In 1996, genetically modified Roundup Ready soybeans resistant to Roundup became commercially available, followed by Roundup Ready corn in 1998. Roundup Ready soybeans patent expired in 2014. Current Roundup Ready crops include soy, maize (corn), canola, sugar beets, cotton and alfalfa, with wheat still under development. Additional information on Roundup Ready crops is available on the GM Crops List. As of 2005, 87% of U.S. soybean fields were planted with glyphosate resistant varieties.
While the use of Roundup Ready crops has increased the usage of herbicides measured in pounds applied per acre, it has also changed the herbicide use profile away from atrazine, metribuzin, and alachlor which are more likely to be present in run off water.
An injunction in the case of Center for Food Safety v. USDA in September, 2010 prevented farmers from planting Roundup Ready sugar beets across the United States until a remedial environmental impact report could be filed, prompting some fear of a sugar shortage.
Some microorganisms have a version of 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS: EC 22.214.171.124, 3-phosphoshikimate 1-carboxyvinyltransferase; 5-enolpyruvylshikimate-3-phosphate synthetase; phosphoenolpyruvate:3-phosphoshikimate 5-O-(1-carboxyvinyl)-transferase) that is resistant to glyphosate inhibition. The version used in genetically modified crops was isolated from Agrobacterium strain CP4 (CP4 EPSPS) that was resistant to glyphosate. The CP4 EPSPS gene was cloned and inserted into soybeans. The CP4 EPSPS gene was engineered for plant expression by fusing the 5' end of the gene to a chloroplast transit peptide derived from the petunia EPSPS. This transit peptide was used because it had shown previously an ability to deliver bacterial EPSPS to the chloroplasts of other plants. The plasmid used to move the gene into soybeans was PV-GMGTO4. It contained three bacterial genes, two CP4 EPSPS genes, and a gene encoding beta-glucuronidase (GUS) from Escherichia coli as a marker. The DNA was injected into the soybeans using the particle-acceleration method or "gene gun". Soybean cultivar A54O3 was used for the transformation. The expression of the GUS gene was used as the initial evidence of transformation. GUS expression was detected by a staining method in which the GUS enzyme converts a substrate into a blue precipitate. Those plants that showed GUS expression were then taken and sprayed with glyphosate and their tolerance was tested over many generations.
In 1999, a review of Roundup Ready soybean crops found that, compared to the top conventional varieties, they had a 6.7% lower yield. This so called "yield drag" follows the same pattern observed when other traits are introduced into soybeans by conventional breeding. Monsanto claims later patented varieties yield 7-11% higher than their poorly performing initial varieties, closer to those of conventional farming, although the company refrains from citing actual yields. Monsanto's 2006 application to USDA states that RR2 (mon89788) yields 1.6 bu less than A3244, the conventional variety that the trait is inserted into.
- "Monsanto Company History". Monsanto.com. 2008-11-03. Archived from the original on 2008-04-23. Retrieved 2010-08-22.
- "Monsanto Will Let Bio-Crop Patents Expire". Business Week. January 21, 2010. Retrieved 25 January 2010.
- "Monsanto Genuity Roundup Ready canola trait". Genuity.com. 2008-11-03. Retrieved 2010-08-22.[dead link]
- "Monsanto Genuity Roundup Ready sugarbeets trait". Genuity.com. 2008-11-03. Retrieved 2010-08-22.[dead link]
- ISSAA GM database approval entry for alfalfa event MON-00101
- ISAAA GM approval database entry for wheat event MON71800
- International Service for the Acquisition of Agri-Biotech Applications - GM Crop List
- USDA/APHIS Environmental Assessment — In response to Monsanto Petition 06-178-01p seeking a Determination of Non-regulated Status for Roundup Ready 2 Yield Soybean MON 89788, OECD Unique Identifier MON-89788-1, U.S. Department of Agriculture Animal and Plant Health Inspection Service + Biotechnology Regulatory Services page 13 
- National Agriculture Statistics Service (2005) in Acreage eds. Johanns, M. & Wiyatt, S. D. 6 30, (U.S. Dept. of Agriculture, Washington, DC).
- Charles Benbrook. Evidence of the Magnitude and Consequences of the Roundup Ready Soybean Yield Drag from University-Based Varietal Trials in 1998. Ag BioTech InfoNet Technical Paper Number 1
- Development and Characterization of a CP4 EPSPS-Based, Glyphosate-Tolerant Corn Event,G. R. Heck et al. Crop Sci. 45:329-339 (2005). Archived 2009-03-19 at the Wayback Machine
- Molecular basis for the herbicide resistance of Roundup Ready crops, T. Funke et al., PNAS 2006 103:13010-13015 
- Caviness, Charles E.; Walters, H.J. (1971). "Effect of phytophthora rot on yield and chemical composition of soybean seed". Crop Science. Madison, Wisconsin: ACSESS. 11 (1): 83–84.
- Roundup Ready 2 Yield- Monsanto Web site http://www.monsanto.com/rr2y/
- "Microsoft Word - RR2Y USDA Revised 11.03.06a.doc" (PDF). Retrieved August 22, 2010.