Glyphosate resistance

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Glyphosate resistance or glyphosate tolerance describes the resistance of plants and other organisms to the plant protection product and total herbicide glyphosate , mainly known under the brand name Roundup . The effect of glyphosate is based on the blockade of the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) in the plants, which leads to a metabolic interruption and thus to the death of all non-resistant plants.

Glyphosate resistance occurs naturally in numerous bacteria whose bacterial EPSPS differs from that of plants and is therefore not blocked by glyphosate. On the plant genetic engineering different transgenic crop plants have been developed by a registered schleustes bacterial gene from the soil bacterium Agrobacterium tumefaciens also comprise bacterial glyphosate tolerance. The transgenic form of the plants accordingly forms an enzyme analogous to the plant EPSPS with the same function, which is not blocked by the herbicide. As a result, appropriately modified plants become resistant to the plant protection product and enable the plant protection product to be used during the cultivation period. Instead of the usual use of various herbicides for weed control in conventional agriculture, it is possible to use glyphosate alone.

Since glyphosate was originally exclusively produced and sold by Monsanto based on patent law , glyphosate-resistant crops were developed by various companies together with Monsanto. There are now several producers of herbicides containing glyphosate. As a result of the widespread use of glyphosate, many weeds have naturally developed resistance to the herbicide, which in the long term could pose a threat to the success of the plant protection product and the transgenic crops tailored to it.

Characteristics and genetic modification

Glyphosate-resistant plants do not differ in appearance or other properties from the corresponding conventional crops. The only difference is that they produce an enzyme from a bacterium that is different from the plant's analogue enzyme and is resistant to the use of the plant protection product glyphosate. The starting point for the genetic modification are varieties that are supplemented with genetic material from Agrobacterium tumefaciens via green genetic engineering .

Mode of action of glyphosate and glyphosate resistance through the introduction of the resistant bacterial gene Agrobacterium CP4 EPSPS.

The genetically modified plants contain a gene from the CP4 strain of the bacterium, which makes them resistant to the active ingredient glyphosate. Glyphosate is a broad spectrum herbicide that blocks the function of 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) in all parts of the plant and thus blocks the shikimic acid pathway for the production of certain amino acids. More precisely , it inhibits the biosynthesis of the proteinogenic aromatic amino acids phenylalanine , tyrosine and tryptophan . The inserted gene produces a bacterial EPSPS (CP4 EPSPS) that is insensitive to glyphosate.

International use of glyphosate-resistant crops

In some countries there are approvals for the cultivation of the following transgenic crops with glyphosate resistance. The following plants are grown for commercial purposes:

The glyphosate-resistant rapeseed ( Brassica rapa ), potatoes ( Solanum tuberosum ) and wheat ( Triticum aestivum ), which are also approved , are not grown.

Glyphosate resistance is only of significant commercial importance in soybeans, maize, rapeseed and alfalfa. In 2016, the areas cultivated with herbicide-resistant plants worldwide amounted to 161.9 million hectares, with glyphosate resistance making up the majority of herbicide resistance.

Development of resistance in weeds

Amaranthus palmeri ; This common weed has developed glyphosate resistance in several US states.

The extensive and one-sided use of glyphosate, especially on areas with glyphosate-resistant crops, has led to the development of glyphosate-resistant weeds . Through mutations and the high selection pressure , these plants have developed resistances that bridge the metabolic pathways blocked by glyphosate and thus enable the plants to survive despite the use of glyphosate.

The heavy use of herbicide-resistant crops in the USA, Argentina and Brazil has favored this development. Resistance from weeds has also become known in Europe, although hardly any transgenic plants are grown, but glyphosate is also used in conventional agriculture . In 2017, 39 glyphosate-resistant plants were listed in an international database. Due to the widespread use of glyphosate-containing products, this process is expected to intensify in the future. Against this background, measures are recommended that reduce the selection pressure on weeds and a broader range of weed control is recommended. Genetic innovations, novel full-dose herbicide mixtures and alternatives to glyphosate are named as possibilities. Mechanical and precision-engineered arable farming methods as well as plant cultivation practices such as planting and crop rotation planning are to be used to reduce the dependence on glyphosate. This diverse approach is necessary so that the benefits of glyphosate and other herbicides can continue to be used in the future.

