Glyphosate-tolerant cotton: Genetic characterization and protein expression

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 R(3) and R(5) 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.