Glyphosate (N‐phosphonomethyl‐glycine) is the active ingredient the nonselective herbicide Roundup. The sensitivity of crop plants to glyphosate has limited its in‐season use as a postemergence herbicide. The extension of the use of Roundup herbicide to allow in‐season application in major crops such as soybeans [Glycine max (L.) Merr.] would provide new weed control options for farmers. A glyphosate‐tolerant soybean line, 40‐3‐2, was obtained through expression of the bacterial 5‐enolpyruvylshikimate‐3‐phosphate synthase (EPSP synthase, EPSPS) enzyme from Agrobacterium sp. strain CP4. Line 40‐3‐2 is highly tolerant to glyphosate, showing no visual injury after application of up to 1.68 kg acid equivalent (a.e.) ha−1 of glyphosate under field conditions. Molecular characterization studies determined that the single genetic insert in line 40‐3‐2 contains only a portion of the cauliflower mosaic virus 35S promoter (P‐E35S), the Petunia hybrida EPSPS chloroplast transit peptide (CTP), the CP4 EPSPS gene, and a portion of the 3' nontranslated region of the nopaline synthase gene (NOS 3') terminator. Inheritance studies have shown that the transgene behaves as a single dominant gene and is stable over several generations.

One important aspect of the safety assessment of genetically engineered crops destined for food and feed uses is the characterization of the consumed portion of the crop. One crop currently under development, glyphosate-tolerant soybeans (GTS), was modified by the addition of a glyphosate-tolerance gene to a commercial soybean cultivar. The composition of seeds and selected processing fractions from two GTS lines, designated 40-3-2 and 61-67-1, was compared with that of the parental soybean cultivar, A5403. Nutrients measured in the soybean seeds included macronutrients by proximate analyses (protein, fat, fiber, ash, carbohydrates), amino acids and fatty acids. Antinutrients measured in either the seed or toasted meal were trypsin inhibitor, lectins, isoflavones, stachyose, raffinose and phytate. Proximate analyses were also performed on batches of defatted toasted meal, defatted nontoasted meal, protein isolate, and protein concentrate prepared from GTS and control soybean seeds. In addition, refined, bleached, deodorized oil was made, along with crude soybean lecithin, from GTS and control soybeans. The analytical results demonstrated the GTS lines are equivalent to the parental, conventional soybean cultivar.

The safety of 5-enolpyruvylshikimate-3-phosphate synthase enzyme derived from Agrobacterium sp. strain CP4 (CP4 EPSPS) was assessed. CP4 EPSPS is the only protein introduced by genetic manipulation that is expressed in glyphosate-tolerant soybeans, which are being developed to provide new weed-control options for farmers. Expression of this protein in plants imparts high levels of glyphosate tolerance. The safety of CP4 EPSPS was ascertained by evaluating both physical and functional characteristics. CP4 EPSPS degrades readily in simulated gastric and intestinal fluids, suggesting that this protein will be degraded in the mammalian digestive tract upon ingestion as a component of food or feed, There were no deleterious effects due to the acute administration of CP4 EPSPS to mice by gavage at a high dosage of 572 mg/kg body wt, which exceeds 1000-fold tha anticipated consumption level of food products potentially containing CP4 EPSPS protein. CP4 EPSPS does not pose any important allergen concerns because this protein does not possess characteristics typical of allergenic proteins. These data, in combination with seed compositional analysis and animal feeding studies, support the conclusion that glyphosate-tolerant soybean are as safe and nutritious as traditional soybeans currently being marketed.

Genetically modified cotton lines have been developed that are tolerant to glyphosate, the active ingredient in the herbicide Roundup. The new lines were generated by Agrobacterium tumfaciens-mediated transfer of a gene encoding 5-enolpyruvylshikimate-3-phosphate synthase isolated from Agrobacterium sp. CP4 (CP4 EPSPS). Lines were screened via greenhouse spray tests and field evaluations to identify agronomically acceptable lines with a commercial level of tolerance to glyphosate. Two lines were characterized. Lines 1445 and 1698 were transformed with different vectors that encode for the CP4 EPSPS and the neomycin phosphotransferase II (NPTII) marker protein. Both lines contain a single DNA insertion that segregates in a typical Mendelian fashion. Line 1445 contains a single copy of the CP4 EPSPS gene, whereas the line 1698 contains two copies of the CP4 EPSPS gene at a single insertion site. The stability of each DNA insertion was demonstrated by Southern analysis across the R3 and R5 generations. The expression levels of the CP4 EPSPS and NPTII were quantitated by ELISA in leaf and seed samples collected in 1993 and 1994 field trials. The use of glyphosate-tolerant cotton will enable the grower to take advantage of additional weed management alternatives. Keywords: Cotton; genetically modified; herbicide tolerant; Roundup

An important aspect of the safety assessment of genetically modified crops to be used for human food and animal feed is the product composition, including nutrients and antinutrients. Cotton lines have been developed that are tolerant to glyphosate, the active ingredient in the herbicide Roundup. The glyphosate-tolerant lines were generated by the stable insertion of a glyphosate tolerance gene in a common variety of cotton. The glyphosate tolerance gene encodes for 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) from Agrobacterium sp. strain CP4 (CP4 EPSPS). The composition of the cottonseed and oil from two glyphosate-tolerant lines (GTCot), 1445 and 1698, was compared to that of the parental variety Coker 312 and to published values for other commercial cotton varieties. The nutrients measured in the cottonseed were protein, fat, fiber, carbohydrate, calories, moisture, ash, amino acids, and fatty acids. The antinutrients measured in the cottonseed included gossypol, cyclopropenoid fatty acids, and aflatoxin. In addition, the fatty acid profile and α-tocopherol levels were measured in the refined oil. These analyses demonstrated that the glyphosate-tolerant cotton lines are compositionally equivalent and as safe and nutritious as the parental and conventional cotton varieties commercially available. Keywords: Cotton; genetically modified; herbicide tolerant; Roundup