a broad spectrum of
weeds.
The gene encoding an enzyme that cleaves the C-N bond of
glyphosate (glyphosate oxidase; GOX) was isolated from E. coli.

25. Molecular Approach for
the development of
Glyphosate Resistant
Crops

26. ADOPTION RATE OF GLYPHOSATE-RESISTANT CROPS IN THE
UNITED STATES.

27. GLUFOSINATE
Glufosinate or its ammonium salt DL-phosphinothricin is an active
ingredient in several nonselective herbicides such as Basta, Rely,
Finale, Ignite, Challenge, and Liberty.
It interferes with the biosynthetic pathway of the amino acid
glutamine and with ammonia detoxification.
Phosphinothricin is an glutamine synthetase inhibitor that binds to
the glutamate site. Glufosinate-treated plants die due to a buildup of
ammonia and corresponding decrease in pH in the thylakoid lumen,
leading to the uncoupling of photophosphorylation.

28. GLUFOSINATE RESISTANCE
Glufosinate-detoxifying genes bar and pat were isolated and
characterized from Streptomyces hygroscopicus and S.
viridichromogenes, respectively (Thomson et al. 1987)
Both bar and pat were demonstrated to code for a 21-kDa
phosphinothricin acetyltransferase (PAT)
 is required for the production of an essential intermediate (N-
acetyldemethylbialaphos) in the biosynthesis of the tripeptide
bialaphos.
Acetylation of the free amine on glufosinate makes the molecule too
bulky to fit in the active site of Glutamine Synthetase.

29. CROP PLANTS TRANSFORMED WITH THE BAR OR PAT
GENE CONFERRING TOLERANCE TO GLUFOSINATE
Crop Species
Alfalfa Medicago sativa
Broccoli Brassica oleracea
Canola Brassica napus
Carrot Daucus carota
Corn Zea mays
Cotton Gossypium hirsutum
Lettuce Lactuca sativa
Melon Cucumis melo
Potato Solanum tuberosum
Rice Oryza sativa
Sugarbeet Beta vulgaris
Sugarcane Saccharum officinarum
Tobacco Nicotiana tabacum
Tomato Lycopersicum esculentum
Wheat Triticum aestivium

30. BROMOXYNIL
Bromoxynil is a nitrile herbicide, trade names include Brominal,
Bromotril, Bronate, Buctril, Certrol B, Litarol, M&B 10064, Merit,
Pardner, Sabre, and Torch.
It is used for post-emergent control of annual broadleaf weeds.
It works by inhibiting photosystem II of photosynthesis.

31. BROMOXYNIL RESISTANCE
Gene encoding broxynil resistance was isolated from
Rhodococcus species with nitrilase enzyme production.
The gene doesnot impart resistance to other classes of PS ii
inhibiting herbicides, thus linking the transgenic crop to a
specific herbicide.
The first introduced commercial herbicide-resistant crop (HRC)
was bromoxynil-resistant cotton.
Bromoxynil-resistant canola became available to Canadian
farmers in 1999 but has had only limited success.

32. SULFONYLUREA AND
IMIDAZOLINONE RESISTANCE
They are very potent inhibitors of the acetolactate synthase (ALS), a
key enzyme of branched chain amino acid synthesis.
Commercially available ALS inhibitor-Resistant crops have been
produced by mutation.

33. Commercially available Herbicide crops in world

34. ROUNDUP READY® CANOLA
CROP MANAGEMENT PLAN
(CMP)Objective : The Roundup Ready
canola Crop Management Plan details,
strategies that can be implemented on-
farm to manage risks to the integrity of
grain supply-chains and the
sustainability of agricultural production.

35. Understanding glyphosate resistance risk
Resistance management principles for Roundup
Ready canola
Pre planting, In crop and Post harvest activities
Weed control rating etc.

36. ADVANTAGES OF TRANSGENIC
HERBICIDE RESISTANCE
oIncreased yield performance
oBroader spectrum of weeds controlled
oReduced crop injury
oReduced herbicide carry-over
oUse of herbicides that are more environmentally friendly
oNew mode of action for resistance management
oCrop management flexibility and simplicity

37. DISADVANTAGES OF TRANSGENIC
HERBICIDE RESISTANCE
*Single selection pressure and weed resistance
*Shifts in weed species
*Gene flow and contamination of organic crops

38. IMPROVEMENT OF
BIOCONTROL AGENTS

39. NEED OF BIOTECHNOLOGY
 A host-specific hypervirulent pathogen that controls a major
row-crop weed to the extent that farmers require, (i.e. similar
to control achieved with a chemical herbicide)
 The ecological balance achieved with classical agents in an
extensive pasture or forestry situation cannot suffice in
intensive agriculture.
 A wide variety of transgenic viruses, bacteria, and fungi have
been successful in controlling many of weed sps. (Vurro et al.
2001a).

40. MYCOHERBICIDE
Many fungi of native origin are pathogrnic to specific species of
weeds. Such fungi are used to kill the weeds selectively and eliminate
them from the area. These weed-killing fungi are called
mycoherbicides.
Eg : Alternaria alternata is used to control the weed Water hyacinth
developed by india

41. BIOTECHNOLOGICALLY UPGRADING
MYCOHERBICIDES
Organisms can potentially be modified to increase
pathogenicity by transformation with genes for virulence from
other species, by increasing the endogenous expression of
genes, or by transfer from other organisms by protoplast
fusion (Gressel 2002; Harman and Stasz 1991; Harman and
Donzelli 2001; Kistler 1991).

