Evaluation of Glyphosate Application on Transgenic Soybean and its Relationship with Shikimic Acid

Glyphosate [N-(phosphonomethyl) glycine]-resistant crops (GRC) are the transgenic crops most extensively grown worldwide, with soybean being the major GRC. It is important to evaluate the impact of glyphosate on transgenic soybean and its relationship with shikimic acid. A field experiment was conducted at Engenheiro Coelho-SP, Brazil, during the agricultural year 2007/2008 to evaluate the effect of glyphosate on the growth, development, and seed quality of GRC soybean variety BRS Valiosa RR. A randomized block design was used with four replications. Glyphosate was applied at 720 and 960 g a.e. ha(-1) (acid equivalent) and in sequence at the doses 720/720, 960/720, and 960/720/720 g a.e. ha(-1) (acid equivalent). To evaluate transfer from GRC soybean to non GRC soybean cultivated in nutrient solution, a pot experiment was conducted at Instituto Biolegico, SP, Brazil. Glyphosate was applied on the GRC soybean (M8045RR) at 2,400 g a.e. ha(-1). Both GRC soybean and non GRC soybean were sown in the same box with nutrient solution. At 0, 1, 3, 7, and 10 days after application, shikimic acid was measured by HPLC and the glyphosate and aminomethylphosphonic acid (AMPA) levels in nutrient solution were determined by GC-MS. The results showed that yield, plant height, seed oil, and protein contents were not affected by glyphosate application. GRC soybean accumulated shikimic acid in the field. Glyphosate and AMPA were released through the roots of GRC soybean, and subsequently taken up by non-GRC soybean, exerting inhibitory effects on their shikimic pathway.