Unwanted glyphosate-resistant plants can also arise from crossing the EPSPS gene from resistant transgenic plants into non-resistant cultivated varieties or wild forms. This applies to rapeseed, maize and cotton. In oilseed rape and white ostrich grass, transmission to related species has even been observed. Outcrossing of the EPSPS gene to rapeseed was detected in the Basel Rhine port, although the cultivation of genetically modified rapeseed is not permitted in Switzerland. It seems that conventional wheat from Canada is contaminated with glyphosate-resistant rapeseed and that it was able to settle in Switzerland when it was reloaded in the Rhine port.

Movies

Individual evidence

  1. ^ Center for Environmental Risk Assessment, ILSI Research Foundation: A Review of the Environmental Safety of the CP4 EPSPS Protein. May 26, 2010 ( PDF ( Memento of the original from March 22, 2012 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this note .; 654 kB). @1@ 2Template: Webachiv / IABot / cera-gmc.org
  2. ^ SO Duke, SB Powles: Glyphosate: a once-in-a-century herbicide. In: Pest. Manag.Sci. Volume 64, No. 4, 2008, pp. 319-325. doi: 10.1002 / ps.1518 .
  3. ↑ ISAAA: GM Events with Glyphosate herbicide tolerance. Retrieved August 6, 2017 .
  4. ↑ JR Reichman et al.: Establishment of transgenic herbicide-resistant creeping bentgrass (Agrostis stolonifera L.) in nonagronomic habitats. In: Mol Ecol. Volume 15, No. 13, 2006, pp. 4243-4255. doi: 10.1111 / j.1365-294X.2006.03072.x .
  5. ↑ Canadian Food Inspection Agency: DD1998-21: Determination of the Safety of Monsanto Canada Inc.'s Roundup® Herbicide-Tolerant Brassica rapa Canola Lines ZSR500, ZSR502 and ZSR503. Retrieved August 6, 2017 .
  6. ↑ ISAAA: Global Status of Commercialized Biotech / GM Crops: 2016. (PDF) In: ISAAA Brief No. 52. pp. 92–94 , accessed on August 6, 2017 (English).
  7. ↑ a b T. A. Gaines et al .: Mechanism of resistance of evolved glyphosate-resistant Palmer amaranth (Amaranthus palmeri). In: J Agric Food Chem. Vol. 59, No. 11, 2011, pp. 5886-5889. doi: 10.1021 / jf104719k .
  8. ↑ a b Jerry M Green: The rise and future of glyphosate and glyphosate-resistant crops. In: Pest Management Science. Volume 74, 2018, p. 1035, doi: 10.1002 / ps.4462 .
  9. ^ I. Heap: The International Survey of Herbicide Resistant Weeds. In: weedscience.org , accessed December 12, 2017 (online)
  10. ↑ GU Ryffel: Transgene flow: Facts, speculations and possible countermeasures. In: GM Crops Food. Volume 5, No. 4, 2014, pp. 249-258. doi: 10.4161 / 21645698.2014.945883 .
  11. ↑ J. Schulze et al.: Unexpected Diversity of Feral Genetically Modified Oilseed Rape (Brassica napus L.) Despite a Cultivation and Import Ban in Switzerland. In: PLoS ONE. Volume 9, No. 12, 2014, p. E114477. doi: 10.1371 / journal.pone.0114477 .
  12. ↑ J. Schulze et al .: Low level impurities in imported wheat are a likely source of feral transgenic oilseed rape (Brassica napus L.) in Switzerland. In: Environ Sci Pollut Res Int. Volume 22, No. 21, 2015, pp. 16936-16942. doi: 10.1007 / s11356-015-4903-y .