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APS206: Biotechnology & Food Security > Lecture 8: GM & crop protection: Herbicide tolerance > Flashcards

Lecture 8: GM & crop protection: Herbicide tolerance Flashcards

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1
Q

Threats to crop productivity:

A

-Weeds
-Pests
-Disease
Adverse environmental conditions (drought, frost & salinity)

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2
Q

By far the majority of GM crops approved for use have been…

A

crop protection applications

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3
Q

method behind herbicide tolerance, why do we make them

A
  • create transgenic crops resistant to common herbicides
  • fields cane sprayed with herbicide when the crop is growing
  • weeds killed but crop unaffected
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4
Q

benefits to HT (herbicide tolerance)

A
  • easy for farmers to manage weed problems

- a great commercial opportunity for the Agro companies that can sell both the Ht and the herbicide as a package

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5
Q

Ht can be used alongside ____ to become ‘stacked’

A

alongside Bt - Bacillus thuringiensis toxin (insect tolerance)
Multiple Ht or Bt genes may be incorporated into on crop
-majority of GM maize and cotton are ‘stacked’

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6
Q

Uptake of Bt maize in the Eu (Spain)

A
  • Bt farmers sprayed significantly less insecticide than conventional farmers
  • profit per hectare was increased
  • 5% of the total acreage in 1998 now 30%
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7
Q

uptake of adoption of genetically engineered crops in US is

A

HUGE

-to be adopted so quickly by farmers must get really quick & good response

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8
Q

EU vs USA uptake of Bt maize (& really general)

A
  • Virtually no adoption in EU apart from Spain

- EU trials peaked in 1997 & now dropped - due to EU views

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9
Q

what plant processes do herbicides affect:

A
  • light processes
  • cell metabolism
  • growth cell division
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10
Q

Are herbicide tolerant crops always GM?

A

NO, herbicide tolerant crops are not always GM - but the majority planted today are
-can be simply selected by conventional methods (& therefor not regulated)

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11
Q

Glyphosate is..

A

an excellent herbicide

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12
Q

why is glyphosate a good herbicide?

A
  • non-toxic (Debatable)
  • Breaks down quickly in the soil
  • Acts systemically against plants (sprayed on top will kill underneath as well, kills rhizomes)
  • Acitive agent of ‘Round up’ - out of patent protection
  • INITIALLY little or no resistance to weeds
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13
Q

problems with glyphosate as a herbicide:

A

-use in non-GM application is limited to pre-emergence (field clearance)

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14
Q

‘round up’???

A
  • commercial product, glyphosate key ingredient

- spray & kills weed growing, not seed bank (including weeds)

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15
Q

traditional weed control:

A
  • Ploughing

- -buries weeds and crop residues which then decompose

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16
Q

positives to ploughing:

A
  • aerates the soil

- brings nutrients to the surface

17
Q

negatives to ploughing:

A
  • can increase soil erosion
  • formation of a plough pan –> this affects root development
  • reduces earthworms
  • affects drainage
  • labour intensive for farmers
18
Q

low-till/ no-till agriculture:

A
  • -> NO PLOUGHING

- no disturbance of soil through tillage

19
Q

low-till/ no-till agriculture positives:

A
  • reduces soil erosion
  • reduces fuel costs
  • improves soil structure
20
Q

low-till/ no-till agriculture negatives:

A
  • previous crops & weeds must be controlled

- can lead to increased herbicide usage

21
Q

Glyphosate mode of action:

A
  • glyphosate inhibits EPSPS, essential for the shikimic acid pathway
  • we don’t use this pathway so it doesnt affect us (not toxic)
  • All plants EPSPs are inhibited by Roundup
  • The EPSP enzyme form the soil bacterium Agrobacterium sp. C4 is NOT inhibited
22
Q

engineering resistance to herbicides:

A
  • Find an EPSPs enzyme which is not inhibited by glyphosate
  • engineer plants to contain this enzyme
  • plants become resistant to the herbicide
23
Q

are there weeds resistant to glyphosate

A

resistant weeds very unlikely but is happening

24
Q

application of resistance to herbicides:

A
  • fields can be sprayed post-emergence
  • ‘environmentally friendly’ herbicides can be used
  • soil tillage reduced minimising soil losses & run-off
25
Q

potential problems with application of resistance to herbicides:

A
  • transfer of genes to weed species
  • crops can themselves become weeds
  • increased selection pressure leads to weed resistance
  • more herbicide may be applied
  • improved weed control may affect wildlife
  • same company owns seed & herbicides
26
Q

Round up ready crops: Commercialised by ____ in:

A
  • Monsanto in..
  • cotton
  • maize
  • soybean
  • -monsanto sell the seed and the herbicide (discourage competitors)
27
Q

timeline for bringing Roundup ready soybean to market:

A

14 years from first transgenic plant to US commercialisation (source Monsanto)

28
Q

how weeds evolve resistance:

A
  • Herbicide application is a powerful selection pressure
    1) Herbicide sprayed
    2) Resistant plant survives & sets seed
    3) Herbicide is used on weeds with more resistant plants in population
    4) eventually majority of plants are resistant
  • –Repeatedly applying the same herbicide exerts the same selection pressure over & over
29
Q

resistance to glyphosate is

A

RISING e.g. Argentina in GM soybean

30
Q

problem: same company owns seed & herbicides

A

GURTS complication–> companies want to make seed that produce crops that don’t produce viable offspring, so farmers can’t use their crops for future crops, company has full control

31
Q

how do we solve the problem of weed resistance?

A

1) produce GM plants resistant to a range of herbicides

2) Stack resistance genes

32
Q

how do we solve the problem of weed resistance? produce GM plants resistant to a range of herbicides:

A
  • use can be rotated

- weeds may be less likely to form resistance

33
Q

GM plants resistant to herbicides have been ___

A

DEVELOPED

34
Q

how do we solve the problem of weed resistance? STACK RESISTANCE GENES

A
  • if the probability of finding a resistant mutant is 10^10
  • then the probability of finding a mutant resistant resistant to 2 herbicides will be 10^20
  • but the maths is wrong if you already have population of weed resistant to one herbicide
  • multiple resistance has been found some weeds
35
Q

whats the way forward to solving the problem of Herbicide-resistant weeds

A
  • new herbicide resistant crops

- integrated weed management

36
Q

whats the way forward to solving the problem of Herbicide-resistant weeds: NEW HERBICIDE RESISTANT CROPS

A 
SHORT TERM: 
-intensification of selection pressure 
increase in herbicide use 
-sole use of herbicides 
LONG TERM: 
-increase in resistant weeds 
-increase in non target effects 
-fewer control options
37
Q

whats the way forward to solving the problem of Herbicide-resistant weeds: INTEGRATED WEED MANAGEMENT

A 
SHORT TERM:
-reduction in selection pressure 
-decrease in herbicide use 
-use of multiple practices 
LONG TERM: 
-reduction in the severity of resistant weeds 
-environmental quality increases 
-preservation quality increases 
-preservation of knowledge
38
Q

integrated Weed management methods of action:

A
  • crop rotation
  • cover crops
  • competitive crop cultivars
  • appropriate use of tillage
  • more targeted herbicide application to reduce weed populations
  • combining crop rotation & appropriate herbicide use has additive benefits

APS206: Biotechnology & Food Security (19 decks)

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