Mechanism of Roundup Ready plants, Evaluation of Round-up and current situation

Why Round-up Ready plants are resistant to Glyphosate 

Glyphosate is the active agent in the herbicide Round-up from Monsanto. It is very effective because it inhibits the shikimate pathway enzyme EPSP-Synthase which is found in every plant.[1] End products of the Shikimate pathway are three Amino acids that are necessary for the protein synthesis beneath these there are also intermediates that are used for secondary metabolic compounds.[2] This means, that a plant dies if this synthesis way does not work. 

Chemical Structure of Glyphosate.[3]

Monsanto developed also a method to make plants resistant to their herbicide, this plants are called Round-up ready. With the soil bacteria Agrobacterium sp. strain CP4 can t-DNA from the bacterial Plasmid be transmitted into the Plant Genome, on this DNA is the CP4 ESPS-Synthase from another bacteria encoded, which is resistant against Glyphosate.[4] The function on a molecular level is based on the difference of one Amino acid in the EPSP Synthase, in the CP4 Form it is an Alanine and in the normal Form it is a Glycine. This conformation leads to a condensation of the bound Glyphosate, which has now a high energy level and with that no effect as an inhibitor.[1]

Advantages of Round-up ready Plants 

With Round-up ready plants pesticide applications can be reduced by 37% because there is only glyphosate necessary instead of several other chemicals which are partly much more toxic.[5]  In India the use of Round-up ready plants reduced the cases of pesticide poisoning drastically.[6]

Due to more effective pest control and as a result of it less loss of crop, farming gets more efficient. As a result of a broad literature research of different researches Klümper and Quaim quantify the increase of crop yield with genetically modified plants by 21%. [5]

Disadvantages of Round-up ready Plants 

The use of just a few round-up ready breeds all over the world is problematic because of resistance developments in pests and weeds. If such a resistance develop fast, there can be a huge loss in crop yields. A resistance can easy develop in an environment with a lot of glyphosate.[1] There are already resistant weeds that make the use of other pesticides necessary.[7]

Another controversy is the accumulation and toxicity of Glyphosate in Round-up ready plants. The plants seam to accumulate the pesticide and have a less healthy and nourishing composition.[8] But in this field a lot of different literature with contractionary statements can be found.

Current situation

Today they are six Round-up ready plants: Rape, Cotton, Maize, Soya Bean, Sugar Beet and Wheat. They represent the gross of the genetically modified (GM) plants which grows on 181 million hectares in 28 countries worldwide. 75% of these area is in the USA, Brazil and Argentina. There are oppositions and prohibitions against GM plants in many countries but the proportion on the total agriculture land increases steady since 1996, in 12 of 18 years with double-digit growth rates.[9] 

 

 

This graph shows the development of the area cultivated by GM plants in millions of hectares by country until 2008, the huge proportion of the USA, Argentina and Brazil is eye-catching.[10]

This map shows the legal state of GM plants around the world. But also in the green marked countries a lot of different restrictions exist, in some only scientific use is allowed.[11]

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[1] Funke, T., Huijong, H., Healy-Fried, M.L., Schönbrunn, E. (2006). Molecular basis for the herbicide resistance of Roundup Ready crops. Proceeding of the national Academy of Science of the United States. 103(35), P. 13010-13015.

[2] Herrmann, K.L., Weaver, L.M. (1999).The Shikimate Pathway. Annual Review of Plant Physiology and Plant Molecular Biology. 50, P. 473-503.

[3] Wikimedia Commons: called up 02.03.2015 from: http://commons.wikimedia.org/wiki/File:Glyphosate.svg?uselang=de

[4] Padgette, S.R., Kolacz, K. H., Delannay, X., Re, D.B., LaVallee, B.J., Tinius, C. N.,  Rhodes, W. K., Otero, Y.I., Barry, G.F., Eichholtz, D.A., Peschke, V.M., Nida, D.L., Taylor N.B., Kishore G.M. (1995). Development, Identification, and Characterization of a Glyphosate-Tolerant Soybean Line. Crop Sciences. 35(5), P. 1451-1461.

[5] Klümper, W., Qaim, M. (2014). Meta-Analysis of the Impacts of Genetically Modified Crops. PLoS ONE. 9(11), DOI 101371.

[6] Kouser, S., Qaim M. (2011). Impact of Bt cotton on pesticide poisoning in smallholder agriculture: A panel. Ecological Economics. 70(11), P. 2105-2113.

[7] Hartzler, B. (2008). Managing the Risk of Glyphosate Resistant Weeds. Iowa State University, Weed Science.

[8] Bøhna, T., Cuhraa, M., Traavika, T., Sandenc, M., Fagand, J., Primiceriob, R. (2014). Compositional differences in soybeans on the market: Glyphosate accumulates in Roundup Ready GM soybeans. Food Chemistry. 153, P. 207-215.

[9] James, C. (2014). Global Status of Commercialized Biotech/GM Crops: 2014. ISAAA Brief No. 49. ISAAA: Ithaca, NY.

[10] Wikimedia Commons: called up 02.03.2015 from:

http://commons.wikimedia.org/wiki/File:Gmo_acreage_world_2008.PNG

[11] Wikimedia Commons: called up 02.03.2015 from: http://commons.wikimedia.org/wiki/File:Gm_accept_map.png