Development, Identification, and Characterization of a Glyphosate‐Tolerant Soybean Line

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.