42. Biocontrol agents could also be engineered to convey
genes that convert pro-herbicides to herbicides.
This would then allow the mycoherbicide to be applied
together with the pro-herbicides.
This would have distinct advantages with weeds with
underground propagules such as Cyperus that regrow
after foliar killing.
As the biocontrol agent is specific to the weed, it
would not cause the conversion of pro-herbicide to
herbicide in crops cultivation

43. Another approach to enhancing the efficacy of a
mycoherbicide is to introduce genes that will affect
phytohormone levels in the target plant.
Cohen et al. (2002) introduced two genes encoding
enzymes of the auxin pathway into the plant
pathogens Fusarium oxysporum and F.
arthrosporioides, resulting in transformants that
synthesized high levels of auxin.
These transformants were more virulent to the
parasitic weed Orobanche aegyptiaca than wild-type
pathovars, presumably because the high auxin levels
produced effects like 2,4-D.

44. A weakly mycoherbicidal strain of Colletotrichum coccodes, Virulence was increased nine
fold and was more rapidly effected. By introducing NEP 1 encoding a phytotoxic protein.

45. DEVELOPMENT OF
TRANSGENIC
ALLELOPATHY IN CROPS

46. ALLELOPATHY
Allelopathy is a biological phenomenon by which an
organism produces one or more biochemicals that
influence the growth, survival, and reproduction of
other organisms. or “Plant-produced herbicides”

48. Three methods for using allelopathy in weed
management:
–As a winter cover crop, with residue providing
allelopathic compounds
–As a living mulch during the cropping season
–As an isolated compound from an allelopathic plant,
applied as an herbicide

49. METHOD OF APPLICATION
In most cases where phytotoxic allelochemicals have been
identified, and there is limited knowledge about their
biosynthetic pathways.
There are several ways to do expression profiling, two major
approaches are:
mRNA is isolated from tissues that are and are not expressing
the trait of interest. These pools of mRNAs are then compared.
An expressed sequence tag (EST) database is created for the
tissue/organ where the allelochemicals is highly expressed.
 The identified gene of interest for the production of
allelochemicals are transferred to the desired crop plant.

50. A regulation of the biosynthesis occurs and the release rate to
enhance the release of allelochemicals or to prolong the period
of release of allelochemicals has been suggested
Use of biotechnological transfer of allelopathic traits between
cultivars of the same species or between species has also been
proposed.

51. Genetic engineering offers the possibility of
generating crop varieties with enhanced
allelopathy by enhancing gene expression of
existing allelochemicals pathways or
introducing genes for synthesis of new
allelochemicals into crops efficient.

52. Identified nine QTL(Quantitative trait loci)s controlling allelopathic
effects of rice on E. crusgalli on chromosomes 1, 2, 3, 4, 5, 8, 9 and

53. CLASSIFICATION OF ORYZA SPS.
Classification of wild Oryza sps. and the feral forms of
cultivated rice was difficult.
Cultivated Rice Weedy Rice

54. MOLECULAR SYSTEMATICS
Molecular systematics has been of great assistance
and has often provided the decisive data in many
cases on whether two similar species were actually
one, or were separate, or were hybrids.

55. PROBLEMS WITH MORPHOLOGICAL
DATAo Convergence and parallelisms
o Phenotypic vs. genotypic differences
o Evaluation of homology
o Misinterpretation of change or polarity
o Limitation on number of characters

56. ADVANTAGES OF MOLECULAR
SYSTEMATICS
o Can obtain phylogenetically informative characters from any
genome of the
organism
o Assumes that genomes accumulate molecular changes by
lineage, as morphological characters do
o Possibly greater assurance of homology with molecular data
(less likely to misinterpret characters.
o Principal advantages are the much greater number of
molecular characters available & greater comparability across
lineages

57. The classical taxonomy is so complicated that It
was found using molecular techniques such as
phylogenetic analysis etc., many accessions of wild
rice species were corrected in the collection of
International Rice research (Martin et al., 1997)

58. TYPES OF MOLECULAR DATA
DNA Sequences
DNA Restriction Sites : RFLPs
Allozymes : Different forms of proteins
Microsatellites : DNA regions with tandem repeats.
RAPDs : Random amplification of polymorphic DNA
AFLPs : Amplification Fragment Length polymorphism

61. CONCLUSION
Transgenic crops are strongly impacting weed
management choices. They offer the farmer a
powerful new tool that, if used wisely, can be
incorporated into an integrated pest management
strategy that can be used for many years to more
economically and effectively manage weeds.

62. REFERENCE
Amsellem, Z., Cohen, B.A., and Gressel, J. 2002. Engineering hypervirulence
in a mycoherbicidal fungus for efficient weed control. Nat. Biotechnol. 20:
1035-1039
Gressel, J. 2000. Molecular biology of weed control. Transgenic Res. 9: 355-
382
Khanh, T.D., Linh, L.H., Linh, T.H., Quan, N.T., Cuong, D.M., Hien, V.T.T.,
Ham, L.H., Trung, K.H. and Xuan, T.D. 2013. Integration of Allelopathy to
Control Weeds in Rice. Herbicides – Curr. Res. and Case Studies in Use. 10:
57-112
Roush, T. R. 2012. Biotechnology and weed management. In: Rowe, B.,
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Results for Agriculture. Proceedings of the 10th Australian Agronomy
Conference, Hobart, Tasmania, pp. 15-19
Song, Z.J., Wang, Z., Feng, Y., Yao, N., Yang, J. and Lu, B.R. 2015. Genetic
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63. THANK YOU