Toxicity vs' Genetic engineering

1
Toxicity vs. Genetic engineering

• Management of GMHT-crops and conventional crop
  management

2
Atrazine

• 2-Chlor-4-ethylamino-6-isopropylamino-1,3,5-triazi
  n
• C8H14CIN5
• Effect inhibition of photosynthesis in weeds
• Persistent to biological degradation
• Toxic to waterorganism
• Not lethal for mammals
• Max. content in food plants 0,1 mg/kg
• Max. content in maize 1 mg/kg

3
Problem Contamination of surface water and
drinking water

• Ban on triazine-herbicides
• Germany March 1991
• Austria 1995
• EU 2003

4
Broad-spectrum herbicidessince 1980

• Difference to common herbicides
• Higher efficiency
• Faster degradation
• Better toxicological qualities
• PROBLEM not selective cause damage to weed as
  well as to cultivated plants

5
Developement of GMHT-plants

• GMHT - genetically modified herbicide tolerant
• Genetic engineering
• Changes in the DNA cause resistence to
  herbicides
• GMHT-practice modified plant and herbicide as a
  package

6
Glufosinate

• Glufosinate active substance of a
  broad-spectrum-herbicide synthetical copy of
  the aminoacid phosphinothricin produced by
  Streptomyces viridochomogenes
• Effect inhibition of the glutamine-synthetase
  (important enzyme in Nitrogen-cycle of plants)
  plant dies
• Herbicide-tolerance is reached by gene-transfer
  from the bacterium to the plant
• The transfered gene encodes for the enzyme
  phophinothricin-acetyl-transferase harmless
  degradation of glufosinate

7
UK Farm-Scale Evaluations

• Compared the effects on biodiversity of
  management of GMHT-crops with conventional crop
  management for 3 years
• 60 to 70 fields - planted with beet, maize and
  rape
• Each field split half conventional variety -
  half GMHT variety
• GM-maize and GM-rape tolerant to glufosinate
• GM-beet tolerant to glyphosphate

8
Parameters

• Weed density
• Biomass (weight of weeds collected from a fixed
  area)
• Seed rain (seeds falling from weeds)
• Seed bank (seeds left in soil)
• Reproductive rates

• Influence on
• Invertebrates
• Detritivores and herbivores
• Epigeal and aerial species
• Bees, butterflies, beatles, etc.
• Birds, mammals,...

9

• GMHT crops received less herbicide-active
  ingredient per crop, with later and fewer
  applications than the conventional varieties
• GM crops benefit the environment ???

10
GMHT beet and rape

• Weed density decreased
• Biomass 1/6 to 1/3 of that in conventional plots
• Seed rain reduced, effects on the seed bank in
  the following year
• Seed bank long time influence on biodiversity
  and food availability
• Reproductive rates were by about 50 for most
  weed species

11
Effects

• reduced weed abundance in GMHT crop management
• abundance of invertebrates on the soil surface
  is lower in GMHT beet and rape
• reduction of food for mammals, birds, bees and
  butterflies
• decrease of nutrients recycling within the soil
• increase of detritivores under GMHT management

12
GMHT maize

• Results seem to be positive
• Higher weed density
• Higher late-season biomass
• Increase of seed rain
• corresponding effect on invertebrates higher
  abundance on the soil surface
• greater plant cover and flowering in field
  margins

13

• Apparent benefits of GMHT maize are likely
  accounted for by the relative toxicity of
  atrazine used on most of the conventionally
  treated maize
• Atrazine management causes lower weed
  densities and biodiversity than GMHT crop
  management!

14
Conclusion

• GMHT crop management is less harmfull to soil,
  water and mammals
• Long term effects caused by massive changes in
  biodiversity are not assessable